What AWG for 7.5kw - 36amp heater?


Hello,
I would like to install a Dayton, ceiling mounted, electric heater in my 2 1/2 car garage/woodshop.
The heater runs on 208 or 240volts - 36.5amps - 7,500watts and puts out 25,600BTUs.
What size awg wire would I need for this heater?
The wire will run from the main panel and hard wired to the heater.
Any advice will be greatly appreciated!!!
Thanks, Roy
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If you're running cable, you'll need 6\\2g or if you're running conduit and THHN you can use #8

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A #8 NM cable is good for 40 amps, which is not large enough for a heater that draws 36.5 amps

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What neck of the woods do you live in? Depending on you elec cost, that sounds like a lot of amps and $$$. Have you considered gas or oil heat? Is it feasible for your garage?
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Mikepier wrote:

My workshop is an attached garage and I live in the Seattle area so winters aren't all that bad here. Although, you wouldn't know that by looking outside today! 6 inches of snow and and a low of 18* tonight, this RARELY happens.
The distance from the main panel to the heater would be approx. 20-25 feet. I have room in my 200 amp panel for a 50amp 2 pole circuit to power the unit. This panel also powers the other lights/outlets in the garage as well as the rest of the house.
I got an estimate of $3,000 to have a Reznor type natural gas heater install, this includes the unit and piping gas to the garage. Since the gas meter is on the opposite corner of the house, they would have to pipe it over to the garage.
I talk to my gas/electric utility company about costs and this is what they said. For $100 in natural gas, I would spend $156 in electricity for the same amount of "power". So I realize that gas is a cheaper fuel. Electricity costs me 8.6 cents per kilowatt hour. So to run a 7.5kw heater will cost me $0.65 an hour to run. I'll run the heater 1-2 hours per day, which maybe 4-5 times a week. This is how much I run my 23,000btu kerosene heater now. So in a month I'll pay between $13-26 a month for electric heat. The unit it self will cost me approx. $500 and I will hang the heater and run the wire myself. I just need a qualified electrician to hook the wire to the panel, maybe $100.
So I can spend approx. $600 to have the electric heater installed or $3000 to go with gas. That's why I considering electric heat. If I were in the shop all the time, say 40 hours/week, then I would go with gas.
Roy
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Your electric is about half what I'm paying in CT. In your case, the payback for gas is much too long to consider it.
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RBM (remove this) wrote:

I believe the OP said that the heater was 208/240 volt. Most residences do not have 208 volt service. For 7.5 kW, the 36.5 amp draw should be for a 208 volt service. For a 240 volt service, 31.2 amps. 125% of 31.2 = 39 amps. He could use a 40 amp circuit in that case, assuming no motor. Either way, I would strongly recommend using copper wire, in fact, his local electric code may require copper wire to heating units. A separate disconnect should not be required since the panelboard is in sight of the heating unit.
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Your right, I just looked at his amperage draw and assumed it was for 240 volt

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Roy Fek wrote:

But? Wiring distance is not given. Is it a separate free standing garage/woodshop building? Or attached to house? Questions? Voltage drop/wiring distance? Is/will there be other electrical wiring to that woodshop/garage area? If so is it a separate service or are outlets, garage lights, shop tools etc. also wired to other fuses/circuit breakers on the same main panel? Cos there are some rules about having 'mixed' services in same building?
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