13
6. ELECTRIC CONNECTION TO THE FURNACE
W
R
G
Y
W
R
G
C
Y
UNIT TERMINAL
CONNECT
OR
THERMOSTAT
TERMINALS
FOUR
WIRES
TWO WIRES
heating only
FURNACE
24-VOLT
TERMINAL BLOCK
TWO WIRES
COOLING SYSTEM
N
O
C
N
C
I O
C
OL
Y
R G B
W R G
Y
W
R
Y
R
G
Y
C
THERMOSTAT
TERMINAL
4 WIRES
2 WIRES
heating only
wiring
nuts
FURNACE
24-VOLT
TERMINAL BLOCK
2 WIRES
COOLING SYSTEM
NO
NC
C
UNIT TERMINAL
CONNECT
OR
N
O
C
N
C
I OC
O
L
Y
R G B
VE0108A
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.
F
OR
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
ALTERNATE
FURNACE
INTERLOCK
WIRING
.
STANDARD
FURNACE
INTERLOCK
WIRING
ALTERNATE
FURNACE
INTERLOCK
WIRING
WARNING
!
