How many BTU A/C ?

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I would like to put a "window" a/c unit in my shop. What BTU would I need to cool a 24X40X12 high shop ? I would like something that would actually cool it down and shut off, not run constantly to try and keep up. Thanks, Iowa883
BTW : lets say cool it down to 75 degrees , I also have R19 insulation in the walls and blow in 6"thick on the ceiling . If this would help out your calculations.
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Sorry dude a "window ac" is not what your looking for. My home has a 2.5 ton unit package unit and is about the same size as your shop.
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On Sun, 03 Jul 2005 09:42:30 -0500, Iowa883 wrote:

A "window" type unit will not be able to cool that space. Not even close.
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Actually, it can. Not some tiny wimpy unit, but probably two good sized ones. You have two considerations. The overall Btu needed to remove the heat, and also, you must also have proper air circulation. A single unit is not going to move the air needed to make the entire shop comfortable.
I'd consider mounting something like two 15,000 or 18,000 Btu units through the wall. It would probably be cheaper than a single central unit and a duct and blower system. Stop one is to determine the real needs and then figure how the best way to get it.
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On Sun, 03 Jul 2005 16:40:33 +0000, Edwin Pawlowski wrote:

The original poster said "a window a/c". He didn't mention multiple units.

I believe that's what I said, isn't it?
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No, you said:

You offered no reason, no alternatives, no nothing but a simple declaration that it would not work. It can, in fact work and I've seen it done a few times. Best solution? I don't know. It is probably the cheapest compared to a setup with evaporator, blower, remote condenser, mounting pad, etc.
A single unit may even work with some secondary fans for air circulation. I've not seen the actual space so can't give specifics.
I'm sure the OP learned something from your post. Thank you for participating.
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Iowa883 wrote:

I'm not doing the calculations for you, but I can point you to an online tool.
Read up before you make any decisions. The AC shouldn't be oversized for various reasons - it shouldn't shut off too soon.
http://tinyurl.com/acg33
R
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To help you out a bit as the others have chickened out! I have a 24x38x9 foot shop, insulated similar to yours. I bought a used 11,000 BTU window shaker, it was cheap, so I was not out much. It would not keep up unless I let it run constantly. Opening the overhead door to run a vehicle in would cause it to lose ground and not catch up. It did a wonderful job of humidity removal, so even if the temps rose close to 80F it was still more comfortable in the shop than without the AC.
I have since replaced the furnace and added central air to the shop. I went with a 1-1/2 ton condensing unit and it does well. I can leave the doors open, then close the shop up, and it will catch up and cool the shop down to the set temp in a reasonable time.
Now factors as windows, doors, and quality of the doors will have a big effect on BTU needed, so your results my differ from mine. Considering your shop has about 50% more cubic feet than mine I would guess you will need at least 2 ton to cool it. Two ton window units are unheard of so one unit will not do it. Perhaps two of the larger window units, (10,000 - 11,000 BTU), will make a dent in the BTU load. Anything less and I would not bother. You better get out you credit card! Window units of this size are $500 - $600, unless you can dig up a couple used units! E-mail is good. Greg
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Two Ton Window units are not all that unheard of... That's 24000 BTU's of cooling. Back in the 70's we had Sears put in a 28000 BTU window unit for our house to cool the lower level of about 1200 sq. feet. Even on the lowest setting on the hottest day of the year it was almost instant relief from the heat as it would spit out ice cold air out the front. I don't think we ever used the high setting.
The unit was a monster, but fit in a regular window and needed cross braced support arms that rested on the bricks below to hold up the projecting end. Also, it was too heavy to move so it was designed to stay in place during the winter months. Sears sold a cover for the outside to keep the ice and snow out of it. Needless to say, it required a special 240 V. circuit and it was not cheap to run.
Beachcomber
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Thirty years ago you had 24,000 BTU AC, does help much today! They probably exist, but it would be rare! Greg
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wrote:

Not rare at all. Most any place selling window units will have one or two different models in this size or larger.
Steve B.
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Greg O wrote:

I picked up a 11,800 btu like-new for $20.
http://washingtondc.craigslist.org/fur/85580838.html
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Roughly same size shop as ours...
We use a 3-1/2 ton "package heat pump unit"......self-contained....this sits on a pad outside with both ducts running through the wall and into the shop....you might also see this style of unit referred to as "ptac" or "rtu".....
Probly at first glance the 3-1/2 tons would seem oversized for this climate...but...we have heat gains that wildly vary depending on what work is actually being processed on any given day--this being due to some fairly large electric motors, hydraulic units, etc.....
Probly better yet would be if we were to also add a small window unit, and run it more or less constantly in order to help keep humidity under control.
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Iowa,
You have about 1000 square feet. My hoouse is 2000 square feet in myrtle Beach, SC and a 2-ton heat pump heats and cools it just fine. On that basis a 1 ton window unit would do the job for you.
However, if your weather is different than mine, and it probably is, slightly larger or smaller may be required.
To do a proper load calculation, you also need to know the area of the windows, which type they are, which way they face, how big the overhang is and how far above the windows the overhang is. You need the same thing for doors, except direction is not very important. R-19 in the walls and ceilings is better than most home shops, so that helps.
Is this a home shop, or a commercial shop? How many people are in there? How many, what wattage, and what type of lights?
What type of machinery, how much power does it use, how many pieces of equipment, what duty cycle and what hours of operation?
What indoor temperature do you need?
Are you running any exhaust fans or makeup air fans? How many and what CFM?
How tight is the construction?
Lots of variables involved here. If you size it off Square Feet of floor space, even if you allow for ceiling height, you may be way off on your sizing.
Stretch
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Stretch,
Not a big deal, but could you perhaps leave some more attributes in your posts ???
It appears from here as though you had answered the op's question through my post--where in actuality my own hvac situation is fairly well under control....
On the other hand, I'm somewhat flattered if in fact you skipped over the previous posts and then chose mine to be the first one you decided to read.
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On Mon, 04 Jul 2005 00:29:21 -0700, PrecisionMachinisT wrote:

I think the real reason was his complete and utter cluelessness. Not uncommon in those posting to Usenet from Google Groups.
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I think there's probly hope for him, judging from the quality of information he has given in the past.
Otherwise, I wouldn't have even bothered.
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For something like that, consider a mini-split heat pump, especially if you want heat and you don't have access to natural gas (just electricity).
There are lots of manufacturers (mostly Japanese where they were invented), but I just installed a Sanyo for a space in my home that's about 800 sq. feet. I put in a 12,500 BTU unit March 05, have operated it for four months and it works great. You might need the 18,000 BTU unit for the insulation level you have. Check out Sanyo's http://tinyurl.com/b32m6 . It's a more significant purchase (approx. $2500 installed if you buy the unit online and then find a local HVAC installer), but it's more versatile (giving you heat and cool) and produces heat at 1/3 the cost of standard electricity-based heaters.
Don't blindly oversize your unit...cycling mechanical equipment too much reduces its life span....
Andre' A.
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That 40' length is the major problem. You won't get any kind of decent cooling with a single wall unit.
Is it possible to partition the shop into two 24x20' areas?
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wrote:

The biggest 230 volt Friedrich or General Electric that you can find & fits into your window. 28,000 BTU will do. The Friedrich's are much more expensive. The large GE's always cooled well.
http://www.friedrich.com/current/prodline.asp?line=QMHD
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