# circuit breaker selection Maybe OT

• posted on October 12, 2003, 10:51 pm
This may be a bit off topic, however, I have just wired in an electric heater for my shop. The heater is a 208/240V @ 19.6 amps. The breaker that supplies my shop (detached) is a double pole 10A 10AWG 3+ground. Question is: If the main breaker from the panel is 10A, is that per voltage lead, or overall. If the heater requires almost 20A, then do I want a 220 single pole (double 20A with trip cap on top) or double 10A.
Any help appreciated
Brian

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• posted on October 12, 2003, 10:52 pm
Size the breaker to protect the wire - 10AWG = 25-30A. The breaker should be a double slot (pole) 25 or 30A.
ELAhrens Apprentice Termite

voltage

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• posted on October 12, 2003, 11:10 pm
Brian: The good news is the cable is correct for the heater. The bad (sorta) news is that the double pole 10 amp breaker is going to limit you to 10 amps at 240V. What you need is a 2 pole 30 (yes, thirty) amp breaker. As a rule, no circuit should be loaded to more than 80% of capacity, which is 18 amps on a 20 amp circuit. Code calls for #10 AWG wire for a 30 amp load, so the cable is OK, just replace the breaker with a 2 pole 30 Amp one, hook one colored wire (red or black) to each of the poles, and you should be good to go. Just one thing else: get the receptacle to match the plug on the heater cord, or if no cord, get a 250VAC, 30 Amp plug and receptacle, and some 10/3 SO cord to hook it up, and you are well on your way....
Brian Klar wrote:

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• posted on October 13, 2003, 10:35 pm
I have changed the breaker in the home box to 30A. For a test, I turned the heater on, all the lights, and ceiling fan, along with the table saw and miter saw. All went fine, without a hitch.
Thanks to all,
Brian
Bob Walters wrote:

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• posted on October 13, 2003, 11:07 pm

the
isn't 80% of 20 16?

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