507827-01
Issue 1813
Page 4 of 4
Two-Stage Heating and Single-Stage Cooling with
Two-Stage Thermostat
1. Mount DPST relay(s) (supplied with kit) next to the
blower control board of Furnace 1. Use kit supplied
self-tapping screws to mount DPST relay(s) to the
control bracket.
2. Connect the thermostat with Furnace 1, Furnace 2,
and the DPST relays as shown in Figure 4 through
Figure 6. Use the female quick connect terminals
supplied in kit and the proper length of 18 gauge wire
(field supplied) to complete wiring.
3. After wiring is complete, cycle both high and low
heating modes and cooling modes to verify both are
working properly.
FURNACE
1F
URNACE
2
THERMOST
AT
TWO STAGE HEAT ONLY
W1
R
C
Y1
Y2
G
W2
W1
R
C
Y1
Y2
G
W2
W1
R
C
Y1
Y2
G
W2
Figure 4.
FURNACE
1F
URNACE
2
THERMOST
AT
TWO STAGE COOL ONLY
W1
R
C
Y1
Y2
G
W2
W1
R
C
Y1
Y2
G
W2
W1
R
C
Y1
Y2
G
W2
Figure 5.
FURNACE
1F
URNACE
2
ISO RELAY
THERMOST
AT
FAN TWIN ONLY
W1
R
C
Y1
Y2
G
W2
W1
R
C
Y1
Y2
G
W2
W1
R
C
Y1
Y2
G
W2
Note
: Furnace transformers must be in phase while twinning.
Figure 6.
