I am changing two thermostats on electric baseboard heaters from single pole to double pole so I can turn them off without flipping the breaker. The heaters are on the same dedicated circuit. The 1st box has 3 white wires wired together and 2 black. It did not matter how I wired the double pole in this box - it either blew the circuit or did not work. I re-installed the single pole thermostat with its green and black wires to the black wires in the box and rewired the 3 white wires together. The 2nd box has only 2 white wires. I have a double pole wired there, but it won't shut off - but it also is not tripping the circuit breaker. I have the 2 black wires in the box to the 2 black wires on the thermostat and the 2 white connected to the 2 red. I read in another post about checking the load vs feed but am not sure about that. I think the load wire is the hot wire from the box and the feed would go to the heater. Is that correct? Help!

"D"

Just how new at electricity are you? I'm not trying to belittle you as much as I am trying to level set you.

Let's start at the breaker, please. Is the breaker a 220 VAC breaker? What is the amperage on the breaker?

Normally, baseboard headers require 220 VAC. To get this, a double pole single throw breaker is used. A 3 wire cable of the correct gage is used. Black is inserted into one breaker and red is inserted to the second breaker. White is inserted in the Neutral Bus bar and ground (green or bare) goes to the ground bus bar.

Another method is to use the black to one breaker. White to the second breaker and bare to Neutral.

Visually inspect your wiring and let us know what you have. If you are real new at wiring, I suggest that you call an electrician before you get dead by playing with hot wires.

Oh by the way, "Hot" means it is carrying voltage. Feeder means it is feeding the load. Load is the device or fixture that is fed.

Since you said nothing about red, but did mention white, you must have the normal set up of 2 conductor NM-B (Romex) with the black and white connected to opposite phases at a double pole breaker. Most heaters don't use a neutral. Recheck the box with 2 black and 3 white. If you have NM-B cables, each should have a black and a white. I also wonder about the box with only 2 whites. I would hope that if it is singles in conduit, nobody would have run white as hot.

If you have 3 black white pairs in the thermostat box, one should be hot from the breaker, and the other 2 each feed a heater. Can you identify how the black wires were originally connected to the thermostat, were the terminals marked line and load? If so, you want the black originally connected to the line terminal and the what paired with it connected to the line terminals of the new thermostat. Then connect the other 2 blacks to one load terminal and the whites to the other. If it has screws, you may have to pigtail the 2 wires to a third short one that goes under the screws. Put the second box back just like it was. If it is fed from the first one, it should still work, 2 white wires and all.

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Originally Posted by labman

Since you said nothing about red, but did mention white, you must have the normal set up of 2 conductor NM-B (Romex) with the black and white connected to opposite phases at a double pole breaker. Most heaters don't use a neutral. Recheck the box with 2 black and 3 white. If you have NM-B cables, each should have a black and a white. I also wonder about the box with only 2 whites. I would hope that if it is singles in conduit, nobody would have run white as hot.

If you have 3 black white pairs in the thermostat box, one should be hot from the breaker, and the other 2 each feed a heater. Can you identify how the black wires were originally connected to the thermostat, were the terminals marked line and load? If so, you want the black originally connected to the line terminal and the what paired with it connected to the line terminals of the new thermostat. Then connect the other 2 blacks to one load terminal and the whites to the other. If it has screws, you may have to pigtail the 2 wires to a third short one that goes under the screws. Put the second box back just like it was. If it is fed from the first one, it should still work, 2 white wires and all.

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Hi, I know nothing about this stuff. I was asked to fix a thermostat in a rental property that is 15 years old with electric baseboard heaters. The bedroom heater was not working, but the ensuite bathroom heater with its own separate wall mounted thermostat is working. I removed the bedroom thermostat and discovered it was never connected as it just fell to the floor. The thermostat box has 3 sets of wires (each with black/white/copper). The 3 black wires were connected with a marrette and the 3 white wires were connected with a marrette.

I am assuming that one wire set is hot from breaker, and the other 2 are feeding the bathroom and bedroom heaters. (I think I'm right because when I separated the three black wires the bathroom heater did Not work) If this is the case will the solution suggested above by Labman work?

Thanks

It should. All you have to do is identify the hot from the breaker and connect it to the line terminals. Then connect the other 2 to the load terminals. With a meter and the power off, you could check each pair for resistance. The pair that is open is the feed and goes to the line side. Connect the other 2 to the load side.