Electrical – Old electric baseboard heater thermostat wiring

electric-heatelectricalthermostat

I have a question about an old federal pacific baseboard heater thermostat's wiring.
I disconnected this thermostat 2 weeks ago, thinking that we were going to remove the heater. Now we've decided to keep the heater, and I don't remember how the thermostat was wired.
The therm box has two lines in it: one in, one out. Each line has 1 black, one white, and one bare ground.
I have attached a pic of the back of the thermostat. It only has 3 places to connect. Poles 2, 3, and 4.
Can anyone help me out and tell me what hooks to each pole?

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Best Answer

This is 240V split-phase, so both hots are equivalent. The white wire should be remarked one of the 8 legal hot colors, since it is not a neutral. If I were wiring this in conduit, with the choice of any of 8 colors, I would use black and black because the hots are interchangeable; no need to distinguish hots from each other.

This thermostat is single pole. They make a double-pole version where terminal 1 is populated, that one connects 1-3 and also 2-4. This one simply leaves in terminal 3 as a convenient splice block, it connects to no other terminal ever.

Pick one wire from each cable; join them (I don't care how as long as it's code legal; feel free to use terminal 3 as a splice block).

Of the two remaining wires, put one on each of the terminals 1 and 3.