5. ELECTRICAL CONNECTION TO THE FURNACE
Never connect a 120-volt AC circuit to the terminals of the furnace interlock (standard wiring). Only use the low
voltage class 2 circuit of the furnace blower control.
For a furnace connected to a cooling system:
On some older thermostats, energizing the "R" and "G" terminals at the furnace has the effect of energizing "Y" at the thermostat and
thereby turning on the cooling system. If you identify this type of thermostat, you must use the
STANDARD FURNACE INTERLOCK WIRING
W
R
G
4 WIRES
2 WIRES
heating only
W
R
G
C
Y
Y
FURNACE
24-VOLT
TERMINAL BLOCK
VE0350A
THERMOSTAT
Y
TERMINALS
LOW VOLTAGE
CLASS 2
2 WIRES
COOLING SYSTEM
!
WARNING
ALTERNATE FURNACE INTERLOCK WIRING
4 WIRES
2 WIRES
heating only
W
R
R
G
C
Y
Y
FURNACE
24-VOLT
TERMINAL BLOCK
17
ALTERNATE FURNACE INTERLOCK WIRING
THERMOSTAT
W
R
G
Y
TERMINAL
LOW VOLTAGE
CLASS 2
NO
NC
C
2 WIRES
.
COOLING SYSTEM