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Heating, Air Conditioning, Fridge, HVAC/Installing a line volt thermostat


Hello Mr. Cook:

I have 240w baseboard heaters in my condo. They currently have Honeywelll dial type thermostats and I want to change them to a new Honeywell Digital unit (non-programmable Line Volt PRO 7000).

I have 2 concerns: 1. The existing unit uses 2 black wires. The 2 red wires on the unit just feed back into the back of the thermostat itself (not used). The new unit has 2 red and 2 black wires. I assume I can just wire nut the red wires and use the black only just like the old unit.

2. The new unit use 14 guage wire while the old thermostat had 12 guage wire. The baseboard heaters are hooked up to a double. Pole 20 amp breaker. Does the thinner wire on the thermostat itself make a difference. I didn't think its good to tie 14 guage wire into 12 guage.

Any help or suggestion would be greatly appreciated


The manufacturer can get by with 14 gauge wire because it is so fine stranded it increases its value. I don't have the wiring diagram but from the description the old thermostat was only breaking one of the two 120 volt legs feeding the heater. You are correct that just using the black wires will be the same connection but the stat may require the full 240 volt connection if it operates on 240 volts in which case this thermostat will not work on this application. You will have to check with the manufacturer of the stat to ensure it will work only partially connected. It could also damage it if connected to just 120 volts. Thanks J

Heating, Air Conditioning, Fridge, HVAC

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J Cook


With 25+ years experience, I am familiar with residential, commercial, and industrial HVAC equipment including but not limited to boilers, chillers, reciprocating and screw compressors. I am trained in all manners of control wiring.


I currently have three HVAC licenses and Refrigeration license by the State of North Carolina. I have been in this field for over twenty years. I have been a service technician for a contractor and also worked at a state college in the repair and maintenance of steam lines and equipment. I am currently the Building Maintenance Superintendent for a municipality.

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