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Old 10-20-2009, 07:39 PM   #1
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T stat with 2 wires on 240?


I recently installed a 240V hydronic electric baseboard heater in a bathroom.
The thermostat that I purchased to control the heater was sold with the heater as a kit from a company in SC. The T stat has a triac in it to vary the current (or is it voltage?) supply to the heater, based on rise needed, room temp......
This T stat is single pole. I'm now hearing that single pole on 240 is against code in the US. Does the triac change that or should this product not be sold here?

Wiring is as follows:

1 side of supply to T stat
2nd side of supply to heater element
2nd side of heater element ( temp limit switch) to other side of T stat

Am I safe?
Heater has a chassis ground that is connected to supply ground

Thanks.

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Old 10-20-2009, 08:19 PM   #2
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T stat with 2 wires on 240?


A switch must turn both legs off but your thermostat is considered control wiring and may switch just one leg.

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Old 10-20-2009, 08:30 PM   #3
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T stat with 2 wires on 240?


Great - thanks for the clarification.
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Old 10-20-2009, 10:33 PM   #4
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T stat with 2 wires on 240?


Single pole line voltage thermostats do not provide "disconnecting means" for connected heating units. Because of this, they do not have an "off" position.
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Old 10-20-2009, 11:04 PM   #5
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T stat with 2 wires on 240?


While they make two pole full line voltage/current controlling thermostats for electric heaters, it is actually rare that both poles open or close automatically at exactly the same time. I have even used some whose calibration is off far enough that turning the dial manually also has the poles opening and closing at noticeably different dial positions.

In normal operation with both leads to one heater connected, this usually means that one of the contacts does all of the switching under load. If instead the double pole thermostat is used to control one lead respectively of two heaters, usually the temperature will fall further enough that the second heater will be switched off (and on again) before the first is switched back on.
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Last edited by AllanJ; 10-21-2009 at 07:49 AM.
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Old 10-21-2009, 07:15 AM   #6
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T stat with 2 wires on 240?


That is correct. The only way to ensure both poles are open with a double pole thermostat is to turn it "off"
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Old 12-13-2011, 07:52 PM   #7
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T stat with 2 wires on 240?


so it's ok to use single pole t stat on 240V?

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