How to Connect a Three-Wire Thermostat With Black, White & Red

Baseboard electric heaters connect to thermostats with black, white and red wiring. In addition to the current-carrying wires, a bare copper ground wire is used for added protection against electrical shock. Whether the thermostat is wall-mounted or installed directly onto the heater, the wiring connections to the heater are the same. Once you determine the location of the thermostat, you can connect the wires using the proper tools, materials and basic electrical wiring skills.

Voltage tester
Wire stripping pliers
Wire nuts
Electrical tape

Instructions

- 1
  Turn off the power supply to the heater at the main electrical box.
- 2
  Test the supply wires using a voltage tester to ensure there isn't any power.
- 3
  Strip 1/2 inch of insulation from the black, red and white thermostat and power supply wires using wire stripping pliers.
- 4
  Connect the red wire from the thermostat to the black wire from the power supply with a wire nut. Tighten the wire nut clockwise by hand.
- 5
  Connect the black wire from the thermostat to the black wire from the heater with a wire nut.
- 6
  Connect the white wire from the heater to the white power supply wire using a wire nut.
- 7
  Connect the bare copper ground wire from the power supply to the ground wire of the thermostat with a wire nut.
- 8
  Wrap the wire nut connections with electrical tape, winding clockwise. Overlap the tape from the wire nuts onto the insulated wires to ensure no part of the connection is exposed.

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