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TheKid72 · Jul 25, 2007, 07:21 PM

My house has a combination of baseboard and ceiling cable heat. One baseboard has been nothing but trouble - just a small 24", 500 watt unit for the laundry room. It shares a thermostat (SPST) with a 1000 watt baseboard in the bathroom - which is the next room. That heater has worked great for the 50 years this house has been standing. But this location had the original heater fail when the house was new.

While doing some updating last winter, I finally replaced it. That unit failed immediately. Got weak heat from a cold start for seconds, then dead. Figuring I had a bad unit, I replaced it with one that worked right away and did for a couple months. Until it too died. No heat... but the other heater on the circuit heats like mad.

With power cut, I've found that the high temp cutoff is closed, and the element reads 17 ohms (wires disconnected). With power restored, the 2 leads each measure 125 volts in reference to ground, which is right for this house' AC coming in. But across the two - 0! They are in phase. Also the thermostat makes no difference - always 125VAC to ground x 2 and 0 VAC across the hot lines. No wonder I have no heat!

I have not checked the other heater for voltage feed, voltage drop, resistance, etc. Also I have not removed the leads from the working heater and rechecked the dead heater, thinking I am getting a false 125 volts on one of the legs due to one leg passing current through the working element.

Where should I go from here? I know enough circuit tracing to confuse myself!!

acetc · Jul 25, 2007, 09:05 PM

I know what you are saying about confusing, the reading across the thermostat would be correct. The thermostat is nothing but a switch that connects one wire to the other, the high temp. limit is closed which is correct because it is also a switch to complete the circuit to the heater. Think of electricity as water flowing through a pipe the flow (current) goes from the breaker to the thermostat through the limit to one side of the heating element and out the other side of the element and back to the breaker panel to a neutral (115 Volts) or a different leg of the incoming power (230 Volts)
When you check for voltage across the thermostat and you get 125 volts to ground on each side but "O" volts when checking across this means that the thermostat is closed and calling for heat, you should also get the same reading on the limit switch.
Now we get to the heater element, THIS IS NOT A SWITCH, this is the load and you should see voltage across the element (two wires connected to heater element) and the element should be getting hot, if it is not getting hot then it may be burned out and you can determind this with an OHM meter, if does not register a resistance in the wiring then it is bad.
If for some reason you may get a voltage reading on both sides of the element to ground but "0" voltage across it then the leg (wire) leaving the heater is not completing the circuit back to the breaker panel. Hope this is helpful. Mike

acetc · Jul 25, 2007, 09:21 PM

If you can find these two wires in the breaker panel they should read voltage across them, perhaps a bad breaker or bad wire connection.

TheKid72 · Jul 25, 2007, 09:26 PM

Mike, Thank you for your input. You have given me a couple troubleshooting ideas, and I'll do some more testing.

I was puzzled by the 125 volts on each leg - both in phase, but that was tested without a load from this heater. The other heater (wired in parallel) could easily cause that false reading. I will disconnect the other heater's element and retest.