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Pre-Charged Line Sets Are For Real, Right?

pre-charged line sets

Pre-charged line sets aren’t exactly 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!

Pre-Charged Line Sets Are the Real Deal

A picture is worth a thousand words, so a YouTube video has to be worth like a novel or something. Anyway, 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.

No vacuum? Are you kidding me?” – St2288

How is that possible?” – E Money

Don’t you have to use a vacuum pump or purge the lines?” – Juan Silva

Wait a sec, no purge of the line-set or vacuuming them down first?” – Butchtropic

Yeah, there are a few skeptics.

So, Are Pre-Charged Line Sets Real or What?

Yes! For the last time, yes!

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.

418 thoughts on “Pre-Charged 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. 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.

  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. Unless your wire run is really excess ,i.e. 125-150, 175 ft or more,, more than likely a circuit from a viable load center will support 15 amps on #14 AWG. 2 bit electricians who think they’re rocket engineers make comments like that thinking old school and what it took to start wound motors back in the day.. You might mention it is inverter dc technology to your “electrician” and see if a light bulb goes off. you might also mention ” works as designed ” means the manufacturer knew what they’re stating when they engineered ,tested ,sold and wrote the nameplate.. IMO.

  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.

        1. It needs to reside loosely coiled. If you want to have it inside the wall, we’re fine with that. You may need to make sure your local building codes allow it.

  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.

    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.

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. 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!



  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  21. 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).

  22. 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.

  23. 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.

  24. 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.

  25. 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.”

  26. 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.

  27. 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.

  28. 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.

  29. 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.

  30. 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.

  31. 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.

  32. 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.

  33. 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.

  34. 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.

  35. 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.

  36. 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.

  37. 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.

  38. 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).

  39. 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.

  40. 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.

  41. 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.

  42. 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.

  43. 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.

  44. 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?

  45. 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.

  46. 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?


  47. 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.

  48. 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.

  49. 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.

  50. 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.

  51. 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.

  52. 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.

  53. 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

    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.

  54. 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.

  55. 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.

  56. 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…

  57. 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.

  58. 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.

  59. 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.

  60. 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.

  61. 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.

  62. 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.

  63. 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.

  64. 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.

  65. 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.

  66. 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.

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

  67. 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.

  68. 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.

  69. 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?

  70. 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

  71. 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!

  72. 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!

  73. 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.

  74. 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.

  75. 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.

  76. 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.

  77. 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.

  78. 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.

  79. 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?

  80. 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.

  81. 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.

  82. 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.

  83. 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?

  84. 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.

  85. 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.

  86. 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.

  87. 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.

  88. 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.

  89. 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.

  90. 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.

  91. 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?

  92. 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.

  93. 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.

  94. 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?

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

  96. 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.

  97. 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.

    1. Currently, the DIY unit come with the line already connected to the air handler. What you’re talking about may be possible with a future generation DIY product, but it is not possible with the present equipment.

  98. I want to hang the interior unit on an east wall and have the exterior compressor on the west wall. Everything I see, shows the lines exiting the wall directly behind the interior unit( off to one side, but still covered by the interior unit). Is this the only option or can I run the precharged lines, inside and exit on an adjacent wall?

    1. Most installations place the outside condenser immediately opposite the interior air handler. Strictly speaking, this isn’t required. The condenser can be placed at any location close enough (approximately 25′) for the linesets to connect.

      As far as running the lines on the inside of the building to the opposite wall, there are a couple things to keep in mind. First, obviously, you need to make sure you have sufficient lineset length to get to the spot where you want to place the condenser. Second, make sure the condensate drain hose (part of the line bundle) is always angled downward, so water can flow outside.

      1. Thank you for the response. I just re-read my question, and for clarity, it should read “ the interior unit on an east wall and the exterior unit on a SOUTH WALL. Adjacent, not opposite. DUH…….

        Regardless, it sounds like my concern can be resolved.

  99. HI, I install a 12 DIY mini split about 2 months ago. I realized the other day that the bottom outside line is frozen, but not solid frozen. Happens really when its very hot and humid out. The air inside it still blowing out very cold. What I did was I checked and sprayed for leaks outside on the lines, but found nothing. I cleaned air filters also. The one thing that it helping a little is I put a rubber installation coping around the line as it was exposed a little. I am hoping it really isn’t a leak and maybe cause its so hot out. Do you really think I may have a small leak?

    1. It could have been a leak, but a refrigerant leak isn’t the only reason you might find ice on an HVAC system. If the lines accumulate too much dirt and dust, that can lead to a condensate build-up that will eventually start to create ice in certain conditions. Excess humidity can compound on that. If the problem continues, give us a call at 270-366-0457 and speak with our tech department.

  100. Is there a reason my unit leaks inside when on “swing?” Also, I’ve been smelling mold in the house and see it on the plastic outside of the line set. Is there risk of the air coming into the house having mold from that? Also having trouble making the app connect to the unit. Thanks for any help! In general it works great.

    1. Water should not be coming out of the inside unit. There may be a clog in your drain line somewhere. If water is backing up regularly, that could lead to mold growth. Also, it is always a good idea to thoroughly clean the interior unit approximately once per year.


    1. Unfortunately, production of a multi-zone DIY product has been pushed back. We currently do not have an release timeline.

  102. Looking at ordering the 24k DIY system and had a question. The unit will be install off the west side of our house and we have a carport that is open on two sides. Could the outdoor unit be installed under the carport.

  103. I have installed the 12,000 DIY unit and so far so good. Question: How often do the filters need to be cleaned/replaced, and, where does one purchase replacement filters?

    Thank you

  104. 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?

  105. 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.

  106. 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

  107. 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?

    1. Jeff, I have the same issue. Did you obtain instruction on how to handle this problem? Did they suggest releasing the pins/wiring terminals in the plastic connector, pulling the cable through the conduit and, then, reinserting the wiring terminals? Releasing the pins is a common solution, but you need know the proper way to release them without damage.


      1. I just completed releasing the pins in the connector at the compressor end of the cable from the air handler by inserting a small finishing nail into the rear of the connector on the side of the terminals with a small plastic tab. It wasn’t too easy because the round nail tended to roll to the side, but when I got it centered and pushed all the way in, the terminal pin could be removed. By removing all three terminal pins I could feed the cable through a liquid-tight conduit and connector (be sure to feed the bare terminal pins through the cover and liquid-tight lock nut at this point) and then inserted the terminal pins back into the plastic connector body. Worked like a charm.

    2. I just installed the 18k DIY unit and for the sake of speed I used white 1/2″ sticky back foam tape around the jacketed part of the wires. Mine was already wired, so I put the sticky back side out, and slide it up the wire and into the knockout hole enough to where it expanded on both sides and stuck to the edges of the knockout hole. (I DID use the internal strain relief the unit came with to support the wires).
      Another idea is to get a rubber grommet the right size and either expand it over the plastic connector and then fit it into the knockout….or after the fact …slit it, put it on the wires and then super glue the slit and then fit it. Hope this helps!!

  108. How often should the defrost cycle come on and how late no should it last? This is our first winter with DIY 24000 unit and it goes into defrost mode consistently when temp reaches 73. Outstanding de temp is only in mid 40’s.

  109. I recently acquired a property that has a Mr Cool unit installed in a garage. I would like to move the entire unit from garage to my house. I cannot move unit without disassembling hoses from outside to inside. Will the unit need to be recharged if I disconnect these lines?

    1. If it is a MRCOOL DIY, it can be disassembled and moved without recharging. If it is an Advantage, Olympus, or other mini-split product, it would need to be properly charged again. Also, it would need to be moved by a professional if it is not a DIY.

  110. The latest Mr Cool DIY installation manual includes a chart of recommended torque values for the lineset connection at the condenser. However, it does not include the Coupling size (last 2 part numbers) for one line on my unit. What is the recommended torque range for part number -09?


    1. As a follow-up to my post, I received a prompt call back from support and was told that the torque range for the -09 part is 30 to 35 foot-pounds, just like the -08 part included in the installation document.

  111. Hi can you make the Olympus Hyper Heat DIY Pre-Charged, all we use is DIY 24k BTU at this time for heat all winter i would like to upgrade to Olympus Hyper Heat.

  112. I have a garage that measures 18’x 18′. I have however walled off a section (6′ x 11′) for an ‘office’. I am looking at a DIY unit to provide both heat and cooling options. First, what is your recommendation? Second, I’ve seen rumblings in some of the above posts on a 3rd generation unit. We are nearing the end of 4th quarter, do you have any updates? Third, do you have any updates on a dual zone version (DIY)? Finally, when recommending an option, please let me know what size breaker/disconnect that is required. I have a 20 AMP 220v disconnect circuit pre-wired and available. The garage is also very well insulated on all exterior walls as well as the roof joists. A dry walled ceiling has also been installed to minimize cooling and heat loss.

    1. A 12k BTU mini-split should be able to provide ample capacity for an 18 x 18 space. Properly positioned, you should not need a dual-zone installation to cover the office and the rest of the garage. We do not have any updates on a dual-zone DIY at this time. 3rd generation DIY products should be available with major retail partners by the end of the month. The DIY 12k is a 20 amp, 120 voltage unit.

      1. What will be the differences between the 2nd generation and 3rd generation DIY models that will be available at the end of the month?

        1. The 3rd generation will be higher SEER (more efficient) and have a slightly different installation. However, the basic design is just as amateur installation friendly as our 2nd Gen DIY.

  113. We are now at the beginning of December, and all major retailers still dont know when the 3rd generation DIY units will be available for sale. Can you provide any updates?

    1. The 3rd Generation DIY is available now. You can find them on Amazon and IWAE. You could also contact the Home Depot ProDesk, but they should be showing on Home Depot online very soon.

  114. If I have a 24k outside unit and a 12k inside unit, would they be compatible? I’m only trying to cool a 91sf storage room, but I’m trying to get it down below 40 degrees to make a DIY walk-in floral cooler.

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