Window A/C Unit for Garage

[sediener]

I'm preparing for this summer and plan upgrade my shop by adding insulation to the garage door and a window AC. Any recommendations on which brand to get or stay away from?

It's ~25x20 with 12 ft ceiling so I figure 8-10k BTU.

What do you think?

- Steve

[Tarhead]

This is one of those "It depends" answers. It depends how cool you want to keep it and how well you're insulated. I've got a 12,000btu dual hose portable unit. It uses outside air to cool the compressor/condensor so I'm not constantly pulling in hot/humid air and using up the cool inside air to exhaust. I can keep my shop at ~78 when it's in the mid 90's outside with midafternoon sun on one of the long walls. My area is about the same as yours. Just getting the humidity down and using a big fan in addition to the A/C makes a lot of difference.

[mkepke]

I think you're probably low on the BTUs, although Tarhead seems to be having good success @ 12K BTU.

I put a 20K BTU unit into my 24x36x9' shop. It's oversize for a residential application, but in a hobby shop I wanted the extra capacity for a reasonably quick cool down from ambient temperature - I only run the AC when I'm actually in the shop. Not more than a couple hrs a day, I'm afraid.

-Mark

[AndyBarnhart]

Tarhead (I would call you Mark, but that could be confusing in this thread),

Is the filter taped on an extra because of shop dust?

I have been thinking about one like yours with a window adapter. I don't want to do anything involving holes through the siding as we are contemplating selling in the not too distant future.

[Ray Martin]

Steve,

The first thing that came to my mind was insulation. Since the garage is not living space, there might not be much insulation in the walls. If the garage door ever gets opened, you'll have an almost instant change to whatever the outside temp and humidity is. If you only run the A/C unit when you are using the shop, it will take some extra muscle to make the shop cool and dry in a reasonable amount of time. I'm not an HVAC guy, but I'd probably vote for more cooling power than would be called for with a normal room calculation.

Ray

[Tarhead]

Andy,
The filter that came with the A/C unit was just a screen. I beefed it up and it does a good job trapping dust.

[JimmyC]

Steve,
I found a calculator for A/C btu's on the net:

http://www.cooloff.org/sub_cool.html

Dependending on insulation, the size works out closer to 13,00 btu. Remember that you might want to add 10-20% since you are not going to keep it on all of the time.

Good Luck,
Jimmy

[AndyBarnhart]

Originally Posted by JimmyC

Steve,
I found a calculator for A/C btu's on the net:

http://www.cooloff.org/sub_cool.html

Dependending on insulation, the size works out closer to 13,00 btu. Remember that you might want to add 10-20% since you are not going to keep it on all of the time.

Good Luck,
Jimmy

Excellent points! My garage walls are insulated, but the doors are not. I would want to be able to back a car out, close the door, turn it on and have it cool ASAP, though "P=Possible" is likely to be downgraded to "R=Reasonable". In years past, I sometimes put a window fan in the garage to blow air out, left the door into the house open and opened a window in the house. I just do that for a few minutes to bring it down a few degrees and then it will stay about the same if I don't open the big doors.

[sediener]

Originally Posted by Ray Martin

Steve,

The first thing that came to my mind was insulation. Since the garage is not living space, there might not be much insulation in the walls. If the garage door ever gets opened, you'll have an almost instant change to whatever the outside temp and humidity is. If you only run the A/C unit when you are using the shop, it will take some extra muscle to make the shop cool and dry in a reasonable amount of time. I'm not an HVAC guy, but I'd probably vote for more cooling power than would be called for with a normal room calculation.

Ray

I had the builder over to fix a few things and asked him how much of the garage was insulated and he claimed that all walls were insulated. I only wish he added in an insulated garage door. But that is pretty easily fixed.

Originally Posted by JimmyC

Steve,
I found a calculator for A/C btu's on the net:

http://www.cooloff.org/sub_cool.html

Dependending on insulation, the size works out closer to 13,00 btu. Remember that you might want to add 10-20% since you are not going to keep it on all of the time.

Good Luck,
Jimmy

I found one which took into account the insulation of the room, number and type of windows, external walls and their orientation to the sun and it came up with 10k so I was trying to oversize it a bit to 12K. I might go up to 15k just to speed the cooldown since I won't have it on all the time.

Thanks for all the responses.

Steve

[JimmyC]

Steve,

You figured it out the way I would have by adding 20 %. The one thing that I have found over the years is that the new refrigerant doesn't cool as well as the old freon. I had both in my old house and found out that I needed 6,500- 7,000 btus in the same room that had used 5,000 btus (freon). The charts were never changed to account for the change in the refrigerant. On a good note, with the 12' ceilings and the fact that heat rises and cold falls you shouldn't worry too much. 8' ceilings would have more problems.

If you're fully insulated 12,000 btu should work fine. I don't know what the difference in initial cost is, so buy appropriately. You can't have too much a/down here.

Good luck,
Jimmy

[JackLeg]

Steve: I have a 14X25 bonus room office over my garage. It's sheetrocked and insulated, has windows in each end.

I have a 12.500 btu window unit that does all I need even in the hottest weather.

JM2CW

[Jonz]

I have about the same size garage with uninsulated doors, plus a small shop in the back which is where the window mine is mounted in is. There are double doors opening into the garage. Last year I bought a 12k btu Frigidaire unit from Lowes or HD, can't remember, but it cooled it all summer well. I leave it on all the time but set low most of the time. I didn't run excessively or have any problems at all but I don't think I would go any smaller, especially not leaving it on all the time.

Be sure you read review if you can, these new ones are not built like the old ones. I found mine didn't have a condensate drain, but lots of people in reviews complained about it spitting water inside (as did mine) so I drilled a couple holes in the pan and let 'er rip.

[Douglas Robinson]

For very little $ you can purchase sheet of insulation at the BORG and fit it into your garage door. This will help with AC and noise. A very wise investment!

Doug

[Glennbear]

Originally Posted by Douglas Robinson

For very little $ you can purchase sheet of insulation at the BORG and fit it into your garage door. This will help with AC and noise. A very wise investment!

Doug

I totally agree, BTDT :

http://www.ncwoodworker.net/forums/s...ad.php?t=12486