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View Full Version : Thermostat -- What is the "X" wire?


jond
Oct 29, 2005, 01:35 PM
On my old Rheem thermostat there's 7 wires:
Green - G
Red - R
Blue - B
Yellow - Y
Brown - X
White - w2
White(looks like its just jumped from e to w2).


I have a new honeywell digital thermostat and there's no X hookup on it.
It has the following hookups but not all need to be used:
Y2
L
E
AUX/W2
S1
S2
RC
R
W / O/B
Y
G
C


So I know that my current:
G, R, B, Y, and W2 map directly over.
For e should I jump it from W2, or just not hook it up?
And X I have no clue at all. It looks like it either goes to C, RC, S1, S2, L, or Y2

labman
Oct 29, 2005, 02:37 PM
Most thermostats and HVAC systems stick to the R, W, Y, G, and B for the basic hot, heat, cool, fan, and common. I am not sure if there are conventions for additional functions, 2 stage heating, outside temperature sensors, switching heat pump systems, etc. Best thing to do is to go to the furnace and try to identify what the brown wire was connected to and what it needs. Then, from the directions for the Honeywell thermostat, figure out where to connect it.