Honeywell RTH5100B 6. Compare letter designations on your old and new thermostats.

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Step 7. Connect Wires to New Wallplate (Cont)
6. Compare letter designations on your old and new
thermostats.
Do not connect more than one wire to each
terminal. Be sure to read the notes referenced in
the numbered triangles above. These numbered
notes appear on the next page.
G
O/B W
NOT
USED
Y
R
RC
or R
New
Thermostat Possible letter designations on the labeled wires
M22055
Do Not Connect
RC
or RH, 4, V
R
or Y1, M
Y
or W1, H, O, B
W
or F
G
or X, B
C
1
2
2
3
4
1