White Rodgers UP310 Install Manual page 12

Do you have a "B" wire?
Labeling the "B" wire can be tricky. It could be labeled as "C" or "O/B" depending on whether you have an "O" wire
connected to your old thermostat. Please pay attention and follow the asterisk (*) comments below while labeling.
* Label "B" as "C" only if the old thermostat also had a wire in the "O" terminal block. If there was no wire in the "O"
terminal block, label the wire as "O/B"
** On heat pump systems with separate W2 and E wires, label both wires W/E (2 wires on one terminal)
3.4 Identify jumper wire
For terminal RC and RH:
On your old thermostat, if...
Terminal RC and RH are connected
with a jumper wire
There's only one R wire (RC, RH, R or R5)
coming out of the wall
Two separate R wires come out of the wall, and they
are NOT connected by a jumper wire
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Then, on your new thermostat...
Leave the RC/RH jumper wire in its place
Leave the RC/RH jumper wire in its place
Clip the jumper wire between RC and RH on
the back of the new thermostat