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awgn70 · Oct 9, 2009, 01:45 PM

Hello -- this is potentially a dumb question, but I have a 1970's era house w/ 240v baseboard heat controlled with single-pole (copper) thermostats. I have a Honeywell TL8230A programmable thermostat which expects a double-pole box. Is there any way I can make this work? I've combined "control" and "load" wires and the digital control activates, and there's even a relay "click" on and off as I adjust the temperature setting, but no power gets to the baseboard element. Seems tantalizingly close, but perhaps I simply bought the wrong thing.

BTW, I'm being very careful to cut power before I do anything... :-)

Missouri Bound · Oct 9, 2009, 05:02 PM

That thermostat requires 208-240 volt to operate. Your old thermostat was beaking only one leg of the circuit, leaving the other hot leg connected where the new thermostat breaks both legs of the circuit. Are both legs available in the box? You need both legs to the thermostat for it to operate properly.

awgn70 · Oct 9, 2009, 07:57 PM

Ah, the other leg is not present inside the box but I can check to see if it runs behind the box -- we'll see and I'll post what I find.

If this doesn't work, I believe that the RLV430 would work with a two-wire config? That's what the Honeywell tech help guy told me. (dang, I'll have to eat the $60 on this TL8230A, I guess)

KISS · Oct 9, 2009, 08:51 PM

The programmable stats actually draw their power through the heater element. That's how come they don't require batteries and it's also why you need two poles.

Usually 240 volt stats are two pole except they function in a weird way. One pole is an on/off switch and it's on for all but the OFF position. The other pole is thermally switched by a bi-metalic piece of metal.