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Small Shop Air Conditioner Size redux

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Forum topic by TelescopeMaker posted 1489 days ago 2132 views 0 times favorited 14 replies Add to Favorites Watch
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TelescopeMaker

65 posts in 1654 days


1489 days ago

Topic tags/keywords: air conditioning humidity small shop question

I am concerned about rusting my tools and adversely affecting my lumber.
I’m sizing of a window AC unit (thru the wall) for an 11×19 stand-alone shed. It’s got no windows, is partially shaded in the morning, but heavy afternoon sun. Atlanta GA is 80-90 degrees in the summer with 90-60% humidity. It has R13 insulation and rests on a concrete pad.
The air conditioner calculators say that need a 2800BTU AC unit, but they don’t make units that small, so the lowest size is 5000. But they always warn about using oversized units because it may not dehumidify it very well.

I read where people say that the AC will cool it off so fast it won’t have time to de-humify it at the same time. Cool air means it has a chance to condense, and That can be really bad on tools and wood.

How do you handle the humidity for such a small shop or is it going to matter much?

Is 5000 to small? too big? should I opt for 12k btu? Should I look for one that will de-humidfy separately? Any suggestions?

TIA
-Bill

-- Telescope Maker, Woodworker, Brewer, Gizmologist, Gardner, Lawn Mower


14 replies so far

View dmorrison's profile

dmorrison

145 posts in 1896 days


#1 posted 1489 days ago

They do make 2500BTU air conditioners

http://www.cedarwoodfurniture.com/petcool.html

http://www.eicsolutions.com/2500btu-thermoelectric-air-conditioner.php

But I’m sure they are very expensive since they are specialty units.
Buy the 5000BTU unit and a dehumidifier. That combination should handle the heat and humidity

Dave

View MarkwithaK's profile

MarkwithaK

370 posts in 1812 days


#2 posted 1489 days ago

I work in HVAC/R and can confirm that too big of a unit will not remove the humidity from the conditioned space. Just makes it cold and wet, this can also lead to mold. With such a small space you’ll have a hard time finding an economical source of cooling.

-- If at first you don't succeed then maybe skydiving isn't for you.

View TelescopeMaker's profile

TelescopeMaker

65 posts in 1654 days


#3 posted 1489 days ago

Thanks Mark. So what do you think, is a 5000 BTU model too much for a shop that size? Will an extra dehumidifier do the trick? BigBox has has an AC unit for $99. might be worth a shot? or should I get the 6500 BTU model?

-- Telescope Maker, Woodworker, Brewer, Gizmologist, Gardner, Lawn Mower

View MarkwithaK's profile

MarkwithaK

370 posts in 1812 days


#4 posted 1489 days ago

Eh you’re taking a chance either way really. If you look at it this way….2800 btu’s is just less than 1/4 ton of cooling capacity, 6000 is 1/2 ton.

-- If at first you don't succeed then maybe skydiving isn't for you.

View Vicki's profile

Vicki

937 posts in 1978 days


#5 posted 1488 days ago

I don’t know all the math answers, but I have a 12X18 shed on crush r run base with a 5000BTU. I’m on the Eastern Shore of MD. On days when it’s over 90 my little unit can’t keep up. I wish I’d gotten a 6000BTU. My walls and ceiling are insulated.

-- Vicki on the Eastern Shore of MD

View TelescopeMaker's profile

TelescopeMaker

65 posts in 1654 days


#6 posted 1488 days ago

Thanks Vicki. I got a look at your shop pictures, and it’s about like mine. I have to say, I am envious you got as much in there as you do. Thanks for the tip, I think I will go for the higher BTU model.

When I replaced 3 out of the 4 walls last year, I raised the cieling just like you – vaulted like that, and I love it. It is nice to be able to flip a sheet of ply without taking it outside first. I left room on the floor to put down flooring on sleepers with insulation under them. But one thing at a time ;)

-- Telescope Maker, Woodworker, Brewer, Gizmologist, Gardner, Lawn Mower

View Vicki's profile

Vicki

937 posts in 1978 days


#7 posted 1488 days ago

My ceiling is only about 6 1/2 – 7 ft inside, which works fine for me (5’5”), but when taller men come in they have to duck a bit. A higher ceiling would have been nice for when I make a bookshelf or want to stand boards up, but I guess the lower ceiling makes it cheaper to heat and cool.

-- Vicki on the Eastern Shore of MD

View TelescopeMaker's profile

TelescopeMaker

65 posts in 1654 days


#8 posted 1488 days ago

7’ inside. Ahhhh. Ok, now I know I will be getting the larger size. Thanks a million.

You know it wouldn’t take that much to swap that roof out for a barn like roof… Think of the storage ;)

-- Telescope Maker, Woodworker, Brewer, Gizmologist, Gardner, Lawn Mower

View abbyandal's profile

abbyandal

3 posts in 1212 days


#9 posted 1212 days ago

I’m curious about what size you ended up going with? And did you have any luck? For anyone else coming across this problem, there are some good sizing guides here: Portable Air Conditioners

View Bertha's profile

Bertha

12951 posts in 1327 days


#10 posted 1212 days ago

Why not add a stand-alone dehumidifier. I’ve got a small one in my shop (alongside a 5000 BTU window unit) and I haven’t had rust problems (knock on wood).

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View dbhost's profile

dbhost

5378 posts in 1866 days


#11 posted 1212 days ago

Not sure how relevant this is to you, but…

My shop is a small attached garage, 18’x20’, with 9.5’ ceilings, and an additional 5.5’x2.5’ bump out. I have R30 in the ceiling, R10 with radiant barrier on the 2 overhead doors, R19 on the common wall, and nothing anywhere else…

The calculators say I should use an 11K BTU A/C, I am using a 12.5K BTU unit, and have no problems overcooling the space. My humidity is about the same as yours, but my heat is notably higher.

I have only very recently finalized the permanent installation / sealing of the system, so air infiltration from the outside is no longer a problem, dehumidification of the space is pretty easy…

My A/C unit has options for cool, dehumidify, or fan only.

My neighbors has a similar to yours, but different sized shed shop. 12×16, 8’ ceilings, R30 / radiant barrier in the ceiling and only R10 in the walls (the same foam board rig I use on my garage doors, but on his walls… ) He cools with a cheap Goldstar 5K BTU window unit that he picked up off of a Craigslist curb alert (the original owner bought it undersized, and couldn’t take it back, couldn’t manage to sell it etc…). It works well for him with no humidity / mold issues 5 years now… His A/C unit is MUCH louder than mine, but that’s okay…

I would control the air coming in / going out of the building. You don’t want to end up air conditioning the outside world you know!

For what it’s worth, If I had a stand alone building like his 12×16, or yours, I would look for one of the smaller A/C window units that also does heat to knock out 2 problems at once…

-- My workshop blog can be found at http://daves-workshop.blogspot.com

View Bertha's profile

Bertha

12951 posts in 1327 days


#12 posted 1212 days ago

I wish I had opted for the heat pump when I installed my window unit. It was 95F outside when I bought it and heating wasn’t on my mind:)

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View dbhost's profile

dbhost

5378 posts in 1866 days


#13 posted 1212 days ago

You never see heat pumps down here in the Houston area. I have no idea why. I always assumed it had something to do with the humidity…

-- My workshop blog can be found at http://daves-workshop.blogspot.com

View ferstler's profile

ferstler

333 posts in 2154 days


#14 posted 1212 days ago

I have a 6500 btu unit in my 240 square foot shop. It iis mostly in the shade, and has minimal insulation (R5 foam sheets under the roof, with a bit more of that about half way around the shop). I hope to incrementally add insulation as time goes on, having it fully insulated eventually, except for the floor, which is double-layer plywood over a tight crawl space.

In any case, the AC unit works to perfection in there during the hottest and most humid time of year in Tallahassee, which is probably worse than Atlanta. I keep it at 82 degrees when I am not in there (an easy load for the unit), and lower it to 75 when I am working (it runs a lot then, however). So far (two years, with the first year dealing with a shop with no insulation at all), it has had no problems. I also have a separate dehumidifier that I use when it is neither hot nor cold outside, but still humid. I use a space heater in the winter.

Actually, the shop is so small and packed with gear that I do most of my work out on an adjacent deck, but I need the AC and/or dehumidifier in operation when work is not being done, so as to keep the tools from rusting.

Howard Ferstler

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