Garage AC in Phoenix, AZ

[SteveDixon]

Hi,

Hope this is an appropriate question, thanks in advance for any advice.

I've got a 21 x 22 garage/workshop that I want to cool. I am considering a through the wall 18,000 btu unit. I've insulated pretty well, but you know we have pretty serious summer heat! (Forecasting 108 today). I don't need it cooled 24 hours a day, just evenings after work, and probably 6-8 hours each weekend day.

My question is are there any brands I should favor over others? I've always kind of been a Sears guy, and they obviously have the Kenmores. There are also the various flavors at Home Depot, Lowes, Walmart, etc. What would a smart shopper try to do?

Thanks again.

Steve

[jchunter]

Consumer Reports has done a couple of test reports on small A/Cs.

Here is an alternate solution: I mounted a small evap cooler in my garage and one of the exhaust vents is in the ceiling of my workshop - exhausting into the attic. It is easy to keep the garage and shop at about 80 (a bit more in monsoon season), even though it is not insulated. When one of the cars is brought in, hot as hell, the evap cools it off quickly. As an extra bonus, the wall that separates the garage from the house no longer contributes to the heat load of the house. The cost to run the evap is nil.

[CottyGee]

Another Phoenix dude here. I happen to have done exactly what you're planning to do. You want to oversize! If you don't, you won't be able to get the pulldown you need.

My room is converted from the 10'x20' single stall on my 3-car garage. There is one 20' ~R19 exterior wall (visible from the street), the single-car garage door opening, another 20' wall that's about R23 or so that faces the uninsulated finished 2-car garage, and the back wall is an interior (conditioned space) wall. The ceiling is 8', and R60ish cellulose. And I have a 20 cubic foot top-mount fridge in there from 1990 or so, which of course adds some heat. The room is OBSESSIVELY sealed, tho not foamed (tho I used 48 tubes of calk after framing and before drywall, and the garage-side wall has r13 batts, a radiant barrier w/ 3/4" air gap, sealed w/ calk, stapeled into each 2x4, and 1" of Johns Manville high density foamboard /w its own radiant barrier, and then sheetrock on both sides, textured and painted).

I put in an 11 EER Panasonic 12,000 BTU casement thru-the-wall unit (120v). It works well, tho I might be tempted to do something else if I were to do it again.

If you want something really nice, there's no doubt about it - you want a mini-split. If I were doing it, I'd go 18,000 BTUs, so I could stay cool even with the garage door open a foot or so for ventilation. (It serves as a cigar smoking room, so outside air ventilation is important.)

With my 12,000 BTU unit, I can get it down to the mid-70's in about an hour on a hot day. On a 110ºF day, with the room pre-cooled to the low-70's, I can open the garage door an inch or so and maintain about 78ºF or so.

With a mini-split, it's gonna cost you a TON more - like maybe 5X as much. BUT, you'll gain in efficiency and in flexibility, if you pop for one of the super-slick super-efficient DC inversion units.

If you go cheap like I did, you should probably get a unit with an electronic timer. I can set mine to turn on upto 12 hrs. in the future in 1 hr increments. I have it set to come on about 90 minutes before I'll be home - it's also my workout room.

Also, a dedicated electric circuit isn't a bad idea. That's what I did - a 20 amp 120 v. line. I get zero dimming when it cycles. The 6,000 BTU window shaker I put into our bedroom to augment our pathetic old (undersized) A/C makes the lights dim when it cycles - it's just on a regular shared circuit.

If you have any other questions, please feel free to email me - the addy's in my profile.

[kuryakin]

If it was me, I'd use an inverter mini split. Then you can go oversize, and the variable speed compressor can adjust when the load isn't so large.
Question for everyone else: Does anyone make an inverter through the wall A/C?


Hi,

Hope this is an appropriate question, thanks in advance for any advice.

I've got a 21 x 22 garage/workshop that I want to cool. I am considering a through the wall 18,000 btu unit. I've insulated pretty well, but you know we have pretty serious summer heat! (Forecasting 108 today). I don't need it cooled 24 hours a day, just evenings after work, and probably 6-8 hours each weekend day.

My question is are there any brands I should favor over others? I've always kind of been a Sears guy, and they obviously have the Kenmores. There are also the various flavors at Home Depot, Lowes, Walmart, etc. What would a smart shopper try to do?

Thanks again.

Steve

[tpa-fl]

Panasonic / Sharp seem to make the better window shakers... Depending on what kind of "shop" you have, maybe a mini-split or PTAC (motel style through-the-wall ACs) as long as it wouldn't be too dusty. I'm with the others -- oversize. Chances are that you're not real worried about dehumidification out in AZ and dropping the temperature quickly is most important.

[SteveDixon]

Nice of you all to reply. Couple of dumb questions, going to the mini-split takes it out of the realm of a diy, no? I'm assuming this since I don't think I've ever seen them for sale anywhere, and if half of it is outside and half inside, I'm guessing the system has to be charged after the install? I do like the idea, since it would obviously be easier to patch up small holes if I moved and wanted to take it with me. Everyone is saying oversized, so if I'm thinking 18,000 btu for a space 21 x 22 is that oversized enough? Thanks again for your help.

Steve

[Mstrav]

I think a side draft evap cooler is the best bet for diy. If you leave it off and decide to turn it on at 4 in the afternoon the evap can get it there. the mini split would take forever and use way more power. you also would need an electricion, refer lines (flairing), a drain line and some landscaping for the condensor. In other words you have to pay someone like me to put it in and it might be way out of your budget

get an evap, 110 volt w 2-speed motor. put a hose connector on it for water or do a nice permanent install. you could upgrade the straw pad to cool pad for a little better performance. also the bleed of kit is important cause phoenix water is crap. a $12 in line filter would help a little.

I hate when I drive up the street and see these things hanging of the side of a house and sitting on blocks. do a little re-search and try and keep it behind the fence. as far as relief you will have to crack the garage door every time, or use a relief or up-duct to shoot it out through the attic. this could give you a bonus of lowering attic temps, but there are firewall and moisture isues of going into the attic.

If you are in a nice neighborhood if you have cc&r's then you really wont be aloud to see it from the street.

good luck, matt

[CottyGee]

18,000 BTU will be awsome, provided you've insulated adequately. At least it would with my particular room. I remember than several sites I ran across for sizing window shakers said I should have 6,000 BTUs for my 20x10 room - and that included the additional BTUs for the fridge. So, 12,000 is double-sized. TRIPLE would be loads of A/C, at least for my room.

As for DIY, I dunno. I do recall finding some mini-splits for sale online a couple of years ago, but I don't know if trying to do a DIY is advisable. Probably not.

An evap would suck, IMO. But I guess it depends on how comfortably you want to be, and whether you want to be out there during monsoon season. A swamper works great during the fringe months, but when it's 110ºF, they're not a tremendous relief. And when the dew point pops over about 55ºF, fergitaboudit! Swampers during monsoon are virtually useless. But, clearly a swamp box is super-cheap to own an operate! And you can get into a Shop Cool little tiny swamp box for $200. It plugs into an extension cord and hooks up to a hose.

I dunno what a mini-split would run you, but it's gotta something along the lines of a really nice state-of-the-art LCD TV. Man, I've been jonsing for one of those on a fully articulating cantilever mount for my garage workout/cigar room conversion!

Good luck. If you can swing the bucks for a mini-split, you won't regret it. FWIW, the install is pretty simple from what I've read, so I don't think it should be terribly outrageous to have it done...

[Mstrav]

yes but every time the garage door opens, its gone, in addition the biger window shakes are 220 or 110 with a 20 amp.

I agree above 110 the performance drops, but soon as the sun is down untill 11:00 the next morning awesome.

the mini split or window unit would have to run all the time to keep the walls and interior cooled off, and would have a hard time catching up that day if the garage door is opened.


either way, good luck

[CottyGee]

When the garage door opens, it's not "gone". Sure, the air heats up when the garage door is open. But it's the room itself and its content that holds the cold.

The A/C does not have to run all the time to keep the walls and interior cooled off. That's specifically why you have to oversize. Trust me, I know - I've got a room the same size as the OP is proposing, and a 12,000 BTU window shaker in Phoenix is clearly adequate. Heck - it cools faster than my house does, even WITH my new systems! And with 18,000 BTUs in an inverter-style... Well, that'd be Nirvana!

[jchunter]

There is a huge difference between cooling just the shop and cooling the shop and garage. For the shop only, you could do well with an A/C but when you toss in the garage, you have to contend with superheated cars.

The engines run close to 212 in Phoenix and the rest of the car can be over 150, especially if it has been parked in the sun for any time. I don't know how many BTUs but it is somewhere between a gazillion and a bazillion. :D :eek: A medium sized swamp cooler can deal with most of this heat in a half hour or so but I think even the largest window A/Cs would be incapable of bringing the temp down in any reasonable time period.

[CottyGee]

Ah... Well, I don't put a vehicle into my room, so I don't have to deal with that heat. Good point tho - if the OP plans on putting a vehicle in there and then trying to cool off the space, that'd be a pretty difficult task.

As for engines, the cooling system runs at 200+ºF, but the engine - the exhaust manifold is up around 1,000ºF, and the block is certainly hotter than 200ºF. But you're right - that's one heluva heatload. The air movement of a swamper alone probably does more for that heat than the actual cooling...

[sammy37]

I just put a 23,000 btuh a/c unit in the wall of my 2 car garage, it cools down the garage quicker than the evap, and with the price of evaps going up, you can buy the a/c unit a little cheaper. Most houses here have the electric panel on the garage, so running a 220 volt circuit to the unit is easy.

[jchunter]

Yeah, I hadn't considered the exhaust manifold temp and the catylitic converters have to run even hotter 1800 deg?? ...

When my wife comes roaring in, with flames trailing out the back :D that SUV spikes up the garage temp quickly. I have a downdraft cooler (flat roof) that uses the thick Master Cool pads and it works for quite a while on that car but brings the highest temps down quickly.

Edit: The cooler brand is UltraCool. It comes with 2 speed 1/2hp motor and digital thermostat. I run it on low speed unless both cars come in at the same time.

[CottyGee]

I would think a big cooler would be ideal for that. No way A/C would ever get rid of that heat. The only way to get rid of it is to blow it out of there... There's just too much of it!

[JDrew]

i sugest ductless split system. that way you can get the tonege u want and no duct work ness... with no big holes to install. i go by 1 ton per 400 sf. im new to hvac game (just a rookie) so just a sugestion, i would look into it. not shure who makes the best or cheepest (just a idea) good luck :D

[CottyGee]

i sugest ductless split system. that way you can get the tonege u want and no duct work ness... with no big holes to install. i go by 1 ton per 400 sf. im new to hvac game (just a rookie) so just a sugestion, i would look into it. not shure who makes the best or cheepest (just a idea) good luck :D
1t/400 sf will not be adequate for a decent pulldown. Using that formula, he needs a 6,000 BTU unit, which won't be enough. He's got a little more than 200 square feet.

[JDrew]

1t/400 sf will not be adequate for a decent pulldown. Using that formula, he needs a 6,000 BTU unit, which won't be enough. He's got a little more than 200 square feet.

would u sugest supply fan CottyGee?

[CottyGee]

would u sugest supply fan CottyGee?
Huh? I don't even know what a "supply fan" is. :eek:

I suggested he think about an 18,000 BTU DC inversion mini split, if his pocketbook can handle that.