Lennox Twinning Kit 16W72 User manual

507827-01 Issue 1813 Page 1 of 4
Save these instructions for future reference
INSTALLATION INSTRUCTIONS
Twinning Kit 16W72
For Single and Two Stage Gas-Fired Furnaces with Constant
Torque Blower Motors
This manual must be left with the homeowner for future reference.
This is a safety alert symbol and should never be ignored. When you see this symbol on labels or in
manuals, be alert to the potential for personal injury or death.
(P) 507827-01
*P507827-01*
WARNING
Improperinstallation,adjustment,service,ormaintenance
can cause property damage, personal injury, or death.
Consult a qualied installer, service agency, or the gas
supplier for information or assistance.
CAUTION
Label all wires prior to disconnection when servicing
controls. Wiring errors can cause improper and
dangerous operation.
WARNING
Risk of electrical shock. Disconnect all
remote power supplies before installing
or servicing any portion of the system.
Failure to disconnect power supplies can
result in property damage, personal injury,
or death.
Parts List
Quantity Part
5 DPST Relay
30 .250 Quick Disconnect Terminal
10 Self-Tapping Screws
1 Installation Instructions
Application
This accessory kit is used to operate two gas-red furnaces
that are intended to be “twinned together,” meaning
connected in a shared duct system controlled by a single
thermostat.
• Do not twin more than two furnaces at a time.
• Must be installed and wired in accordance with local
codes.
• Used for single-stage heating/single-stage cooling
with a single-stage thermostat.
• Used for two-stage heating/single-stage cooling with
either a single-stage or two-stage thermostat.

507827-01Issue 1813Page 2 of 4
System Operation
With this twinning accessory kit, it is important to
understand upon a call for heat from a single thermostat,
that both circulation air blowers will come on and go off
at the same time. In addition, the induced draft blowers
of both furnaces will be energized, the pressure switch of
each furnace will close, the gas valve of each furnace will
open (either high or low re depending on furnaces), and
the burners of each furnace will ignite. Thirty seconds later,
both circulation air blowers will be energized.
When the heat demand is satised, the heating relays of
each furnace are de-energized and close each furnace’s
gas valve. Both furnace circulation air blowers will continue
to run until the blower off fan period has been met.
• Single-stage furnaces twinned together with a single-
stage thermostat will operate each furnace at the
same time.
• Two-stage furnaces twinned together with a two-stage
thermostat will operate each furnace such that rst
stage heat of each furnace operates at the same time.
When second stage heat demand is needed, both
furnaces will transition to high heat at the same time.
• Two-stage furnaces twinned together with a single-
stage thermostat will utilize control boards 7.5/10 min.
stage transition. Each furnace must be set to same
setting.
Installation
To twin two gas-red furnaces, follow these directions
along with the appropriate application section and wiring
schematic.
Single-Stage Heating and Cooling with Single-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 relay as shown in Figure 1 through
Figure 3. Use the female quick connect terminals
supplied in kit and the proper length of 18 gauge wire
(eld supplied) to complete wiring.
3. After wiring is complete, cycle both heating and cooling
modes to verify both are working properly.
FURNACE
1F
URNACE 2
ISO RELAY
THERMOSTAT
HEAT TWIN ONLY
W1
R
C
Y1
Y2
G
W2
W1
R
C
Y1
Y2
G
W2
W1
R
C
Y1
Y2
G
W2
Figure 1.

507827-01 Issue 1813 Page 3 of 4
FURNACE
1F
URNACE 2
ISO RELAY
THERMOSTAT
COOL TWIN ONLY
W1
R
C
Y1
Y2
G
W2
W1
R
C
Y1
Y2
G
W2
W1
R
C
Y1
Y2
G
W2
Figure 2.
FURNACE
1F
URNACE 2
ISO RELAY
THERMOSTAT
FAN TWIN ONLY
W1
R
C
Y1
Y2
G
W2
W1
R
C
Y1
Y2
G
W2
W1
R
C
Y1
Y2
G
W2
Figure 3.
Two-Stage Heating and Single-Stage Cooling with
Single-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 1 through
Figure 3. Use the female quick connect terminals
supplied in kit and the proper length of 18 gauge wire
(eld supplied) to complete wiring.
3. Set DIP switches of Furnace 1 and Furnace 2 control
boards to same furnace mode DIP switch setting for
single stage thermostat, 2nd stage timing setting
and blower off setting. See the furnaces’ installation
instructions for additional detail.
NOTE: Units are factory shipped with DIP switch
settings for two-stage thermostat operation.
4. After wiring is complete, cycle both high and low
heating modes and cooling modes to verify both are
working properly.

507827-01Issue 1813Page 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
(eld 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
THERMOSTAT
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
THERMOSTAT
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 1FURNACE 2
ISO RELAY
THERMOSTAT
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.