Installation Guide
Wiring
CAUTION: ELECTRICAL HAZARD. Can cause electrical shock or equipment damage.
Disconnect power before wiring.
Wiring
Keep wires in this
shaded area
1
2
3
Loosen screw terminals, insert
wires into terminal block, then
re-tighten screws.
Push excess wire back into the
wall opening. Keep wires in shaded
area as shown at left.
Plug the wall opening with non-
flammable insulation to prevent
drafts from affecting thermostat
operation.
Terminal Designations
Conventional Terminal Letters:
Y2 2nd stage compressor contactor
W2 2nd stage heat relay
Heat Pump
Conventional
G
W
C
Fan relay
1st stage heat relay
NOTES
Common wire from secondary side of
cooling system transformer
1st stage compressor contactor
Heating power. Connect to secondary
side of heating system transformer.
R & Rc terminals
In single-transformer system, leave metal
jumper in place between R & Rc. Remove
metal jumper if two-transformer system.
Y
R
Rc Cooling power. Connect to secondary
C terminal
side of cooling system transformer.
The C (common wire) terminal is optional
when thermostat is powered by batteries.
Heat Pump Terminal Letters:
L
Heat pump reset. L terminal powered
continuously when System is set to Em
Heat.
W (O/B) terminal
If thermostat is configured for a heat pump
in the Installer Setup, configure changeover
valve for cool (“O” factory setting) or heat
E
Emergency heat relay
Aux Auxiliary heat relay
G Fan relay
O/B Changeover valve for heat pumps
(“B”).
L terminal (Output)
C
Common wire from secondary side of
cooling system transformer.
Compressor contactor
Heating power. Connect to secondary
side of heating system transformer.
Heat pump reset. L terminal powered contin-
uously when thermostat is set to Em Heat.
Configure thermostat for 2 heat / 1 cool heat
pump in the Installer Setup.
Y
R
Rc Cooling power. Connect to secondary
Wire specifications
side of cooling system transformer.
Use 18- to 22-gauge thermostat wire.
Shielded cable is not required.
4