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How to Install a Ductless Mini-Split Air Conditioner | This Old House

This Old House plumbing and heating expert Richard Trethewey explains how to install a mini-split air conditioner. (See below for a shopping list and tools.)

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Richard traveled to Tampa, Florida to help a homeowner find a cooling solution for his garage. The homeowner used the garage as a workshop in the summer months, but said that it was too hot and humid in there to work comfortably. To solve the problem, Richard and local expert David Zimmerman installed a “mini-split” air conditioner. The system uses no ductwork. Instead, an air-handler unit is mounted inside on a wall, and the condenser unit is mounted outside.

Shopping List for How to Install a Mini-Split Air Conditioner:
– mini-split air conditioner [https://amzn.to/2vyimyj] – ground pad [https://amzn.to/2Veahyb], for supporting condenser unit
– 1-inch-diameter PVC pipe and assorted fittings [https://amzn.to/2WkL6q7], used as condensate drain line
– PVC primer [https://amzn.to/2GQcbe7] and cement [https://amzn.to/2vxt6x3], used to join together PVC drain line 5. armor-sheathed electrical cable [https://amzn.to/2PKKGH1], provides line-voltage power to the air conditioner
– low-voltage wire [https://amzn.to/2LkaPOu], sends signal from air conditioner to condenser

Tools for How to Install a Mini-Split Air Conditioner:
– drill/driver [https://amzn.to/2UR4vxf] – 1 _-inch hole saw [https://amzn.to/2IVdvjo], used to make hole for refrigerant lines
– level [https://amzn.to/2ZVAu3l], used to level pad that supports condenser unit
– drywall saw [https://amzn.to/2WjOQIz] or jigsaw [https://amzn.to/2PKAgar], used to cut hole in interior wall
– hammer [https://amzn.to/2ZTYvYy] – pliers [https://amzn.to/2Vbozzj] – wire strippers [https://amzn.to/2LkgVhP]

The “Mr. Slim” ductless mini-split air conditioner was manufactured by Mitsubishi Electric [https://metahvac.com/].

It was Installed by David Zimmerman, Zimmerman’s Air Conditioning & Heating, Inc.

Additional assistance was provided by Ryan Hansen, electrician, Hansen Electric, Inc.

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How to Install a Ductless Mini-Split Air Conditioner | This Old House


  1. Can I use this through the hols house

  2. Can you also pressure test by cracking open the high pressure slightly?

  3. The design makes this AC a possible alternative to ductless DYI systems. It works great. The remote control could be more visual aid oriented like a backligh design. Is impossible to see the lcd at least for me. Easy install https://www.youtube.com/post/Ugkx_hHgTlzH3uk31Fe2RVS3xEbXHGaN_z5Tation. Came on time . Great comfort around the house 5 🌟 again. Follow mfg instructions for care and all and this should be the only AC you need for those of is that don't live in new homes with central AC

  4. There was no liquid tight flexible conduit on the communication line from the inside unit to the outside unit and then there was – magic!

  5. Can u set it without a remote control. We moved into a home that has the unit but no remote came with it

  6. Can anyone tell me how to 'turn off' the refrigerant line? Is it just that allen key at the source? I have to move the bracket up on the wall of our indoor head unit so the drain hose is sloped downhill to drain properly. All the tubing is sprayed foamed into the wall tho and i fear messing up the bend thats already in the copper lineS. Id like to detach the copper lines at the head unit to place it on the ground while i re position the bracket – but i feel like 2 people are going to have to hold it in the air for me while i attempt to remove the copper lines (if thats the even possible). Am i thinking this right!?

  7. It sure is nice having the breaker box right next to the unit. Mine is on the other side of the house.

  8. Have been very happy with our mini-split but a slug (or something) crawled across the outside unit PCB and got fried and in the process fried the board. They are a BEAR to try and work on. Just getting them apart was a challenge and I've been taking things apart my whole life. Actually never was able to get the PCB out.

  9. You guys are fantastic love y’all mane

  10. I lived in Mexico and everywhere I've stay there is a min split on the wall, its so efficiency and cool way better than the standard USA AC with ducts… so my question why USA hasn't catch on? Price?

  11. I was waiting for a time elapse temp verification. I wanted to see you guys cooled off. MR ZIMMERMAN —->Excellent, thorough demonstration walk through. You are truly a PRO!

  12. Should be on a stand in case of heat use .

  13. Why not buy pre insulated lines ? Wire to small and not armored.

  14. Should really use a spade for the ground you can’t really get a good bite doing it that way on the outdoor I could easily pull that off

  15. My only add would be something to keep bugs from nesting inside the condensate drain. Mud daubers would clog that in a heartbeat, A small bit of very coarse STAINLESS steel wool would do the trick.

  16. I have so many questions… wouldn’t it be a waste to install that in a block garage? There’s prob so much heat and cooling loss from that garage… no insulation. Also did he not use nylog on the flare fittings?? And you don’t suck out nitrogen with vacuum pump.. you just release it

  17. I’m convinced! I need Dave Zimmerman in my life! Lol

  18. I grew up watching This Old House. I used to watch it as a kid to pass the time, as a young teenager I found myself using knowledge and techniques from this show. As an adult, I now thoroughly enjoy watching these gentlemen repair or install just about anything. I hope this show is on forever and I intend to leave PBS in my will.

  19. When he broke out the nitrogen, I threw up my arms and realized I have to pay someone…

  20. Can you use the heater unit without the outside unit hooked up 12000 btu mini split

  21. They’re using Mitsubishi; it is without a doubt the best manufacturer of these type of units.

  22. That flex from the disconnect to the out door unit looks like garbage. Not enough length too much as the crow flys. 🤮

  23. My AC is cold for few minutes only and after that , only the fan works ; purchased another one and I still have the same problem ! Please help ; thank you in advance

  24. What if the room I want this installed in doesn't have an outside wall? can the outside unit be placed in the attic?

  25. About how much do these run?

  26. What brand and btu model is this garage mini-split?

  27. How about a ecoflow in the basement for privacy

  28. how to aplly work ac at there
    i technition indonesia work at ac 10 years

  29. Mitsubishi Electric is the best brand to get when it comes to Mini Split A/C

  30. Excellent walkthrough. The tools, time invested and know how demonstrated have made me confident enough to hire a professional

  31. Now that's the way to explain something!! I totally understood! Thank you for the details. I'm heading to the store right now!!!

  32. He did not check to see if the copper line was kinked.

  33. Only in America would you see citizens installing their own AC cause they can’t afford installation charges.

  34. not really ductless when you're running a duct through the wall(s) and required plumbing

  35. 2 things de-bur the pipe before you flare it. And put a small drop of oil on the back side of the flare to help when tightening down.

  36. Thank you! I'm having mini-splits installed and now I'll know what to expect. Great informative video, appreciate it!

  37. I see a couple issues that this guy has missed
    no torque specs on wrenches , so crank it down, NOPE no oil on flare connections. dry fit NOPE.that insulation on refrer tubing will be gone next year UV light.. Should have used UV resisant.
    tape on drain line. WHat haapens when the drain gets plugged, and you use "the perfect gas" to clear line and BOOM. the tape lets go. you dont pull nitrogen out , you bleed it out.
    no NO LOSS FITTINGS ON GAUGES… NOT ALLOWED….. MITSUBISHI tells you and teaches you, REMOVE hose from evacation port BEFORE OPENING VALVES silly. these are critacally charged lines.
    I though this rich guy was or is an expert. NOPE. THIS OLD HOUSE WITH A BUNCH OF OLD PROS> NOPE Just a money maker and most projects probably go OVER budget with TOH, due to the cast screwing up the job,… Call a Professional this company isnt that guy.

  38. A 1.5 ton mini split from Mitsubishi installed with electric disconnect is $4500-5600 installed for the garage.

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