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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have 4 wires coming from the wall. goes to W. Red goes to

Customer Question

I have 4 wires coming from the wall.
White goes to W.
Red goes to R.
Yellow goes to Y.
where does blue go? there is no corresponding letter.
Honeywell model TH8110U1003.
Submitted: 1 year ago.
Category: HVAC
Expert:  Rick replied 1 year ago.

Where did it go on the old thermostat? If you don't know then you need to go to the thermostat terminal strip on the furnace and see where it's connected.