BTU calculator

Dale and Janet

OK, thanks for all the input on our garage heater choice (see post some ways down). Still trying to determine appropriate BTU capacity. Used a BTU calculator on the web, and it suggested about 14500 for 23X23X10, average insulation. But the default setting under "tempature rise" was "10". If I made that entry higher, say "20", the BTU result shot WAY up. So does this mean that 14500 BTU will raise (and hold) the temperature ONLY 10 degrees in some certain period of time? (That will not do, especially given the <20 degrees we've had last night). What exactly does the field for "temperature rise" on the BTU calculator mean? Thanks

scrook_2

what calc & where?

Perhaps it is detla Temp inside to outside?

Ray Landry

A quick calculation used in the feild is length x width x height x 5. Using that I came up w/ a demand of 26450 BTU's. Any local plumbing supply house can calculate your btu load, I think it's generally free too.

I would guess that constant of 10 for the temp rise was every hour it will raise the room temp ten degrees.

Ray Landry

A quick calculation used in the feild is length x width x height x 5. Using that I came up w/ a demand of 26450 BTU's. Any local plumbing supply house can calculate your btu load, I think it's generally free too.

I would guess that constant of 10 for the temp rise was every hour it will raise the room temp ten degrees.

Dale and Janet

thank you Ray

as you may or may not know from our previous posts, we've gotten a 17000 BTU electric heater, but it's still in the box until I can get a better handle on whether it will be adequate and efficient (in the cost-to-operate sense). Your observation leads us to believe it may not be adequate. Thanks again.

Mijola

For your attached gargage, how many walls do you have in common with the main house? This will affect the amount of heat loss from the garage.

Dale and Janet

common walls

one, through which there is an entrance door. The remaining three are R-13 with 5/8 drywall, and the overhead door is something like R-7, an insulated Clopay model from HD. Any insights?

Mijola

Based on NE Ohio, I assume your outdoor design temperature is 0 degrees F (meaning the outdoor temperature is above 0 degrees 99% of the year). So, if you want to keep your garage at 70 degrees inside, your delta T between the inside and outside is 70 degrees. If you multiply the area of the walls by 70 degrees, then divide it by the R value of the walls, that will give the heat loss through the walls. Use the same logic for the roof and the garage door. You do not need to account for the common wall, since there is very little, if any, temperature difference. Add a 50% safety factor to account for any air leakage you may have through the walls (there will be some), and use this number as the BTUH output capacity that you need from your heater.

Based on what I have followed throughout your message traffic, I would say that the 5000 W heater that you have already purchased will work just fine.