What size A/C unit for shop?


I am in the process of building a general purpose / woodworking shop.
Location - Baton Rouge, LA - high humidity area
Two small 3' wide X 2' high insulated windows facing south very near the top of the walls.
Size will be 20' X 22' (440 sq. ft.) with 10' ceilings.
Walls will be 4" - drywall / R-15 batt / 7/16" OSB / Hardie Plank.
Ceiling will be - drywall / R-49 batt / to open attic.
Attic will be well ventilated with (2) 14" turbines.
Roof will be shingled with Solar Board for roof decking.
Any suggestions appreciated . . . . . would really like to hear from someone living in this climate with a simular sized insulated shop . . . . Steve
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On Tue, 23 Aug 2005 20:03:02 -0500, "Steve DeMars"

My guess, 9,000BTU +/- 1000 A big window shaker.
That would work in Florida
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wrote:

the
someone
Just for comparison, I live in Maine, and in a 32 x 24 with 8ft ceilings, a 10,000 BTU window unit BARELY cuts it on 85+ degree days with tools running. Should have gotten the 12,000.
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I live in Austin, TX. I had a 12000 BTU portable A/C in my garage and it didn't do squat. I have a 24000 BTU mini split on order.
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wrote:

You don't figure that garage door was losing a lot of your cooling do you? What was the R factor of your walls?
The OP is talking about a pretty tight room. In Louisiana humidirty is an issue and oversizing a unit will just make it worse.
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I had cellulose blown into all walls. The door is insulated and has weathstripping on all sides. The ceiling has 6"-12" of insulation depending on location.
I imagine that the garage door was still leaking some but I had it about as insulated as I could get it.
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wrote:

You have something creating a big heat load. The rule of thumb for old Florida CBS houses, virtually no insulation and leaky awning windows is a ton per 400- 500 sq ft..
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I do have a gas water heater in the garage. It is in a closet but the door and closet are leaky. I have wondered if causes it to stay warm.
The funny thing is that in the winter I can easily heat the garage to a nice level using a $15 heater the size of a shoe box. But I can't cool it for anything. That's why I went overkill on the 2ton A/C.
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Yep! Ever been in an adult beverage establishment that was nice & cool but felt "clammy"? Too big an A/C unit, chills & stops cooling without taking the humidity out of the air. I'd a lot rather have a slightly undersize unit that may not get quite as cold as you want, but runs constantly, sucking the humidity out of the air. The low humidity will make it feel cooler than it is.
--
Nahmie
The greatest headaches are those we cause ourselves.
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HVAC pros use a Manual J for calculations. There are some web sites that do have some basic programs that will be close. http://whirlpoolcoolingcalc.e-net.com/calculator/default.asp
I don't know what assumptions they make for insulation, window type, construction type, etc. There may be more accurate ones than this.
--
Ed
http://pages.cthome.net/edhome/



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Ask whoever is sizing the AC to consider that you will be running tools such as a dust collector and airfilter plus significant lighting while trying to cool the shop. The motor and lighting load is significant. All of it will become heat within your shop.
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The number of lights and other electric motors that will be continuously or intermittently running will have a drastic effect on your heat load. If you are running an air cleaner and a dust collector continuously the electric motors that power them will give off considerable heat that the air conditioner will have to remove to bring the temperature down. For example, when I run a 3 hp Unisaw, a 3 hp dust collector, a 1/3 hp air cleaner and 6 eight foot forusent light strips at the same time, that will overwhelm a 18,000 BTU air conditioner. My shop is located in West Texas near Abilene. My shop is in a metal building with 3 inches of insulation on the walls and ceiling. It is 24' X 24' and the air conditioner will maintain a 72 degree temperature with these appliances turned off and heat up rapidly if everything is turned on at the same time when the outside temperature is above 80 -85 degrees.
Also, the 12" planer, and the 1 hp drum sander when used for extensive periods of time will heat up the shop.

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wrote:

3400 BTU per 1000 watts
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Sounds like you are taking care of insulation concerns. I personally think sizing it for equivalent residential floorspace would put you in the ballpark. The machines in my shop certainly won't generate any more heat than our range, hair dryers, microwaves, televisions, etc. Also, unless you have a lot of helpers hanging around the body-temp effect should be less.
BTW, I live in south central kansas. Admittedly a little less humid that your neighborhood. However 100 degrees and mid 70s humidity is common. Today is expected to hit 90/90 (degrees/humidity). Come on October.
Buy lots of filters.
RonB
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Steve
I just built a 26'X36'workshop in Lake Charles, LA. Ceilings are 8 ft around perimeter with 18'X 20' tray 9'6" high in the center. I went with a 2 1/2 ton heat pump on the advice of my a/c guy. He had originally suggested/priced a 2 ton unit, but changed his mind after seeing the shop. I got electricity turned on at about 4:30 yesterday evening, but had to leave for work this morning. Unfortunately, I'll be gone for 21 days, any performance data I could give you would probably be too late.
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