Robertshaw RS9210 Installation Manual page 11

Alternate Wiring (Conventional Systems)
If labels do not match letters on the thermostat, check the chart below and connect to terminal as
shown here (See notes, below).
or
If there is a C or X wire available then you can connect with C terminal. If there is
no C or X wire then no need to connect with C terminal.
If you have a heat pump without auxiliary/backup heat connect either the O or B, not both.
If you do not have a heat pump, do not connect O or B. Wrap bare end of wire with electrical
tape.
Place a jumper (piece of wire) between Y and W if you are using a heat pump without
auxiliary/backup heat.
or or or
WIRING
or
9