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Do I run 12-2 wire to a wall thermostat and heater off a 20 amp breaker? Does the black and white wire go to a double pole breaker?

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    Make sure you know whether you're using a line-voltage thermostat (which will directly turn the power on and off) or a low-voltage thermostat (which controls power indirectly via a relay). The wiring is very different for the two types. – Hank Oct 9 '14 at 3:29
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It is safe to assume you mean 500 watt and not 500 amp.

Yes, you should run 12/2 cable from a double-pole 20A breaker to the thermostat and then from there to the heater. This is the easiest way to run this circuit. Be sure to re-mark the white wire to a "hot" color with tape or easier yet a permanent marker. Use a color like red, blue or black.

Be sure to use a double-pole line-voltage thermostat.

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500 amps is a pretty decent baseboard heater.

A 500 watt heater doesn't need 12/2 wire. 14/2 is fine. It's only pulling 2 amps. Yes, the black wire goes to one side of the 15 amp double-pole breaker and the white wire goes to the other side.

The separate thermostat will probably be a control rather than a power switch, this means small signal wire can be used instead if 14/2. Check the instructions, control voltage is a factor.

  • The wire should be sized for the breaker, not for the load. So if you have it attached to a 20 amp breaker, you need 12 gauge wire, even if your heater will only draw 2 amps under normal operation. (If a 15 amp breaker is used, 14 gauge is fine.) – Ben Miller - Reinstate Monica Oct 9 '14 at 5:01
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    Also, it is common practice to use #12 for electric heat loads. They can add up fast. Sure, if it's just this one heater and nothing will ever be added 14/2 is fine, but as stated MUST be on a 15A breaker. – Speedy Petey Oct 9 '14 at 11:15
  • Also, what do you mean by the "control voltage"??? Line voltage electric heat uses line voltage at the thermostat, unless a special external low voltage control is used so that standard low-voltage thermostats can be used. White-Rogers makes such a control. – Speedy Petey Oct 9 '14 at 11:17
  • 'Control voltage' would be something like 12v going to the thermostat, just like your furnace. – paul Oct 12 '14 at 15:32

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