Baseboard electric

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  #1  
Old 01-06-06, 02:14 PM
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Baseboard electric

I ran 12/2 romex for auxiliary heat to all the rooms in the upstairs remodel, intending to install 120V heaters. They are very difficult to find. In doing the math, it looks like I could use the 240V ones with 2000W on a circuit and only use 8.3 amps, with 12 ga wire okay for 25 amps. I believe I would then need a different thermostat, and the 240 breakers, but otherwise would end up okay. Having only run 220 for dryers and ovens, I am looking for either confirmation or a big smack upside the head. And then what amperage breaker? I wasn't going to put more than the 2-1000W units on a circuit. Thanks, Chrise
 
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Old 01-06-06, 02:42 PM
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12 gauge wire is rated for 20A, not 25A.

You are allowed to utilize this circuit at up to 80% capcity continously meaning 16A, therefore you can have up to 3800W of 240V heaters on a 20A circuit. You will need double-pole 20A breaker(s) and double-pole thermostat(s), depending on how many heaters you install. The thermostat should be sized for the heaters it controls; so if you only have one 1000W heater per thermostat, each thermostat only needs to be rated for 1000W.

When using Romex for a 220V circuit, it is required that you color in a few inches of the white wire with a black, red or blue sharpie marker in each junction box to indicate that it is used as a hot wire instead of a neutral wire.
 
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Old 01-06-06, 02:55 PM
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Energy use

Are the 220V heaters significantly cheaper to operate? I don't know how to figure that.
 
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Old 01-06-06, 03:17 PM
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Are the 220V heaters significantly cheaper to operate?
Same price to operate. A Kilowatt Hour is a Kilowatt Hour no matter what the voltage is.

Doug M.
 
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Old 01-06-06, 03:47 PM
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Would a baseboard heater be considered a continuous load and require 80% loading max, or do they cycle off/on in less than 3 hours?
 
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Old 01-06-06, 04:24 PM
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Originally Posted by dougm
Same price to operate. A Kilowatt Hour is a Kilowatt Hour no matter what the voltage is.

Doug M.
Unless you figure the power curve, and you may save a penny a month.
 
  #7  
Old 01-06-06, 05:39 PM
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Electric heat is pure watts. The advantage of 240 over 120 is that for a given KW load you can use smaller wire. In a large installation, there can be cost saving on the wire.
 
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Old 01-06-06, 05:59 PM
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There are quite a few 80% rules in the code. Continuous loads are only one such rule. Although a baseboard heater is not a continuous load, it is still limited to 80% of the circuit capacity due to other codes.
 
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Old 01-06-06, 06:31 PM
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John,
For my future reference, could you help me with a reference? I looked through 422.11 with no luck.
 
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Old 01-06-06, 07:01 PM
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Try 424.3(B) in the 2005. They do actually say it is a continuous load in this version of the NEC, so I was wrong earlier. I think it was worded differently in earlier versions.
 
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Old 01-06-06, 07:48 PM
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Thanks John
 
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