240V baseboard heating

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  #1  
Old 06-12-07, 07:34 PM
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240V baseboard heating

Bought this house 2 years ago, a prior owner took out the furnace and replace all heating with 240V baseboard heating suplemented by wood burning stove. He did work himself and the elctrical work is horrible (spliced wires tucked into walls etc). I'm replacing 1 baseboard heater in a bath with under floor heating and fixing wiring as I go along. While trying to fix wiring I found that in one 240V circuit, there are 4 baseboard heaters 2 at 300W and 2 at 750W for a total of 2100W. The wiring is 14/3. Have not traced the wiring to the the distribution panel yet. I will in the morning.

Is this OK? Also what should the breaker size be?

Thanks
 
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Old 06-12-07, 08:25 PM
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14 wire is to be on no larger than a 15 amp breaker, which would be large enough for the 2100 watts.

2100 watts of heater would need an 11 amp circuit. A 15 amp breaker provides a 12 amp continuous use circuit.
 
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Old 06-12-07, 08:27 PM
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2100W / 240V = 8.75 Amps.

14 AWG is typically rated for 15 A breaker. Recommended load is usually 80% so that's 12A. So you have about 4A 'headroom."

If there's some specific code requirement for heavier gauge for heat, or a particular wire type or rating for heating use, hopefully someone else will chime in.

But if you have found a splice not in a junction box, you would be well-advised to check the wiring from end-to-end or have an electrician check it. As you may know there are probably millions of homes with problem wiring. Only a very small percentage of these will ever cause property damage or injury, but this is a lottery that no one would want to "win".

Also be aware that receptacle outlets are usually not permitted where the cord would have to cross the heater, such as above a wall-mounted heater.

I wonder if the electric heat was simply installed to meet a local building code requirement, and never intended to be used.
 
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Old 06-12-07, 08:32 PM
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nap, what is the calculation to arrive at the 11A figure? I though this was a straightforward computation.

"2100 watts of heater would need an 11 amp circuit."
 
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Old 06-12-07, 09:13 PM
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Fixed heating appliances need to have their branch circuit be sized for 125% of the connected load.

2100 watts times 125% equals 2625 watts. Divided by 240 volts gives 10.94 amperes, rounded up to 11 amperes.

In this particular case the 80% rule for continuous load on a circuit breaker is not used as it is taken into consideration with the previous calculation. A 15 ampere 240 volt circuit may supply up to 2880 watts of fixed heating load.
 
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Old 06-12-07, 09:56 PM
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thanks furd. I was going to post a follow up explaining that but arg's post was adequate in computation. In calculating the 80% he did, that would mean a heater load of 12 amps is accceptable since 12 X 125% is 15 amps.

I just went about it a bit backwards from the way you were thinking argmematey.

we both got to the correct solution just going different directions.
 
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Old 06-13-07, 12:13 PM
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Thanks

Guys, Thanks for all the input. The wiring is actualy 12/2, not 14/2 my mistake and is on a 15 amp breaker. So it looks like I'm ok with the load. To fix the mess with the conections I will be rewiring all 2 heaters and properly connecting the wires in J-boxes and re-routing wires behind the sheetrock where they belong, not in a crevice between the floor and the bottom of the sheetrock covered with some moding etc.

Thanks again.
 
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