I think it’s time to add a/c to the garage

The garage temps have officially reached "sweltering & unbearable" this weekend, even after attempting to cool it off with fans in the evening. Obviously this will hamper DSM progress if the weather continues - and being summer on the MS coast it almost certainly will. It's time to get some a/c out here.

However, there are a couple complications. 1.) There are no windows in the garage - which I'm happy about from a security standpoint - and there's no available wall space to install a window anyway. 2.) I don't have much extra electrical capacity, so I'll have to use the 20-amp breaker that my lights are on(all LED).

I have a 5'x6' door on the west end, which is where the peak is. I don't use the door much, just ventilation occasionally, or if I need to pull the mower in. So I'm thinking about cutting a hole above it that's just large enough for whatever a/c unit I find & framing it in. The condensation dripping outside won't be a problem because I really don't use that door often, and there's a concrete ramp that will drain the condensation away from the foundation.

I have a couple questions I've not been able to find answers for though:

1. How many BTUs can I run off 15-amps? I'm not finding any specs for any units I've found current draw, so I need to size the unit based on max BTUs.
2. Will I encounter any problems installing it about 7' above the floor? Obviously it'll be drawing warmer air up there, but it'll also disperse farther into the garage.

The garage is stick-frame, vinyl sided, in uninsulated, and about 22'x30'. So I don't expect to cool the whole space to 72*, but if I can get a nice cool spot in the path of the unit, while dropping the humidity & temp a couple points/degrees, it should make working out there bearable. 

In reply to Pete Gossett (Forum Supporter) :

I can run a big room A/C on a 15 amp breaker it cools about 30x30' 

We had a wall A/C unit in our old house that worked exceptionally well at cooling the main area of the house. You could put one of those in and still have full use of your door.

it might be worth looking into what insulating your garage would run you. Is the space already sheetrocked, or are the studs exposed?

In reply to frenchyd :

Any idea how many BTUs that is? That's where I'm having difficulty - selecting a unit that's not too large for my circuit, based on BTUs. 

In reply to dj06482 :

It's bare studs. I know I can't hang insulation directly under the roof, so I'd have to deal with that if I insulate it. It nowhere near air-tight either, so that would mean more effort & expense to correct that.

In reality I'm not out there enough to be worth the expense & effort to insulate it well enough to make a difference, but I definitely need to drop the temp & humidity a bit to be able to work in the evenings out there. 

I added 2 splits to 2 of my garage. 
 

3 car garages each. 24,000 BTU 

local korean guy is Mitsubishi dealer. He brings off brand and install on wekeend 

$1,300 installed with the split included 

I have 4 in other parts of house - oldest Being 9 years old. Very happy with them 

in Asia - splits are everywhere 

this allows me not to waste the central air 

This is what you need:

Mr Cool diy mini split

Costco has them on sale a few times a year. 

I know you can get 12,000 BTU in 115-volt.  Not sure about 15,000?

I'm thinking of doing the same thing, but I have a window.  Priced out insulating the garage, but I'd rather spend a couple hundred bucks and just have a window unit blow cold air on me the few hours during the few months that I'd need it.

Edit:  Yup!  15000 BTU available in 115-volt.

I got one of the delongi 10,000btu portable ac units 2 years ago and it was life changing. 90 degree sunny days are easy to work through.it claims to cover 400sf. I can’t vouch for that, but my 240sf show is well controlled despite some pretty big air infiltration conditions.

for about $250.00 it was well worth it even if it breaks down this year.

I have a window unit mounted in the uninsulated wall of my garage. It was my plan to use it to stabilize the temperature and humidity, as it's also used for painting storage.

The vents and interior of the AC unit collected so much water that it would soak the wall and puddle on the floor, even though I also have a dehumidifier running. 

I wonder if the lack of insulation around the AC unit was a factor, or if something is wrong with it.

I'd recommend insulating it.

My 1065 sqft shop is 2x6 and fully insulated (the only windows don't open, and face North), and stays cooler than my 2x4 house in summer (as long as I don't open a door and let all the heat in).  No A/C.  Summers here approach 100°F

Granted, that's money - but the insulation makes it more comfortable for me (summer and winter), and quieter for the neighbours.

1988RedT2 said:

I know you can get 12,000 BTU in 115-volt.  Not sure about 15,000?

I'm thinking of doing the same thing, but I have a window.  Priced out insulating the garage, but I'd rather spend a couple hundred bucks and just have a window unit blow cold air on me the few hours during the few months that I'd need it.

Edit:  Yup!  15000 BTU available in 115-volt.

 

Any idea if that 15000 BTU is at 15-amps or 20? That's what I'm having difficulty confirming. 

I have a good sized floor a/c unit I got for like $50 during the winter when nobody wants an a/c unit, had it running today and it cools down my office very well, and in particular where my 'thinking chair' is in the office is where the cold goes.   My guess is its 8k btu, 115vac.

Just to throw it out there, a car a/c unit is quite powerful, so its possible to run it off a small motor, or heck park a car next to the shed and idle it with a/c one and pipe into shed.  :)  A prius is good for this plan, as it boots up the gas motor as neccessary to keep the a/c going and bats charged.

Pete Gossett (Forum Supporter) said:

1988RedT2 said:

I know you can get 12,000 BTU in 115-volt.  Not sure about 15,000?

I'm thinking of doing the same thing, but I have a window.  Priced out insulating the garage, but I'd rather spend a couple hundred bucks and just have a window unit blow cold air on me the few hours during the few months that I'd need it.

Edit:  Yup!  15000 BTU available in 115-volt.

 

Any idea if that 15000 BTU is at 15-amps or 20? That's what I'm having difficulty confirming. 

Mr Cool 12k BTU runs on 115 volts and requires a 15 amp breaker. The specs are on the website for all of them. 

If you're planning on living in the house for awhile, insulation might be worth the additional cost. It will prevent the building from heating up as much in the first place, and obviously means the AC has to run less which saves money on utility costs every month for as long as you own the place and also extends the life of your AC unit. It will also reduce condensation issues inside your garage, which should keep projects, tools, and the wooden framing of your garage in better shape.

If you're going to only run it while you're in there it probably doesn't matter, but bigger isn't always better when it comes to ac units. Oversized units don't run long enough to dehumidify properly so you end up with cold clammy air. But again if it's only running for a half hour here or there, it's probably not important to size right. 

Thanks everyone! It looks like around a 550 BTU unit should cool it down enough to be tolerable, especially if it blowing my general direction. 

Pete Gossett (Forum Supporter) said:

1988RedT2 said:

I know you can get 12,000 BTU in 115-volt.  Not sure about 15,000?

I'm thinking of doing the same thing, but I have a window.  Priced out insulating the garage, but I'd rather spend a couple hundred bucks and just have a window unit blow cold air on me the few hours during the few months that I'd need it.

Edit:  Yup!  15000 BTU available in 115-volt.

 

Any idea if that 15000 BTU is at 15-amps or 20? That's what I'm having difficulty confirming. 

The LG unit offered at Lowe's says 1260 watts and okay on 15 A. outlet.  I wouldn't figure on being able to use anything else on that circuit though.

You can always go with the ghetto fabulous Macgyver air conditioning unit.

You need a box fan, small pump, some metal tubing, plastic tubing to run into the ice chest, an ice chest and some zip ties.

Take your coil of metal tubing and zip tie it to your box fan.  Connect metal tubing to small pump, like the ones used for a fish pond, using some rubber/plastic tubing.  Pump goes in the ice chest, circulates ice water through tubing.  You can screw the box fan to the top of the ice chest.  Put water in the ice chest with a few frozen gallon jugs of water floating in it and it will stay cold a long time.  Does not draw much running a fan and a pump, will run off a battery.  Far superior to a mister/swamp cooler.  I put one together when I lived in Texas, gave it to a friend when I left.  You have that thing blowing on you while you are laying under a car it makes the experience much more tolerable.

What about an attic fan up near the peak to get rid of all the hot air up high and it will circulate air in from the outside. It makes a huge difference and is what I did in my old garage. If I kept the doors closed, it was very manageable throughout the day.

You can hook it up to a thermostat and/or humidistat so you don't have to remember to turn it on and off.

In reply to lotusseven7 (Forum Supporter) :

I thought about that, and it would help in certain circumstances. Like last night, the temps had dropped down to the upper-70's & there was a nice breeze, so I opened the 2 overhead doors, the walk-in door on the side, and the service/lawnmower door opposite the overhead doors. With 2-floor fans going + the breeze, it cooled down to outside temps within about 10-minutes. Often though when it's still in the 80's and humid at night - which is about that time of year - a vent fan wouldn't really be enough. 
 

We also have ridge vents on the roofs down here, so by cooling off the space with a/c it'll evacuate the hot air through the ridge vent more quickly. 

When I used to be a mechanic, one shop I worked at was very long, bays on either side, and big doors on either end.  We used to open the end doors, and hose the floor down with water.  A light breeze always ran through the shop, and the wet floor cooled the shop down considerably.

I don't use this in the garage but we have something similar in a bedroom not well served by AC

https://www.bestbuy.com/site/honeywell-450-sq-ft-portable-air-conditioner-white/8478046.p?skuId=8478046

Exhaust hose that would be easier to deal with than installing wall unit, plus portable to move closer to car or workbench.  And could be moved to the house if main AC ever fails.