ICP NAHA00601WK Installation Instructions Manual

INSTALLATION INSTRUCTIONS

TWINNING KIT

NAHA00601WK

Please read these instructions completely before starting the
installation.

SAFETY CONSIDERATIONS

! WARNING

FIRE, EXPLOSION, ELECTRICAL SHOCK AND CARBON
MONOXIDE POISONING HAZARD

Failure to follow this warning could result in personal injury,
death and/or property damage.

Improper installation, adjustment, alteration, service,
maintenance, or use can cause carbon monoxide poisoning,
explosion, fire, electrical shock, other conditions, which could
result in personal injury or death. Consult a qualified service
agency, local gas supplier, or your distributor or branch for
information or assistance. The qualified service agency must
use only factory−authorized kits or accessories when
modifying this product.

!

FIRE, EXPLOSION, ELECTRICAL SHOCK, AND CARBON
MONOXIDE POISONING HAZARD

Failure to follow this warning could result in dangerous
operation, personal injury, death, or property damage.

Furnaces shall NOT be twinned (i.e. tandem or staged
operation) unless approved in factory technical specifications
literature for the furnace. A factory authorized, field−supplied
Twinning Kit MUST be used. Consult furnace pre−sale
literature for specific models approved for twinning and the
correct twinning kit. Twinned furnaces must be installed on
both a common supply AND a common return duct system
as shown in the Twinning Kit Installation Instructions. Only
two furnaces can be twinned on a common supply and
return duct system using a factory authorized twinning kit.

WARNING

gloves. Have a fire extinguisher available during start−up,
adjustment steps, and service calls.
Recognize safety information. This is the safety−alert symbol

. When you see this symbol on the unit and in instructions or

manuals, be alert to the potential for personal injury.
Understand the signal words DANGER, WARNING, and

CAUTION. These words are used with the safety−alert symbol.
DANGER identifies the most serious hazards which will result

in severe personal injury or death. WARNING signifies hazards
which could result in personal injury or death. CAUTION is
used to identify unsafe practices which may result in minor
personal injury or product and property damage. NOTE is used
to highlight suggestions which will result in enhanced
installation, reliability, or operation.

TABLE OF CONTENTS

SAFETY CONSIDERATIONS 1................................

TABLE OF CONTENTS 1.....................................

INTRODUCTION 2..........................................

DESCRIPTION AND USAGE 2................................

ELECTROSTATIC DISCHARGE (ESD) PRECAUTION 4..........

MULTIPOISE SINGLE−SPEED AND TWO−SPEED

NON−CONDENSING HSI FURNACE MODELS 4................

INSTALL FURNACES 5......................................

DIMENSIONS 5.............................................

CONNECT ELECTRICAL COMPONENTS—HEATING 11..........

CONNECT ELECTRICAL COMPONENTS−COOLING 15..........

VENTING 15................................................

GAS SUPPLY PIPING 15......................................

ELECTRICAL SUPPLY CONNECTIONS 15......................

START−UP AND ADJUSTMENT 16.............................

SEQUENCE OF OPERATION 19...............................

Installing and servicing heating equipment can be hazardous
due to gas and electrical components. Only trained and

qualified personnel should install, repair, or service
heating equipment. Untrained personnel can perform basic

maintenance functions such as cleaning and replacing air
filters. All other operations must be performed by trained
service personnel. When working on heating equipment,
observe precautions in literature, on tags, and on labels
attached to or shipped with unit and other safety precautions
that may apply.
These instructions cover the minimum requirements and
conform to existing national standards and safety codes. In
some instances, these instructions exceed certain local codes
and ordinances, especially those that may not have kept up
with changing residential construction practices. We require
these instructions as a minimum for a safe installation.
Follow all safety codes. In the United States, follow all safety
codes including the current edition of the National Fuel Gas
Code (NFGC) NFPA No. 54/ANSI Z223.1. In Canada, refer to
the current edition of the National Standard of Canada, Natural
Gas and Propane Installation Codes (NSCNGPIC),
CAN/CSA−B149.1 and .2. Wear safety glasses and work

! WARNING

ELECTRICAL SHOCK AND FIRE HAZARD

Failure to follow this warning could result in personal injury,
death, and/or property damage.

Turn off the gas and electrical supplies to the furnace and
install lockout tag before performing any installation or
modification. Follow the operating instructions on the label
attached to the furnace.

!

CAUTION

CUT HAZARD

Failure to follow this caution may result in personal injury.

Sheet metal parts may have sharp edges or burrs. Use
care and wear appropriate protective clothing and gloves
when handling parts.

443 06 2403 01 6/12/2018

INTRODUCTION

IMPORTANT: Only the furnace sizes listed in Table 2 can be

twinned. Both furnaces must have the same product number,
including heating and cooling sizes, to achieve correct
operation.

This furnace twinning kit permits connection to the following
furnaces to operate as a single unit on the same duct work:

S Two multipoise, 33.3 inch (846 mm), single−speed,

non−condensing furnaces (See Figure 1, Figure 2 and
Table 2)

S Two multipoise, 33.3 inch (846 mm), two−stage,

non−condensing furnaces (See Figure 1, Figure 14, and
Table 2)

!

UNIT AND PROPERTY DAMAGE HAZARD

Failure to follow this warning could result in unit and
property damage.

A non−condensing furnace shall NOT be twinned with a
condensing furnace. Two−stage condensing or
non−condensing furnaces shall not be twinned with any
single stage furnace. Do not twin furnaces that have a
different number of blower motor speed taps together.
Furnaces shall only be twinned in the positions shown.
Variable−speed furnaces shall not be twinned.

WARNING

DESCRIPTION AND USAGE

Refer to the appropriate section for your furnaces.
SECTION I: Models N8MSN & N8MSL Multipoise

Single−Speed Non−Condensing HSI Furnaces

S Single−Stage Heat with Single−Stage Gas−Heat Thermostat
S Two−Stage Heat with Two−stage Gas−Heat Thermostat

Models F8MTL & G8MTL Multipoise Two−Stage
Non−Condensing HSI Furnaces

S Two−Stage Heat with Single−Stage Gas−Heat Thermostat
S Two−Stage Heat with Two−Stage Gas−Heat Thermostat

DUCT CONNECTIONS

All furnaces must have a common supply plenum attached to
the furnaces or evaporator coils prior to any branch supply
trunk or take−off. The height of the plenum should be at least
as high (upflow/downflow) or as long (horizontal) as the width
of one furnace. Supply air dampers, when used should be
installed in the branch ducts, not in the common plenum. Fire
or smoke dampers, when required by code may be installed in
the common plenum. Refer to the damper manufacturer’s
ratings installation instructions for proper application. The
damper should not create undue restriction in the open
position.

All furnaces must be installed to ensure sufficient return air to
both furnaces:

S For upflow furnaces: A combination of one full side of each

and bottom inlet plenum or bottom only inlet plenum shall be
used for return air to each furnace. The preferred method is
to have all return air brought into the bottom of the furnaces
through a common bottom plenum. The bottom return−air
plenum shall be at least as high as the width of the furnace
bottom return−air opening. When there are height limitations,
the bottom return−air plenum height can be reduced to 8 in.
minimum (203mm) if one entire side return−air opening of
each furnace is used in conjunction with the bottom return
opening. Rear inlet plenums shall not be used. (See
Figure 1) Connect all return trunks or branch return ducts to
common return plenum.

S For downflow and horizontal furnaces: All return air must

be brought into the bottom opening of the furnace through a
common return air plenum. The return−air plenum shall be at
least as long (horizontal) or tall (downflow) as the width of
the furnace return−air opening. (See Figure 2) Connect all
return trunks or branch return ducts to common return
plenum.

S For all furnaces: Fire or smoke dampers, when required by

code may be installed in the common return plenum. Refer
to the damper manufacturer’s ratings installation instructions
for proper application. The damper should not create undue
restriction in the open position.

!

FIRE HAZARD

Failure to follow this warning could result in improper
auxiliary limit operation, fire, personal injury or death.

Do not remove the center return−air partitions between
the furnaces.

Staged heating operation is permitted only with this twinning
kit. With the single−speed, non−condensing furnaces, the
left−hand furnace is used for first−stage heat, and both
furnaces are used for second−stage heat. With the two−stage,
non−condensing furnaces, low−gas heat in both furnaces is
used for first−stage heat, and high−gas heat in both furnaces is
used for second−stage heat. This kit ensures both furnace
blowers operate simultaneously so air flows through the duct
work rather than recirculating in a loop between the furnaces.

WARNING

2

Specifications subject to change without notice.

443 06 2403 01

Common

A

Supply Air
Plenum

Figure 1 − Upflow Ductwork Connections

Common

A

Supply Air
Plenum

Twinned Furnace

Common
Return

A

A

Example 1

Example 1 Notes:

Return duct cannot obstruct access to either furnace
Return Air can enter thru any combination of:

a. Left side only
b. Right side only
c. Bottom only
d. Back of platform when height of platform

equal Dimension A as shown

e. Any combination of a, b, c, d

Air
Plenum

Figure 2 − Downflow/Horizontal Ductwork Connections

Return
Air
Plenum

B

Example 2 Notes:

When furnaces are installed Back-to-Back (not shown)
return duct MUST connect to the common return plenum
and side inlet of BOTH furnaces
Return duct cannot obstruct access to either furnace

Twinned Furnace

8 MIN

Common Return
Air Plenum

Example 2

Return
Air
Plenum

B

A02223

Common
Return
Air
Plenum

A

A

Twinned Furnaces

Common
Supply Air
Plenum

Example 3 - Downflow Applications

Example 3 Notes:

Do not connect return air to any side of the
furnace
Connect return air plenum as shown

A

A

Common
Supply Air
Plenum

Example 4 Notes:

Do not connect return air to any side of furnace.
Do not stack condensing furnaces of top of each other
When furnaces are installed Side-by-Side (not shown),
return connection is similiar. Depth of plenum
Dimension A must equal to the front width of one furnace

Twinned furnaces
Stacked* (80% ONLY)



A

Example 4 - Horizonal Applications

A

Common
Return
Air
Plenum

443 06 2403 01

Specifications subject to change without notice.

3

Table 1 – Kit Contents

DESCRIPTION PART NO. QTY

Sealing tape 2

External extension harness 327962701 1

Main twinning harness 327957701 1

Secondary twinning harness 327959701 1

Twostage furnace wiring diagram 337068101 1

Single stage furnace heat wiring
diagram

Single stage furnace/twostage
heat wiring diagram

Label 327956101 1

Tape 1

Bag Assembly includes:

Snap bushing 2

Screws (HEX HD 6B X ¾) 10

Screws (flat head) 1

Wire tie 4

Clamps 2

Installation Instructions 1

Auxiliary door switch bracket 1

337070101 1

337069101 1

NOTE: As a result of staged heating with single−speed
furnaces, the air temperature distribution in the supply plenum
may be uneven when only 1 furnace is heating.

NOTE: Refer to the Installation, Start−Up, and Operating
Instructions supplied with each furnace for information on
venting, clearances, start−up, maintenance, and other
information not covered in this publication.

See Table 1 for kit contents.

ELECTROSTATIC DISCHARGE (ESD) PRECAUTION

!

UNIT DAMAGE HAZARD

Failure to follow this caution may result in unit and
component damage.

Failure to follow this caution could result in unit and
component damage. Electrostatic discharge can affect
electronic components. Take precautions during furnace
installation and servicing to protect the furnace
electronic control. Precautions will prevent electrostatic
discharges from personnel and hand tools which are
held during the procedure. These precautions will help
to avoid exposing the control to electrostatic discharge
by putting the furnace, the control, and the person at the
same electrostatic potential.

CAUTION

A02224

1. Disconnect all power to the furnace. DO NOT TOUCH
THE CONTROL OR ANY WIRE CONNECTED TO THE
CONTROL PRIOR TO DISCHARGING YOUR BODY’S
ELECTROSTATIC CHARGE TO GROUND.

2. Firmly touch a clean, unpainted, metal surface of the
furnace chassis which is close to the control. Tools held
in a person’s hand during grounding will be satisfactorily
discharged.

3. After touching the chassis you may proceed to service
the control or connecting wires as long as you do
nothing that recharges your body with static electricity
(for example; DO NOT move or shuffle your feet, DO
NOT touch ungrounded objects, etc.).

4. If you touch ungrounded objects (recharge your body
with static electricity), firmly touch furnace again before
touching control or wires.

5. Use this procedure for installed and uninstalled
(ungrounded) furnaces.

6. Before removing a new control from its container,
discharge your body’s electrostatic charge to ground to
protect the control from damage. If the control is to be
installed in a furnace, follow items 1 through 5 before
bringing the control or yourself into contact with the
furnace. Put all used AND new controls into containers
before touching ungrounded objects.

7. An ESD service kit (available from commercial sources)
may also be used to prevent ESD damage.

SECTION I: MULTIPOISE SINGLE−SPEED AND

TWO−SPEED NON−CONDENSING HSI FURNACE

MODELS

SINGLE−STAGE TWO−STAGE

N8MSN F8MTL

N8MSL G8MTL

NOTE: Throughout these instructions, when the furnace
installed side−by−side, the left−hand (LH) side will be referred
to as the LH furnace, and the furnace installed on the
right−hand (RH) side as the RH furnace. When the furnaces
are installed back−to−back, the left−hand (LH) side will be
referred to as the LH furnace, and the furnace installed on the
right−hand (RH) side as the RH furnace when viewed from the
side with the extension harness installed.

4

Specifications subject to change without notice.

443 06 2403 01

Figure 3 − Dimensional Drawing

FLUE

PROCEDURE 1 — INSTALL FURNACES

A. Upflow/Downflow, Side−by−Side Position

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
Table 2.)

2. Remove outer door and blower access door.

3. For upflow and downflow applications:
a. For upflow applications: Bottom return air usage is

required as part of any upflow return air
configuration. If additional return air is to enter 1 side
of each furnace, in addition to bottom return air, cut
open 1 entire return−air opening in appropriate side
of each furnace. (See Figure 1)

UNIT DAMAGE AND FIRE HAZARD

Failure to follow this warning could result in fire,
personal injury or death.

DO NOT use the back of the furnace for return−air duct
connections, as limit cycling will occur.

b. For downflow applications:

!

Return air can only be connected to bottom opening
of furnace. A common return air plenum is required
for proper auxiliary limit switch operation. (See
Figure 2)

Table 2 – Dimensions − in. (mm) for Single Stage and Two−Stage with PSC Blower

A B C D

CABINET WIDTH

Model Numbers

0451408 14−3/16 (360) 12−9/16 (319) 9−5/16 (237) 12−11/16 (322) 4 (102) 104 (47)
0451412 14−3/16 (360) 12−9/16 (319) 9−5/16 (237) 12−11/16 (322) 4 (102) 107 (49)
0701408 14−3/16 (360) 12−9/16 (319) 9−5/16 (237) 12−11/16 (322) 4 (102) 111 (50)
0701412 14−3/16 (360) 12−9/16 (319) 9−5/16 (237) 12−11/16 (322) 4 (102) 115 (52)
0701716 17−1/2 (445) 15−7/8 (403) 11−9/16 (294) 16 (406) 4 (102) 126 (57)
0901714 17−1/2 (445) 15−7/8 (403) 11−9/16 (294) 16 (406) 4 (102) 127 (58)
0902116 21 (533) 19−3/8 (492) 13−5/16 (338) 19−1/2 (495) 4 (102) 140 (64)
0902120 21 (533) 19−3/8 (492) 13−5/16 (338) 19−1/2 (495) 4 (102) 146 (66)
1101712 17−1/2 (445) 15−7/8 (403) 11−9/16 (294) 16 (406) 4 (102) 135 (61)
1102116 21 (533) 19−3/8 (492) 13−5/16 (338) 19−1/2 (495) 4 (102) 146 (66)
1102122 21 (533) 19−3/8 (492) 13−5/16 (338) 19−1/2 (495) 4 (102) 152 (69)
1352116 21 (533) 19−3/8 (492) 13−5/16 (338) 19−1/2 (495) 4 (102){ 149 (68)
1352422 24−1/2 (622) 22−7/8 (581) 15−1/16 (383) 23 (584) 4 (102){ 163 (74)
1552420 24−1/2 (622) 22−7/8 (581) 15−1/16 (383) 23 (584) 4 (102){ 170 (77)

*5−in. or 6−in. (127 or 152 mm) vent connector may be required in some cases.

{135 and 155 size furnaces require 5 or 6−in. (127 or 152 mm) vents. Use a vent adapter between furnace and vent stack. See Installation Instructions for complete

installation requirements

in (mm)

OUTLET WIDTH

in (mm)

TOP AND BOTTOM FLUE

COLLAR in (mm)

WARNING

BOTTOM INLET
WIDTH in (mm)

COLLAR*

in (mm)

SHIP WT (KG)

443 06 2403 01

Specifications subject to change without notice.

5

!

UNIT DAMAGE AND FIRE HAZARD

Failure to follow this warning could result in unit
damage, fire, personal injury or death.

DO NOT use the back or sides of the furnace for
return−air duct connections in downflow position, as limit
switch cycling will occur.

4. 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 discard.
e. Reinstall bottom front panel.

f. Stand furnaces upright.

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. Trim off excess material.

6. Remove 7/8−in. diameter accessory hole knock−outs in
blower compartment from mating sides of furnaces. (See
Figure 3)

Bottom
Closure Panel

Bottom Filler Panel

WARNING

8. Bend or remove the supply flanges as required for
upflow or downflow installation. Refer to the furnace
installation instructions for complete details.

9. Position furnaces against each other on return air
plenum, supply air plenum or evaporator coil casing.
Adjust and shim each furnace to align 7/8−in. diameter
holes in both furnaces.

10. 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)below return
air flange, from inside top of return air opening and
through both furnaces. (See Figure 7 as an example.)

11. Drive 1 factory−supplied screw through each hole and
tighten until furnaces are secure and foam strips have
sealed gap between furnaces.

12. Connect return− and supply−air ducts to furnaces. Seal
duct connections to prevent air leakage.

13. 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.

14. Go to PROCEDURE 2A for Single Stage Furnaces or
PROCEDURE 2B for Two−Stage Furnaces.

B. Upflow/Downflow, Back−to−Back Position

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
Table 2)

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 discard.
e. Reinstall bottom front panel.

f. Stand furnaces upright.

4. Applications

Figure 4 − Removing Bottom Closure Panel

Figure 5 − Location of Foam Strips

7. Insert a plastic snap bushing through the 7/8−in.
knock−out from the outside of the casing.

6

Specifications subject to change without notice.

A02232

Figure 6 − Attaching Furnaces Together at Discharge

Opening

a. For upflow applications:

Bottom return air usage is required as part of any
upflow return air configuration. If additional return air
is to enter 1 side of each furnace, in addition to
bottom return air, cut open 1 entire return−air

443 06 2403 01

opening in appropriate side of each furnace. (See
Figure 2)

!

UNIT DAMAGE AND FIRE HAZARD

Failure to follow this warning could result in unit
damage, fire, personal injury or death.

DO NOT use the side of the furnace for return−air duct
connections, as limit cycling will occur.

b. For downflow applications:

Return air can only be connected to bottom opening
of furnace. A common return air plenum is required
for proper auxiliary limit switch operation. (See
Figure 3)

5. Apply 2 factory−supplied foam strips to the back of each
furnace. Locate strips equal distance from top and
bottom as shown in Figure 5. Trim off excess material.

6. Determine which side of furnace will be used to route
external extension harness. Remove 7/8−in. diameter
accessory hole knockouts in blower compartment side
selected to attach harness to. (See Figure 3)

7. Bend or remove the supply flanges as required for
upflow or downflow installation. Refer to the furnace
installation instructions for complete details.

8. Position furnaces back−to−back on return−air plenum,
supply air plenum or evaporator coil casing. Adjust and
shim each furnace to align both furnaces.

NOTE: External extension harness cannot be used on the
same side of the furnace that the return air ducts connect to.
Locate harness on opposite side of furnace when side return
air is used.

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. (Similar to Figure 6) Drill two
1/8−in. holes, approximately 1 in. (25 mm)below return
air flange, from inside top of return air opening and
through both furnaces. (Similar to Figure 7)

10. Drive 1 factory−supplied No. 6 X 3/4−in. LG 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.

WARNING

A02219

Figure 7 − Attaching Furnaces Together at Return Air

Opening

12. Move 115−v junction box JB in either furnace from
left−hand side to right−hand side if required. Refer to
furnace installation instructions for complete details.

13. Go to Step 2A for Single Stage Furnaces or Step 2B for
Two−Stage Furnaces.

C. Horizontal, Back−to−Back Position

When twinning furnaces in the horizontal position,
consideration must be made to the type of building
construction. Attic floors should be constructed to support
normal live and dead loads of the furnaces and the person(s)
servicing them.

Trusses, wood and metal are engineered for specific
applications, and may not support the weight of two (2)
furnaces suspended from the top chords or the bottom chords
of the trusses. Long horizontals spans may flex or sag,
resulting in damage to the building. Contact the truss
manufacturer for additional design and engineering assistance.

Do not suspend furnaces with straps or suspend furnaces from
roof decking.

For attic installations on a platform (See Figure 8):

1. Construct a platform from 3/4−in. (76 mm) (nominal
plywood), extending out 30 inches (762 mm) from the
front of each furnace.

2. Maintain all clearances to combustibles per the furnace
Installation, Start−up and Operating Instructions.

3. Follow all additional building codes.

4. Long truss spans may require additional support along
the bottom chord of the truss. Consult the truss
manufacturer’s guidelines for engineering assistance.

5. Long rafter or attic joist spans may require additional
support along the bottom of the rafter or joist. Consult
local or regional building codes for design and loading
requirements.

443 06 2403 01

Specifications subject to change without notice.

7