Thermostat/EMT heat ?


Old 02-12-02, 07:18 AM
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Question Thermostat/EMT heat ?

I recently bought a new house and i believe the thermostat is wired up incorrectly and perhaps i have a misunderstanding of the
purpose of the EMT mode of the thermostat. For a bit of background, the unit is a lennox that's about 25 or more years old.

Thermostat problem: I live in North Alabama where it gets reasonably cold to me, low of 24 last night. and the heat will run and run and run and the heat strips will never come on, even if the emt switch is on. The t-stat has 5 wires running to it if that makes any difference. When the emt switch is on and the light on
the t-stat lit that indicates EMT heat whenever the temp drops down and the t-stat kicks the unit back on the EMT light goes out.

It's a honeywell thermostat that has 2 mercury bulbs in it. I presently have the lower mercury bulb adjusted to where the heat strips come on whenever the heat comes on because we're freezing to death. The unit will now run and get the house warm and kick off. Otherwise the heat would run & run without the heat strips and never get the house above 60.

I purchased a digital thermostat hoping it would solve the problem only to find that newer t-stats expect 6 wires and i only have 5. from spending some time with my multi-meter it appears that i'm missing a common wire.

Maybe i've given enough info for someone to help me out ?

EMT heat: I was under the evident misperception that when the EMT switch was on that the heat strips came on whenever the heat came on. Am I wrong ? if so, what is the EMT switch 'supposed' to do ?


- jack

Last edited by morpheus; 02-12-02 at 09:13 AM.
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Old 02-12-02, 03:37 PM
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From your symtoms, your in the wrong place. There is nothing wrong with the t'stat. Your 1st stage heat, which is the heat pump, is not working properly. Their are a variety of problems that can cause this, from dirty filters, coils, low on freon, bad compressor, electrical relays.. Call your local service company to check it out and ask the service tech questions. It'll be worth the service call...
Old 02-13-02, 07:21 AM
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ok, thanks. though i've had one company out once and the said it was working properly but i'll try a different company.

just for my knowledge, what exactly is the EMT switch designed to do ?

and what/when should make the heat strips kick on ?

- jack
Old 02-13-02, 03:29 PM
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Em.=Emergancy heat. When your heat pump is not working properly or at all, you may switch the t'stat to Em heat. When you switch the t'stat then uses your 2nd stage/Em heat as if it was the 1st stage primary. 2nd stage usually only comes into play when the outdoor temp gets below 35d, and should not be on all the time.
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