Installation Guide

17
5. ELECTRICAL CONNECTION TO THE FURNACE
WARNING
!
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 ALTERNATE FURNACE INTERLOCK WIRING.
STANDARD FURNACE INTERLOCK WIRING ALTERNATE FURNACE INTERLOCK WIRING
W
Y
R
G
Y
C
UNIT TERMINAL CONNECTOR
THERMOSTAT
TERMINALS
COOLING SYSTEM
NO C NC I OC OL
WRGY
W
R
Y
R
G
Y
C
THERMOSTAT
TERMINAL
4 WIRES
2 WIRES
heating only
FURNACE
24-VOLT
TERMINAL BLOCK
2 WIRES
COOLING SYSTEM
NO
NC
C
UNIT TERMINAL CONNECTOR
VE0350A
NO C NC I OC OL
WRGY
4 WIRES
2 WIRES
heating only
FURNACE
24-VOLT
TERMINAL BLOCK
2 WIRES
LOW VOLTAGE
CLASS 2
LOW VOLTAGE
CLASS 2