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BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22541
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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I have a CT87N thermostat.....I didn't make a note of what

Customer Question

I have a CT87N thermostat.....I didn't make a note of what terminals the wires were connected to on the Honeywell RTH 2218 (we don't want a programmable one) The wires coming out of the wall are White, Red, Blue and Green. There are 2 terminal sections on the CT one....the terminal on the left ; G W Y B....on the left; R Rc and O....its just a gas furnace with air
Submitted: 2 years ago.
Category: HVAC
Expert:  BillyHvac replied 2 years ago.
wire as follows:
red to r/rc
white to w
blue to y
green to g
Usually there is a yellow wire that would go to Y...but many homes were wired with a cable that did not have yellow and had blue instead. So when yellow is missing, we use the blue on Y.