A/C unit sizing for BrewHaus

I'm buying a window A/C unit for the BrewHaus today. It's 240 square feet in a warm to hot climate. I'm going to insulate it very well.

I'm looking at a 8,000 BTU unit, but am wondering if I should go to 10,000. Would that be overkill?

Here's the average temps for Austin, Texas.

Economically speaking, from an electricial usage stand point it's more cost effective to have a small unit that runs almost nonstop rather than a large unit that cycles on and off.

That being said it really depends on how you plant to use it. If it's just for fermentation the small unit might be better. But if you plan to try to counter balance the heat from a full boil you might be better off with the larger unit.

I would look for the one that is the most efficient. The higher BTU should cool faster so it would run less often, but that is just a guess.

Take a look at this.

http://www.fedders.com/SelectionGuide_files/selectionGuide.htm

A 7k BTU should be fine, but they recommend 10-20% more BTU's in a warmer climate, meaning you would be looking at a 8k unit. However they state add another 4k BTU if you are cooling a kitchen, and another 25-30% BTU's depending on insulation.

So my recomendation would be to go with a 10k unit.

How are you planning to use the AC unit? To maintain comfortable working temps? Fermentation temps? Lager temps? Are you doing your brewing in the cooled area?

Keep this in mind, the lower the BTU of the unit, the better it does at dehumidifying. If you go too big, it runs for 2 minutes per cycle to hit the set temp but it leaves the room musty and damp. I vote 6-7k.

Bobby_M said:

Keep this in mind, the lower the BTU of the unit, the better it does at dehumidifying. If you go too big, it runs for 2 minutes per cycle to hit the set temp but it leaves the room musty and damp. I vote 6-7k.

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That is relative to the room size, a 6k window unit in a 200sq ft room removes the humidity just as well as a 8k unit in a 350sq ft room. Assuming all other conditions are the same between both rooms.

HarvInSTL said:

Take a look at this.

http://www.fedders.com/SelectionGuide_files/selectionGuide.htm

A 7k BTU should be fine, but they recommend 10-20% more BTU's in a warmer climate, meaning you would be looking at a 8k unit. However they state add another 4k BTU if you are cooling a kitchen, and another 25-30% BTU's depending on insulation.

So my recomendation would be to go with a 10k unit.

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I saw the Fedders recommedation site before I posted. I just wondered if anyone in the South had put A/C in a shed. I'm leaning towards the 10K unit due to the heat and insulation type since it will have 2x4 walls and an open ceiling.

I'm also building a small cold room and installing a 5k BTU with analog thermostat that can be bypassed. Still thinking on the size of that one. I want to be able to keep 20 cornies chilled as well as several cases of bottles.

I think your insulation is key. If you're insulating the hell out of it, you'll probably be able to comfortably cool it with a smaller unit. If you're entertaining, you might have people coming in/out frequently too.....(especially if they're peeing on the tree ) so take that into consideration....

ScubaSteve said:

I think your insulation is key. If you're insulating the hell out of it, you'll probably be able to comfortably cool it with a smaller unit. If you're entertaining, you might have people coming in/out frequently too.....(especially if they're peeing on the tree ) so take that into consideration....

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That's the question. How much insulation can I squeeze in a wall thickness of just under 4 inches? What's the best type of insulation without breaking the bank?

I was thinking of putting paneling up, but after looking at sheet rock, it looks like that will add a level of insulation as well.

this isnt specific to a brewery but we recently added a lot of insulation to our house. We used the solid Styrofoam interlocking panels (extruded polystyrene) and instead of adding it in the walls between 2x4 / 6's we covered the inside wall floor to ceiling and interlocked and sealed the Styrofoam together so there were no gaps. we've done most of the house and laid down insulation in the attic as well since hot air rises. Our heating bill is cut in half. So if you can afford to lose a few inches on each wall this maybe the most efficient way to insulate. And im thinking if you have a lot of people coming and going from this shed using a revolving type door as a kind of air lock would be more energy efficient but Ive never seen a residential building with a revolving door, I dont know how expensive it might be.

The most cost-effective (DIY) insulation will be high-density fiberglass batts. They will be rated at R-13. Your main heat intrusion will be through the 2x4s, the door and any windows. I recommend an insulated steel door and double glazed windows. A 1/2 inch layer of rigid foam on the outside under the siding will act as a moisture and thermal barrier. Foam (1-2") is also a great idea under the roofing, if you aren't finishing & insulating the ceiling.

And a good vent system while you are brewing.

If you're building the cold room anyway, you could use the same A/C unit for both spaces. Think of the cold room as the ice chamber in the son of fermentation box and the general brewing room as the ferm chamber. The controller in the cold room keeps it at your 40F set temp or whatever it is then you can have a fan come on to move that air into the main room when necessary.

Not a bad idea, but when you goto pump cold air out of the cold room your temps are going to fluctuate. Plus you will have to put in some kind of vent system that will allow air to come into the cold room when the main room needs to be cooled and closed otherwise.

Too bad Austin seems to be too humid for swamp cooling.

david_42 said:

The most cost-effective (DIY) insulation will be high-density fiberglass batts. They will be rated at R-13. Your main heat intrusion will be through the 2x4s, the door and any windows. I recommend an insulated steel door and double glazed windows. A 1/2 inch layer of rigid foam on the outside under the siding will act as a moisture and thermal barrier. Foam (1-2") is also a great idea under the roofing, if you aren't finishing & insulating the ceiling.

And a good vent system while you are brewing.

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I have an insulated steel door and the window is doubled glazed low E. I will insulate under the roofing. I'll check into the rigid foam siding today. Good idea. Thanks.

Virtuous said:

Not a bad idea, but when you goto pump cold air out of the cold room your temps are going to fluctuate. Plus you will have to put in some kind of vent system that will allow air to come into the cold room when the main room needs to be cooled and closed otherwise.

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Exactly.. and I don't think it would be a problem.


Let's say the cold room controller is set to 40F with a 3f dif. Your main room fan controller is set to 74F with a 3F dif. Your main room hits 77 and fan kicks on, the supply and return swing louvers open. You'll end up raising the cold room up to say 65F pretty quickly and the A/C would have long kicked on by then. The fan will run until the outside room is down to 71F and shut off. Meanwhile the cold room would probably hover between 50-60 while the A/C is running. Once the circ fan shut off, it wouldn't take very long to get it back down to 40F. The mass of beer in all the kegs in there wouldn't fluctuate from 40f more than 1F if that.

It's kinda like opening the door on a refrigerator in a tiny room for a short time. The cold box recovers quickly.

Worry more about the insulation in your roof than your walls, you'll have much more heat loss/gain there than you will in your walls.

sigmund said:

Worry more about the insulation in your roof than your walls, you'll have much more heat loss/gain there than you will in your walls.

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+1 on that, a blazing Texas sun beating down on your roof.

I got a 300 sf addition that isn't on the main HVAC (3.5 exposed walls) and I went with the 10,000 btu Fedders wall unit and it does a great job (100+ Jun-Sep). Not the humidity you get here but I'd go 10k if I were you.

http://www.fedders.com/catalog/appliances/roomac/6000_1200_BTU_Fedders.htm

Not sure what your plans are for heating if any but you may consider one of their heat/cool models for winter use. I didn't go that route as I have a wood burning stove in my man cave. If I recall; the $ jumps pretty good though.

http://www.fedders.com/catalog/appliances/roomac/Heat_Cool_Fedders.htm

Maybe already in your plans but build the space in the frame/wall instead of taking up a window where you can watch those deer eat your spent grains.

Oh and if you go Fedders, there fan runs continuously; just the compressor cycles. Doesn't say anywhere that's the case so I thought mine was busted until I called them .

I went with the 10K LG unit from the Depot for $199 and I bought 2 5K units for the cold room at 99 each (I have a spare, since I am cutting a perfect hole for it). I'm putting foil backed OSB for the roof and I'm adding a layer of OSB for the sides, followed by a Tyvek wrap before the siding goes on. Picked up the lumber for the 6'x12' porch today too as well as nails and truss straps.

So far, I'm in about $3,100 including the 3 A/C units. Still gotta insulate it, add the venting system, and wire it with a 100 AMP service.

***BierMuncher pulls up a folding lawn chair and a porta keg to watch Edwort sweat his what-nots off....BierMuncher does so love to observe others at work...***






By the way...that RyePA I snatched....priceless...

Sounds like you're in really good shape and still well within your budget, IIRC. I can't wait to see this thing come to fruition!

I'm assuming you've had a bit of sticker shock on the foam panels; I know I was shocked when I bought some to make my lagering box... That stuff was 1/4 the price 10 years ago.

and wire it with a 100 AMP service.

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Good God man, what are you running in there aside from the AC's?!? You can run an entire house off of a 100AMP service panel. I would think that 60 would be more than sufficient.

MA_Brewer said:

Good God man, what are you running in there aside from the AC's?!? You can run an entire house off of a 100AMP service panel. I would think that 60 would be more than sufficient.

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yeah, 60 AMP will have to do. That's what I have available in my main box at the house. I guess I'll get by.

BierMuncher said:

***BierMuncher pulls up a folding lawn chair and a porta keg to watch Edwort sweat his what-nots off....BierMuncher does so love to observe others at work...***






By the way...that RyePA I snatched....priceless...

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You lucky bastage, since myself and a couple other people were using pin locks we got bumped to the back of the line. Take a wild guess what happened when they were filling up the last ball lock.

No free Rye PA for Anthony.

HarvInSTL said:

You lucky bastage, since myself and a couple other people were using pin locks we got bumped to the back of the line. Take a wild guess what happened when they were filling up the last ball lock.

No free Rye PA for Anthony.

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Oh dude....

That sucks. I'd have never imagined that they'd run out. That fermenter was still sitting at 400+ gallons when I left.

I guess it was my lucky day...but I feel bad.

MA_Brewer said:

You can run an entire house off of a 100AMP service panel. I would think that 60 would be more than sufficient.

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I, in fact, do run my entire house off of 100AMP. 1550sf 2-story with 850sf basement. *teardrop*

Because I need to put so much into my house (roof ASAP, central air ASAP, broken windows ASAP, siding 4-10 years, electric wiring 4-10 years) I don't think I'm EVER going to get my brew shed. ._.

HarvInSTL said:

You lucky bastage, since myself and a couple other people were using pin locks we got bumped to the back of the line. Take a wild guess what happened when they were filling up the last ball lock.

No free Rye PA for Anthony.

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Time to dump the pin locks and convert! Just go to the light!

BierMuncher said:

***BierMuncher pulls up a folding lawn chair and a porta keg to watch Edwort sweat his what-nots off....BierMuncher does so love to observe others at work...***






By the way...that RyePA I snatched....priceless...

Click to expand...

Not yet buddy, or, I want mine