Heating Load Conductor Sizing

Old 05-12-15, 03:40 PM
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Heating Load Conductor Sizing


I have two heating loads within 40' of my 277/480 panelboard. One is 16.6a and the other is 23.5a. They can both be circuited to a 3-pole 480 volt circuit. They are continuous load.

I have sized the conductors by (16.6+23.5)*1.25 to get 50.1 or #6 AWG.

Is this correct? Do I need #6 throughout the circuit?

Old 05-12-15, 03:49 PM
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Will you be running an additional breaker, for protection, at each heating unit ?

You can't connect two units to a single breaker as the breaker size is too large to correctly protect each heater.

Last edited by PJmax; 05-12-15 at 05:02 PM.
Old 05-12-15, 08:13 PM
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You need to refer to the manufacturer's instructions for maximum overcurrent protection for each heater.
Old 05-16-15, 01:36 PM
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Ultimately, Joe is right.

Is this a commercial or residential (480V acreage shop?) setting though?
CEC states you can put multiple heaters on a circuit so long as they do not exceed 60A commercially (unless the loads are balanced, then you may exceed in a 3 phase system) and 30A in a residential setting. Maybe the NEC has the opposite opinion on this subject but I can't see it being much different.
CEC has crazy sizing rules for heating circuits so someone versed in the NEC should help you with that.

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