pre-charged line sets

Precharged Line Sets Are For Real, Right?

  • October 19, 2016
  • By MR COOL

Precharged line sets aren’t a new innovation in the HVAC industry, but they’re not exactly widespread either. When we tell people our MRCOOL DIY line sets do not need to be vacuumed down, plenty of installers out there, professional or otherwise, just don’t believe it. But, hey, don’t take my word for it!

Precharged Line Sets Are the Real Deal

A picture is worth a thousand words, so a YouTube video has to be worth at least a novel, right? Check out the comments in our 2nd-generation DIY install video and you’ll find plenty of folks who don’t quite believe. If you don’t want to take the time, then I’ll sum up the highlights for you.

So with this unit u don’t vacuum the line?” – Cesar Aburto

no vaccuming?” – Luigi Urbina

I just purchased one I don’t need to vacuum my line????” – EL Camaron

So, Are Precharged Line Sets Real or What?


We here at MRCOOL did not invent pre-charged line sets. They’ve been around for years, but were mainly confined to the modular and mobile home market. That might be one reason why so many people have not heard of them. Don’t worry! Pre-charged line set technology proved itself years ago.  Basically, all we’re doing is applying them in an innovative way.

Innovative How?

One or two manufacturers have used a version of pre-charged line sets on ductless mini-split units before, but we are proud to say that no one has taken it as far as we have. The MRCOOL DIY 2nd-generation Ductless Mini-Split Heat Pump is truly cutting edge technology. Our unique approach makes line sets easy and safe to handle. Best of all, any smart homeowner can put one of our DIY units up in a few hours with no specialized tools.

It’s like they’re comfort made simple or something.

650 thoughts on “Precharged Line Sets Are For Real, Right?”

          1. You can move the compressor, but the unit would need to be turned off and the compressor detached from all connecting electrical and refrigerant connections before moving.

        1. Do you have any guidance for installing a pvc condensate drain line on a mini split cassette unit? The installation instructions are vague …. particularly on what size of pvc to use and the best way to connect the pvc to the unit.

          1. Is the evaporator prechared? My old line set is damaged. I have a new line set for it

      1. Pre-charged lines do not need to be evacuated. If you have a line that says it needs to be evacuated, it is not one of our pre-charged lines.

      2. Did you buy the Mr Cool “Advantage” series because you saw it was less expensive than the DIY series? The Advantage is substantially less expensive than the DIY because the Advantage does not have the precharged lines and requires purging and charging.

      3. Line sets should airways be evacuated before releasing refrigerant. Shame on Mr. Cool for stating otherwise. Even if there isn’t moisture in the system, evacuation checks for leaks so you can fix them before releasing freon. Furthermore, if there is a leak there would be moisture in the system which would ruin it in short time.

        1. The DIY has pre-charged line sets that are accurately charged, sealed, and ready to be connected to the air handler and condenser, so there is not a need for evacuation.

        2. Any line set that has been properly installed by any compentant DIYer and has been inspected the connection fitting properly for damage to the fitting or to the “O” ring should not leak. That is why MR COOL states to leak check the fitting as a part of the installation. I don’t work for MR COOL and am not afiliated with them in fact I’m not an HVAC tech, but I did purchas a system from them and had no problems with leaks because as they said in previous comments, pre-charged Linesets are not a new technology and have been proven so issues related to this are slim to none if installed properly.

  1. What size wire is required for the DIY 24k btu? The specs state a minimum circuit ampacity of 15a. That would mean 14 gauge wire. My electrician says 12 or even 10 gauge.
    Also can I use a 30 amp disconnect or it has to be 25amp?

    1. There should be a wiring chart in the installation manual on page 17. We would recommend a 12 gauge. Your disconnect should be 25 amp or more.

    2. I’m installing a 36K two zone system with 24K and 12K air handlers.
      1. Can line set exit the left side while looking at front of air handler? Any specific problems? Move drain hose connection to left side? Adequate room for fittings?
      2. After exiting the air handler the line set continues horizontally 5′ along the wall before exiting to the outside and dropping vertically. Will a 1/4″ drop in level from the air handler to the outside exit provide adequate drainage?
      3. The 36K condenser is rated at 30A, will #10 copper wire from the panel be adequate?

      1. 1. The line set should only exit the right side of the air handler.
        2. That should be fine. Sloping downward should work for the drain line, there’s only a concern if there’s any slope upward.
        3. 10 AWG wire is preferred for the 36k.

        1. Facing the air handler, can I straighten the lineset 189 degrees to the right? The videos I am seeing show the lineset pulled 90 degrees perpendicular from the air handler. Can I pull it 180 degrees?

        2. Why can’t the line set exit on the left side of the unit? There is a knockout on either side of the interior unit.

          1. Technically it would be possible because of the knockouts, but the angle would be too extreme for the line set connection, so we really recommend against doing so.

  2. How long are the line sets included with the 36k BTU? Can the excess line set be rolled up? I have about a 12 foot run from where the indoor unit is to where I will be installing the outdoor unit.

    1. I believe the line sets on that unit are 25 feet. Yes, the excess can be rolled up to look quite neat. That’s what most people do in fact.

      1. MRCOOL had very good product for DYI like me, the only thing MRCOOL did not support is more than 25 feet pre-charged line. I am willing to pay extra for another 25 feet pre-charged with connectors such as air-compressor connector then I can extend the line to 50 feet. My room in in the second floor.

        1. I am successfully to install 50 ft line of Ductless Air Conditioner with different brand name (Pioneer 24K cost ~$1300.00) with extra step by vacuuming the 50ft line and add about ~1 lbs R401a. It is easier than I thought. Total tools and additional material cost me less than $300.00 – System is working excellent. Before decided DYI, I got several quote from local with the price range from $3000.00 – $4000.00, with DYI, it is significantly good saving for retiree.

      2. Where does the rolled up extra portion of line set reside? Is this technique only used when the line sets are run inside the wall? I can’t imagine how the extra line set coiled up would look good on the exterior of a house and how it works with a line set cover. Please explain.

  3. Is there an option to get longer line sets?
    I want to install the air handler in a remodeled attic, so the distance from the top to the ground is closer to 32 feet. Also is there a maximum height distance that you cannot go beyond?

    1. There is not an option right now for longer line sets. We’ve got some things in the works, and that is a product we hope to roll out eventually. Can you give me some more details about how you want to install the unit?

      1. I am in the same boa as Chuck. My run is close to 40 feet. I’d love to buy a 12k unit but the lack of line options is a deal buster. 🙁
        Any ideas on how to find a reasonable HVAC tech to install?

        1. You can always use Google, of course. I know some people have had luck using Craigslist and Angie’s List.

          1. That depends on multiple factors. The biggest factor is local installation costs. It can vary widely across the country.

      2. Same here. I need about 50 feet of lineset to get from the indoor unit to where I can put the outdoor unit. I don’t suppose there is a way to connect two 25 foot lengths? If I can get 50 foot linesets I’d buy three systems.

        1. Unfortunately, there is not. However, that may be possible with the 3rd generation system due sometime in 2019.

          1. Since we’re putting together a list of requests, here are some things that you might want to offer, whether they would be included in the next DIY system, or sold as accessories:

            1. Multi-zone Systems (I’d have bought two three-head DIY systems this year, if they were available, and I still need a two-head DIY system)
            2. Condensate pumps (It’s not always easy to find an all-downhill route for linesets)
            3. Hyper Heat kit (an electric coil kit that plugs into the standard DIY unit to allow operation in colder environments)
            4. Linesets in various lengths


          2. I just purchased the diy unit and found out I need more than the 25′ line sets. You mentioned above they will be available in 2019. Are they available now? Can I add copper line to make it longer? Is the refrigerant in the outdoor unit or indoor?

          3. On the DIY unit, the lines come charged, so you cannot cut or modify them without professional training and equipment. Unfortunately, the variable-length pre-charged lines are still in product development.

    2. For those of you needing to install the air handler more than 25 feet above ground level, one option you could consider is to wall mount the condensor unit instead of placing it on a pad on the ground. The condensor unit runs very quietly so there should not be bothersome noise or vibration from an exterior wall mounted unit. You just need to get a bracket with adequate clearance from your exterior wall.

  4. I have some suggestions:

    – Smaller capacity! 12k BTUs is super overkill for a bedroom; something around 3000 is more reasonable. All the better if this raises the SEER and HSPF numbers.
    – Short linesets: if I’m going right through a wall, I don’t need 26 feet.
    – A standard wall plug; no hard-wiring!
    – Get the price under $1k

    If you sold units with those features, I’d buy four, like, yesterday.

    1. Thanks, Nate.

      – Interesting idea.
      – The problem there is about manufacturing cost. We’re working on a way to give customers more precharged lineset options, but it’s still very early in development.
      – That could be possible if we made a smaller capacity unit, but none of the current units can be safely plugged into a standard wall socket.
      – Nate, most dealers sell our Advantage units at around $700.

  5. Regarding the 24k btu, the electrical data on the brochure states “max fuse 25amps”. I read this as saying the disconnect must be fused at 25 amps. However, one of the answers to the questions above says ” preferably non fused”. Can you please clarify the requirements ? Does it require just a 25 amp breaker at the panel or the 25 amp breaker at the panel and the 25 amp fused disconnect?

    1. You do not have to have a fused disconnect. You may have a non-breaker disconnect. At the breaker panel, it has to be 25 amps. The outside disconnect is only for servicing the unit.

    1. The pre-charged linesets only come in 25′. You can get a variable length with an Advantage or Oasis unit. They are not DIY, but they are very good units. A 12k should be sufficient for 500 square feet, but you might want to get an 18k just to be sure.

        1. We have DIY ductless mini-split heat pumps and Packaged DIY units. If it doesn’t say DIY in the title, it’s not DIY. Well, not without some specialized tools and training anyway.

  6. Can u cut the pre charge line set and wiegh the 410a back in I had a homeowner call me today and he said he bought one of these units and the line is to long I am licensed tech

    1. Yes, that would be possible. The refrigerant lines with a DIY unit are pre-charged, but other than that they are basic refrigerant lines.

  7. Another question, if I decide to move a installed diy unit to another room will the lines have to be charged?

    1. If the unit is installed and then uninstalled correctly, no, you would not have to charge the lines. If errors occur and refrigerant escapes the system, then it would require charging to the appropriate capacity.

      1. Do you guys make a 3 zone system in the DIY? I have a small 2 bedroom cabin approx 800 SF. I’d really like to have an indoor unit in each bedroom and one in the living room that is open to the kitchen.

        1. We do not currently offer a DIY multi-zone unit. For that, I would recommend the Olympus. It will require a contractor to install, as special equipment is necessary. Alternatively, you could install multiple DIY units.

      1. No I’m asking about the range the inverter throttles down to and up to. I’m guessing 18,000 btu and 24,000 btu is the most it puts out during high load but what’s the lowest it puts out when the load is low like during the shoulder seasons?

          1. Thank you very much for this information that’s exactly what I was looking for. Does the hyper heat units have the same range as well for the 18,000 and 24,000 units.

  8. Thanks for the reply last question,is it more efficient to leave the unit on for longer periods of time or is it better to shut it off if I have to leave the house for an hour or so?

    1. Typically, shutting the air conditioning off for short periods to save money doesn’t really work. The only time I do something like that is when I’m going to be away from home for a few days. I also never turn the unit off completely. Dehumidification is an important part of air conditioning, and keeping interior humidity at a reasonable level can help prevent mold growth. Just set the temperature higher than what you would normally comfortable with, but not so high that the unit never kicks on.

      1. So, should unit be shut down in those temps and auxiliary heat take over? Do you have any units designed for lower ambient?

        1. Yes, that would be recommended. Our Oasis Hyper Heat units are designed to operate more effectively at lower temperatures.

  9. I have the DIY 18000 BTU. I have heard there are alot of problems using the smart phone app. I can’t even get the QR code to read without it saying illegal code! What can I do, and when will the app be taken care of so it works? That’s one of the reasons I purchased a Mrcool!

    1. The ‘illegal code’ error message usually display when you scan the wrong area of the box. Give us a call at 270-366-0457, ask for tech, and they’ll walk you through the process.

      1. Did you put the Indoor unit in AP mode? (by holding the led button on the remote for 4secs) I had the same problem when I bought it last year

  10. Any plans in the works for a multi zone DIY unit?

    We have a single level 1100 sf house (26×43), our Split Ac went out and I am
    looking at all possibilities for replacement. The house is open kitchen, living and dining room followed by a hall with 2 small bedroom and one larger master. Ceiling Mounted return vent in hall for central gas heat and ac.

    Wondering if one 24k unit on living room wall opposite the return vent (hall is off living room center and runs down center of house) would work. When needed turn on furnace blower to circulate air through out the house? Could probably wire furnace blower to come on at a set temp in cool mode (with current ac disconnected of course)?

    The price of your unit beats a $4000-6000 split ac install. Bearing the fact in Boise Idaho we need AC only 3-4 months of the year (wife’s View) 2-3weeks in August (my view)

    1. We have had internal discussions about a multi-zone DIY system. However, if we deploy a product like that, it won’t be anytime soon.

      A 24k in the main living area should be sufficient for a lot of your cooling needs. You could then put a 12k or 18k (at most) in the master bedroom. Together, I think those two would be sufficient for your entire house. You could probably wire the blower to act as an improvised cool air circulator, but I don’t think that would be necessary. Proper mini-split placement should meet your needs without having to worry about jury-rigging your heater.

      1. Thanks for the quick reply. Trying to avoid the cost of 2 systems. I keep pondering If one 24K would work for whole house.
        As to the furnace I think all it would be is; disconnecting the control wire to the current outdoor unit. Setting the thermostat to cool position and temp say to x degrees. This will force the blower to come on till the bedroom area reaches x degrees. Distributing cool air to the bedrooms.

        Our duct work is in a crawl space and not in the attic so it stays pretty cool in the summer.
        Returns are insulated and in the attic though. Right now it is 81 outside left windows open last night and blower running no ac on it is a col 72 inside.

        1. A 24k is going to be good for around 1000 square feet. If you wanted one system for the entire house, you may want to move up to a 36k.

    2. Walt, if you haven’t already made a purchase maybe I can shed some light. Your floor plan is exactly like mine, only my sq footage is 1565. I mounted a 24k unit high on the great room wall opposite the hallway and cold air return. The unit does a marvelous job heating and cooling the 700 sq ft great room. In winter, I installed a floor to ceiling curtain to keep the great room heated evenly. Since we don’t heat the back of the house except at rising and retiring, this has saved a lot of burned gas and we now keep the great room at an even 72 deg in winter instead of a drafty 69. Circulating cool air with the gas heater on fan, is a technique we used to cool the house down pre mr cool when afternoon temps dropped. I can see no reason why using this technique would not be a quick and easy way to circulate cool Thru out the house just as the gas furnace would circulate heat

  11. I just installed the 18K DIY unit and love it…was very user friendly..
    I will be moving next year and will be taking the Mini-Split with me to the new residence..

    My ? is ,I know how to pump down a unit ,with the proper gauges and vacuum pump.,but how would this apply to the DIY18K ??
    basically I am asking ,”when I am installing the unit back in the new location,do I follow the same procedures as when it was brand new,or do I need to purge the Lines like a normal non-diy install?
    I have searched for answers on Google but not alot of information as far as DIY pre-charged lines and what to do after disconnecting for move to new location

    1. When you’re taking it apart, you’ll basically want to do the installation backwards, so to speak. Make sure the valves are closed before you disconnect the refrigerant lines, of course. When you’re putting it back together, do it the same way you did it the first time. If ever thing goes as planned, you should not need to vacuum the lines or add any additional refrigerant.

      1. I don’t understand your reply. So, if the refrigerant lines are pre-charged, and then the DIY owner re-seals the outside unit ports (by closing the 5mm allen screws) to the lines, and then disconnects the lines. (I think these are steps you’ve outlined, above). Then, when the lines are disconnected from the outside unit, the lines lose their charge.

        At that point, at re-installation time, the DIY owner is calling a tech to vacuum purge and re-charge the lines.

        I’m attempting to be clear, and demonstrate you’ve apparently left something out of your explanation of re-connection.

        1. They should not lose their charge. The connection couplings should mechanically close once they’re detached.

        2. Bob, I believe the lines have internal stopper valves at the coupling ends. The stoppers are pushed open when the coupling is screwed together, but when unscrewed, either internal pressure or a mechanical spring closes the valves inside the lines.

  12. I found your air conditioners and the reviews are great. They are back ordered or not available every site I find. What is your production schedule? I’m looking to get one delivered to Home Depot in Galveston, if that matters. Looking forward to installing a 36K DIY in my beach house. My window units can’t keep up!



  13. On the 18k diy mr cool one line set is bigger around than the other does it matter which one screws onto the top and bottom of outside unit?

    1. Make sure you connect the line sets properly in accordance with the instructions in the Installation Manual. Yes, one is larger and one is smaller, and it does matter where they are attached.

  14. The manual shows the location of the pass thru hole in the wall is either in the lower left or lower right corner of the indoor unit. The unit as delivered has the tubes bent tightly to cross over to the right side, then the tubes are wound up in the box in what I can only describe as a tight oval. I was going to install the pass thru on the lower right (facing the unit), but the bend in the tube there is pretty tight and I am fearful of bending the tube too tightly or even kinking it, or breaking it if I try to straighten it out. Is there any reason I shouldn’t make the pass thru hole more toward the middle of the unit (just inboard of the wall bracket)? Then I would be bending the tube in a place it has not been prestressed.

    Otherwise, is there a procedure for unbending the tubes to get the pass thru on the right side without risking damage?

    1. I don’t know of a reason why you couldn’t modify the position of the wall hole so long as it can be maneuvered through undamaged. I would recommend you follow-up with our tech guys. Call 270-366-0457 and ask for tech.

  15. Re: DIY 18 for 750 sq ft shop, well-insulated, eastern MA. You’ve stated that lowest outside temp for heat is “low teens”. Is this for making its rated amount of heat, or for making any heat at all? Thoughts on installing compressor in adjoining garage, which even though unheated, never gets really cold (below 15-20°)? Would that benefit the low-temp winter operation? Or should I leave my oil burner functional?

    1. There are a lot of factors to take into account in your example here. Any heat pump, ours or otherwise, takes heat out of the air and puts it inside your house. The colder it gets outside, the harder it is for the unit to gather that heat, so efficiency drops. The AHRI only rates units down to 17 degrees, so that’s the lowest verifiable operating rate we can provide. If you had the condenser in an insulated garage, that could help maintain even efficiency for a longer period of time. However, while the interior air handler would be heating your shop, the condenser in the garage would, in effect, be acting as an air conditioner. The garage location would benefit winter heat pump heating, but at some point, I’m not sure exactly when, the condenser would cool the garage to such an extent that it compromised its own efficiency. Personally, I would try to get as much heat as I could efficiently from the mini-split, then turn the oil burner when it just gets too cold.

      Hyper heat units like our Oasis Hyper Heat and others can handle lower winter temperatures, but, since they’re heat pumps, all of them ‘bottom out’ at some point.

      1. I appreciate your reply, and that makes sense. Gets into the question of how much “heat” can you suck out of “cold” air. As an aside, the shop equipment generates waste heat in the room, and I really don’t need supplemental heat until the outdoor temp is below 30-ish. Bigger issue is winter nights, when the outside temp can be lowest, machinery is off, and I want to maintain that equipment at 60-65. I’m only at the early investigating stage, and again thanks for the reply.

  16. I understand one should switch to other heat sources past -17 degrees, but I would like to know if the unit compromised at colder temperatures (Canadian winters can get below -40)? For example, if I accidentally don’t realize the tempature has a sudden drop to -20, will it simply be ineffective or can it potentially hurt the unit? Also, is it perfectly safe in extreme cold when shut off for the cold winter months?

    1. It will shut down and go into defrost mode. Being exposed to extreme weather should not damage the condenser. It is a good idea to prevent snow and ice from building up around the condenser, but that’s a good rule to follow with any HVAC unit.

      1. AHRI rates heat pump efficiency down to 17 degrees, so that is correct. But where did you get the -17 number from? I’m not aware of any heat pump that would heat efficiently that low.

        1. The user “me” on August 1, 2017 at 11:07 am said “I understand one should switch to other heat sources past -17 degrees” and I wanted to clarify for anyone else who came across the post that it’s 17, not -17.

          1. I have a hyper heat in another brand that puts out 125* in 0* weather. The Mr Cool Oasis hyper heat is designed to run down to -22. Obviously the efficiency drops the colder it gets but the numbers I have seen are from about 1.6 to over 2x the efficiency of electric resistance heat at 5* ambient. (Outside temp) Many of them are still around 3x as efficient as resistance heat at 17*.

    1. Everything should be in stock right now except for DIY 12k units. More of those should be back in inventory in 3-4 weeks.

  17. I would recommend MRCOOL to start making pre-charged lines in different sizes like 5′, 10′, 15′, 20′ 25′ and so on. One should be able to order it based on one’s requirement. In my case I want to buy 5 DYI unit but with different sizes of lines to make the installation looks better. What are your thoughts.

    1. This is something we go back and forth on. On the one hand, we want to give people as many options as possible. On the other, we want to minimize the potential for an install going wrong, and different length linesets would necessitate a non-factory installed connection to the air handler. It’s a tough call. We’re going to stick with a single lineset size for now, but that may change in the future.

      1. I second this. Perhaps 3 line set lenghts 15, 25, 35.
        And perhaps ability to daisy chain so You can make your own 30 out of two 15s. More revenue for you and more flexibility for client as they will pay a premium for a 15 over a 25.

        1. You can link line sets together using Quick Connect coupler kits! They are available along with additional line sets at any of our retailers. We also have 16′ line sets.

    1. For some models a P6 error code is a condenser high-temperature protection warning. What model are you using?

  18. Can I mount the outdoor compressor unit on the roof about 5 ft. above the indoor unit? Unfortunately I can’t mount the outdoor unit on the ground below the indoor unit and meet the 12 inch clearance criteria behind the unit within the 26 ft. coolant line length. Do I have to worry about sun exposure of the unit on the roof. I live in AZ.

    Thank you

    1. The compressor can be mounted in any relation to the air handler so long as you make sure the drain hose is configured properly. It should still work in direct sunlight. If you can arrange some sort of shade, that would be ideal though.

      1. Do you have brackets for roof mounting – specifically for the pitch of the roof to make it level? Would be cool if you had adjustable angle roof mounting brackets to adjust to your pitch.

  19. I just installed a 12 k DIY unit on our 4 season room and it works great but I really wish you could provide different length line sets to make the end job look much neater. I saw an earlier comment that said “I would recommend MRCOOL to start making pre-charged lines in different sizes like 5′, 10′, 15′, 20′ 25′ and so on.” Why would it necessitate a non-factory installed connection to the air handler? I know a production lines like one size fits all but many of us would gladly pay the extra cost to get the line length we need with the correct charge. I currently have a need for another unit with a line set of 6 to eight feet and would love a DYI solution again but with the length issue I’ll go with another product that wont be DYI. I’ve read that coiling extra line set be-hide the condenser is not a good thing and could create oil traps bla, bla, bla. You guys are close to making an even bigger hit than you already have with a few tweaks like different line set lengths.

    1. We would love to be able to do it, and we’ve had a lot of internal discussions to that end. As of right now, we won’t have variable lengths in 2017-18. There is a chance we will develop a variable lineset DIY product by 2019 though.

  20. Thanks for your reply. I understand that gearing up to make a change like variable line sets might take awhile but can you comment on coiling up extra line set and storing it behind the condenser? It it in anyway detrimental to to the compressor? Will it cause an oil trap? The “non-DYIers say it’s bad for compressor life. Besides looking like you know what, is coiling up 20 feet of it ok?

    Thanks again.

    1. Carefully coiling the excess lineset behind the condenser should be fine, but make sure it does not interfere with air flow through the condenser. It should not cause a problem.

  21. Hi. I’m looking to purchase and install a 12k DIY unit for my home office in the basement of my house. The floor above the basement overhangs front and back around 2′ each.

    In the instructions, the drain line is bundled with the rest of the line set. Would it instead be possible, for a neater installation and a smaller hole through my concrete block, to coil the line set in the overhang immediately above the outside unit (and drop the line set from there), and separately have a smaller hole through which the drain line would go?

    This way, the larger hole gets drilled through the wood overhang, line set is concealed (distance from the inside unit to the outside would be all of maybe 6 feet of line), and the drain hole is much smaller.

    I assume the only line where downward angle matters is the drain, right?

    How tight can the line set coil get before kinking? Could it fit between 16 OC joists in that overhang?


    1. You are correct that the only line where downward angle matters is the drain. It can be separated from the other lines. You can really do anything you want with it so long as it will drain properly.

      In terms of how ‘tight’ the line set coil can get before kinking, there is a lot of flexibility in the lines. It should be able to fit between 16″ joists. Just be careful, of course.

  22. I bought the 24k Mr. cool for 240 volt. The wire diagram shows L1 red and L2 black and ground. Where does the neutral (white) go? On the ground screw with the copper wire?

    1. If you have a WHITE conductor in your power supply cable, it should be attached to the ground screw with the bare copper ground, both at the unit and the disconnect. A 220v circuit does not have a neutral.

      1. connecting a neutral on the ground would be a code violation of the 2017 NEC , This type of connection is grandfathered for
        things like ranges, but a new install would require a green or bare wire from the panel EGC to the ground screw on the unit. the advantage of the 2017 code is a separate ground wire can be run to to a an Equipment Grounding Conductor on another branch circuit as long as they are fed from the same panel. (Licensed electrician and Universal HVAC).

  23. One of the posts above you said that an installed unit may be uninstalled and moved without recharging if done properly. Can you list the steps necessary to accomplish this as I need to move a 12k unit and replace it with a 24k?

    1. The key area to focus on is the refrigerant piping connection on the condenser. Refer to section 6, page 23 in the installation manual. Basically, you are going to run the piping connection install process backwards – remove the valve covers, close the valves with a 5mm Allen wrench turning clockwise, replace the valve covers, use wrenches to open the connectors, attach the plastic seals (if you still have them) to the connectors. Obviously, the unit should be completely turned off/disconnected from power when you do this.

  24. Having trouble getting these shipped to Hawaii, is it because they are pre charged? Ca these be transported by normal methods such as FEDEX or would they need to ship by boat?

    1. I’m not an expert on shipping to Hawaii. However, we ship them to customers using normal means, so there should not be any special requirements.

  25. I understand that your standard units are rated to produce heat down to 17 degrees, and that for colder climates, you offer the Hyper Heat series. Is there any DIY product that offers Hyper Heat?

          1. I’m sorry to hear that. For what it’s worth (Which I realize isn’t much) I’ve got two floors that I want to put systems in. Each requires dual zone, and I’d like to do hyper heat. The DIY option is what attracted me to MrCool, but if I can’t do that without voiding the warranty by using a non-DIY unit, then I’ll probably go with a local pro installer, and the systems they carry, even though it will likely triple what I end up spending. Thank you for your quick responses.

          2. The number of contractors installing MRCOOL products across the country is growing. Have you tried looking for a MRCOOL dealer in your local area? Alternatively, you may be able to find an installer willing to use equipment you’ve already purchased. Not all installers require their customers buy directly from them.

  26. We live nc mountains in zone 5 but our temps seem to be a little different then most zone 5. Our average high in July is is 71 but only above 80 for about 10 days during the entire summer. Our average low in Jan. is 19.

    Our home is about 12K sq. ft. and I can mount the air handler in the cathedral ceiling wall in the center room of the house. The main reason for wanting a unit is to remove humidity when it hits those 10 days or so during it gets over 80 degrees

    I am thinking a 18K would be better than a 24K to get the humidity out as it would run more. What do you think?

    Also since the unit would be in the middle of the house which unit (Oaisis or DIY)would give better distribution of air flow?

    And one more. Could you explain how the hyper heat is different from the regular Oasis unit and what the benefit would be for my application?


    1. An 18k that runs longer would dehumidify longer. However, you should get the size you need. If you need more dehumidification, we recommend you switch the unit to Dry Operation. This will provide more dehumidification.

      In terms of air flow, there shouldn’t be any significant difference between an Oasis and a DIY.

      The Oasis Hyper Heat performs more efficiently at lower temperatures than a DIY unit. For example a 24k DIY (AHRI 8994007) unit will produce about 15.9k BTUs at 17 degrees. An Oasis Hyper Heat (AHRI 8977714) will produce about 17.2k at the same temperature.

      Also, when you said you have 12k sq. ft. did you mean 1200 sq ft or 12,000? Because if it is 12,000, I think you might need more than one ductless unit to cover that!

      1. Thanks for your quick reply,

        I meant 1200 sq. feet and the room I want to put the air handler in is in the middle of the house. Wooded area not a lot of direct sunlight. Still think I need more than a 18K unit?

        What is dry operation?

        Would 15.9k BTUs at 17 degrees be able to maintain a temperature of 70 degrees in a 1200 sq. ft. house?

        1. Given your summer temperatures are rather mild, you may not need more than an 18k

          Dry operation is when the unit runs on a lower cool setting, so that it runs longer and dehumidifies more effectively. If the interior temperature is where you want it, but it’s still a bit too humid, let the unit run on dry mode for a while.

          As to your question, I’ve sent a message to the tech guys to find out what they think.

          1. So, here’s what one of our tech guys said, “I have no idea what the btu requirement for the specific structure is, however my best guess is probably not.”

  27. Hello I have purchased one of your 24k DIY units but would like to shorten the lines. I know that the Hyper Heat models specify a minimum line length of 10 ft before needing to remove refrigerant however there is not a length specified for this model. Could you give some insight on what this length would be?

    1. We do not recommend modifying the length of the line set at ALL on a DIY unit. If you want a unit in which the line length can be modified, we recommend our Advantage Series. Since the DIY lines are pre-charged, they would have to be vacuumed before modifications were made. Which would also necessitate vacuuming the air handling unit, since the line set and the air handler are preconnected. Without proper licensing, modifying the line length on a DIY unit would void the warranty.

      1. I have an HVAC technician that could vacuum the lines. Isn’t it the unit that is precharged opposed to the lines?
        What would you recommend doing with the excess line?

        1. On the 2nd Generation DIY unit, the line sets, the condenser, and the air handler are all precharged. Customers do different things with the excess line. Some people bundle and leave it propped behind the unit, some build boxes or other housing to store the unit, some have it running along the wall protected with LineGuard, etc. It just varies from customer to customer. Again, if you’re going to have to go to the trouble of having a tech vacuum the lines, I really do recommend the Advantage over the DIY. The DIY is designed to avoid that sort of thing, but the Advantage will work just fine. And it’s cheaper!

          1. Josh, the whole point of the MrCool DIY series is that you don’t need to mess with the lines. There’s no vacuuming needed, there’s no HVAC license needed. There’s no special tools needed. This is all thanks to the fact that they already have refrigerant in the lines, whereas most HVAC eqipment is sold with lines that require all that additional work and expertise.

            The disadvantage to the DIY line is you end up with pre-determined lineset lengths, and may need to coil it up somewhere.

            What the MR COOL rep is trying to tell you is that if you aren’t okay with having that excess lineset laying around, then their non-diy systems would have been a better option. The Non-DIY linesets don’t have refrigerant in them yet, so they’re much more practical for a licensed technician to modify. If you want to modify the lines on a DIY system, you not only negate all of the benefits of getting a DIY one, you also have made more work for the technician vs just getting a non-diy system to begin with.

          2. Would you be able to tell me if the bolt mounting pattern on the outdoor unit of the Advantage 24k unit is the same as the DIY 24k unit? If so I will return the DIY in exchange for the Advantage.

  28. Hi I have received my DIY 24k and notice it comes with a sealed bag of neoprene. What is this for? It doesn’t seem to say in the instructions.

  29. Forgive me if this question has been answered. My eyes started to blurr reading all these great posts and replies.
    I just purchased the DIY HP 18K 230A. I will be installing in my detached garage/shop/man cave (550 sq ft). I don’t care if the lines are mounted inside or outside. Is there any advantage/disadvantage to the location of the bulk of the 25′ lines?
    Seasonal exterior temps range from avg mid 90’s in summer – avg mid 30’s winter. The garage is finished and insulated.

    1. Whether the bulk is inside or outside, there is unlikely to be any performance difference that you would notice.

  30. Do these units have a condensate pump, or do they just drain by gravity? I’d like to install one on an interior wall and run the linesets through the attic. If there’s no pump, I guess pI’ll have figure out somewhere to drain the condensate inside the house.

    1. They drain via gravity, so, yes, figuring out a drain in that kind of installation would be necessary.

  31. On your 24000 diy pump, installation was a breeze watched the video and pretty self explanatory. It was shipped in the most armour plated setup I have ever seen, job well done. But you need to include a weather tight fitting for the indoor unit to connect to the compressor. The clip is to big for any type of normal fitting to work. You have to cut and resplice to get it to work. If you fixed that and had a option for shorter linesets or custom lenghts you would sell me 2 more for sure.

    1. Different lineset lengths is a common request. We have been exploring that option for a few years. Hopefully we get it on the slate in 2019.

  32. Is there a programmable thermostat available for the 36k DIY? If not is there some way to set different temps for different times of day, e.g. 74 8a-8p and 78 8p-8a?

    1. There is not a programmable thermostat available. You can use the remote to program the unit to change temperature at a set time.

  33. I need a 35’ line set. Can I purchase a pre-charged line set from a mobile home site and use it with a MrCool DIY unit?

    1. Definitely an interesting idea, but it won’t work without a lot of headache. The lines on the DIY are pre-connected to the air handler, so you would have to do some fairly significant modifications to remove it and attach another line set. All of which would definitely void the warranty.

  34. I’ve purchased and installed two of your DIY units, a 24k and a 12 k unit. They both work great and I’m planning on buying another 12k unit soon. Excellent product!
    I have two questions/comments.
    1. When using the sleep mode it would seem to me that it would make more sense if after going thru the seven hour sleep mode that the unit would return to the primary set temp. rather than shutting down. This would make more sense to me as most people would want the unit to crank back up to the primary temp. when they are waking up rather than shutting down.
    2. When using the wifi smart phone app I can’t find a way of seeing what the actual room temp. is. All it seems to show is the set point temp. I’d like to know the actual room temp. so I can tell if things are actually working correctly. I know somewhere in either the unit or the remote there is a temp. sensor that can read the room temp.

    1. 1. You could always use the Timer On button to set the time you want the unit to come on.

      2. While there is a sensor in the unit that reads the room temperature, this is not part of the data that the app can translate.

  35. I tried to use 10 ga wire to run between my disconnect and the condensor (DIY 18k), since that was what was on the old unit. I found that the L1 and L2 screws won’t clamp down on the thicker 10 ga wire. I went down to 12 ga, and they seem tight but those screws are awfully short. Any thoughts on this? Otherwise, I had no issues with the install. Thanks.

    1. If you are using solid copper 10 AWG wire, you can hammer it flatter to get it under the screws, or else attach spade connectors that can then go under the screws.

  36. I want to put your system on my third floor but I’m not sure the 25 foot line is long enough. Do you have longer pre charged lines that you sell?

    1. We do not have longer pre-charged line sets. However, you could use a wall mount to secure the condenser to an outer wall. Placing the condenser on the ground is not required.

  37. Add me to the list wanting shorter linesets or custom lengths. I could use a 7-8 foot lineset.

  38. I have a 3 car garage where I planned to install a 24k DIY unit based on the information in previous comments. The garage is about 850 sqft. I used one of those online calculators, and the result indicated I needed only about 10k BTUs for cooling. So I am wondering if the 24k unit is overkill. Should I go with the 24k unit, or should I consider something smaller?

    Some additional info. I live in southcentral New Mexico (desert, very arid, except for monsoon season). The garage has no windows and no external doors (although I plan to put in a service door in the future). The garage doors are both insulated, and the ceiling height is about 9 feet.I plan to put in two ceiling fans as part of this installation to circulate the air.

    Thanks for the advice.

  39. I have purchased the DIY 18,000 BTU unit. I am going to cut the line set off and install a shorter line set. The liquid line consists of two small capillary lines that turn into 1/4 inch copper. Are these lines acting as the restriction in the system or is there a expansion valve closer by the evaporator. I am going to run one 1/4 inch copper and one 1/2 inch copper.

  40. I just got a 12k DIY unit and it has a big yellow sticker on it that says caution lines must be evacuated, I thought you dont have to evacuate these systems thats why i purchased it could you please shine some light on this subject as soon as possible Thanks

    1. The tag should definitely not have language about evacuation on the DIY. There should be a yellow tag that instructs the valves must be opened after a sealed connection is made. You should check the model numbers. Either you received the wrong product from the seller or the factory placed the wrong stickers (most likely the former).

  41. Why are you reluctant to offer a 2 or 3 zone DIY system?
    I think from a marketing standpoint it would be easier to promote than a 1 zone window unit alternative at your price point.

    1. From a marketing standpoint, a multi-zone DIY system is great. From an engineering standpoint, there are multiple issues that have to be worked out before the technology is ready for market. Multi-zones are just a lot more complicated than a single condenser-air handler set.

  42. I have just finished installing a DYI 24000 btu’s . My comments on it are .I saw some body posting about the screws that attach the wires in the condenser are extremely small , even after they are tightened the seem kind of flimsy at best .And I agree completely .
    Bought the unit to cool down a two story cabin and after a lot of debate about the air handler position , decided to install it in the second floor where it gets the hottest . That left the kitchen – living room area a little warm . As an experiment dug a hole in the living room ceiling leading to the upstairs room floor and installed a little fart fan that was laying around as an improvised air circulator … Man the difference was amazing…the hole house got so cold we had to raise the temp because it got so cold .Super happy with the unit and I would recommend your product to anybody . The noise level of this thing both inside and out is ridiculously low , the build quality looks great .

    Which leaves only one question : Can the lines be mounted flush to the side of the unit ? I have seen some cut-off’s on the side of the air handler …but can the lines be bent all the way to the right of the air handler as to mount the lines flush to the inside wall ? Which would basically mean : Can the lines on the air handler be rotated 180 degrees from the original packing position ?

    1. Glad you’re enjoying the unit, Andres! As to your question, the lines can go out the right side of the unit, flush with the wall (which is what I think you are asking). The only caveat would be to ensure the drain hose is angled properly.

  43. Most any HVAC how-to says coiling refrigerant lines is a no-no. Something about trapping refrigerant oil.
    So with the outside unit sitting below an inside unit on a single level home, I’ll have about 15 extra feet of line set – and I can simply coil it? Horizontal or vertical? Does it matter?
    Has something changed over the years in line sets?

    1. If you are going to coil it, coil it horizontally behind the unit. Many homeowners run the full length of the line set down a wall to keep it as straight as possible. For example, you would run it down to the ground, then left or right across the the outside of the building, then install your condenser at the maximum extension point. I just think it looks a lot neater that way, and you don’t have to have the extra coiled line laying around anywhere. As to line sets and refrigerant oil, I know that can be an issue with slight kinks or leaking, but properly installed that shouldn’t be an issue.

  44. Well the DYI is out. I planned on installing on n outside wall, but I have a nice looking house and coiling 20 feet or so of line behind the unit is not appealing. I had nearly decided to go with the Advantage and pay someone, but the warranty is terrible. Why is the DYI warranty three time longer? Seems counter intuitive. Also, does the contractor need to do the full install to avoid voiding the warranty?

    1. A contractor would need to install the Advantage to ensure the warranty is valid. The Advantage is an economy product, so the warranty terms as not as beneficial as a premium model like the DIY. In terms of installation, you don’t necessarily have to coil the lines behind the unit. If the environment around the site permits, you can move the location point of the condenser, run the line along the length of the wall, and conceal it with an attractive cover set like our LineGuard.

      1. Mr. Cool continues not to recognize the need to custom make the desired line set length. Doesn’t seem like it would cost them anything to lope off 10 or 15 ft. of line set. Even if they charged more for the service I don’t think we would mind to make it look better. They say if your going to coil the line set, coil it horizontally behind the unit. Can you imagine how awful that would look mounted on an outside wall?
        I installed a DYI unit and played out the 25ft of line set when I only needed 15. Installation could have looked much better. I would have installed another DYI unit at another location but I only needed a 6ft line set so I went to a different brand and paid a small fee for having it done right. I’ve seen many posts asking for different length line sets so they must not need the business that bad to give the customer what they want.

        1. John, we definitely recognize customers want a variable line length, but, unfortunately, it is not as easy as we would like. It is something we are working on, and it is an option we will offer as soon as practicable.

  45. As a follow up, most people install on the outside wall (I assume). Seems like you would save considerable money on lines and refrigerant with the shorter houses, and frankly sell more units.

    1. Yes, most people do install the condenser on an outside wall. We currently offer 25 foot refrigerant lines to ensure the product is as flexible as possible.

  46. We are getting ready to install a 9000BTU unit 240 volt. The spec calls for using 14 gauge wire with a 15 amp breaker. This seems undersized to me. I would go with a 12 gauge wire and 20 amp breaker. What do you think?

  47. What’s the difference between a advantage 18k unit and a diy 18k unit? Why do I need to evacuate one and not the other? Both look to have the same linesets and connections? I am in New England and am looking to get some heat in the shoulder months are there any advantages to one or the other or the hyper heat?

    1. The Advantage is a conventional ductless mini-split. The DIY is designed for do-it-yourself connection, so the lines are pre-charged and sealed. No vacuuming or charging the system is required. Which means they are much, much easier for the average person to install. The Oasis Hyper Heat is designed for cold climate heating. If you’re in New England, that might be the best option for you.

      1. And can you get a hyper heat with pre charged line sets? I am a home builder so the installation should not be a problem i have evacuated units before helping my HVAC guy but I have heard that if it’s not installed by a licensed tech voids any warranty?

        1. Unfortunately, the Hyper Heat is not available with the pre-charged line sets that the MRCOOL DIY comes with. The warranty for the Hyper Heat does require “a state certified or licensed HVAC contractor”. So long as your state certifies you to install equipment like this, your warranty will be honored.

  48. I’m thinking of installing a couple feet above the ground, can i coil the extra line horizontally, underneath the unit? For the 220 volt unit, would i run just three wire, L1, L2 and ground, no white neutral? Color suggestions for the wires?

    1. Yes, you can coil the line horizontally. For electrical questions, please contact our tech support at 270-366-0457.

      1. Is the DIY 18k unit AHRI Certified? If it is, I can get a rebate from my power company.
        Rebate verbage
        ◦Your new ductless system must be AHRI Certified® as a mini-split heat pump, use inverter technology, have a minimum HSPF of 9.0, and be a minimum of 1.0 ton in heating mode.

          1. Great!

            Now i see they want the certification number. Can you provide that for the 18K unit?


  49. I have just ordered the DIY-24-HP-230A. I am anxious to install it. Were in the middle of a heat wave here in East Texas. I want to make a concrete pad with four bolts sticking up to hold down the outdoor unit. Could you give me the exact measurements of the holes in the feet of the outdoor condenser? Also, all of the install videos show people running the lines out of the right side of the indoor unit. I am wanting to go out the left side. Does the left side work and look just as good?

    1. The distance between the holes is 21.5″ long and 13.25″ wide. The conduit cable can go out on either side of the air handler. There are perforated sections that you can knock out to accommodate the install. As far as how it looks, well that is in the eye of the beholder.

  50. Can I run the 25′ DIY pre-charged lines upwards into the ceiling from evaporator on bedroom wall, and than snake it horizontally across the inner ceiling to adjust the length, than down the wall to the condenser on outside house?

    1. You can run the refrigerant line and the communicating wire in that way. However, the condensate drain must always be angled downward to prevent water leaks.

  51. Two more questions. Is the Advantage a variable speed compressor?
    If I run 50′ lines to the Advantage and I vacuum it, will I have to add freon since lines are over 25′ ?

      1. I thought the Advantage was a 2 stage because there was no mention that it was a variable speed?
        If I use 25′ lines on the Advantage can I just vac and avoid adding freon?

        1. It uses a variable-speed inverter. You shouldn’t have to add any charge for the Advantage with 25′ lines, but you should always check with gauges to ensure it is properly charged before activation.

  52. Last question. Can I oversize a variable speed split a/c buy putting an 18k DIY in a 300 square foot master bedroom with 10′ ceilings, walk in closet, master bathroom. BTU Calculators come up with 12k. I have read that oversizing an inverter variable speed is ok and may be better. Thanks.

  53. Hi , I have a small house 976 sq ft, one large open living room kitchen combo and down a narrow hallway 3 small bedrooms and one small bathroom. I was wondering if I should purchase the DIY 36K BTU unit and place it in the living room across from the hallway if it would be capable of cooling and heating the whole house, if I were to install ceiling fans in all the bedrooms and living room. I currently have gas wall heaters and am getting new vinyl windows installed. I live in Southern California and have a 1950s build no insulation house.

    1. Properly placed, a ductless product like the DIY 36k can distribute conditioned air very effectively. Ceiling fans will help as well. An alternative would be a multi-zone with two or there smaller capacity air handlers. However, the DIY 36k is definitely the more cost effective choice.

    2. I don’t know where you live but it sounds to me like 36K would be over sized. I am considering both the DIY and Oasis Hyperheat units. I can do the DIY unit myself but the Oasis unit has better features mostly savings on heat but also the air distribution is better. I will do almost all the Oasis unit myself but will need to get a licensed HVAC person to do the final hook up of the lines and charge the system so it will cost me a little more than the DIY unit.

  54. Hey:

    I live in a cold area where -4F is not unusual for a few weeks of the year. I have been trying to figure out how many BTUs are produced by the hyper heat as the outside temperature declines from 20F to -20F. Is there a chart for that?

    It is hard to figure out what size to buy without this data because I have to buy for the cold days.


    1. The exact BTU performance would depend on the particular Hyper Heat model. For example, the 24k produces 24k BTUs at 47F and 15400 at 17F. Performance will depreciate accordingly down below zero, and the unit must spend some time in defrost mode to prevent ice from building up on the coil.

  55. Just installed a Mr Cool 12000 DIY , was real simple compared to the other 4 LG ones I did prior although this installation was a little more complex on where the wall unit was ( 2nd floor ) versus the outside condenser but hey I am cable guy for 34 years so running wire and hiding it is my deal .My only concern is , as read prior posts , if you need just a little more feet on the precharged line sets. Just wondering why there’s not an additional kit you can buy with the connectors and let’s say a 15′ precharge line set that can be purchased separately to get you where you need to go ? Tell Mr Cool they have a great product blows away the rest !! Lastly , my friend , who is a HVAC , was so impressed with my other mini split installs offered me a job ! lol

  56. on the DIY 18k unit, is it possible the get the pipe connection in the wrong order when connecting them, or is it fool proof?

    1. It is as fool proof as we can make it. The connections are different sizes, and they have different colors. Connect the ones with gray caps together, and then connect the ones with blue caps together.

  57. Purchased and installed 18k diy mini split over 2 years ago and couldn’t be happier. I’m writing to ask for instruction for cleaning the indoor unit. All mini splits are prone to mold buildup on the blower wheel. Can you provide instruction for removing the cover and cleaning the coils and blower wheel? A video showing this cleaning would be great!

    1. The indoor air handler definitely does need to be cleaned. We would recommend you use a mini-split bib kit. We do not sell them ourselves, but you can find them online for reasonable prices. When you’re cleaning the product and need technical support, you can always call us at 270-366-0457.

  58. Building a 48′ x 24′ garage with lots of windows. The back half of the garage has a ceiling height of 20′ and the front half is 9′ tall with a loft above it. Thinking about installing 2 mini split units to cool and heat my garage. I live in Utah where temperatures are commonly below freezing in the winter and 90 to 100 degrees in the summer. What size units would you recommend?

    1. This is not an exact science without seeing the space, but I would likely recommend two units with one positioned in the loft and the other on the ground floor. Two DIY 12k or 18k units should be sufficient.

  59. I was just looking at Mr Cool 24k BTU Installation documentation and see reference to “2nd Generation”… Plan to buy on Amazon; how do I know if I’m getting 2nd Gen or not??? Thank you, Bob

    1. I’m a fan of Amazing for buying many things. But this would not be one of them. Who do you call with questions or problems? I have 4 of the DYI units that I installed in my house. I bought them all from Ingram’s Water and Air. Shipping was prompt and any questions I had were answered by them immediately

      1. Ingrams has these on their site already. They’ve been very helpful and responsive in my experience. That would be my choice.
        I have two of them and they’ve been nothing short of fantastic. 😉

      2. That’s a good question Dale and I honestly don’t know for sure but what I can say is that while I’m buying the Mr Cool mini split off Amazon, the “seller” is Ingram’s Water and Air… And Ingram’s seems to have a hight seller rating… I would think in this case and for this product and DEPENDING on what the issue is with the mini-split your recourse would be through one or combination of Amazon, Ingram’s, or Mr. Cool themselves…

  60. Can the DIY unit’s line set be bent 90 degrees in order to stay within a 2×4 wall? Ours is new construction so the studs are still open. If yes, from the back of the inside unit, can the line set run up into attic, make a coil of extra line set up there, then travel down between studs and exit with a 90 bend to the connect to the condenser? My goal would be to avoid having a coil of line outside.

    If all this is practical, can the drain line be easily separated from the line set so that it can run directly downward for its pathway outside?


    1. Yes, you can do that, but you can’t do a ‘hard’ 90 degree turn. It will need to be more of a swooping bend. Be careful not to kink or crimp the line while bending it. Otherwise, everything else in your plan is good to go.

    2. Condensate drain can exit right or left on the air handler and can be completely separate from the line set.

      The first couple of feet on the lineset is very rigid and either exits straight out the back on the left size, or it fits in behind the air handler and exits on the right side. Since this part of it is so rigid, surely bending it 90* into a 2×4 stud wall would kink it. You would want to remove the insulation and use a tube bender, or at least ensure that it does not kink.
      Personally I would not hide the lines – if you ever want to remove the DIY unit it comes off WITH the line set. JMHO.

      I don’t see a problem running up then down, but perhaps an installation pro can chime in on that. Many have been installed with excess lineset coiled behind the compressor or otherwise vertical coils, however the majority of installers frown on this and even MrCool advised me that the lineset should be arranged in a horizonatal sloping fashion so that compressor oil cannot collect in the line loops.

  61. Thank you both for the comments. It sounds like its questionable to make the 90 degree swooping bend at behind the air handler and also again down near the outdoor unit, [which would keep the line set inside the wall for a neater look].

    The comment about the line set being part of one (?) of the units and hinting that future changeouts could be a problem, makes me wonder if I shouldn’t purchase the ‘non-DIY” system for my situation [ whereas I don’t want to see the lineset in any manner running down the outside wall]?

    Best Regards

    1. That’s one option. I would discuss it with a professional installer – one that can do the work and one that will guarantee it to work successfully.
      The only difference between the DIY and the non-DIY is the connector for the lineset – everything else is the same. So you can do it with your DIY unit, just know that if you will like never be able to remove said lineset. Otherwise it should no pose a problem should the air handler need replacing, you can disconnect it there. Also know that you would then need a conventional vac/test/charge and turn up like a non DIY unit.

      In my case, if either component fails, we simply shut the valves off and disconnect the lineset and power, and replace either component, hook back up and go. And I’m not hiring a $150/hour HVAC guy to try to get it to work. And when it doesn’t he’ll tell you it’s not his fault. 🙂

      1. The DIY lineset can be safely disconnected without specialized tools should you ever wish to move the DIY unit to a different location.

        1. Hmmm…I thought that’s what I said. Perhaps it wasn’t clear.
          The lineset connectors have a shraeder type valve that isolates and caps them off.

      2. even a non DIY unit should have the line set accessible for 2 reasons, the first is to keep things like pictures being hung on the interior walls from puncturing the lines (much more expensive to repair). the second one even with the best brand the unit will need to be replaced possibly 2 times in your lifetime. placing them on the outside with a cover may not look as nice but think when its time to repair replace the inside walls having to be removed to do the repair vs just pulling the plug in a 3-1/2″ hole I have recommend this to my clients and yes I have had nails, drill bits and screws driven into the line sets over the years.

  62. Ah, re-read what I originally posted – about disconnecting from the air handler – so that has the same shraeder valves on that end as at the compressor end? Can be disconnected from either unit then?
    If that is the case I was not aware of that.
    And if so then what is the design purpose of the straight section of rigid pipe at the air handler end? It makes installing it much more difficult than at the compressor end.

    1. The first generation DIY units did have valves at the air handler that could be disconnected. The second generation is connected directly to the air handler. They could not be disconnected from the air handler without specialized tools and equipment.

      1. So I was right in the first place. Thank you. LOL
        Why is the lineset rigid for the first couple of feet where it is connected to the airhandler?

        The rest of the lineset is super easy to deal with, very flexible and easy to run. Getting the last feet of it and the handler fed through a wall port and the unit hung is much more difficult, especially with a 2 or 3 ton unit up a 10′ ladder.

  63. When will 3rd Gen DIY become available? My install requires a run over 25 feet and I heard the 3rd Gen DIY may have an option for different length pre-charged lines.

        1. We are interested in offering pre-charged lines in different lengths, but we cannot commit to a release date for those products at this time.

  64. I am weighing the idea of buying one of your DIY units but I have a couple questions.

    I have a 500 sq ft shop with no insulation in the walls and a large garage door on the sunny side. In addition we see temperatures of 130* in the summer. What size do I need to support this, I want to be able to crank it down and cool it off and hold temp quickly during the summer.

    Am I able to run the excess line back and forth down my wall as opposed to coiling it up behind the unit?

    If I install this myself is the warranty valid?

    1. If you wanted to oversize, you could install the DIY 18k (750 sq ft coverage).

      You can run the excess back and forth as opposed to coiling it.

      Yes, the warranty is valid if you install the DIY yourself.

        1. The MRCOOL DIY units use a DC inverter, and that reduces the negative impact of oversizing. However, it does not entirely eliminate it. A 24k is designed to provide coverage for 1000 sq ft. Given that you have a space that is 500 sq ft, the 18k should be more than sufficient.

  65. The wall that I’m mounting the unit to currently does not have drywall because I’m redoing the garage. would it be alright to zig-zag the line set back and forth between the wall studs to use up the extra length? The outdoor unit will only be about 3 feet from where the line exits and I’d rather not have the line set coiled outside.

  66. I will be getting 2 of these DIY units and would like your opinion. The house is in NY and was built in 1930. The first room is 540 square feet and has is okay insulated but not great. It has a couple of leaky windows that will be replaced this summer hopefully. The kitchen is in this area. I read the 12K might be okay for cooling but not too good for heating and am woried that the 18K might hit cooling temp fast and won’t dehumidify.
    The second room is 400 sq. feet. It is not insulated well at all. Has much better windows. Also would need to heat this room too.
    I was thinking the 18K for the first room and 12K for the second. What is you opinion? Thanks.

    1. The 18k should dehumidify effectively. If there is excess humidity during cooling season, you can always run the unit in Dry Mode to reduce humidity to your preference level.

      It seems like you need substantial heating. A Hyper Heat unit might be a better option in that case. However, those are not DIY.

      1. I do have pellet stoves in both sides as well as oil heat. I just wanted to get as much out of these as I can. I want to go with the DIY units so I don’t need to hire anyone. The prices I got for estimates were crazy so just for principal I want to do it myself. Do you think the 12K unit would be okay for the 400 square foot room? Thanks for the quick response.

        1. Yes, the DIY 12k should be fine for the 400 sq ft room. Though you should definitely try to improve the insulation as that will help a lot with efficiency.

  67. Will Mr Cool offer different physical size ceiling cassettes any time soon? I would like one that fits in between ceiling joists without modifying the ceiling joists. Most ceiling joists are 16″ on center. I know of one other brand that offers a ceiling cassette that will fit between joists. It seems like this would be a very popular option and I am surprised it’s not available.
    Also, I assume since longer line sets aren’t available then shorter line sets probably aren’t either? Can a custom length line set be ordered from Mr Cool?

    1. The only product with a set length is the MRCOOL DIY. All our other products can be installed with line sets of varying lengths, usually between 15′ and 50′.

      We do not have plans to offer a different ceiling cassette at this time.

  68. Does the MRCOOL Oasis Hyper Heat 9000 btu have time settings to turn the unit on and off on certain days/times?

  69. Planning on 18K DIY or Advantage unit for garage. Really only need 12-15′ line set. If I have my HVAC tech empty 25′ precharged set, reduce length to desired, install and recharge does that void warranty. Coiling excess refrigerant lines into 1-2 loops seems like the low spot would create problems.
    Will the 15′ lineset I can get for the Advantage series fit on DIY without or with minor modifications?

    Or am I better just getting the Advantage series even though warranty much shorter?

    1. So long as a licensed professional modified the lines on the DIY, it would not void the warranty.

      Theoretically, the Advantage line set could work on a DIY, but it would require so much field modification that it probably would not be worth it.

      Getting the Advantage would certainly be more cost effective up front. If you want a conventional unit with more warranty, you could also look at the Oasis ES or Oasis Hyper Heat.

  70. How many times can the DIY indoor and outdoor unit be connected and disconnected before the coupling tapping ring wont longer hold the pressure in the refridgerant lines? In the installation manual it says if disconneting the lines once it will void the warranty.

    On my house i have a hot side 34 degrees celcius with little wind and a cool side 30 degrees celcius with some wind in the same direction as the wall (if mounting to this wall the wind will hit the compressor from the side). Where is it best to install the compressor?

    1. I’m not sure how many times they can be connected and disconnected before it becomes an issue. We certainly recommend you disconnect them as few times as possible.

      As regards the installation, the temperature difference should not be a major factor and neither should moderate wind. So install the condenser in the location that best serves your needs.

  71. Any problem using teflon tape on the fitting threads if precharged line connections begin losing pressure?

    1. The tape should not cause a problem. Properly tightened though, the precharged lines should not lose pressure in ordinary circumstances.

  72. I am picking up my 18K btu unit on Sunday and have a question. I read some of the installation instructions online until I get the complete instructions with the unit. I see it says allow 12″ of space between the outdoor unit and the wall. But they also say I can wall mount it, which would be less then 12″ I would think. Do you think I am better off with a ground or wall installation? Thanks.

    1. You can use either a pad on the ground or a wall mount to install the condenser. We recommend a foot of clearance to allow for proper air flow around the condenser. Strictly speaking, the condenser will work effectively closer to a wall, such as when you’re using a wall mount, but we always err on the side of an overabundance of caution.

      1. Thanks for the response. So I just picked up the unit from Lowe’s. When they rolled it out they had the condenser on a pallet on it’s right side sticking up lengthwise. I see it says all over the box that “this side must face up”. Before I open it, is this going to cause a problem?

        1. As long as the unit is not otherwise damaged, it should be fine. I would suggest letting the unit sit in proper position for at least 12 hours before start up.

  73. My two story house is 1800 square feet. 1st & 2nd floor are both 900 square feet. The 2nd floor has 3 bedrooms. Is there any way I could install a DIY system(s) that would adequately cool my entire house?

    1. A single system would be unlikely to effectively distribute air both upstairs and downstairs. Depending on how air flows between the rooms upstairs and downstairs, one DIY 24k on each floor could be sufficient. However, you would likely be better served by multi-zone Olympus with 2-3 interior heads per floor.

  74. The first floor of my home is 55′ deep by 16′ wide, 850 sq ft. There are no walls between the rooms, but it’s long and narrow. Would the 24k BTU DIY unit cool the entire first floor if I installed the single head unit in the center of the house?

  75. Hi Mr. Cool,
    I am in Southern California 60 miles from the coast which is much warmer than the coastal communities. The room is 15 feet wide, 35 long with a 9-foot ceiling. The only mounting option is 6 feet in on an interior wall facing sliding glass doors and windows. The lines will go through a room that is not occupied and out side from there. The end at the 35 feet is open to the kitchen, which I am not trying to heat or cool. Noise is important because the mount will be above the couch where people are always sitting. What size do you recommend? I would like to order today!!! Thank you for your time, Micheal

    1. Michael, for that installation we would recommend either a 12k Advantage or Olympus unit. The DIY would not be a good fit for this particular job, since you need the line set to extend 35 feet. The DIY line set can only extend 25 feet.

      1. Hi again Mr. Cool,
        I think it was hard to follow my layout description, I said, “The only mounting option is 6 feet in on an interior wall”
        The left side of the indoor unit will be approximately 6 feet from and exterior wall at the bottom end of the 35 foot room. I am going into another room for the exit in order to hide the lines.
        The west side of the room is glass with curtains, the unit will be on the east side of the room 6 feet from the north exterior wall and the kitchen is south 29 feet.
        I am ok with the DIY. I would like your recommendation on the size to order.
        Thank you for your time and patience, Mike

  76. What is the actual usable length of the DIY line set?
    Does the 25′ include the two feet going across the inside of the air handler unit leaving 23′ where it exits the air handler on a right side exit installation. I will need a right side line set exit. This is critical to my buying the unit.

    Thanks in advance!

  77. Hi Mr. Cool,
    Just purchased a 24K DIY unit. While I believe my question’s been answered above, I’ve read conflicting info on this…
    Above you state a 24K unit is good to go on 12 gauge wire with a 25 amp breaker. Would you please confirm this one more time?
    I have no desire to run a 10 gauge circuit, but will if necessary.
    Thank you!

  78. I have a 24×32 garage space I would like to heat and cool. What would be the minimum DIY unit I can get away with? I notice mention of a 3rd get coming out this year…don’t know if it would make sense to hold off for that.

    1. We have not set a release date for the 3rd Generation MRCOOL DIY. For a 24×32 space, an 18k unit would be the minimum.

  79. I’m thinking about purchasing a Mr. Cool 3 ton split unit.
    Looking through your blog with dates that I’ve noticed from 2017-2019 there has been no movement regarding varying size line sets. My situation is different from other senarios I’ve read. I need either 15 ft to mount the condenser/compressor unit on the ground or just enough maybe 5 ft to mount the unit on the exterior wall of the house. Come on guys it’s like 4 years with this line set question.
    I’m sorry a good and proper installation doesn’t have over in my case 15 ft of line curled up like a outside water hose on a reel. Looks like I’m going to have to buy a vacuum pump, some nitrogen a good flaring tool and use a different brand.

    1. The issue isn’t a technical one. The problem we keep running into is finding the right lengths to fit the most people most of the time. Which requires research and data. If it were simple we already would have done it.

      However, if you are going to buy a vacuum pump and pursue a conventional installation, we do sell conventional ductless products as well.

      1. I wish I had the problem of too much line…. But anytime you have a set line amount you are going to run into issues like this

        For me I need about 55′ . Ideally if you sold 15′ extensions which could be added the the existing 25′ line set , people could just order the existing extensions with their base unit . Then you need to deal with the issues which come with the splicing of wires and possibly discharging the system because of an extension.

  80. Hello, I purchased a 24k DIY unit and have several questions:

    1. My 17ft x40ft 680 square feet open area consists of the family room, dining room and kitchen. The ceiling height steps from 9ft to 12ft. Due to the 25 ft line set length constraint, I can only put the inside unit on the corner of the 17ft exterior wall. One 40ft west facing wall is full of windows and doors. The other 40ft section has no exterior wall. Is this going to be a problem cooling and heating this area? I understand ideally, the inside unit should be centrally located but in my case, there is no wall space to mount it on. Any suggestion would be appreciated.

    2. I like to run the lines down the inside the wall. What are the diameters (large and small) of the two refrigerant lines, including insulation? Can they be routed inside PVC pipes? The control wires and drainage lines will be routed separately.

    Thank you.

    1. 1. If that’s the best place to put it, then that’s where it has to go. It should work fine. One thing you may want to consider is to get a ceiling fan for winter to push the heat back down.

      2. The liquid line is 3/8 inch and the suction line is 5/8. They can be routed inside pipes. However, you could also use our LineGuard product as well.

  81. Need to move the 24k DIY to pour concrete slab. My question is it the reverse as set up, shut breaker down, disconnect wiring, close refrigerant valves, and then disconnect lines? Anything I have forgotten? Thanks

    1. That’s basically it. Just run the installation backwards (while referring to the manual). And make sure you have the valves 100% closed before you disconnect the lines.

  82. Currently remodeling. We have the walls open to the studs. When we run the lines from the indoor unit to the outdoor unit can the extra line be kept behind a finished wall instead of having a coil outside?

    1. The unit would operate fine this way. You should check local codes to make sure they don’t have a problem with you running the electrical line inside the wall.

  83. In southern Arizona (Tucson area), I have a 461 sq ft insulated garage with an east facing insulated garage door. The garage has a 9 ft ceiling. What size DIY HP unit would I need to cool this area. I’ve seen websites that recommend increasing the size of the unit 20% if the ceilings are over 8 ft and to increase the size 30% if temperatures often exceed 90 degrees. What would be the base BTU requirement and how much should it be increased for environmental factors?
    What improvements can we expect with Generation 3?
    Thanks and Best Regards!

    1. Those are decent rules of thumb. The only way to be precisely sure in terms of heat load calculation is with a Manual J. However, ductless units like the MRCOOL DIY use an inverter compressor, so over-sizing is not as major a problem as with a conventional HVAC system. In your case, the DIY 24k would probably be a solid option.

  84. Instructions/specs for the DIY units indicate 12 inch minimum clearance behind the outside unit. I’d like to mount the unit on the ground, but cannot achieve this minimum. I assume this can be reduced and the unit still operate effectively. What is the actual minimum that can be used while not voiding the warranty?

  85. Hi, I am interested into your DIY solution but the 25′ refrigerant line limit is a problem, i need longer lines (approx 35-40 ft). You mentioned earlier in this post that the 3rd generation of DIY unit might become available in 2019. Any update on this? Thank you so much.

  86. Hi. I have 2 of the DIY units. The 18K and the 12K. I would like to use some of those A/C drain pan and tube tablets to prevent buildup and future odors but don’t see how to get to the drain pan. Am I able to get to it somehow and if so how? Thank you.

  87. I have a the 18k DIY unit. If I leave unlimited space behind and on top of the outside unit, is it OK if the sides of the unit have only 2″ of distance from the walls? Even if it’s not ideal I’d like to know if it’s acceptable.

    1. It’s definitely not ideal. Maximum clearance around the condenser is very important. The unit would continue to operate in a confined area, but operating performance could be impacted over the operational life of the unit.

      1. OK I have a different possible location that would leave all clearance distances as per the manual, except for the smaller part in the front of the unit where there is no fan. So the fan would have empty space in front, but the front part of the unit without a fan would be in front of a wall. All other surfaces would have the required clearances. Is that OK, or at least better?

          1. by the way, what’s the main purpose of the clearance specification on the lateral side with the lineset, since there are no cooling pipes there?

          2. Ideally, you want unobstructed air flow on all sides of the unit. A condenser can pull in a large volume of air during operation.

  88. My shed is only 12′ by 12′, while the line is 25′. I would rather not coil the excess line behind the outside condenser unit. Can I run the line outside and vertically down the back wall of my shed, then across the bottom length horizontally, and once more around the corner to the condenser unit within the accessory line covers. In other words, can the lines be safely run around corners within the accessory line covers without damaging the lines?

  89. I just purchased and installed a 36000 DIY mrcool, LOVE IT. I might add that I would like to know if I buy another, might it be an option on the air handler to make the connection lines to be able to be swivel connection. as I had to turn my connectors 90degrees to go through the wall as the hole I put through to the out side wall where needed and was really worried that they might crimp or break bending them..luckily They didn’t thank God. that would have cost me alot of money to fix.

    1. That’s an interesting idea. It’s not something we offer right now. However, the potential to crimp or break the lines during installation is always something we’re looking to reduce.

  90. On the DIY Units is the indoor unit powered by the outdoor unit or is it powered by another breaker ?

    I’m also waiting for the 3rd gen units since my run is going to be at least 50′

      1. Thank you

        I know you have mentioned that the 3rd gen diy has not been announced yet but do you know if it will actually offer a longer lineset or the ability to extend the lineset when it is released ? If it will I’ll gladly wait for its release but if it will not then I’ll consider some other options .


        1. As always, the ability to offer variable length DIY lines is something we would love to be able to provide some day, but it may be some time before we can do so. I could not in good conscience advise you to hold off on an air comfort solution on the chance that the 3rd generation might offer such capability.

  91. I am replacing just the inside half of the unit with a new one from MR Cool. Is all the coolant in this half of the unit? Do I just disconnect the old copper lines and connect the new ones? Or, is there coolant in the outdoor unit that will be lost? Will I need a professional to do this? I had no problem installing it myself the first time.

    1. Coiling the excess line and storing it behind the condenser is fine. Just be sure not to coil it too tightly.

  92. I have a shelf below my mini split. Is it ok to have a tv on the shelf below the mini split? The shelf is 4 feet below my mr cool mini split.

    1. You should keep the mini-split away from electronic devices as much as possible to avoid operating interference.

  93. Hi guys,
    Putting in my MR Cool this weekend DIY 18K BTU unit. I noticed you mentioned 3rd generation of the DIY units were coming out in 2019. What are the differences going to be? Not concerned with the length of the line as 25 feet is fine for me…just curious? I noticed you have the 3rd generation of your other units but unable to discern what was added from the 2nd generation.

    1. The plan is for the 3rd generation DIY to be Energy Star rated just like the 3rd generation Advantage.

  94. I bought a Mr Cool 24K DIY unit February this year, installed it in March and started using it regularly in April/May. I installed the air handler in my 3 car garage; living in Florida my primary goal for the mini-split is to remove humidity from the garage interior. Cooling is secondary; to wit the t-stat is usually set at 82 degrees. I am very happy with the unit thus far and have no issues or concerns however I do have questions about the differences between Cool Mode and Dry Mode. As I said I live in FL, Tampa so I would assume Dry mode is best for me in my case but maybe not? What are the pros and cons of each mode? Can you please explain how or why Dry mode and Cool mode perform differently? What are the differences at the air handler vs the compressor outside; what’s going on under the skin? Does the compressor not run as often in Dry vs Cool mode? Is one Mode more efficient than the other? Is one Mode more expensive to run than the other? Thanks in advance for prompt reply; best regards, Bob

    1. Dry mode’s main utility is in dehumidifying. Basically, the compressor runs at a lower rate for a longer period of time to remove more humidity than it might during regular operation. If you don’t have a problem with high humidity in your home, your best option is to use Cool mode.

  95. I just purchased a 24K DIY unit, waiting for it to arrive. Location of the unit will use up nearly all the 25 ft line; about 20 ft will be attached to the wall. The problem now is finding an appropriate line set cover for that length, but every on-line vendor I have checked (Home Depot, Amazon, Ebay, etc) all say the Mr Cool brand is out of stock or unavailable, and the only ones in other brands are something like 7.5 ft long, and come only in a kit. None sell individual pieces separately, so I would have to order 2 or 3 kits, which would be expensive and leave me with a lot of unneeded extra pieces. Secondly, the line will cross over a drip moulding on the wall and I need some way to bridge that, maybe a flexible piece but can find nothing of the sort. I prefer not to have to jury rig something, for example using downspout. Please advise.

    1. Yes, LineGuard kits are currently out of stock. For technical support regarding installation, please call us at 270-366-0457.

  96. How many units can be connected to the same breaker box ? Can I connect 3 or 4 15 amp units to the same breaker box?

  97. I have read many of the blogs where customers have installed more than one DIY unit. How is this possible when there are power restrictions? None of the information I have read states that it is okay to install more than one 15 amp unit to the breaker box. So how are multiple DIY units installed?

    1. We agree with you. If people are installing multiple DIY condensers on the same breaker, that would not be recommended. It would void the warranty. The only way to install multiple DIY units on the same building would be to use a separate disconnect box for each unit.

  98. I just installed a DIY 18K-230 unit. It works well in cool and heat, awesome power really. BUT the inside unit drips major quantities of water on the floor. This is with the baffle horizontal. Also I don’t see a condensate drainage line at the condenser end. There’s the two refrigerant pipes and the electrical cable but nothing else inside the plastic lineset sleeve.
    The amount of water leaking on the inside is major. It means we can’t use the unit for cooling. If this isn’t fixed pronto we have to return the unit. Major headache.

    1. All DIY units come with a clear, flexible plastic hose should be connected to the air handler to drain the condensate outside of the house. This is detailed in the installation manual. Locate the drain hose and connect it to the air handler. This will solve the water problem.

  99. So I just ordered a 24 K DIY and am super excited.
    My question is this: The 25′ lineset will be too long. Is it ok just to leave the excess coiled up near the outside unit?

  100. Does the inside unit run on low voltage or just the compressor-just wondering what the high voltage is converted to

    1. The interior air handler connects to the outside compressor. The compressor must be wired to a disconnect box.

  101. HI I recently bought a DIY 12k for my living room, but I think I can use an 18k in this room now. I would like to move my 12K to the back of the house in a different room and buy an 18K for front room. Before I do anything I wanted to know if I can do this? From my understanding I can shut the one valve off run the unit for ten minutes until it is blowing out warm air. Then close second valve. This will put the 410A back into the Unit. Can I do this then disconnect the unit and move it? Then re hook it up in back room without vacuuming it since this is a pre charged line set or you prefer a differnt way thanks. This unit works great, but i realized i need a bigger size for this room now.

    1. It is possible to disconnect a MRCOOL DIY and move it. Though we would recommend you contact our tech support at 270-366-0457 to have them walk you through the process.

  102. So I’ve set the outside compressor on the pad in preparation for mounting it with screws and I notice 2 things:

    1. Each of the back two feet have a pair of pre-drilled screw holes that correspond to the holes in the rubber pads they will sit on, but the front two feet have just the large center hole and no pair of pre-drilled screw holes that correspond to the screw holes in the rubber feet for them. Is this normal? I’d assume all four “feet” would be the same for mounting purposes.

    2. When I insert the rubber seal onto the drain joint and install it under the unit in the base pan hole as directed, it protrudes so far down towards the pad that the unit cannot rest evenly on it’s four feet. Even if I remove the rubber seal and simply hold the drain joint in the base pan hole, it still prevents the unit from sitting on all four feet, rubber pads or not. Please advise.

    1. We are aware of the problem and are trying to get the factory to correct the clearance issue for the bottom drain fitting. In local installations we normally use any available material under the rubber to provide the additional clearance. Depending on your geographic location you may not need to use the fitting at all since it’s purpose is drainage for defrost operation in heating mode, and that may not be a major concern in your area. With regard to the rubber pads, as long as they fit under the foot they are OK- in many instances the rubber pads are not used at all.

  103. It sounds like efficiency is relative to outdoor temperature and the higher the outdoor temp the higher the efficiency. The 12k DIY has an 8.8 HSPF rating. At what outdoor temperature is it working at 8.8 HSPF? At what temperature does the efficiency start to go above 10 HSPF?

    1. HSPF is the efficiency performance while heating. Heating efficiency starts to drop as the outside temperature decreases.

  104. Looking to use one of the DIY kits in our detached accessory dwelling unit. Details: new construction, walls R21+5, below grade basement walls R-15, SIP roof R-40 with light colored roofing, minimal solar gain in summer due to overhangs and trees, and 9′ ceilings. Looking to install head on main floor (280SF) which is open floor plan to heat and cool main floor. Lower level (270sf) will have cadet heater for supplemental heat in bedroom and heated floor floor bathroom. So the DIY wall unit really only needs to heat the upstairs 280SF (can’t make heat sink, hence the cadet downstairs) But we figure the DIY wall unit will provide cooling for main level and lower level since cool air will flow down the stairwell. The cooling load for downstairs shall be minimal since it is half underground. Was going to go with 12k system, but wonder if 18k would be better, or overkill?

    1. With new variable-speed technology, oversizing an AC system is not the problem it used to be. The 18k system would not be a bad choice.

  105. I had an issue with indoor 36k handler and was replaced under warranty. Out door unit and lines were drained. When hooking up new lines is there enough fluid to charge entire system or will outdoor unit need charged

  106. The outdoor unit has two knockouts for electrical connections – one for the main 220V power, the other for the electrical connection to the indoor unit via the line set. I connected the 220V power no problem with conduit and liquid-tight connector. The problem I have is with the connection to the line set power – the other knockout. Since there is a clip connector on the end of that, I cannot run it through any kind of conduit or liquid-tight connector. Too big. So what I have now is simply a cord (line set power) fed through a bigger hole (knockout). Definitely not best practice. Since the outdoor unit and the line set are all supplied by MR Cool I would think that a proper solution would have been supplied with the product. Was there and I just missed it? If not, is there a recommendation to do this the right way?

  107. I just purchased the 12K unit and plan to install it after we complete our detached garage with apartment. I would like to install the line set on the interior of the upstairs wall and bring it down into the garage and then go out but in the instructions it says do not plaster over the line set. is it possible that I run the condensing lines inside the wall and not punch out to the exterior from directly behind the inside unit? Currently, the interior of the habitable space is framed I can either install a large conduit to run the line set down the wall if necessary but want to make sure that there’s not going to be a problem with condensation.

    1. Our recommendation would be to run the line on the exterior of the building down to the condenser. This would not cause a problem with condensation.

  108. Is it possible to hook up a multizone with the pre-charged lines? We are buying a 2 story and want 1 unit up and 2 down.

    1. We are working on a multi-zone DIY that would use pre-charged lines. It may be available later this summer.

    1. It is used to seal the wall sleeve. Also, you can always call tech support at 270-366-0457 should you have questions during installation.

  109. Hello,
    Your multi-zone diy brochure says that you can add several pre-charged lines to reach longer distances.
    Can I do that for a one zone DIY 36000 btu unit ?
    What is the max distance / number of couplers allowed ?
    Where can I buy pre-charged line extension and coupler please ?

    Thanks for your help !

    1. You could use a coupler for a DIY single-zone product. The max distance would depend on the particular model. They are not out yet, but we do anticipate making them available this summer.


  111. I’m looking on-line at install manual (V04.21.2020) for the DIY® E Star™ Series (DIY-12-HP-115B) and find the directions for the line set connections to be a bit confusing.
    Page 20 says to first connect the lines to the indoor unit. Page 22 says to wrap the lines, wire and drain together and then pass the length of the lines through the wall hole and mount the inside unit. however the picture on page 20 shows the connections as actually on the outside of the wall, unwrapped.
    Page 27 has instructions for connecting the pipes to the outdoor unit, and shows that they are not yet connected to the indoor unit. This is the opposite of the above.
    1. What is the proper order for connecting the lines?
    2. Assuming they are long enough, can you pass the lines, wire and drain that come attached to the indoor unit first, and then connect to the line-set on the outside? Seems like that would be simpler.

    1. You should connect the lines to the indoor unit first, wrap them, pass them outside, then connect to the condenser. Should you have other questions during installation, you can always call our tech team at 270-366-0457.

    1. We hope to have DIY Multi-Zone inventory available in the last week of May or the first week of June.

  112. Dear Support,
    I have pre-existing electrical, drainage, and refrigeration lines installed as potential in my new house. Can I install a Mr. Cool system onto pre-existing refrigeration lines and still do this installation diy?
    Please advise.

    1. Provided that the electrical, drainage, and refrigeration lines are the same size as required by the unit that you plan to install, it could theoretically work. However, you could not use a MRCOOL DIY system with those pre-existing lines, since our DIY requires special linesets.

  113. I need to move the inside unit to another relocation. Can I remove the precharged lines and re-attach it again without having to recharge the refrigerant?

    1. Provided you carefully close all the valves (essentially running installation backward), it is possible to detach the lines and move the unit.

    1. Yes, the coupler kit will allow you to couple two DIY lines together. Most dealers should be making that available this week.

      1. Hello,

        Expanding on Gordon’s question somewhat.

        I have measured the distance from indoor unit to outdoor unit and it is roughly 55′ apart. If I use the kit’s included 25′ line set line and purchase a 25′ pre-charged line set extension it would be slightly short (25’+25′ = 50′). Would it be possible to use the kit’s 25′ line set and combine two 16′ pre-charged line set extensions (25’+16’+16′ = 57′)? Is there a maximum on the number of line sets which can be connected together?

        Thank you,

      2. With the coupler kit, how do I connect the control wires together where the coupling goes for the coolant lines.

        Where can I buy the coupling kit
        And order the two line sets to connect together

        1. The coupler kit should be available through most dealers soon. Line sets are available through most dealers.

  114. where I can I purchase your 16′ refrigerant lines with the special valves so I don’t need a pump?

  115. I want to buy a MrCool 24k mini split from costco but was wondering how long the pre charged refrigerant copper lines are that come with it?! I need 10-12 ft max. If they are 20-25 feet long what do I do with the extra length?! Exchange? (I cant cut assume) I hear coiling isnt good …

    1. The current generation DIY units come with a 25′ line. You should not cut it. Coiling and storing nearby is the preferred method.

  116. I recently purchased the Advantage 3rd Gen instead of the DIY on accident. Is the Advantage precharged with refrigerant? I’m not an HVAC professional but I’ve already connected the coiled 16 ft line to the inside unit and the signal cord. One, I’m trying to see if I need an HVAC professional come and finish the install and two, The directions were not too clear on connecting the signal cables and I was wondering which color line goes to what number connections inside the unit and in the fan. Thanks!

    1. Hi, Daniel. We do recommend that you have a professional complete the installation for the Advantage. The condenser is pre-charged, as is typical.

  117. I would like to purchase either a 12000 or 18000 btu DIY MrCool. I need 32 feet of line set. Can I extend the precharged 25 foot line set the additional 7 feet I need?

    1. You can extend line set length with one of our coupler kits. It allows you to connect two lines together.

  118. I just purchased and installed the 24,000 diy 230v mini it..super simple works great for cooling my house in Florida..
    I have an RV I just built and want a diy for it..but I need a 110v 9000 BTU.. do you make one?

  119. I was planning to order a 12K DIY kit from Costco, and they were no longer on their website. Is Costco going to be selling these again?

  120. I just got the diy unit but mine didn’t come with a pre charged line set. I saw on an HVAC website that I can’t get one shorter than 25 ft. Is that correct? I saw one for Me. cool at Lowe’s and it was 16 feet. Is that acceptable?

    If I need one that is 25 feet can you recommend a seller?

  121. I need to run 60 feet of pre charged line for a 2.5or 3 ton unit for my garage. Is it possible? Which unit would you recommend. Thanks .

  122. Good morning I have Mr 36K It will not get cold Have P-6 code comes up can you let me know what I can Do

    1. This could be an error with the discharge temperature sensor. Please give us a call at 270-366-0457 so we can help rectify the issue.

  123. I recently installed a 24000 btu Mr cool diy with a 25ft pre charged refrigant line. Everything went well accept for the connection of the way I bent the refrigant lines to line up with the condenser. I think I should have routed the line from the top down making a less of a bend. I would like to correct by removing the lines and re position the lines. My question is, can I disconnect and reconnect the diy precharged lines without losing refrigant?

  124. It’s a cool morning today so I decided to test the heat function of my recently installed 24k diy minisplit. It is 71 degrees outside, and set the remote to heat mode 86 degrees, but not getting any heat just cool air. It’s running on heat mode for 20 mintues. Is there a problem?

  125. I want to purchase either a 18000 or 24000 BTU DIY MrCool. But only need a 16′ hose, (10′ is actual length needed) . What dealer in the Los Angeles area would have a 16′ hose as part of the package. Ones I talked to only have it in 25′ length and want me to get a technician if I want it shortened. Or pay extra for the additional 16′ hose.

  126. I read that you can connect two 25ft line sets together to get 50ft of length. Is it possible to connect an additional short set as I project needing approx 60ft of line, from the indoor unit to the outdoor unit.

  127. Can the precharged lines be used with a Signature Gas upflow. 4 ton splits system?

  128. I purchased a 12K BTU Mcool mini for my garage. I do not have a in wall in which to put the cooling line directly behind the condenser as indicated on the template. Can i rum the gas line/drain and power line out the side of the condenser, down the interior wall, then drill the side wall towards the compressor unit? Is there an email that I can send a drawing of what I want to do?

  129. To connect 2 25ft lines together would there be a specific coupler? could you provide a part number for a 24k DIY Mni split system 3rd gen?

  130. Hi
    I purchased a 24k DIY unit from Home depot with 25 ft lines. I need a little more length and see that 35 ft lines are available. Can I return my new (still in the box ) 25 ft lines and pay the differences for the 35’s?

    1. We only offer our DIY mini split line sets in increments of 16′ and 25′. You may have been looking at the line set for the Universal, which is a whole-home heat pump split system. The DIY mini split line sets and the Universal line sets are configured for different products and should not be used interchangeably. We do offer couplers for the DIY, which allow you to combine two line sets to better fit the length you need. You could purchase a 16′ DIY line set as well as our couplers and loosely coil the excess near the condenser.

  131. I recently got the mrcool 36k btu olympus mutli zone mini split with 3 wall units. There is a section in the manual about evacuating the lines, and then this site here. Do I need to evacuate my lines or are they the precharged? Also, I haven’t been able to figure out if I need to have the main unit charged with refrigerant?

  132. I recently purchased the DIY 12k unit with the 25’ line. I already installed and have tested it. It works great but I’m not a fan of the extra long coiled left over. Can I replace it with a 16 foot line even though I have already installed and started the system?

  133. I am ready to purchase a Mr Cool, 18k, 3rd gen, DIY, 25′ lineset unit. I ‘cannot’ exit the indoor unit to the right or rear. I must exit left first, then down. Please send me the protocol to do this, so I can plan for it and place the order right away.

  134. Can I use a, correctly sized (btu), 16ft precharged line set on a Perfect Aire diy unit?
    Both seem to share the same fittings and both have precharged lines.


      1. Thank you for your reply.

        I have another question. I recently bought a 12k diy kit with the 25ft line set and want to know if I can use the mr cool 16ft lineset with it.
        Would I have to make any changes to the units? Or is it ready to use with the 16ft?


  135. Hi there. I’m trying to find a spot to mount my 18K DIY condenser on the exterior wall. I read that the clearance in front of the unit should be 80″. I think the location I was thinking of mounting has closer to 70″ clearance in front of the unit. Sides and above have ample space.

    Would my Mr. Cool DIY system still run well, even though the clearance in front of the unit would be approximately 10″ less than recommended?

    1. The clearances in the manual are based on a ground mount. If you’re using a wall mount there will be more air space around the unit overall, so there should not be a major issue with such a minor reduction.

  136. I like the universal series heat pump with pre-charged lines. I want to replace my hvac next year . I have an opening already second straight to crawlspace. Does the flexi-insulation have to stay on both lines? or just the suction refrigerant line?

    1. We always recommend insulating both lines, but, strictly speaking, you would not have to keep the insulation on there if you don’t want it.

  137. I recently purchased an 18K Mr. Cool Mini split unit. It came with 16′ refrigerant and drain lines. I need the 25′ lines. Can I return the shorter lines and purchase the 25′ line?

  138. I purchased a 27k BTU 22 SEER Multi-Zone MrCool DIY 2 Zone that came with a 3 zone condenser. Is it possible to add another air handler later on without losing any refrigerant.

    Laso I need to move an air handler that I have already mounted and hooked up to the line set. It is not hooked up to the condenser yet. Is it possible to disconnect the line set and move the air handler and rehook up the line set without losing any refrigerant.

    1. Yes, it is possible to add another air handler to a multi-zone unit at a later date. This can be done without refrigerant loss. It is also possible to dismount and move a previously installed air handler. Should you need assistance while doing either, you can call us 270-366-0457.

  139. We installed our DIY 12k system earlier this year but our room configuration has changed and we need to move the inside unit around the corner to a different wall. (Our compressor will not need to be moved.) How easy should it be do this without having to recharge the unit?

    1. Moving the DIY air handler is possible. Special care would need to be taken to ensure all the valves were properly closed before any lines were disconnected.

  140. We had a small leak and it is now fixed but outside coils are frosting over (low Freon). We need to charge the systems but I can’t find the charge pressures anywhere in the manuals.

  141. I install mini split and LADBS inspector told me that inside unit is close to gas stove. What is standard distance of any major heating source to the unit? Length and width?

    1. We do not recommend installing a mini-split near any source of heat, steam, or combustible gas. We do not have a standard distance. We recommend installation in accordance with local codes and regulations.

  142. Will I lose any refrigerant if I use the line set couplers when putting them together prior to my final hook up to both my air handlers and condenser? I’m putting extensions on three of my air handlers back to the condenser.

    thank you,

  143. I recently bought two 24k advantage series units. My question is, can you buy the pre charged lineset and use them instead of the uncharged lineset they came with?

  144. Where can I find the proper procedure to relocating the preprimed lines version of the mr cool? I’m about to install the system but plan to move it in a few months.

  145. I need to extend one air handler line set by 10-15′ and another by around 2′ I moved the compressor as close as possible, what do I need to do now, it is a diy unit with a 36.000 btu outdoor unit.

    1. We have line sets as well as Quick Connect couplers available at any of our retailers. The Quick Connect couplers allow you to link two line sets together to meet the length requirement for your installation.

    1. When you’re ready to connect the pre-charged line set, only uncoil as much as you need. Keep the remaining line set coiled horizontally (flat with the ground) near the compressor.

  146. Two questions on a basement MrCool wall unit:
    1) The wall unit is going to be lower than the condenser. Is there a problem with the refrigerant line running uphill?
    2) The wall unit will be hanging on a solid cement wall. I will need to run the lines sideways out of the wall unit. Can I punch a hole in the wall unit to allow the lines to exit to the side instead of out the back?

  147. So if I need to add more refrigerant line then the 25 ft that come does that mean I have to add more refrigerant since its longer.

    1. No, not on our DIY system. The pre-charged lines have refrigerant in them, so should you need to use a coupler kits for longer lines, there will already be additional refrigerant inside the additional lines.

  148. I recently purchased a 23000 BTU MrCool unit. It is installed and working fine. However, no where in the instructions did it tell me to lay the excess lineset horizontally. I have it in a vertical position. Comments above you say to lay it horizontally. I have approximately 4 feet coiled. Will this shorten the life on my new unit? When I received the unit the lineset was missing protective covers on 3 of the 4 lines, found them in the box. Additionally many fins on the cooling unit were bent much to my displeasure. I think you should be aware of the lack of quality control in shipment. Thanks in advance for a response.

    1. We apologize for this. If you would like, you can give us a call at 270-366-0457. We recommend laying the excess line horizontally for the best operation and efficiency, but how you have it placed shouldn’t noticeably impact the unit’s lifespan.

  149. What is the purpose of the nonstick tape wrap? Do I need this on portions of the lineset inside the house ? The lineset arrived wrapped in a very thin plastic sock. (Thickness of a grocery store plastic bag). Do I remove this prior to any wrapping.?

    1. The tape is to help keep the lines together. You can remove the plastic or leave it in place so long as the connection points are exposed for an effective installation.

  150. Do you have available and can supple longer lengths of refrigerant lines and/or (line sets)?
    The distance between the outside condenser and the inside ductless unit is approx 30 ft.
    If not, where do you recommend this additional length be purchased? Thanks – wwm

  151. The 3rd gen 3 zone system I’m looking at from Home Depot can come in 16/16/50′ line sets. Is the 50′ two 25s? If so, can I combine a 25 with the 16 to get 15/25/41?

    1. I’m not sure what specific listing you’re looking at. However, the DIY and DIY Multi-Zone have two line lengths: 16′ and 25′. You can use our coupler kit to combine these lines.

  152. Two questions:
    1) Do any of your vendors sell using a configurator? I know what total size I need, I know which of your air handlers I need, and I know which combinations of line lengths I need (Assuming I understand correctly from your answer above that DIY only has 16 and 25′ lines, with couplers available). It’s frustrating looking through all those individual package descriptions hoping to find what I want…

    2) Can the compressor be above grade for a basement air handler? (I would run the drain separately)

    1. 1) You may be able to call our retailers to set up a custom order, but as we don’t sell directly, we can’t provide comprehensive information regarding this. Take a look at for easy access to our retailers for the DIY.

      2) You can install the compressor above the air handler. It seems that you’re aware of needing to do something about the drain line so that it can properly drain, so you’re already set on the right course!

  153. Well, now that I’m here, I note that the Universal, which has a side-discharge compressor that would be much better for my installation, also has pre-charged lines. It seems to me that that would make it installable by a do-it-yourselfer. Is there some complication that makes it inappropriate for DIY installation?

    1. Technically, no, but you need to be completely sure that you are confident in your installation skills. You can also always give us a call at 270-366-0457 during normal business hours for guidance on your installation.

  154. Thanks for your responses, Mr. Cool!
    One last question before I pull the trigger: Instructions mention that the default configuration of the indoor units exits the lines on the right hand side, but that it is possible to exit them on the left side. I’ve been looking for clarity on this and am unable to find clear reference on how that would work. Is this a special order? Is it straightforward to do? I would imagine we’re talking about a 90 degree turn at the connection, and running a length of line along the bottom inside the case, but I would also imagine that the radius of that bend would be a serious challenge to the lines….

    1. It is technically possible because there are knockouts in the air handler, but it would make for a more difficult installation, because it is not a typical installation and there is no guidance in the manual for that reason. You can always give us a call during normal business hours at 270-366-0457, as our tech team can offer the best assistance and advice during your installation.

    1. We do not have 50′ pre-charged DIY lines. However, you can use a coupler kit to connect two 25′ lines.

  155. When I received one of my line sets, the plastic seals had fallen out. Does that mean it’s no longer charged?

  156. what are the exact measurements of your 25 feet line? does that include the connection areas to the head and condenser? I have an install that may come down to every inch.

    1. Exact length based on my measurements is the metric reading on the box, which is 7.5 meters. That converts roughtly to 24’7″.
      As for the 16′ DIY lineset, that’s 5 meters –> 16’5″

      Almost everything now a days is made to metric standards, but is marketed in the US with imperial labeling.

  157. I need to replace a diy lineset, I know I can close the valve on the outside unit but what about the air handler? Will I need to pull a vacuum after i replace the line?

  158. I’m installing the DIY mini split system on an interior wall. I plan on running the line set in the attic. Can the drain line also go up into the attic? Or does the drain line always need to go down?

    1. You can route the drain line separately so that it can go down, or you can invest in a condensate pump if you want to route it upwards with the line set.

  159. My two-zone system comes shipped with a 3-zone 27k condenser. Does this mean I can add another diy handler with diy lines at a future date? The shipped handlers are 12 and 18k; the future third zone would likely be a basement that’s generally cool but humid.

    1. Or, to put it another way, can you install and operate one zone at a time with a multi-zone condenser? Can I install the first zone’s indoor unit on one weekend, use it to cool the house, and then install the second zone’s indoor unit the next weekend?
      Thanks in advance for your help.

      1. You do not have to operate all possible units at the same capacity all the time. You could run them at different temperature setpoints. We recommend you install them at the same time however.

  160. I am looking to move my mr cool mini split and add more line when I unhook the lines to add will I have to recharge it

    1. If you’re using one of our conventional units, yes. If you’re using a DIY and it is properly disconnected, additional refrigerant should not be necessary.

  161. We are installing the diy18,000 btu multi-zone mini split. Can the line set be extended?

  162. Does the no vac precharged linesets work with your signature series ac condensors? And are your signature series ac condensors factory filled with refrigerant? Im looking at a 3 ton condensor with the coil and gas furnace

    1. The precharged lines are not compatible with Signature Series equipment. Signature Series condenser would be precharged.

  163. I had to replace the condenser unit on my DIY mini split. After disconnecting the lines from the old one and connecting to the new one I am probably short about 2 lb of refrigerant. Would a 28 ox recharge do the trick?

  164. I just installed a 3 zone DIY system (only two heads currently as I’m waiting for an extension for the third head), however one of the heads stopped cooling a couple of hours after installation.
    During installation I tested the lines with the soap and water test, again after 5 minutes of running, and again after 30 minutes and saw no bubbles on any of the connections.
    The other head that’s running was getting ice cold, but the lines began freezing so I have turned off the unit.

    I believe the head that stopped cooling has a leak, even though I did not see it at the joints.
    Can I close the valve at the outside unit and replace the head and line (as I’m not sure which has the leak) with my third unit that is currently not hooked up or used, or would I likely need to recharge the system if one of the lines leaked?

  165. I note that minimum clearance behind the condenser is 12″ for ground mounting, but 6″ for bracket mounting on a wall. And that wall mounting is not recommended for a framed-up wooden house wall.

    Wall mounting isn’t an option for me, but if I simulate it with a secure ground mounting structure that allows significant airflow below the unit, can I use the 6″ clearance? Or is the reduced back clearance for wall mounting due to some other factor?

    It looks like our only placement options are in front of the house, which, even though I can sorta hide it with plantings, is weird, or in the driveway, where a full 12 inches of back clearance puts the unit just a little too much in the way.


    1. That should be possible. If you would like, you can give us a call at 270-366-0457 to speak with tech support so that you can get the best information regarding your installation.

  166. Can I get precharged line sets in different lengths? Or can I hook precharged line sets together? I’m thinking about buying a two head system which comes with two 16 foot lines. One will be slightly less than the 16 feet, but the other will be longer than 25 feet. What can I do?

    1. We offer pre-charged line sets for the DIY systems in increments of 16′ and 25′. You can link two line sets together using a Quick Connect coupler kit, which you can find through our retailers. For example, you could connect two 16′ pre-charged line sets for the second line set run.

  167. I am looking at purchasing a 3 evaporator/ 1 condenser set however i will not be ready to install and connect the third evaporator right away. So my questions is can the system be hooked up like normal and just have the 2 evaporator lines connected while waiting for the third to get connected or do they all need to be connected and in use for the system to work?

    1. Provided you meet the necessary capacity for the condenser, it is possible to connect two air handlers and then connect a third at a later date.

  168. Hello,
    I purchased a 36 k DIY multi zone condenser unit with the intentions of running two 12k heads and one 9 k head. i only have one 12 k head and would like to get it up and running before i can purchase the other two heads. is this possible?

    1. We would not recommend that. You could install the multi-zone condenser and two air handlers, then wait for the third air handler. The reason is that the DIY multi-zone mini-split is not able to properly operate unless at least half of the capacity of the condenser is met by the air handler’s demand.

  169. I will be installing an 18K DIY near a glass window wall, running hoses through a small sliding window and insulating the excess open space with a portable air conditioner sliding door kit. Just a few feet of lineset will be unfurled. For improved appearance, can I place the horizontally laid lineset coil to the side and about a foot below the condenser or should excess lineset remain at least level with the condenser base? Thanks!

  170. Question about the quick connect on the condenser. I noticed that after tightening to the correct torque spec, the larger of the two lines seems to still have some play. For example, when gently pushing a lineset coil to adjust its position, the large diameter copper line actually turns within the fitting. This is true of all three that I just installed, following instructions precisely (I even bought an HVAC torque wrench).
    Since it’s true of all three linesets, I want to assume this is normal, like the way airplane wings disturbingly flex in flight. But I’m awaiting your answer before I open the valves, since I really don’t want to have to find a local HVAC mech to bail me out.

    Thanks in advance for your perspective 🙂

    1. You should be good to proceed with the rest of the installation. However, if you don’t feel confident, you can call us at 270-366-0457 to speak with a MRCOOL tech about any aspect of installation.

  171. Your instruction manual says line set connection are labeled ABCD. Can’t see any markings. Should I assume end with more tubing exposed is for outside unit ? Do you recommend thread sealant such as Nylog or similar on fittings ? Thanks

    1. The ABCD markings are not needed. The small line will only connect to the small fitting on either the air handler or the condenser. The large line will only connect to the large fitting. No thread sealant is to be used on the DIY line fittings. The lines can go either way.

  172. I bought the DIY-18-HP-230B, which came w/25′ line set. I really don’t need this much line set. Is there any way to exchange the unused line set for a shorter one? I haven’t yet completed the install, and line set is still coiled and unused.

    1. We do not sell direct, so do not offer any kind of exchange program. However, many of our dealers do offer our 16′ line set and could be willing to do a trade.

  173. Purchased a DIY Mr Cool mini split at Lowe’s. Thank you for having this specific line information on your website! My contractor and HVAC people thought I was insane or confused or uneducated when I said Mr Cool DIY mini-split lines come precharged and do not need to be vacuumed by an HVAC person. None of them believed me. They kept saying lines had to be vacuumed and it was impossible to be precharged. I’m glad this information is listed on your website – so I could share with them!

  174. I have a Mitsubishi Mr Slim. Can I use your precharged lines to hook it up? Or will I need to pull a vacuum on the system?

    1. Our pre-charged DIY mini-split line sets will only work with our DIY ductless mini-split. Your Mitsubishi unit may require an HVAC professional to install it for you.

  175. I have a Mitsubishi Mr Slim. Can I use your precharged lines to hook it up? Do I need to vacuum the system?

    1. The DIY’s pre-charged line sets would not be compatible with another mini-split. If you would like, you can give us a call at 270-366-0457.

  176. I have a MRCOOL – DIY-36-HP-230B25 DIY 36k BTU 16 SEER and would like to move it can I just close the line set valves and cap it and move it then uncap it and connect line set and open valves?
    Thank you

  177. Can two mrcool outdoor units (each servicing a different section of the house) be placed side-by-side (approximately 1 foot apart) and run at the same time? Will this cause an air flow/intake issue? Thank you.

    1. It’s recommended for the DIY that there be a 24″ clearance on the right side of the unit and a 12″ clearance on the left side of the unit. Otherwise, there should not be an issue.

  178. The instructions in the 3rd gen state the excess coil is to be laid horizontally and not vertically. How important is this? I hear about it causing an oil trap

  179. We just received our Mr. Cool from Home Depot today. When we started unboxing it, we noticed one of the caps of the refrigerant line was off and on the floor of the box. Does this mean the lines are useless now? Will we need to send the whole unit back for a refund?

  180. Is there a pre charged 50ft line set with 50ft communication wire. If not, is the only way to get a DIY line greater than 35ft to use a coupler?

    1. If you are talking about the DIY ductless mini-split’s pre-charged line sets, then the only way to reach a 50′ length is to use a coupler kit, because line sets for that system are available in increments of 16′ and 25′. If you’re asking about the Universal, pre-charged line sets are available in increments of 15′, 25′, 35′, and 50′.

  181. I plan to replace the existing installed 25ft line set on my 24k DIY with the now available precharged 16ft version. Can the 25ft line set be disconnected and replaced with the 16ft line set? (after killing the breaker and closing the condenser valves)

    1. Technically it can, but we would recommend seeking the advice of our tech support team, which you can reach at 270-366-0457, or the assistance of an HVAC professional.

  182. I am in need of the 1/4-1/2 25ft diy pre charged line sets, 4 of them. Why am I having such a hard time finding them for sale? I have a so called diy kit that I cant diy because of non available line sets.

    1. Some of our products are currently out of stock, but we are working as hard as we can on getting them back in as quickly as possible. We apologize for any inconvenience.

  183. I need a 9000 BTU model but could not find the DIY option in the smaller unit. Is it available with the pre-charged lines? Could I buy the pre-charged lines separately?

    1. They are not. The DIY ductless mini-split has its own pre-charged line sets that are only compatible with the DIY. The Universal central heat pump split system also has its own pre-charged line sets, but these are not compatible with any other system.

      1. Does the MRCOOL Signature Complete Split System Air Conditioner Residential 2.5-Ton 16-Seer Central Air Conditioner have a pre charged line set?

  184. Sorry to bother you again, but I don’t quite understand the 2 zone…3 zone and so forth…I live in NC which one would I need? TIA

    1. A multi-zone ductless mini-split allows you to connect more than one air handler to the condenser. This means that you can heat and cool multiple rooms with a single system. If you have more than one space that you would like to be heated and cooled, you might be interested in a multi-zone system. Check out more information here:

  185. Hi,

    I purchased a 4 zone DIY Minisplit system from Home Depot. I am going to install this on my house which has some solid concrete walls. Instead of boring a whole through the wall for the lines set, I would like to run the line set up and through the eave into the attic, then run the line set back down the wall into the the air handler. I have two questions:

    1. If I use a condensation pump for the drain line, is there a limitation on how high the line set travels above the air handler?

    2. I will also have excess line set. Can this be coiled and stored horizontally above the air handler in the attic or does this need to be coiled and store at or below the same level as the condenser? With four line sets, there could be quite a bit of excess line sets which need to be coiled up and stored.

    1. Condensation pumps will have a rating for lift which is the max height it can pump water. The information should be in the condensation pump’s instructions.

      The excess lineset can be coiled either above the air handler in the attic or next to the condenser. If it is left in the attic then steps to prevent any possible condensation damage to the ceiling.

  186. One of your customers is upgrading from your DIY single to your multi zone package and has offered to sell the used one to me for $250. Seems like a great deal! But can it be easily removed from their house and installed on mine DIY?


    1. It is not designed to be moved after installation. While it technically may be able to be uninstalled, that would be difficult, you may run the risk of damaging the connections, and it would void the warranty. If you still wish to proceed, we would recommend seeking the assistance of an HVAC professional to uninstall.

  187. Are the precharged lines pressurized with liquid freon or are they filled with gasseous freon at ambient pressure?

  188. Hello Mr Cool,

    Can you explain something to me about the precharged linesets?
    I bought one and installed it and I am second guessing myself.

    The plastic caps on the ends of the linesets are not the only thing keeping the refrigerant in the lineset right? If I unscrewed the plastic cap and it took me a few minutes to connect the fittings all the refrigerant did not all escape did it? There is a plunger valve that only engages when connected properly?

    I am worried now,

    1. The plastic caps that come on the line set are more of a preliminary measure. You should be fine if you followed the instructions of the manual to install your system and connect your line set. However, if you complete your installation and something goes wrong, please give us a call at 270-366-0457 as quickly as you possibly can.

      1. Hi Mr Cool,

        Thank you for the response.
        It seems to be good. I have not used the A/C yet but the heat pump is good. I did get a DF error but it went away. A quick search on the internet stated it may be low refrigerant so that gt be worried. I soaped my fittings again and it all seems good. Thank you.

  189. 3600 sq. ft, totally open area,12 foot ceilings on 3rd floor of a building with parapet. Basically, 8 squares areas between columns measuring 20′ x 20′ + 2 squares measuring 10′ x 20′. Imagine rectangle 901 x 40′ with line down middle (x axis) w. 20″ on each side of x axis.

    1. Can I place the compressor on top of my roof adjacent to the parapet wall with the indoor air handler below it (instead of above it, as in every YouTube video). Obviously, I realize the drain line has to point down for gravity to work.
    2. Due to Texas climate, I anticipate requiring 9 tons. If all air handlers are placed on same wall, will this result in dead spots? In other words, is a single air handler on 1 wall sufficient to air condition 800 square feet (2 adjacent squares). Casettes are not an option.
    3, Is it better to have 1 air handler/square, with separate air handlers on opposing walls facing one another or a single air handler blowing across the two, 20 x 20 adjacent squares?

    1. The condenser can be placed above the air handler. If you meet the appropriate amount of BTUs needed, there should not be dead spots, but it may be a good idea to have air handlers on opposing walls if possible. You will likely need more than one system with that space. Our largest multi-zone DIY ductless mini-split is a 36k BTU system, which typically covers around 1,500 square feet. The 9k air handler can cover around 350 square feet, the 12k is able to heat and cool around 500 square feet, the 18k covers 750 square feet, and the 24k handles 1,000 square feet. However, the amount of space these units are able to cover may change depending on climate, insulation, the sun exposure that the space receives, and a number of other factors. Visit for more information.

  190. I bought your 12K DIY ductless and installed myself in work shop that has has 280 sq ft but vaulted ceilings. Calculated ~450 sq ft. and spoke with sales team who stated 12K was enough. Yesterday was our first really hot day since install (97 Farenheit) and indoor temp got up to 83 (with therm set on 76). It was working fine other than this and pretty sure install is correct. I checked filters and those are clean. Did I get the wrong size unit? If so, is it possible to switch just the indoor fan and outdoor condenser without having to re-do the lines? Is there something else I can do with existing unit to make it work? I live in Columbia, SC and A/C is the most important function of this so its useless if won’t get temp below 83 on hot days.

      1. That is the same number I have called multiple times previously and left messages without a callback.

        1. We apologize for this. It seems that you may be better off with a larger unit. While you may be able to have an HVAC professional replace the condenser and the air handler without replacing the lines, the pre-charged line set is only meant to be installed once. Do you have a reliable contact number that I can relay to the service team so that someone can reach you? Your comment with your personal information will not be made public, or your personal information will be edited out.

          1. You state multiple times that the DYI line-sets can be disconnected and safely moved. This post says they are designed to only be used once… I need clarity.

            Also, I cannot get in touch with anyone at tech support I have been calling for hours.

          2. I apologize, but the DIY’s line sets are only designed to be installed a single time. While it can technically happen with the assistance of an HVAC professional, your warranty would likely be voided.

  191. So is there actually refrigerant in the DIY linesets initially? Or are the just vacummed and are filled with refrigerant when the charge is released from the condenser? Thanks!

  192. I have the same issue as some other people on here where I received the Mr cool 12k and one of the gray plastic caps is missing and the other one was at the bottom of the box. Should I install it or not? I don’t want to put it all together and screw something up.

  193. I’m getting ready to install a 3-zone system and will have a 14’ horizontal run from one of the air handlers. I’m concerned about ensuring the condensate line drains properly. Should the lines be run exactly horizontal or should I very gently slope them toward the condenser? My house is 75 years old and has settled quite a bit, and I’m sure it will continue to do so. I don’t want to chance that in the future the lines end up sloping away from the condenser. Thank you.

    1. The condensate drain line should be installed at a downward slope to ensure that the moisture drains out of the system. If it is installed horizontally, there is a chance that it could stop up.

  194. For the 18k BTU Handler, are the line sets too small in diameter and require the larger set (like the one used for 24k)? Asking from an efficiency standpoint, friend of mine has 5/8 lines I Believe for his 18k btu. Thoughts?

  195. I agree. A variable speed air handler comes with various fan speed settings. It allows you to choose a speed that works for your cooling preferences. Instead of experiencing cold air blasts, the air handler circulates conditioned air throughout the home. This greatly improves indoor comfort and makes it easier for the AC to cool your home without hot and cold spots.

  196. I see the warranty on the Universal DIY system is 10 year, but I am unable to find any warranty information on the pre-charged novac linesets. What is the warranty on them when installed with the DIY universal system?

  197. Is it possible to relocate an indoor unit and reuse its lineset?

    I have an existing 9K using a 16 foot lineset; it is working fine. I want to relocate the unit to another part of the house. I have a new 25 foot lineset, but if necessary, can I reuse the 16 foot lineset that was previously connected without any additional work (evacuation of lines, etc.)?

    1. The DIY is meant to be installed a single time, so if you want to move it, we recommend having an HVAC professional do this for you. The warranty will also likely be voided.

  198. I have a different brand mini split already installed that is no longer working. I would like to replace it with a Mr Cool model. Can I just hook it up and turn it on using the line that is already run?

    1. While you technically may be able to with one of our other mini-splits, like an Advantage or a Olympus as long as an HVAC professional performs the installation, you would not be able to do this with a DIY mini-split system.

  199. I have a 3rd gen diy…..I will be purchasing a new outdoor unit due to compressor failure. Will the “precharged” lines hold their charge when I disconnect them and connect them to the new unit? I am very bummed that the unit has failed within warranty but because I can not find my receipt the warranty is voided.

  200. While the pre-charged linesets can potentially save money upfront, one problem I see is that it’s not possible to pressure test before releasing the refrigerant into the system. Any leak will result in refrigerant escaping rather than being detected and fixed during a nitrogen pressure test. It’s expensive to have the system recharged (I just paid $650 which I suspect is on the cheaper side for labor and 9lbs of R-410a), if you can find a tech that’s willing to work on one of these systems at all. If you happen to have an HVAC tech acquaintance, I would recommend paying the extra money (probably ~$1,000) and get flared connections for the peace of mind. Just my opinion.

  201. When using a wall mount bracket can the excess coil be laid horizontally a foor or two below the unit or does it need to be at same height?

  202. If I have an Advantage mini split can I can buy your precharged lines and attach them to it? I have such a small room and I can not find a DIY 9,000k BTU unit and am so remote a technician is impossible to get here.

  203. I live in a condo, they agreed to let me install a unit if I can hide all the lines and the condenser is at the back of my unit.
    I can do the condenser on the back of the unit, but if the shortest line set is 16ft I can’t figure out how to hide the extra 4 ft for the 1st floor unit.
    Do you have any shorter lengths of precharged line set, say 12 ft options?
    Additionally, if I purchase a 2 unit/air handler can I run the line set for both (1st and 2nd floor) in one line set cover use a T connection
    that will allow me to connect to the 1st floor unit but continue with the other line set to the 2nd story unit?
    It will look so much cleaner than having 2 line set covers side by each running up the building.
    Thank you for this information.

    1. Unfortunately, we do not offer a line set length that is shorter than 16′. We recommend that unused lengths of line set stay coiled up behind the condenser. There would likely not be enough room for both line set bundles in one cover, but since we didn’t design the line set cover for this application, we can’t exactly say for sure.

  204. Once a 12000btu DIY unit is installed, can it be uninstalled and reinstalled at another location without losing refrigerant ?

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