How to Install a Wall-Mounted Mini-Split | Ask This Old House

In this video, plumbing and heating expert, Richard Trethewey explains the purpose of a mini split ductless air conditioner and the process of getting one installed.

How Does a Mini Split Work?
It’s simple physics—heat will always transfer to cold. Using something called an inverter, the mini split is capable of capturing heat through a cold line of refrigerant and moving it to the desired location.

In the summer, the heat is extracted from the air in the house and dumped outside, making it cold. In the winter, heat is scavenged from the outside and pushed back into the house. This creates heating and cooling year-round.

Because there are no ducts to retrofit, the system is simple for a pro to install. And it provides excellent dehumidification, quiet operation, and great efficiency. Need to adjust the temperature or turn the unit off? Just use the remote control.

How Much Space Can a Mini Split Cool?
A single air handler can heat or cool up to 1,000 square feet, depending on the climate and system size. (In heating mode, it functions down to minus 13 degrees F, not a problem where you live.)

For larger spaces, up to four independently controlled indoor units can connect to one condenser, for the ultimate in zoned comfort.

Time: 4-6 hours
Cost: $2,000 - $15,000
Skill Level: Professional

Where to find it?

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From the makers of This Old House, America’s first and most trusted home improvement show, Ask This Old House answers the steady stream of home improvement questions asked by viewers across the United States. Covering topics from landscaping to electrical to HVAC and plumbing to painting and more. Ask This Old House features the experts from This Old House, including general contractor Tom Silva, plumbing and heating expert Richard Trethewey, landscape contractor Jenn Nawada, master carpenter Norm Abram, and host Kevin O’Connor. Ask This Old House helps you protect and preserve your greatest investment—your home.

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How to Install a Wall-Mounted Mini-Split | Ask This Old House

[nhyankee]

I am the Electrician on this job. Oddly enough my ladder got more air time than I did. At least my work is tight.

[matthewkeethe]

I just finished renovating my house. I got 3 quotes from hvac contractors to install these mini splits. I was in shock by the price. For a 3 zone air handler hooked up to 1 condenser with a very easy run [less than 20ft] per line set, I was quoted up to 16K! The lowest proposal was 11, 800. That was also with all of the walls open.My advice to anyone wanting these is do a lot of homework on installation and just buy the unit yourself. Doing so saved me at least 7-10k

[mneraasen]

Perfect timing!!! I have finally takes my mother into getting one ☝️

[EricVandenAkker]

I love my mini splits. Added one for the master bedroom, primarily for cooling.
I also converted a three seasons porch into a full time office, and I am using a Diakin min split for heating and cooling, year round in Wisconsin.

[trustbuster]

These things are crazy efficient. If you have been running a bunch of window units all summer you will be shocked at how much your electric bill goes down when you have these installed. You can also get bigger ones that flush mount into the ceiling for larger spaces. The only rub is that when you use them in winter they do still start losing their heating efficiency/effectiveness when the temp drops below freezing. You can get ones that are specially designed to work better in cold weather, but for very cold climates you are still likely going to want some form of back-up heat.

[Kittycat]

Had them when I lived in Hawaii. They were great!

[KrysDlite]

I can’t wait to get one installed in my bedroom! I’m so tired of burning up on the 2nd floor. Thanks for this video, I appreciate all the info. ☺️

[fuffoon]

I installed my split myself and called a pro to launch it properly. Yesterday was the first truly hot day since having it. What a pleasure. Outside 92, inside 76. First airconditioning I have needed in 25 years just to sleep.

[artkyger]

Nice video. Thank you. Think I am going to have to do one of these in my house due to rodent contamination in the forced air unit and crawl space.

[simplygregsterev]

One of the best upgrades I made to my house that lacked a central HVAC system. Had it professionally installed as I didnt feel comfortable buying one of those DIY kits. The heat pump is absolutely silent and mounted to my brick with a similar bracket. You don't even hear it running outside unlike all neighbors heat pumps which sound like something off a battleship. If you go the installed route get multiple quotes and get an installer that understands your needs/ expectations. Not someone who wants to make it as easy as possible for them. Carrier Infinity Ductless system.

[walter.bellini]

Really a great video!
I live and are the owners of a 2 family house in NY that uses regular window A/C for the summer and brand new Pearless Steam Boiler for system radiators. Problem has always been that the steam radiators get hot in the lower apt but the upstairs apt is always cold. In order to make them comfortable we have to almost turn on our A/C during the winter. So we were thinking about installing a split system for the upstairs APT.

[NicholasLittlejohn]

It's the way to go for sure. Huge comfort and energy savings. 👏🏼

[johnjerrehian]

Mini splits are the best! Another added benefit is when it is time to replace the units it a lot less money and easy to do.

[uradeutsch]

i had these in my rooms in my apartment while i lived in japan and i loved them. i'm now back in the States and have just the normal 1 central AC for my whole townhouse. it works fine except for my 1 computer room on the third floor. rest of the third floor is pretty fine, it's just the computer room with my PC pumping out heat combined with the fact that heat rises.

thinking about adding a small one of these to that room as I spend a lot of time in there. they really are great

[themessiahssecondassembly]

To my way of thinking, condenser's should always be set two to three feet above the ground on a regular base's, especially if you have a heavy snow or major leaf problem. The damage done by winter snow year after year along with salt, like any other metal product is really bad for the long term use.
The leafs should be enough of a reason because you are constantly having to clean up the unit to keep it from being plugged up for good ventilation through the evap and cooling of the compressor. Just makes more sense to me, but it does make installation and servicing a little harder, which is why I think they always put them on the ground.

[hazamc]

Very Good Video.
Thanks for sharing.❤

[mufasaiam]

These Split AC units are the future. We've been using them in Asia for decades and couldn't ask for anything better

[lambrinos]

Richard, you're the best! You explain things so well.

[kingofthecarwashes]

This is a really good way to cool off your house if you don't have central air conditioning, I would think these units are best for small spaced areas like garages, workshops, shops, and much more, when I grow up I am would like to be an HVAC technician.

[abdul-aziztaha]

Good job...am doing this kind of installation my self since 2008