Furnace Twinning - Goodman GRL SERIES Installation Instructions Manual

FURNACE TWINNING

INSTALLATIONS
NOTE: Run furnaces as individual
furnaces before trying to twin or when
troubleshooting.
Twinning operation of two furnaces,
installed side-by-side, connected by a
common duct system with main power
supplied by the same source, and
controlled by a common thermostat can
be done with the UT Electronic Controls
1095-104 integrated control boards.
➀
Only twin identical furnaces with
identical control boards.
➁
Furnaces must have same heating
and blower capacity.
➂
Only bottom returns can be used.
(Upflow models only)
➃
No more than two furnaces can
share the same supply and return.
IMPORTANT: Twinning furnaces must
operate off the same phase of power.
It should be noted that both blowers will
run simultaneously when there is a call
for heating, cooling or fan.
The status LED will display blink code 5
if twinning is not set up properly (see
Troubleshooting diagram).
IMPORTANT: Only two furnaces on a
single thermostat.
NOTE: Furnaces that are twinned
cannot share a common return or
supply ducts.
34
TWO-STAGE TWINNING OPERATION
USING A SINGLE-STAGE
THERMOSTAT
A two-stage thermostat will give the
most optimum performance. The
furnace (when twinned) can operate
using a single-stage thermostat. For the
first twelve minutes of operation, the
furnace will run at low fire. If the
thermostat does not satisfy in twelve
minutes, the furnaces will automatically
switch to high fire and will run on high
fire until the thermostat is satisfied. See
Figure 31 for the wiring diagram for this
configuration.
UT ELECTRONIC CONTROLS
1095-102 AND 1095-104 IFC
Two-Stage Operation
(See Figure 33)
a. Control board "ONE" is on
furnace connected to the
thermostat.
b. The 24 VAC supply to both
control boards must be in
phase with each other.
c. Connect the "C," "W1," "W2,"
"Y," and "TWIN" terminals to
counterparts on each control.
d. Both control boards must have
switch #3 of SW1 in the
"TWIN" position. See Figure
32 for wiring diagram.