11
443 06 2403 01
Specifications subject to change without notice.
5. Unistrut or similar material may be used, provided that
the furnaces do not sag in the middle or bend or twist at
the support ends. The support material must be secured
to the bottom of each furnace in a manner similar to
securing angle iron to the furnace.
Refer to Figure 3 and Table 2 for appearance and dimensional
drawing of twinned furnaces and their connection locations.
1. Select 2 identical heating and airflow furnaces. (See
2. Remove outer door and blower access door.
3. Remove bottom closure panels from both furnaces. (See
Figure 4)
a. Lay furnaces on back or sides.
b. Remove 2 screws from bottom front panel.
c. Pull front panel forward to remove.
d. Remove bottom closure panel and set aside for
possible use as roll
−
out protection.
e. Reinstall bottom front panel.
f. Stand furnaces upright.
4. For all horizontal applications: Return air can only be
connected to bottom opening of furnace.
5. Apply 2 factory
−
supplied foam strips to mating side of
each furnace. Locate strips equal distance from top and
bottom as shown in Figure 5.
6. Remove 7/8
−
in. diameter accessory hole knockouts in
blower compartment from mating sides of furnaces. (See
7. Insert a plastic snap bushing through the 7/8
−
in. K.O.
from the outside of the casing.
8. Position furnaces on top of each other on platform or
suspended supports. Adjust and shim each furnace to
align 7/8
−
in. diameter holes in both furnaces.
9. Drill two 1/8
−
in. holes, approximately 1 in. (25 mm)below
discharge flange, from inside top of discharge opening
and through both furnaces. (See Figure 6) Drill two
1/8
−
in. holes, approximately 1 in. (25 mm)above return
air opening flange, from inside blower compartment and
through both furnaces. (See Figure 7)
10. Drive 1 factory
−
supplied screw through each hole and
tighten until furnaces are secure and foam strips have
sealed gap between furnaces.
11. Connect return
−
and supply
−
air ducts to furnaces. Seal
duct connections to prevent air leakage.
12. Move 115
−
v junction box JB in RH furnace (as viewed
from the upflow position) from left
−
hand side to
right
−
hand side. Refer to furnace installation instructions
for complete details.
13. Go to PROCEDURE 2A for Single Stage Furnaces or
PROCEDURE 2B for Two
−
Stage Furnaces.
PROCEDURE 2 — CONNECT ELECTRICAL
COMPONENTS—HEATING
A. All Single
−
Stage Models N8MSN & N8MSL Multipoise
Single
−
Speed Non
−
Condensing HSI Furnaces
FIRE HAZARD
Failure to follow this warning could result in fire,
personal injury or death.
Make no connections between the R 24
−
vac connector
in 1 furnace and the R 24
−
vac connector in other
furnace.
!
WARNING
See Electrostatic Discharge Precaution Section.
The twinning kit can be used for single
−
stage or two
−
stage
heating operation. There are 3 harness assemblies included in
this kit. If the furnaces are side
−
by
−
side, only 2 harness
assemblies are required. If the furnaces are installed
back
−
to
−
back, all 3 harness assemblies included in the kit
must be used.
1. Remove outer doors and blower access doors from both
furnaces.
2. If furnaces are installed back
−
to
−
back in any orientation,
the external Extension Harness must be used. The
harness consists of:
a. 54
−
1/2 inches (1384 mm) of 1/2
−
in. flexible steel
conduit
b. (2) 90
_
conduit connectors
c. (1) 4 wire polarized wiring harness d. (1) 2 wire
polarized wiring harness
3. Install the Extension Harness as follows:
a. Remove lock nuts from the end of each conduit
connector.
b. Route the end of the harness, labeled “twinning kit
harness,” that mates to the TRK relay harness from
the outside of the furnace through the 7/8
−
in.
knock
−
out in the casing to the blower compartment.
c. Route the end of the harness that mates to the
4
−
wire harness through the outside of the furnace
through the 7/8
−
in. knockout in the casing to the
blower compartment.
d. Install the lock nuts on the 90
_
conduit connectors.
e. Install 2 kit
−
supplied straps approximately 18 inches
(457 mm) from each end of harness.
Single
−
Stage Heat with Single
−
Stage Gas
−
Heat
Thermostat (Field
−
Supplied)
NOTE
: This application allows both furnaces to operate as 1
furnace in gas heat mode as determined by single
−
stage
thermostat operation. Both furnaces operate in heating mode
simultaneously. See furnace Installation, Start
−
Up, and
Operating Instructions for further details on this heating mode.
1. Install harness labeled “Main Furnace” with TKR on L/H
Furnace:
The Main Harness includes the TKR relay and Auxiliary
Limit switch on the harness. The harness is also tagged
“Main Furnace” near the ends of the plug connector.
a. Secure relay of TKR harness assembly to LH
furnace blower housing using 2 factory
−
supplied
NOTE
: See Figure 15 for Single Stage furnace Twinning Kit
wiring diagram.
b. Connect TKR white wire labeled W from TKR to LH
furnace control thermostat connection W.
c. Connect TKR black wire labeled C from TKR to LH
furnace control thermostat connection C.
d. Connect yellow wire labeled TEST to LH furnace
control TEST/TWIN terminal.
e. If Extension Harness was used, connect 4
−
wire
harness to Extension Harness.
NOTE
: If Extension Harness will not plug in to L/H and R/H
furnaces, extension harness is installed backward. Remove
extension harness and re
−
install in correct orientation.
