What size Mr. cool for a 2 car, 12' ceiling garage?

[zimm17]

After getting quotes from HVAC companies of $6k and $7k to mini split my garage, I want to just do a Mr. Cool unit DIY. I already have the 220v breaker that I added when I put in the Tesla charger and generator transfer switch.

Garage is 20' wide, about 25' deep, has 12 foot ceilings. It's build into my house- so I have the master bedroom over the ceiling. However my exterior walls, why drywalled, have no insulation in them. I have insulated doors too.

I plan to let it run all the time- maybe at 78 degrees for cooling unless I'm out there doing work, then I can cool it down even more. Keeping it around 50 in the winter would be awesome too.

What size should I get? 12k, 18k, 24k?

 

[billconner]

How well insulated? I'm converting a 20x23 attached garage to a room and figuring 12,000 but wonder if I'd get away with 9000. I may yet just add a zone to my boiler, for cost.

 

[zimm17]

I don't think it's that well insulated and it faces east so it get the summer sun all morning. The garage doors have windows too that I'm not going insulate over either. I expect some thermal loss, but if it can take the outside 90 degrees and bring it down to 72, that would be awesome.

 

[billconner]

It will take more expertise than I have for this one. Guessing 12 in Virginia. I am in much colder climate - zone 6. I think you're in zone 4.

 

[zimm17]

Googling the Mr. Cool help section- they seem to be recommending the 18k for garages. My brother in law has a 18k mini split in his 2 car garage and it does well.

 

[Toyo72]

I have an 18k in a similar size space, 10' ceilings, but well-insulated. Even in TX heat it seems like overkill, it will keep the temps as cold as you want to be. I would imagine that with 12' ceilings, and partially uninsulted, 18k should work for you.

 

[zimm17]

Doing some more research, I found I do have insulated garage doors so 3 sides and ceiling of the garage are insulated. Only one outside wall is not. Also my brother's unit is a 12k. So now we're thinking 12k should do the trick.

 

[housewolf]

Doing some more research, I found I do have insulated garage doors so 3 sides and ceiling of the garage are insulated. Only one outside wall is not. Also my brother's unit is a 12k. So now we're thinking 12k should do the trick.

That would be similar to mine. My walls and roof are insulated but not my 12’x10’ door. No ceiling with 12’ walls and I have 130 more sq ft. I have an 18K Daiken and it stays comfortable in 100* outdoor temps. I can’t get the temperature below 78* in those conditions but the humidity is below 40% so it’s plenty comfortable

 

[zimm17]

Well I pulled the trigger on the 12k. It's cheaper, smaller, only 120v/20 amp, shouldn't use as much power and I just to need to keep it comfortable, not 70 degrees. Heck I might just use the de-humidify setting for the sake of the tools. It'll be interesting to see how warm it can keep it in winter before I have to plug in my 240VAC resistance heater.

Update: I finished the install- post is here: https://www.garagejournal.com/forum/threads/finally-installed-the-mr-cool-12k-heat-pump.519908/