INTRODUCING: The NEW 4th Gen DIY Ductless Mini-Split

  • June 6, 2022
  • By MR COOL

Have you ever wanted to directly control how comfortable your home is, but you know that touching the thermostat equals high dollar signs? Now’s your chance to bask in full, complete comfort all throughout the year, because the DIY Ductless Mini-Split System is back and better than ever in its 4th Generation!

What’s New?

Everything that you’re used to with the 3rd Gen DIY is present in the 4th Gen, like impressive heating and cooling ranges, efficiency levels to get excited about, and a simplified do-it-yourself installation, but it’s all better. 

The 4th Gen DIY ductless mini-split has completely updated specs, ensuring extreme efficiency and compliance with new rules and regulations. The 12k has an impressive SEER of 22, making it Energy Star Certified, so you can install this system and enjoy lower bills for years to come. 

How could the DIY’s installation get any easier? It’s already just drill, mount, connect, isn’t it? Your electrician will be excited to work on this unit thanks to the addition of the new DIYPRO™ MC cable, which securely connects the air handler to the condenser. This cable provides protection against weather, pesky animals, even lawn mowers and weed eaters so you can keep enjoying refreshingly cool temperatures in the summer heat and toasty warmth in the winter chill no matter what.

That’s not all, though!

How Many Rooms Can It Heat and Cool?

The single-zone 4th Gen comes in four sizes: a 12k BTU system, which typically covers 500 square feet, an 18k BTU system, which handles 750 square feet, a 24k BTU system that heats and cools 1,000 square feet, and a 36k BTU unit that covers 1,500 square feet. 

These are perfect for more open areas, as there is only one place the air comes from with a single-zone unit. Sometimes one unit is all you need for complete comfort.

If you have a space that needs two units, but you don’t want to deal with two separate installations, we recommend the new dual-zone DIY! This 18k condenser can provide comfort to spaces such as two nearby bedrooms, a dual she-shed and man cave, or any twinning spaces that you can think of!

But what if you want to heat and cool your entire home? Previously, the multi-zone DIY could only support up to four zones, but we’ve added another condenser to the lineup to support 5 zones! In the right conditions, this 48k BTU is able to heat and cool a total of 2,400 square feet! This product will be available soon.

What About the Warranty?

We’re glad you asked, because this mini-split warranty is the best in the HVAC industry!

If you invest in us, we’ll invest in you. For the ultimate protection, you can sign up for a limited lifetime compressor warranty and a 7 year unit replacement warranty! This means that if your compressor breaks down, you’ll get a new one whenever you need, so the comfort never ends! 

The warranty lasts as long as you keep up your end of the bargain. To receive this warranty, you’ll need to sign up for the MRCOOL Care Kit program, to ensure that you’re taking care of your unit. Contained in this kit is a foaming cleaning spray, a bottle and a sprayer to rinse the unit, and a water collection bag with a drain tube to keep your house dry when you’re cleaning the system. Signing up for this warranty also entitles you to a standard 5 year parts warranty.

If you do not sign up for the MRCOOL Care Kit, you’ll still receive the standard 5 year parts and a 7 year compressor warranty. 

Where Can I Buy?

Improved efficiency, updated tech, and the warranty of a literal lifetime sounds pretty exciting right? To get your very own 4th Generation DIY® ductless mini-split system, visit one of our many retailers around the nation, or take a look at Let us transform your home with the power of the new 4th Gen DIY today!

124 thoughts on “INTRODUCING: The NEW 4th Gen DIY Ductless Mini-Split”

  1. I want someone to give me a call so I don’t have to be shopping on the phone for hours I don’t have time for that thanks !

      1. Can Mr cool diy be used in a motorhome? Does this unit plug into a wall outlet or hard wire? 110, 220, or 12v

        1. It could be, if sized appropriately. The system must be hardwired into an appropriately sized disconnect box. The 12k BTU system is a 110V system, and the 18k, 24k, and 36k BTU systems are 220V.

    1. Please feel free to go to our Website at where you can order online. We sell only MRCOOL units. We are still entering some of the new units as they become available so if you can’t find what you are looking for, please contact us at [email protected] and let us know what specific bundle you are looking for and we will get it priced and up on the website for you to order.

        1. Yes, we use Shopify which offers a Shop Pay Payment plan. When you are looking at the product, it shows on the right hand side under the product with a “Learn More” so you can get more information on how the payment plan works. Go to this link on our website and you will see it right under the Price. Please feel free to contact us if you have further questions.

  2. I wish you would add a floor unit to your DYI solution. I have a mid-century modern ranch with large exterior windows, so a wall mount air handler on exterior walls isn’t gone to work. I have one guest room that is completely tongue and groove wood walls, so even if I did have access to exterior walls for a wall unit, I would never drill a hole in those wooden walls. Your ceiling cassette units might work, but my house has a skillion “lean to roof” roof with a very low angle, so space in attic is tight, and your cassettes are not DYI at the moment. I don’t know if it is possible, but if a floor unit can use the square vent hole for the current central air duct, after the duct is removed, then I would be down with that solution, as I have access via basement. I understand that the cassette could be seen as more of a professional install due to attic install, but I can’t see a floor unit being that much more difficult than a wall unit, especially if you have good access underneath via a basement. The crazy labor prices HVAC companies are now asking is just outrageous. They will quote you a small ducted split system for $11K, and a 3 zone mini split for $18K. If you want to make my house a install case study due to how unique it is layout wise, come on down. haha! Thank you for your time, and please release a DYI floor unit. 🙂

    1. We greatly appreciate customer feedback! Thank you for your message to us. Unfortunately, we currently do not have plans to add a floor unit to our DIY ductless mini-split series of products. Once again, thank you for your comment, and we apologize for any inconvenience.

    2. I would like to second this opinion. I also would prefer a floor unit, especially as I am concerned more with heating rather than cooling.

      1. Ditto – a floor or ‘low wall’ unit would be much better for heating-dominated climates…especially if it would draw air in from floor level (as low as possible) and supply air at window-sill height or so…

        1. Agreed

          Need floor unit

          In cold climates a high wall unit doesn’t make sense

          Also older homes with high windows there is no room to place the inside unit

  3. I have a question. I currently have 2 of your units from a few years ago.
    I have a DIY-18-HP-230A and a DIY-12-HP-C-115AE.
    They cool very well. But once it falls to around 40 degrees or less the heat stops heating. I want to know if the 3rd or 4th generation will heat better?
    I want to be able to heat down to at 10 degrees at close to 100% efficiency.
    What is the heating range of the 3rd and 4th generation models?
    And at what temperature do both of those models drop from 100% efficiency?
    Going to be replacing these soon, and don’t know if it’s worth waiting for the 4th Gen.

    1. When it comes to the 3rd Gen, the 12k BTU unit can heat in temperatures as low as -13° Fahrenheit. The 18k, 24k, and 36k BTU units can heat in temperatures as low as -4° Fahrenheit. The 4th Gen 12k, 18k, and 24k can heat in temperatures as low as -13° Fahrenheit, and the 36k can heat in temps as low as 5° Fahrenheit. Performance spec information can be found on our Documentation page, at

      1. Hi,
        The Owners’ manual for the 3rd gen diy says that it heats down to -13F but the spec sheet shows a rating not much different at -22F. I just installed mine and the cooling is great, will this provide any heat if the temperature dips down below -13 as it did a couple of times in 2015 outside of Boston?

  4. ASAP I need a 4th gen 9k + 9k +24K system with a 16ft+25ft+50ft install kit. Please price and send information for ordering system. I’m in the Wilmington Delaware area.

  5. Does the new 4th gen actually stop cooling when the setpoint is reached? My 3rd generation 12K DIY never stops and makes the room a meat locker until I manually turn it off. Mr. Cool support was nearly impossible to reach, and when I did, was not able to provide any solution.

    1. Your system should stop cooling once the set point temperature is reached. Please give us a call at 270-366-0457 as soon as possible.

  6. Does MRCOOL have a floor unit or can it be mounted lower on a wall. I want to replace an old wall mounted motel type ac with MRCOOL in the same location.

    1. The line set lengths are 16 feet and 25 feet. These line sets can be linked together using the appropriate Quick Connect coupler kit.

      1. Where can you purchase the 16 ft line set?

        We are interested in the 27k 3 unit split, however each outer unit will need to be approximately 25 feet from the center unit based on walls and windows, then will require an additional 8 feet from just below the roofline to the ground.

        It seems wasteful to get 2 extra 25ft sets just to reach the ground, but I can’t seem to find anything less than 25ft lengths.

        Thanks for your time

        1. You should be able to purchase it at any of our retailers. The correct model number for a 16 foot line set for this system would be DIY16-1412.

      1. What about a 4th gen condenser and 3rd gen air handler, assuming voltages are the same?
        DIY-12-HP-WMAH-230B (handler) and DIY-MULTI3-27HP230C (condenser)?

      2. Is air handler 4th generation model # DIY-18-HP-WMAH-230C25 compatible with 3rd generation compressor model DIY-18-HP-C-230B as I ordered a complete 3rd generation 18k system from Home Depot and this is what they sent me

      3. Does using 4th gen air handlers with 3rd gen condenser change any of the specs? Heating and cooling maxs to be specific.

  7. Will you guys have a low wall handler for the 48k 5 Zone unit? I have been waiting for four months now for the 4gen and was told by folks to wait for this new release. I have a couple of space where the standard air handler can’t fit. Low wall mounth will be better. Can you folks please let me know. Thanks, Paul H

  8. We are building a new Hangar Home. Metal building with a 1500sq ft. home being built inside of it. Single level two bedrooms. Location is northeast Tx. Thinking I need a system with 4 units.
    Mark German.

  9. do you offer a 12k floor unit (not wall mounted)? Also, we currently have EZBreeze ‘windows’ installed in in 3 season room and they are definitely not as efficient as having double paned windows so not sure if installing a mini split system would be a waste of money due to the energy loss

    1. Unfortunately, we do not have a floor unit. We apologize for any inconvenience. It’s likely that a mini-split system would be more efficient than window units. Take a look at for more information on our DIY ductless mini-splits.

  10. I require a DIY18HP230B50. Your dealer map does not provide retailers in my area but I know Lowes or HD do sell units in my area. Can you provide a list or can Lowes or HD order this bundle for me.

  11. Do the 4th gen air handlers work with 3rd gen condensers? Not sure if the condensers are the same. I bought a multi 36k system when it was 3rd generation and had them ship out the condenser first and 18k Air handler as they were out of stock of the 9k and when they received the 9k air handlers they shipped out 2 4th gen 9k.

  12. Do all diy 4th gens have an inverter compressor? If yes, does the air handler and the compressor stay on constantly if the set point is reached?

    I want them to stay on constantly but just throttle back the compressor cooling power and power use (variable btu output). Can the diy 4th gen do this?

  13. My unit seems to keep running even after it reaches the temp I have the thermostat set on. How do I fix this?

  14. My application will require running the DIY line- sets through an interior wall which will mean that the 90 degree bend will need to be tighter as opposed to if it was run down an outside wall. Is there less of a concern with the fourth generation units as they’re designed with some more protection against kinking?

    1. You should be just as careful with the line set. The line set is not very different between generations. While you should be able to do what you intend, you will need to make the bend extremely carefully.

      1. I also wanted to install the supply limes inside the wall of a RV garage so the lines are not visible outside , I am going to build out the wall the thickness of the exterior wall and mount he handler on that. That way, the bend will be the same as if going through exterior wall. I will use the upper line cover on the bottom where the line goes through the wall to condenser. A little different, but I think it will work.

  15. My MrCool DIY 18k unit will not cool. The E1 has displayed and electric amps were checked so i assume the control panel is bad. It not communicating with each other. I would like a new one under the warranty contract. It was installed on 5/19/2022.
    This problem needs to be addressed ASAP. I purchased the units on Amazon on 4 /10/2022.
    Due to your poor support department I have had togo to the added expense of purchasing a window mount as we are in a heat wave!

    1. We apologize greatly for this. Would you mind sending me a reliable contact number so that someone from our service team can reach out? Your personal information will not be made public.

  16. So I just received my Mr Cool 18K mini split thru Costco. The air handler is a 4th Gen, while the condenser is a 3rd Gen. Why the difference, and is this the normal pairing?

  17. Good Afternoon,

    I have an aging 3Ton central HVAC system that is over 15 years old along with a VERY old resistance hot water heater. I am trying to find out if anyone makes something like your universal series that can also be connected to a hot water tank to use the waste heat from the Heat Pump system and dump some or all of the heat into a hot water tank instead of me having to buy a separate hybrid hot water heater.

  18. Why is there no 9k unit in the 4th generation? More importantly, I have an 80 sq ft insulated studio shed. What is the downside of using the 9k 3rd generation system? Or do you think that it would be just fine? I live in Virginia.

    1. We apologize for any inconvenience. When it comes to performance, the 3rd Generation still holds up well! However, we do not have a single-zone 9k BTU system in our DIY series. It is in our Olympus series. This line of products is extremely high efficiency, but requires an installation performed by an HVAC professional.

  19. Does the gen 3 advantage 18k condensers have freon shipped inside or will I have to add freon? The only difference I see between the DIY and advantage is the line sets being vacuumed.

    1. The Advantage’s condenser is charged. The DIY’s line sets are charged, so there is no additional charging or vacuuming that needs to be done during install.

  20. We have a brand new 4th gen 36k unit with 4 zones. Zone C is freezing cold if it is on and the line set gets frozen within an hour or 2 of being on. Zone D is now not cooling properly and is just blowing air and not cold air. I’ve checked for leaks and “cleaned” it and everything. What should I do? The 4th gen ones come with a low refrigerant/leak detection right? Haven’t seen any warnings on it or anything. What can I do next? Replacement lines? Or? Thank you so much. The other two lines are currently working great 🤞

  21. I have a 1700 sqft home. I currently have an old central ac that isn’t keeping up. The house has 3 bedrooms, a lower level and a big open area (living room, dining room, kitchen. How many units would I need? Also, do you have lines that stretch from one side of the house to the other? Thank you.

    1. Sizing would depend on the specific square footage of the spaces inside your house that you want to heat and cool. Our newest unit in the 4th Gen series, the 48k BTU 5 zone multi-zone DIY ductless mini-split, was recently released. You can find more information regarding sizing and pricing at

  22. Can you purchase a ceiling mount for the
    MrCool E Star DIY 4th Gen 12k BTU unit
    Rather then the wall mount.
    I saw your units at Costco.

      1. Will installing a 12k BTU wall mounted air-handler be problematic for a 150 sqft bedroom? Will installing a 12K BTU cassette style air-handler be problematic for a 100 sqft bedroom? Both rooms have 8′ high ceilings.

        1. A 12k might be oversized for a space like this. Since you have two bedrooms that need heating and cooling, an option that may work is using an 18k BTU dual-zone DIY ductless mini-split condenser and putting a 9k air handler in each bedroom. A 9k air handler would be more appropriately sized for these spaces.

  23. I have a ezpro-12-hp-11516 mini split i am preparing to install in a 10×12 work shed is there a specific reason it needs 90.55inches of floor clearance

    1. This simply allows the best air flow for the unit, but is in all just a recommendation. It will still heat and cool fine if it has less clearance than that. Just be sure to hang it high enough to where you can appropriately feel the air it pushes out.

  24. what are the model numbers for 4th and 3rd generation 2 zone unit:
    MRCOOL 30000-BTU 230-Volt 21.5 SEER 1250-sq ft Smart Ductless Mini Split Air Conditioner and Heater with 25-ft. Installation Kit

    1. The model number for the 3rd Gen condenser that that bundle uses is DIY-MULTI4-36HP230. The 4th Gen condenser’s model number is DIY-MULTI4-36HP230C.

    1. Most of the time, the generation will be in the title. Another way you can tell is with the model number. The 4th Gen will have a “C,” and the 3rd Gen will have a “B.” For example, the model number for our 4th Gen 12k BTU DIY ductless mini-split is DIY-12-HP-WM-115C, and the 3rd Gen 12k BTU DIY ductless mini-split’s model number is DIY-12-HP-115B.

  25. Can you please explain how to run a 4th Generation 36K condenser with 3 handlers (12K, 12K, 9k)? Can each handler be run by itself? Or do you have to run at least 2 when running? Also, does that configuration result in a 33K cap on the condenser output? And if so, is that limitation of concern re. performance? Thank you.

    1. You must make sure that the air handlers meet at least 2/3rds capacity in order to properly operate the system. You would need to run two air handlers at a time with that system. It will produce as much capacity as is demanded when the 2/3rds requirement is met.

  26. Re. SEER for 4th Generation condensers and handlers. Can you please explain how to determine the SEER of a handler? The “Specifications” page from the 5-18-22 4th Generation DIY Series Multi-Zone on-line brochure shows the SEER for the condensers but not for the handlers. My concern is that using a condenser with a 22 or 21.5 SEER may be limited by the handler SEERs–which are not shown on the spec sheet. Thank you.

  27. Re. Determining the minimum clearance for a line set. It appears that the line set requires that a 3 inch hole be drilled in the exterior wall to accommodate the running of the lines from the condenser to the handler. I hope to place a condenser under exterior stairs that are 5 1/2 inches out from the exterior wall. That exterior wall would be the entry point of the line set. Is that enough clearance to run the line set in the space between the exterior stairs and the exterior wall? Thank you.

    1. The required hole is 3.5″ in diameter. As long as the space is at least this large and allows for the possibility of maintenance if necessary, you should be fine.

  28. Does the 4th gen system fix the 3rd generation issue of not maintaining the set point? This was an enormous problem with all 3rd gen units that i myself has to deal with.

    My 3rd gen set temp would be 78f and it wouldn’t cut of until 68-67f which is completely unacceptable. I want to verify this prevalent issue was specifically resolved before I purchase a new 4th gen.

    1. The 4th Gen should maintain set point. There would be an issue if it does not, and in such case, our tech support team should be contacted at 270-366-0457.

      1. I have one 9K and one 18K 3rd gen air handler attached to a 27K compressor. The second system is configured with two 9K air handlers. I have not been able control the room temp any closer than +/- 6 degrees of the set point. I have tried using the remote “follow me” and still get the same results. what am I doing wrong?? I have two of these systems at a cost of around $8000. Surely this is not the way they are supposed to work.

  29. This is my second install and the first one was a breeze and works well.

    On this second install, I had to run all 25 feet of the supplied DIY refrigerant lines, I stretched all 25 feet out to gauge the gradual bends I would need to run. I know the lines need to match up with color coded caps, but does it matter which end of the line goes to the indoor air handler? Are the fittings all the same on both end?

  30. is it possable to run a 12000 btu 120 volt unit with power being provided by a 5000 watt modified sine wave inverter?

    1. I am not entirely sure what you mean by this. If you are asking if the air handler’s line set bundle can exit the unit from the left side when looking at the front of the unit, it cannot. It can either be routed out of the right back of the unit, or out of the right side of the unit.

  31. For the 12k system, can the refrigeration and drain lines on the indoor unit be routed out of the right side of the unit instead of routing to the back (back wall)?

    1. When facing the front of the unit, the line set bundle can be routed out of the side of the air handler because the casing has knockouts.

  32. I recently purchased a 115VAC MrCool minisplit system to go into a room being built on the back of my house. The electrician installing the power box for the system wired the box for 220VAC. When I turned the system on, a large cloud of white mist enveloped the condenser and the system refused to work. I’m told by an AC troubleshooter that the Main PWB is blown. I have no problem taking out the old board and installing the new one but I have several questions: 1. Are there instructions as to how to remove the main PWB? 2. Are there tests that can be run to ensure that all is ok before I turn this unit back on?
    Because this was not the fault of the unit, and because, technically, I’m able to do the work, I would like to know the answers to my questions and get this unit up and running.

    1. Please give us a call at 270-366-0457 as soon as possible so that someone from our tech support team can best assist you with this issue.

  33. Hi, highly interested in 4th gen heatpump. I have 5 areas to cool and the house is 1300 sq.feet. 3 zones on 1st floor will be always used and 2 bedrooms upstairs will be used occasionally. What is better in the matter of saving energy: getting single 48000BTU unit for 5 zones or separate 1-st floor from second with getting 2 units 36000 and 18000? And also Just to confirm: lines provided and sold by MrCool are 16 and 25 ft. but if I needed to run longer line I can get additional lines and link them 25’+25’ or 16’+16’ or 16+25? What is the maximum length of the link?

    1. It would likely be better to get two separate systems if you will not be using some air handlers sometimes. You can link line sets together using our Quick Connect coupler kits. The typical maximum line set length per air handler is 75′, but total lengths may differ depending on the condenser. This information can be found in the manual.

  34. Can the ductless system be mounted under a window instead of over it?
    My wife and I recently bought an older home where the children of the elderly resident had installed a single zone Mr Cool system in the kitchen on the 1st floor. We’ve had the system professionally disconnected and taken down while we do renovations. We’ve decided to install central air on the 1st floor and move the existing system up into the master bedroom. But the old house has tapered ceilings that don’t leave much room over the windows upstairs., However, there’s a perfect spot under a window along the back of the house. Albeit a bit odd looking, could this work? Would it be any different than a floor model? Thanks!

    1. Unfortunately, that wouldn’t be recommended, because the space would not receive proper airflow from the unit. Having a direct, consistent stream of cold/hot air (dependent on the season) could also damage the floors. A floor model blows air upward, a wall-mounted mini-split blows air downward. Both are designed to improve airflow in compliance with their different designs, so you’d get the best usage out of installing it in accordance with the recommendations in the manual.

  35. We are building a 650 Sq Ft ADU. 2 bedrooms, one bath with a kitchen/living room combo. Will I need additional units for the bedrooms?
    The building us about 14′ X 46′. We want to put the main unit on the exterior wall of the living room which means that the front bedroom would be about 25 feet away or so.

    1. If you need to/want to close the bedroom doors and only have one air handler in the main area, then air will not get dispersed to the closed off areas. It’s completely up to your personal preference, but if you’d like for the doors to be shut and for the temperature to be regulated in the bedrooms, a multi-zone might be the best option.

  36. I am interested in installing one of your 36k diy units in my garage. I would like to install the condenser on a wall of a gable above the garage and want to put the evaporator on an inside wall above the door into the laundry room. Looking at the installation manual it looks like the lineset has to go back and down whereas I would need to go straight up through the ceiling into the attic and to the condensor. I know there will be a challenge for the evaporator drain but I could run it to the water softener drain. Would this even be a possible install? I know in Santa Fe NM mini splits are commonly installed on the roof. Thank you, John Winn

    1. If the line set/condensate drain line travels upward at any point, you will need to invest in a condensate pump designed for mini-splits.

  37. It is currently -8 outside and my Mr Cool mini split isn’t heating properly. What can cause this issue? The unit isn’t even a year old. I have 18k BTU 22.7 SEER2 MrCool DIY 4th Generation E Star Ductless Heat Pump Mini Split System. What can I do please answer.

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