I have Honeywell mercury tilt theromometers controlling the baseboard heating in my home. I want to be able to programme the heat to turn on and off as and when it is needed and I bought some Noma Programmable Digital Thermostats to replace them. The Honeywell thermostats work well but when I connect the Noma one nothing happens - no heat - no didgital display - nothing. It looks idiot proof, two wires coming out of the box in the wall, two wires to connect to the Thermostat - what am I doing wrong??

Is the Honeywell thermostat for 110/220 volts? Is the new thermost for 24 volts? This could be the problem

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Originally Posted by hvac1000

Is the Honeywell thermostat for 110/220 volts? Is the new thermost for 24 volts? This could be the problem

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Thanks for your reply, that is exactly the problem. Any suggestions what digital thermostat would be compatible with my baseboard heaters?

This could be a bit of a mess. If it is a 240 volt heater, you should use a double pole thermostat which requires 4 wires.

Code says you only need to break one side of the 220 volts to control the heater element but both sides have to be protected by a over current device. Fuse/breaker.

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Originally Posted by hvac1000

Code says you only need to break one side of the 220 volts to control the heater element but both sides have to be protected by a over current device. fuse/breaker.

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In non-technical speak for the technically challenged please...

I'm having the same problem, but have central heating.

220 volts uses 2 wires for power. Each wire is 110 volts hanse when combined equal 220 volts. Code requires you only have to have a switch or thermostat that opens up one side of the 220 volts not both to control the heater.Now the disconnect/fuses or breaker has to be a two circuit type so all the voltage will be off when servicing.

Quote:

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Originally Posted by hvac1000

220 volts uses 2 wires for power. Each wire is 110 volts hanse when combined equal 220 volts. Code requires you only have to have a switch or thermostat that opens up one side of the 220 volts not both to control the heater.Now the disconnect/fuses or breaker has to be a two circuit type so all the voltage will be off when servicing.

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Is it possible to do what I want to do - or should I abandon all hope of digitally time controlling my heating?