Hey, I purchased your Honeywell RTH2510 Thermostat, but I didn't even think to label the wires when I took the old thermostat off. Upon installation of the new Thermostat (2510) the Air Conditioning...
The connections that you really need to reference would be at the air handler itself. That would tell you which wires go outside to the heat pump and which wires go to the air handler. I can however give you some basics that may help.
Heat Pump Wiring
Terminals/Colors/Function
R- Red- 24v power supply. (Usually a jumper between RC/RH)
G- Green- Fan
W- White- Heat (Sometimes W1-W2, first or second stage heat)
Y- Yellow- Cooling (Same applies as above i.e. Y1-Y2)
C- Common (Most people use blue unless it is used for B terminal and sometimes cooling on older 4 wire systems.
B/O- Reversing Valve for heat pump. Either powered heating or powered cooling, depending on system installed.
Aux- Also used for heat.
Note: Considering that the installer had their own way to run all wires, use different wires, connections, etc. This is just a reference to common wiring in the field.
How the most common system is hooked up:
Thermostat:
Red wire goes to R terminal
Yellow wire goes to Y1 or Y2 terminal
Green wire goes to G terminal
White wire usually goes to W1 or W2 terminal
Orange or Black wire goes to B/O terminal
Brown wire usually goes to Aux terminal
Blue wire goes to C terminal, unless its being used as stated above.
This is without using a fossil fuel kit or zone control board.
Where do they go from the thermostat?
Red goes to the air handler transformer or board and goes outside to heat pump to power low voltage controls.
Yellow wire goes straight outside to Y terminals on heat pump unless going to a board inside first.
Green goes to the air handler fan relay.
Common goes to the air handler and outside to heat pump.
Black or Orange will go outside to heat pump terminals for reversing valve.
White usually goes outside to heat pump,and inside to air handler. Will explain reason further down.
Brown will go to the air handler to the heat relay for the emergency heat.
On a call for heat, with a powered cooling system (more common).
The R, Y, and G terminals energize, sending a signal to start the blower and pull in the contactor outside. Note that the Y terminal is usually cooling, but since this is a powered cooling system, the reversing valve is not energized, causing the system to run in heat mode. If you have powered heating, the reversing valve terminal will energize also. Depending on thermostat, if you set the temp substantially higher than room temp, it may kick on the emergency/aux heat to quickly raise the room temp. On a call for emergency/aux heat, the R, G, and E/Aux terminals are energized, turning on the electric/gas heat instead of the heat pump. This comes in handy since the heat pump can only pull so much heat from outside before its not enough to properly warm the house, usually around 30 degrees outside temp. If you are running the heat pump and the system goes into "defrost", the outside unit will send a signal back to the air handler, through the white wire I mentioned earlier, to tell the emergency/aux heat to come on while it is in defrost mode, providing heat whenever needed.
Again, this is just a reference guide to some basic wiring, but hopefully it will tell you where the problem is or at the least, give you a good start. There are variables in which things can change the wiring like a zoning system or fossil fuel kit. Even then, you should be able to get pretty close. Hope this helps and Happy Holidays!
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