Window air - how big?

[fishman]

This is kind of a multi-part question so bear with me please.

I've got a garage that is finished out and well insulated. Well, the door will shortly be insulated and the rest is done. It's a big one at about 600 square feet. We would like to cool it occasionally to let the little one ride his trike and other stuff. Emphasis would be placed on quick cool-down (I think), rather than maintaining a temperature.

Looking at window units it appears I can get a 12,000 btu unit for $238 at Wal-Mart. It says it will cool 575 to 675 square feet of space. Is this big enough?

It uses about the same electricity as two 6,300 btu units that are about $130 apiece. I have two windows and a plug-in under each. Logically, it seems to me that two sources of cold air would be superior to one. However, the smaller units are rated at 100-150 square feet even though they claim to put out as much cooling capacity, combined, as the 12,000 btu unit. Am I missing something here?

Heat is not much of an issue here in TX, and the combo heating/cooling units are pretty pricey. But I could go with that if folks think that a couple of ceramic heaters on occasion isn't a good idea.

Emphasis on low cost is pretty important.

So should I get the two smaller ones, the one bigger one, or something else? /forums/images/graemlins/confused.gif

 

[gsganzer]

I'd get the one bigger one. Why double the maintenance and chance of failure?

 

[EddieWalker]

In my small apartment that I built onto the container barn I put a small 5,000 unit in the sleeping area and an 8,000 unit in the living area.

Combined they did a good job of cooling a small 400 sq ft of living area, but there was a noticible line as I went from one area to the other.

I'm not very knowledgable on them, but there was definiately a range that they lost effectiveness.

They also drip water like crazy on the outside part of them from condensation. It's quite a bit of water and you need to have a way to get it away from the building. I used a the plastic thing you put at the bottom of a gutter downspout on mine.

The price was just silly for how much more they cost with heaters so I bought two ceramic heaters from Sam's club. I forget how much, but they were pretty cheap. Even have remote controls.

We now use them in our new home of 1,000 sq ft to heat it and found we saved $100 a month on our heating bill by not using the HVAC system!!!!

Eddie

 

[dubba]

If you are looking at the one that has the air outlets on the side, I would question if the outlets are as big as the top outlet models. It seems they added another fan speed to force some more cooling out of the unit.

I would second the one unit theory. If you want rapid cooling then I would oversize the unit. My bedroom is the only air conditioned area in the house. I put in a 18k wall unit to cool 560 sq ft. On a hot, muggy summer day it will take approx 1 hour to cool the room to 68 degrees. I think 2 units would be better a bigger area like both ends of the house etc.

On a side note, Maybe one smaller unit would be better. Just take the edge off. I've found that my kid falls asleep faster if he's been hot & sweaty all day /forums/images/graemlins/smirk.gif

 

[Bird]

First a question, John. Are you concerned with a preference for 120 volt unit or a 240 volt unit? I would think those smaller units would be 120 while the 12,000 BTU unit would be 240 (I think that's what Walmart's website shows). My little shop building is only 21' x 25' and I put a Whirlpool ACE124XR window unit in it for both heat and cooling (I see they now call the same unit an "XS" instead of "XR"). Of course their website shows a MSRP of $599, while I paid $517.44 including sales tax at Lowe's. And you'll see on their specs that it's rated at less than that 12,000 BTUs. Just running mine on "low cool" and about halfway on the thermostat yesterday kept it plenty cool enough with 14 people in there for dinner.

At any rate, given the two choices you listed, my personal preference would be for the one larger unit.

 

[Alan L.]

fishman, if you want a "quick cooldown", the 12K BTU unit seems small to me. I'm afraid it will take quite a while to get the temp down, especially if the garage door has been open and its 90 or more in the garage to start with. Those small units have a rough time bringing it down if its already hot.

If you close the door and turn it on in the morning it might be fairly comfortable in a couple of hours.

 

[Freds]

I would think the bigger the unit the quicker the cool down, so would oversize anything I'm looking at. Also, air movement is important, but you could supplement that with a separate fan or two. Large window units can be quite noisy.
Like any air-conditioning, it works first by pulling the humidity out of the air, so it may not be a bad idea to get a dehumidifier and turn it on the night before you thought you were going to work on your tractor... I mean your kid was going to ride his bike. /forums/images/graemlins/grin.gif

 

[Spiffy]

An air-conditioned garage to ride a bike? I guess they don't make kids as tough as they did when I was growing up - "house feels too hot? it's only 100 in the shade, go outside again and play some more until the house feels cool....." and we liked it! /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

Anyway, I'm thinking, put an 12K or better, 18K 240V in the one window and an exhaust fan in the other (or the fan in the roof and a vent in the windows - it must have intake venting somewhere); you can get thermostats that sense the difference between inside and outside temps. If your night temps are under 65 or so, you could really keep the temps down without needing as much AC.

 

[Sigarms]

Oversizing a unit to exceed a load requirement is a "no no" (hey, the good old days, bigger is always better!).

Laymans terms, you have a "stick" V-8 car, does it get better gas mileage on the highway running at a constant 65 mph or in the city where you are constantly shifting going up and down on your speed?

An A/C unit (window) that is too large cycles on and off frequnetly ("wear and tear" on the parts), uses more power to cycle, and will not dehumidify properly due to the quick time to reach temperature.

Without doing a load calulation to determing the correct load, well, heres an educated guess from my qucik reference guide per window unit sizing chart. 600 sq feet, insulated ceiling under attic, 11k-12k BTUS.

Forgot, depending on the amount of people in the space to be cooled, rough estimate, figure 600 btu's per person, may not sound like a lot, but it can add up.

 

[George2615]

I dont think a 1 ton unit is going to give you a quick cool down. If the area is already hot it wont cool down quick. The 1 ton unit (12K) will cool the area if it's insulated well enough and if given time.