Honeywell RTH7500 Guide D'installation page 14

Installation Guide
Alternate wiring (for heat pumps only)
Leave metal jumper in place, connecting
R & Rc terminals.
If your old thermostat had both V and VR
wires, stop now and contact a qualified
contractor for help.
If your old thermostat had separate O and B
wires, attach the B wire to the C terminal. If
another wire is attached to the C terminal,
stop now and contact a qualified contractor
for help.
If your old thermostat had Y1, W1 and W2
wires, stop now and contact a qualified
contractor for help.
If L terminal is used, C terminal wire must be
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connected (contact a contractor if there is
no C wire).
If E and Aux terminals do not each have a
wire connected, use a small piece of wire to
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connect them to each other.
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