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lee12 12-08-2010 09:36 PM

double pole thermostat for kickspace heater
I purchased a Marley S1504TB kickspace heater to replace a similar older heater (Nutone 9112NT). The older unit had been controlled by a separate thermostat - Honeywell T498. In the instructions for the new heater it states:

'If wall thermostat is used: a double pole wall thermostat of the type where both poles cycle on and off by temperature change cannot be used with this heater. Only one pole may cycle and this pole must cycle heating element only, not motor'

Does this describe ALL double pole thermostats? Are they all 'this type'? If not, how do I know if my thermostat is 'the type where both poles cycle on and off by temperature change'? Aren't double pole thermostats required by electrical code?

The wires running to the heater are black, white and ground. Here are the readings I have taken to try to figure this out:

Thermostat OFF - 0V white to ground, 0V black to ground, 0V white to black
Thermostat ON but thermally OFF - 106V white to ground, 115V black to ground, 0V white to black
Thermostat ON and thermally ON - 115V white to ground, 115V black to ground, 230V white to black

I've taken these reading multiple times with the same results. Kind of confusing to me. Why does the one hot wire jump from 106V to 115V when thermally on but not the other hot? How can I have a 106V hot/ground and a 115V hot/ground that measures 0V across each other?

Any help would really be appreciated. Thanks!

New heater:
Wall thermostat:

kbsparky 12-08-2010 11:21 PM

This particular heater requires the blower motor to continue operating once the thermostat is satisfied to enable a cool-down period. This prevents possible overheating of the unit.

One way to accomplish this is to have the 240 Volt feed run directly to the heater, with a 2-wire switch-loop run from there to the thermostat. Another way would be to install a 3-wire cable from your 2-pole thermostat to the unit.

The active thermostat leads connects between the 2 blue wires found within the heater unit.

lee12 12-09-2010 07:17 AM

Here is the diagram for the thermostat. I look at this and take it to mean that the T2 line (described in item 5) would be appropriate for the motor connection and would allow the 'fan off delay feature' to function. I guess I just want to be able to verify that the heater and/or thermostat is working correctly so that I don't overheat anything. I suppose I could hook a meter up to the heater and see if the fan still runs when the heater stops. The T2 line IS the one that I can measure a change from 106V across ground (thermally off) to 115V (thermally on). The T1 line is the one that measures 115v across ground whether it is thermally on or off. I guess that's what is confusing me, I would have expected the line that's not thermally switched to be ~115v and the line that is thermally switched to be 0v/115v. But then again I'm not too familiar with thermostats or with 230v appliances.

lee12 12-09-2010 12:52 PM

kbsparky - thanks for the suggestions. Your solutions seem to be the only way to make this work. I ended up speaking with the heater manufacturer who verified that there would be no way to make my thermostat work with wiring I have. He said I'd have to replace my 2 wire supply with a 3 wire supply. Since the wires are already in the wall, I'll just return this heater and get a different type without the fan-delay feature.

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