Are All Classic "round" Honeywell Therms Low Voltage? - HVAC - DIY Chatroom Home Improvement Forum

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Old 11-17-2009, 08:13 PM   #1
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are all classic "round" Honeywell therms low voltage?

I have some electric baseboard heating units that are controlled by one of those round classic Honeywell thermostats. It's doesn't have the fan/ac switches. I want to replace it with a digital programmable unit.

Can't pull it off the wall right now, but wondering if it's even possible that this classic round design is switching the voltage to the heaters directly? More likely I think it's standard 24v low voltage controlling a relay somewhere.

Is there a classic round Honeywell thermostat even made to switch 240 volts directly? Or am I ok in ordering an new 24v thermostat to replace it?

thanks for any hints!


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Old 11-17-2009, 08:55 PM   #2
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are all classic "round" Honeywell therms low voltage?

There were/are a few square 110 volt Honeywell tstats that break one leg of a 220 circuit but I have never seen a round one for that job. Most likely 24 volt but you need to find the power source and make sure. Pop the cover off of the tstat, if it has a mercury bulb it is 24 volt and should say T86.


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Old 11-18-2009, 07:33 AM   #3
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are all classic "round" Honeywell therms low voltage?

no.. The main reason is the line voltage must be concealed in the junction box which is rectangular.
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honeywell round therm

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