# heater btu question

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• posted on December 9, 2004, 12:07 am
Is a 30,000 BTU heater big enough for a two car gar-shop with 10 foot ceilings? This would be a ventless natural gas heater.
OR....
Does anyone have a link for a conversion table for BTU needed per square (cubic?) foot?
Thanks!
Joe C.
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• posted on December 9, 2004, 12:16 am

Depends on where you are and how well insulated your building is.
-j
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• posted on December 9, 2004, 12:26 am
I heat a 630 cubic foot, three car garage with 11 foot ceilings with a 24,000 btu kerosene heater and a ceramic heat cube. The garage is pretty well insulated including foam backed door panels. It also shares a wall with the house.
On moderated days (around 40 degrees) I can usually let the kero heater run for an hour or so, turn it off and the cube can keep up.
On really cold Kansas days (0 to teens, both units can keep the temp around 50- 60 depending on wind.
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• posted on December 9, 2004, 1:07 am
RonB wrote:

Hmm. 630 ft³ ÷ 11 ft = 57.27 ft². If your garage were square then it would be about 7.57 ft on each side...
What kind of cars are you parking in there?
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Morris Dovey
DeSoto Solar
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• posted on December 9, 2004, 4:52 am

Maybe RonB is a Shriner?..*S*
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• posted on December 9, 2004, 9:46 am
The same as SK's truck, but without the trailer?
Morris Dovey wrote:

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• posted on December 9, 2004, 6:10 am

Ron,
I think you might have dropped a zero on that cube. Wouldn't 6300 cu ft be more reasonable for a 3 car garage???
Tom Veatch Wichita, KS USA
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• posted on December 9, 2004, 5:05 pm
Tom Veatch wrote:

Joe
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• posted on December 9, 2004, 12:43 am

Depends on a few variables! How well insulated, quality of the doors and windows, outdoor temps for a start. But, a well insulated garage should heat fine with 30,000 BTU. I have a 24'x38' garage with 10 foot ceilings that I heat with 50,000 BTU, insulation is good, but could be better, but the furnace is plenty large. North Dakota climate. I would avoid a ventless heater though. Our area they are not even allowed by code. Greg
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• posted on December 9, 2004, 1:38 am

which means temps down to zero (occasionally, more like teens), ceiling of the garage is drywall with 12" of insulation blown in, but the walls are bare brick. Door is relatively well insulated. Garage dimensions are: 18' X 21' with 9' ceilings (not 10" as in original post). I wouldn't do ventless with kerosene or propane (do they even make them?) but how about with natural gas?
Thanks again,
Joe
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• posted on December 9, 2004, 3:25 am

IMO, not going to make it. I have that sized heater for my shop (propane) , about the size of yours. I get a 30 degree temperature rise, so when it is zero outside, plan on 30 inside. From the end of December until the end of February, I do very little in the shop. Add some insulation on the walls and you will get better performance. If I was buying a heater now, I'd go for a variable model from 30 to 80,000 Btu. If I was going to spend every day out there, I'd install a small furnace. Ed
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• posted on December 9, 2004, 4:11 am
wrote in message

Geez Ed, here I go agreeing with you again! (ABPW!)
To the OP Those bare brick walls are going to be a killer for heat. Some 2x2 furring strips, some 1-1/2 styrofoam, plastic, and a few pieces of sheetrock would help alot! When you were talking ventless I was assuming a ventless wall mount heater. You can buy wall mount vented heaters too, propane or natural gas. I still caution against a ventless heater. I think you will need at least 60,000 BTU, maybe more unless you add some insulation to the walls. Although a 30,000 may buy you some comfort on most days. A Reznor or Hot Dawg heater is really the way to go. Greg
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• posted on December 9, 2004, 7:56 am
Greg O wrote:

Hi Greg. What part of N.D. are you in? I see that Menards has the ventless type heaters in Fargo. I'm surprised they can sell them if they are not code rated. I think that Harbor Freight has them as well. Ciao',
Paul
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• posted on December 10, 2004, 12:20 am

Fargo. Not allowed in the city of Fargo. Out in the sticks you can kill yourself anyway you want, so they can sell them. Here in the big city we have codes to prevent you from doing that! Just mention non-wented heaters to the mechanical imspector and watch him get excited! Greg
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• posted on December 10, 2004, 8:29 am
Hmmm. I'll have to check the codes here in D.L. I was thinking of getting one for my shop. One thing I don't like (as mentioned elsewhere in the thread) is the high condensation you get going from 20 degrees up to 65 or so with the gas heaters. I have a couple of electric heaters now, but usually blast a small gas heater to preheat the shop quickly. I run around wiping everything down as it heats up to fend off the rust. On another aside, I just got an email from the wife & it looks like we're getting a Menards in D.L. Woohoo! Not a Rockler or Woodcraft, but pretty big doin's for us.
Cheers,
Paul
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• posted on December 10, 2004, 3:25 pm

Condensation is from non-vented heaters, vented heaters do not create condesation in the shop as it is vented outside. As for Menards, I rarely go there! The one in Fargo is so damned busy all the time it takes over an hour to get some sticks if you get them out of the yard. I hit the local yards, Simonsons, Crane Johnson. Most of the big box stores' prices are not any better than I can get else where, and get help that actually knows their product too. I may hit Home depot, Lowes or Menards on a sunday when the locals are closed. If D.L. gets a Menards, you will lose the local lumber yards, perhaps a hardware store too! Greg
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• posted on December 10, 2004, 3:56 pm
Greg O wrote:

This is true, and I generally support the "small guy" over the big box retail, but there is an attitude at some of the places in town where if "you don't like it you can go to Fargo". I am also willing to pay more for service, but do not like being gouged. If the service is not there, then you may as well go for price. I agree totally with you however and the places I do frequent that give me service may be hurt. That to me would not be worth the convenience and slightly lower prices. I guess I just want to have my cake & eat it too. Also thanks for the tip on the vented /nonvented condensation problem. I guess I will look into punching a hole in the wall. Not really a big deal I suppose
Paul
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• posted on December 11, 2004, 2:20 am

If you are looking for shop heat, consider a Modine Hot Dawg or a Reznor UDAP heater. I think you can buy the Hot Dawg heater at Mills Fleet Farm for about \$400. Also the venting will add to the cost too. In the end instead of just a convection wall heater you get a heater hanging from the ceiling, out of the way, with a fan to help circulate the air. It depends on how big of shop you are heating as to the size of heater, of course! Greg
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• posted on December 13, 2004, 7:06 am
Greg O wrote:

I'm only going to be heating a largeish single car size garage. I'm not sure right off hand what the measurements are. It is well insulated, but being a garage, there are areas around the door etc., that show some light. I will check into the Hot Dawg and see what size they recommend. Sounds like I will need a good heater. The wife said snowing, blowing and 50mph gusts. Not nice...
Paul
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• posted on December 14, 2004, 1:21 am

1-1/2 car garage should heat very well with a 30,000 BTU Hot Dawg. That is the smallest they make. Weather strip the door well to cut down on the drafts. I assume the overhead door in insulated?
I have a 50,000 BTU residential furnace in my garage. It is a model that can be laid sideways so I hung it near the ceiling, added a air filter and a bit of duct to it. My garage is 24 x 38 feet, and it heats it well, t-shirt weather all year 'round. Plus I also have AC connected to it all to, so in those hot humid, misquito filled evenings I can close the door to stay bite and sweat free! Greg