Mini split ac in garage?

[Scoly2803]

Anyone using a mini split system in their garage? Thinking about a 2 ton with heat to end my misery. Summer is to hot and winter is impossible. Right now am using a window unit under the garage door. I have sealed the opening some but just to much hot air gets in.
With the mini split I could leave the door down and have things pretty well sealed.
Any suggestions?
Steve

[Scoly2803]

Sorry! Have reposted in "shop talk"

[pelligrini]

Where are you located? and what's the size of the room? Is there insulation in the walls & ceiling? How about the garage doors?

I haven't used one, I've got a rather large window unit installed in the wall of my shed. Even though it is 15000 BTU for 10x12, it barely keeps up when it is over 100 degrees out. Having just a 1/2 of siding & asphalt shingles on ply doesn't insulate much.

(looks like the other thread got deleted, maybe a mod could move this one)

[LarryG]

One problem with your current setup is that you're putting the colder, heavier air on the floor, which is where it naturally wants to try to go. Helps cool the ankles but does little up where the rest of you is trying to work. Can you move the A/C to somewhere higher on a wall? And then maybe stir the air around with a ceiling fan?

As Erik says, though, if you don't have at least nominal insulation, you're going to be fighting a losing battle.

I recently posed essentially the same question as yours to our mechanical consultant and to a friend who is an estimator with one of the big HVAC outfits here in town. Both recommended a motel-type PTAC unit over a small split system such as the Mitsubishi. The standard motel unit requires a 42" x 16" wall opening, and of course a 240V circuit.

[Uncle Cracker]

Insulation, air infiltration, wall and window exposure, building materials and prevailing shade are all important components in a load calculation. Some could easily cool with a 2-ton (24Kbtu) mini-split or a "window-shaker". Others could not come close. It depends on how the odds are stacked against you. Even with a properly-sized unit, a low SEER could make your power bill go up so much that you wouldn't use it.

Remember also that cooling is only one function of an A/C unit. The other is humidity control. If you are in a high-humidity environment, much of the energy you pay for will be spent on sucking the moisture out of the air, and out of every surface and every piece of absorbent material in the shop (even the wood). This can be especially troublesome if you let all the humidity back into the environment each day. Then your A/C has to start all over drying everything out each time you use it.

I remember back in my A/C design days that I did a custom home in Venezuela that required 10 tons of A/C just to control the humidity, before dropping the air temperature even one degree...

There's a big difference between cooling the space, and just blowing some cold air on yourself to keep comfortable.

[Scoly2803]

Thanks for all the info.
Room: 22x25x8
Temp/humidity: mid 90's and average 50
Attic insul: no Attic above garage is floored. Can I still blow in insulation through a hole in the flooring?
Only one wall with direct sun. Brick outside sheetrock inside
Sounds like I should address the insulation first then see what I might need.
Looked at the Ptac units and though they are not very energy efficient the price difference($1200 mini split vs $650) would take forever to to make up since I only spend about 10 hrs a week in the shop.
Thanks again.
Steve

[jking]

Thanks for all the info.
Room: 22x25x8
Temp/humidity: mid 90's and average 50
Attic insul: no Attic above garage is floored. Can I still blow in insulation through a hole in the flooring?
Only one wall with direct sun. Brick outside sheetrock inside
Sounds like I should address the insulation first then see what I might need.
Looked at the Ptac units and though they are not very energy efficient the price difference($1200 mini split vs $650) would take forever to to make up since I only spend about 10 hrs a week in the shop.
Thanks again.
Steve

Do you mean the space above the attic is living space? Is this an attached garage?

[Scoly2803]

Attached garage and the attic area is floored for storage, not living area.
Steve

[Uncle Cracker]

Thanks for all the info.
Room: 22x25x8
Temp/humidity: mid 90's and average 50 Not great...
Attic insul: no Attic above garage is floored. Can I still blow in insulation through a hole in the flooring? Yes, but uniform fill may not be possible... and it would require a hole for each joist space
Only one wall with direct sun. Brick outside sheetrock inside Might try insulation board on that one wall...
Sounds like I should address the insulation first then see what I might need. Good plan, if climate control in whole shop is the goal.
Looked at the Ptac units and though they are not very energy efficient the price difference($1200 mini split vs $650) would take forever to to make up since I only spend about 10 hrs a week in the shop. Might not take as long as you think...
Thanks again.
Steve

Beyond the above comments in red, consider insulation for any windows and for metal or fiberglass garage doors, and make sure gaps around your garage doors are well sealed. Remember, though, that if you are allowing climate inside and outside to equalize between workshop sessions, then you are basically negating any insulation you add. You will have to turn your A/C on well in advance of a shop session to get it comfortable, meaning your 10 hour/week operating time will go up dramatically.

I have seen used mini-splits on CL and other places for much cheaper than new. High SEER saves money every minute you run it.

My feeling is that in your case, unless you are moving around to all corners of the shop while working there, you might be better off just blowing cool air spot-on yourself to make it more comfortable, and forgetting about cooling off the whole shop.