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Mike G.
Mike G., Master Electrician
Category: Electrical
Satisfied Customers: 7533
Experience:  Proven Professional 48 years Experience
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I was hoping to replace a line voltage thermostat for a 240

Customer Question

I was hoping to replace a line voltage thermostat for a 240 amp baseboard heater in a home I just moved into. The original thermostat is missing and the box is currently just housing exposed wire (breaker is off). I bought a double pole thermostat but noticed that the box has three cables coming through, with 3 black wires , 3 white wires and some ground wire twisted together. Not sure where to go from here..
Submitted: 10 months ago.
Category: Electrical
Expert:  Mike G. replied 10 months ago.

Hi, I'm Mike G and I'll be assisting you. You'll need a 2 wire voltage tester to identify the hot wires. I suspect that there are more than one baseboard heaters, that's why you have that many wires. Let me know if you have a teeter.

Customer: replied 10 months ago.
No tester unfortunately, but would consider getting one. The black and white wires coming from one of the cables are labeled with red tape, while the other white wires are labeled with black tape.
Expert:  Mike G. replied 10 months ago.

Could be the reds are the hots. Best to be sure and test the wires.

Customer: replied 10 months ago.
Once I have determined the hot wire, how would I proceed?
Expert:  Mike G. replied 10 months ago.

You'll test each pair of wires for 240V. The connect the hot set to the line terminations and both of the others to the load terminations. The T-stat will control both heaters.