Son-in-law purchase Honeywell T87K thermostat to replace older verticle thermosat. When he removed old unti he forgot to mark wires.Furnace is new gas fired boiler heating radiators.
Tried different wiring methods without success ( usedonly two wires) and then when using all three got boiler to turn on but will not shut off unless he reduces heat by moving dial .
Old wires are wrapped in cloth like material and are Black, White and Brown.
Hepl!
You will need to go to the heating system and see what color wires are hooked to that. Typically the black and white wires will be used unless they used another color due to a bad wire. Hook the colored wires to the R or RH terminal on the thermostat and the other wire to the W terminal. You can also try taking the wires you have and one by one twisting them together and have a second person inform you when the heating system turns on. Take those two wires and hook them to the terminals I mentioned above.
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Well I am confused when you mention "colored" wires as all three are of a color ( casing is Black, White and Tan )so which colored wires go to which connector?
I like the idea of twisting two wires togehter to see if the boiler kicks on but when that happens does it matter what wire goes to what connector?
The instructions for the thermosat indicate;
W = Heat
R = Power
Y = Can be used for hot water valve system which I doubt this boiler has.
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