Window air - how big?

fishman · Apr 17, 2006

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 · Apr 17, 2006

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

EddieWalker · Apr 17, 2006

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 · Apr 17, 2006

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 · Apr 17, 2006

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. · Apr 17, 2006

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 · Apr 17, 2006

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 · Apr 17, 2006

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 · Apr 17, 2006

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 · Apr 17, 2006

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.

fishman · Apr 17, 2006

( Are you concerned with a preference for 120 volt unit or a 240 volt unit? )

Well, I have a 50 amp 240 plug next to one of my windows. I believe it's for a welder (at least that's what I'm telling the wife /forums/images/graemlins/smile.gif) However, It could be pressed into service for an AC/heating unit, since that wouldn't be operational while I was welding.

So I would rather use the 120 if possible. However, I think all of my plugs are on a single 20 amp circuit. I think that's minimal for a couple of 1500 watt ceramic heaters, but it should run either of the AC configurations I'm looking at. I'm pretty sure the 12,000 was 120 . . . and that surprised me too. Anything bigger was 240.

It sounds like the consensus so far is to get the 12k unit as a minimum.

fishman · Apr 17, 2006

( the night before you thought you were going to work on your tractor... I mean your kid was going to ride his bike. )

Darn . . . was I that obvious? /forums/images/graemlins/laugh.gif

fishman · Apr 17, 2006

( 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/smile.gif

Hey, has the ice even thawed in South Dakota yet?

It was 98 at my house yesterday. I would have gone tractoring, but decided not to until I can afford an air conditioned cab. /forums/images/graemlins/shocked.gif

George2615 · Apr 17, 2006

I had frost on my windshield this morning (31 deg.) I think we hit our high today of 58 about 3 hrs. ago. Send some our your heat this way. We are ready for it.

Bird · Apr 17, 2006

( I'm pretty sure the 12,000 was 120 . . . and that surprised me too. )

Yep, surprised me, too. I thought all the ones that put out 12,000 BTUs were 230 volt, but looking at Walmart's website it shows the $238 one as 115 volts and the one with supplemental heat as 230 volts for $398. The first window unit I ever bought was a Fedders in 1960. Fedders and Frederick were considered top of the line back then and Fedders was cheaper than Frederick. /forums/images/graemlins/tongue.gif

Bird · Apr 17, 2006

Oops, forgot to mention, I edited your post to get the red out. /forums/images/graemlins/laugh.gif

Spiffy · Apr 17, 2006

( Hey, has the ice even thawed in South Dakota yet?

It was 98 at my house yesterday. I would have gone tractoring, but decided not to until I can afford an air conditioned cab. /forums/images/graemlins/shocked.gif )

The last of the snow dissappeared about two weeks ago. Judging from I29 last weekend, we are now officially in road construction season which will last until next winter! /forums/images/graemlins/tongue.gif /forums/images/graemlins/grin.gif

Alan L. · Apr 17, 2006

Sigarms, I don't doubt you have forgotten more than I will ever know about air conditioning. However I am an expert on Texas heat.

Every home I have ever seen here in this area that has air conditioning sized "by the book" is grossly deficient in the ability to maintain anything close to a comfortable temperature.

I have a rent house that is well insulated and only 5 years old. The central air unit, which was sized "by the book", absolutely refuses to cool the house if you ever allow it to warm up, such as when the house does not have a tenant and so I set the thermostat on 80 or 85. When I get ready to cool it down to work or show it, forget it, I have to run it all night to cool it down.

My A/C guy recommended a 2-ton central unit for the 879 square feet of well-insulated living quarters I live in, which is inside a metal building. I said give me 3 tons, he said this is too much, it won't run enough to properly dehumidify, blah blah blah.

Guess what, it does run enough to keep it comfortable and has the added benefit of actually being able to cool the house. It still takes a while to cool it down if I let it get too hot, and I need every BTU that I have.

Around here its not just hot in the daytime, but it might not get below 80 at night many nights in the summer. As I write this it is 84 degrees at 10:30 PM in April. Its not usually this hot in April, but many times in the summer it is 90 or more after 10:00. Its very hard to get too much cooling.

The subject of this thread was the need to cool the garage quickly. By the time a "properly sized" unit cools down the garage enough to enjoy the comfort, the day will be over.

stevenf · Apr 18, 2006

fishman, you have all sorts of responses and I couldn't help but give you some real world experience from the sticks. We sold our house in town almost 2 years ago and moved to the ranch into a 100+ year old caretakers cabin that has been added onto multiple times to end at its current size of about 1000 sq ft we have 2 of the GE units that Sams sold about 3 years ago they are 6,500 btu cooling only units it is 76 outside right now and 81 inside its 11:55pm the units have run non-stop since around 6:00pm when the wife got home. Bear in mind there is no insulation anywhere its tin roof and tin sides with beeded paneling on the oldest and t-111 on the newer additions and nothing in between but air and 10ft ceilings in the original part of the house which is 2 rooms and about 350sq ft. If the windows were bigger I'd get bigger units and thru the wall isn't an option its a pole built structure with no studs when the wind blows hard I'll swear it makes the t-111 plywood flap inside. Get the biggest unit/s you can afford, that fit you can always turn them down to medium or low cool its hard to turn them above max cool. Also I've added ceiling fans to all the rooms which helps disburse the cooled air. We have the ability to close off the sleeping side of the house and cool only it with one of the units its 2 small bedrooms and a bathroom probably 400 sq ft at night in semi cool weather say -90 outside you could hang meat in there, during the day 100+ it will keep the bedrooms around 80 during the day if its the weekend and they are left on starting Friday night.
Steve

kensfarm · Apr 18, 2006

I think the 12000 btu unit will be fine.. think about what direction the window faces.. preferrably use the east side window so the AC is not sitting in the direct sun during the hottest part of the day. I cool my whole house w/ a single window AC unit on the 2nd floor.. I use a big fan to circulate the cool air throughout the house.. first floor stays nice & cool too!

I've also seen "mister kits" that spray in front of the coils outside to help cool them & help the AC run cooler.. they use about a 1/2 gallon of water an hour.