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# elec baseboard heater and wire guage

#1
04-04-05, 11:11 PM
DomatTL
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elec baseboard heater and wire guage

I amn in the process of putting two 8 foot elec baseboard heaters in my family room. I have run 12/2 from the panel box to the heaters. My question is will the 12/2 carry the load of each heater independently note I will be using heater mounted thermostats. Any help would be greatly appreciated and almost forgot I bought the heaters used and therfore lack paperwork but I believe each heater to be 4500 watts. Thanks!

#2
04-05-05, 06:28 AM
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You have a problem. You don't have anywhere near the capacity in a single 12-2 wire to power 9000 watts.

#3
04-05-05, 09:02 AM
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Originally Posted by DomatTL
I amn in the process of putting two 8 foot elec baseboard heaters in my family room. I have run 12/2 from the panel box to the heaters. My question is will the 12/2 carry the load of each heater independently note I will be using heater mounted thermostats. Any help would be greatly appreciated and almost forgot I bought the heaters used and therfore lack paperwork but I believe each heater to be 4500 watts. Thanks!
Most of the baseboards I'm familar with are designed and built for 250 watts per liner foot. That means you have a total of 4,000 watts.

4,000 watts/240 volts = 17 amps X 1.25 = 21 amps. A 30 amp circuit using #10 AWG wire is required.

What is the square footage of your family room?

#4
04-06-05, 09:45 PM
DomatTL
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Originally Posted by thinman
Most of the baseboards I'm familar with are designed and built for 250 watts per liner foot. That means you have a total of 4,000 watts.

4,000 watts/240 volts = 17 amps X 1.25 = 21 amps. A 30 amp circuit using #10 AWG wire is required.

What is the square footage of your family room?
Thanks for your reply, Thinman. The sq. footage of my family room [ located in the lower level of a raised ranch ] is 442 sq. ft.. I understand your answer is there any way you can think of where I won't have to try and rewire with 10/2 [ it would be difficult but not impossible ] maybe a smaller heater or a different type, I am open to suggestions. Thanks again for all your help. DomatTL

#5
04-07-05, 09:31 AM
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Location: Dry Side of Washington State
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Let me backup here. Are you supplying an individual branch circuit to each baseboard heater or one circuit for both?

If it's individual circuits, then you have it correct.

If it's one circuit for both, then you have a problem and my original answer is the only way to do it right.

I know of two ways, probably more out there, to calculate sizing a baseboard heater.

1st: 442 sq feet X 7.5 ft (floor to ceiling height) x 2 watts = 6630 watts.

2nd: 442 sq ft. X 10 watts = 4420 watts.

Other factors to consider when calculating baseboards are number of windows in the room, size of windows, exterior door, type of insulation and climate.

#6
04-07-05, 10:09 PM
DomatTL
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reply to Thinman - baseboard heaters

Thanks again for your reply and help, just to double check - as I have it wired now one 12/2 cable run from the panel to each individual heater with a separate breaker for each piece of heat, it will be sufficient to carry the load.
I have been under the impression that 12/2 with the proper size breaker can carry a max. of 20 amps. is this correct? Thanks again you've been a great help. DomatTL

#7
04-10-05, 08:42 PM
Jeff Smallwood
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I know this isn't quite the topic at hand, but could someone explain to me if there would be benefits to running 12/3 (or 10/3, of course depending upon load) to these heaters. It sounds like a rather ignorant question but I understand most concepts of electricity but I never quite caught onto knowing when to run /2 as opposed to /3, especially relating to 220v (I do know /3 has 2 hots, though). Could someone take a minute to explain it to me?

#8
04-11-05, 05:36 AM
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A pure 240 volt device needs no neutral wire because it has no 120 volt component. Therefor for a pure 240 volt load you only need 2 hot conductors, plus the ground wire.

Some 240 volt devices (appliances mainly) have a 120 volt component. This 120 volt component needs a neutral wire. Examples of two of these appliances are dryers and ranges. They have a motor to spin the drum and/or a light bulb and/or a clock and timer. They need to be run with three conductor wire, plus the ground.

#9
04-11-05, 08:46 AM
Jeff Smallwood
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I see. Thanks a bunch, racraft.

#10
04-11-05, 10:45 AM
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I agree with Thinman, baseboard heaters of 4,000 watts or greater should be on a 30 amp circuit with #10 wire.

Juice

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