Carrier KGATW0601HSI User manual

NOTE: Read the entire instruction manual before starting the installation.
This symbol →indicates a change since the last issue.
TABLE OF CONTENTS
SAFETY CONSIDERATIONS.....................................................................................................................................................................................1
INTRODUCTION..........................................................................................................................................................................................................2
DESCRIPTION AND USAGE .....................................................................................................................................................................................2
ELECTROSTATIC DISCHARGE (ESD) PRECAUTION .........................................................................................................................................4
SECTION I: MULTIPOISE SINGLE-SPEED AND TWO-SPEED NON-CONDENSING HSI FURNACE MODELS ........................................4
Install Furnaces.........................................................................................................................................................................................................4
Upflow/Downflow, Side-by-Side Position .........................................................................................................................................................4
Upflow/Downflow, Back-to-Back Position........................................................................................................................................................7
Horizontal, Back-to-Back Position .....................................................................................................................................................................8
Horizontal, Stacked Together ...........................................................................................................................................................................10
Connect Electrical Components—Heating ............................................................................................................................................................11
All Single-Stage Models: 58STA, 58STX, 58DLA, 58DLX, 310AAV, 310JAV, 311AAV, 311JAV, PG8MAA, AND PG8JAA
Multipoise Single-Speed Non-Condensing HSI Furnaces...............................................................................................................................11
All Two-Stage Models: 58CTA, 58CTX, 312AAV, 312JAV Multipoise Two-Speed Non-Condensing HSI Furnaces with PSC
Motors................................................................................................................................................................................................................15
Connect Electrical Components-Cooling...............................................................................................................................................................17
Venting....................................................................................................................................................................................................................17
Gas Supply Piping..................................................................................................................................................................................................17
Electrical Supply Connections ...............................................................................................................................................................................17
Start-Up and Adjustment........................................................................................................................................................................................19
Sequence of Operation ...........................................................................................................................................................................................21
SECTION II: SINGLE-SPEED AND TWO-SPEED MULTIPOISE CONDENSING HSI FURNACE MODELS...............................................22
Install Furnaces.......................................................................................................................................................................................................22
Upflow, Downflow, Side-By-Side Configuration............................................................................................................................................22
Upflow/Downflow, Back-to-Back Configuration ............................................................................................................................................27
Horizontal, Back-to-Back Configuration..........................................................................................................................................................28
Connect Electrical Components—Heating ............................................................................................................................................................30
Connect Electrical Components—Cooling ............................................................................................................................................................33
Venting....................................................................................................................................................................................................................34
Gas Supply Piping..................................................................................................................................................................................................34
Condensate Drain Connections ..............................................................................................................................................................................34
Electrical Supply Connections ...............................................................................................................................................................................34
Start-Up and Adjustment........................................................................................................................................................................................34
Sequence of Operation ...........................................................................................................................................................................................36
Fixed Capacity Furnaces...................................................................................................................................................................................36
SAFETY CONSIDERATIONS
Installing and servicing of heating equipment can be hazardous due to gas and electrical components. Only trained personnel should install or
service heating equipment.
Untrained personnel can perform basic maintenance such as cleaning and replacing filters. All other operations should be performed by trained
service personnel. When working on heating equipment, observe precautions in the literature, on tags, and on labels attached to the unit.
Follow all safety codes. Wear safety glasses and work gloves. Have a fire extinguisher available.
Recognize safety information. This is the safety-alert symbol . When you see this symbol on the furnace and in instructions or manuals, be
alert to the potential for personal injury.
Understand the signal words DANGER, WARNING, CAUTION, and NOTE. 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 a hazard which could result in
personal injury or death. CAUTION is used to identify unsafe practices which would 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.
Installation Instructions
KGATW0601HSI
Twinning Kit for HSI Single-and
2-Stage Upflow Condensing and
Non-Condensing Gas Furnaces
Catalog No.: AG-GATW-15 Cancels: AG-GATW-14 Printed in U.S.A. 10-05
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CAUTION: UNIT DAMAGE HAZARD
Failure to follow this caution could result in improper and dangerous operation.
Label all wires prior to disconnection when servicing controls to prevent wiring errors.
INTRODUCTION
IMPORTANT: Only the furnace sizes listed in Tables 2, 3, and 4 can be twinned. Both furnaces must have the same product number, including
heating and cooling sizes, to achieve correct operation.
This furnace twinning kit P/N KGATW0601HSI permits connection to the following furnaces to operate as a single unit on the same duct work:
• 2 multipoise, 33.3 inch, single-speed, non-condensing furnaces (See Fig. 1, 2, and Table 2.)
• 2 multipoise, 33.3 inch, 2-stage, non-condensing furnaces (See Fig. 1, 12, and Table 2.)
• 2 upflow, 40 inch, single-speed, condensing furnaces (See Fig. 20, 21, and Table 3 or 4.)
• 2 upflow, 40 inch, 2-stage, condensing furnaces (See Fig. 20, 21, and Table 3 or 4.)
WARNING: UNIT AND PROPERTY DAMAGE
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.
DESCRIPTION AND USAGE
Refer to the appropriate section for your furnaces.
SECTION I: Models 58STA, 58STX, 58DLA, 58DLX, 310AAV, 310JAV, 311AAV, 311JAV, PG8MAA, and PG8JAA Multipoise Single-Speed
Non-Condensing HSI Furnaces
• Single-Stage Heat with Single-Stage Gas-Heat Thermostat
• Two-Stage Heat with 2-Stage Gas-Heat Thermostat
Models 58CTA, 58CTX, 312AAV, and 312JAV, Multipoise 2-Stage Non-Condensing HSI Furnaces
• Two-Stage Heat with Single-Stage Gas-Heat Thermostat
• Two-Stage Heat with 2-Stage Gas-Heat Thermostat
SECTION II: Models 58MCA, 58MCB, 58MSA, 58MXA, 58MXB, 340AAV, 340MAV, 345MAV, 350AAV, 350MAV, 490AAV, PG9MAA and
PG9MAB Upflow Single-Speed Condensing HSI Furnaces
• Single-Stage Heat with Single-Stage Gas-Heat Thermostat
SECTION III: Models 58MTA, 58MTB, 352MAV and 352AAV Upflow 2-Stage Condensing HSI Furnaces
• Two-Stage Heat with Single-Stage Gas-Heat Thermostat
• Two-Stage Heat with 2-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:
•For upflow furnaces: A combination of 1 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 if 1 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 Fig. 1.) Connect all return trunks or branch return ducts to common return
plenum.
•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 Fig.
2) Connect all return trunks or branch return ducts to common return plenum.
•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.
WARNING: 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, and condensing furnaces, the left-hand
furnace is used for first-stage heat, and both furnaces are used for second-stage heat. With the 2-stage, non-condensing and 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.
—2—
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Fig. 1—Upflow Ductwork Connections
A02223
B
B
A
A
A
A
Twinned Furnace
Common
Supply Air
Plenum
Common
Return
Air
Plenum
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
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
Example 2
8 MIN Common Return
Air Plenum
Return
Air
Plenum
Return
Air
Plenum
Twinned Furnace
Common
Supply Air
Plenum
Fig. 2—Downflow/Horizontal Ductwork Connections
A02224

A
A
A
A
A
A
Common
Return
Air
Plenum
Common
Supply Air
Plenum
Twinned Furnaces
Common
Return
Air
Plenum
Common
Supply Air
Plenum
Twinned furnaces
Stacked* (80% ONLY)
Example 4 - Horizonal Applications
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
Example 3 Notes:
Do not connect return air to any side of the
furnace
Connect return air plenum as shown
Example 3 - Downflow Applications
—3—

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
CAUTION: UNIT AND COMPONENT DAMAGE HAZARD
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.
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 SINGLE-STAGE TWO-STAGE TWO-STAGE
58STA 310AAV 58CTA 312AAV
58STX 310JAV 58CTX 312JAV
58DLA 311AAV
58DLX 311JAV
PG8MAA
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.
PROCEDURE 1—INSTALL FURNACES
A. Upflow/Downflow, Side-by-Side Position
Refer to Fig. 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.)
Table 1—Kit Contents
Sealing tape 2
External extension harness 327957-701 1
Main twinning harness 327957-701 1
Secondary twinning harness 327959-701 1
Two stage furnace wiring diagram 327891-101 1
Single Stage furnace heat wiring diagram 327893-101 1
Single Stage furnace/Two stage heat wiring diagram 327892-101 1
Label 327956-101 1
Tape 1
Bag Assembly includes:
Snap bushing 2
Screws (HEX HD 6B X 3/4) 10
Bag Assembly Includes:
Snap bushing 2
Screws (HEX HD 6B x 3/4) 10
Screws (flat head) 1
Wire tie 4
Clamps 2
Installation Instructions 1
—4—
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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 Fig. 1.)
WARNING: UNIT DAMAGE AND FIRE HAZARD
Failure to follow this warning could cause fire, personal injury, or death.
DO NOT use the back of the furnace for return-air duct connections in upflow position, 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 Fig. 2.)
WARNING: 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 the downflow position, as limit switch cycling will occur.
4. Remove bottom closure panels from both furnaces. (See Fig. 4.)
a. Lay furnaces on back or sides.
b. Remove 2 screws from bottom front panel.
c. Rotate front panel downward 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 Fig. 5.
Trim off excess material.
Fig. 3—Dimensional Drawing
A02235
A
D
E
A
D
E
Table 2—Dimensions (IN.) for Two-Stage with PSC Blower
UNIT SIZE A B C VENT CONN.* SHIP WT. (LB)
045-08/024045 14–3/16 12–9/16 12–11/16 4 116
045-120/036045 14–3/16 12–9/16 12–11/16 4 117
070-08/024070 14–3/16 12–9/16 12–11/16 4 120
070-12/036070 14–3/16 12–9/16 12–11/16 4 126
070-16/048070 17–1/2 15–7/8 16 4 135
090-14/042090 17–1/2 15–7/8 16 4 137
090-16/048090 21 19–3/8 19–1/2 4 150
090-20/060090 21 19–3/8 19–1/2 4 155
110-12/036110 17–1/2 15–7/8 16 4 145
110-16/048110 21 19–3/8 19–1/2 4 157
110-22/066110 21 19–3/8 19–1/2 4 162
135-16/048135 21 19–3/8 19–1/2 4 162
135-22/066135 24–1/2 22–7/8 23 4 174
155-20/060155 24–1/2 22–7/8 23 4 181
5” or 6” vent connector may be required in some cases
—5—

6. Remove 7/8-in. diameter accessory hole knock-outs in blower compartment from mating sides of furnaces. (See Fig. 3.)
7. Insert a plastic snap bushing through the 7/8” knock-out from the outside of the casing.
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. below discharge flange, from inside top of discharge opening and through both furnaces. (See
Fig. 6.)
Drill two 1/8-in. holes, approximately 1 in. below return air flange, from inside top of return air opening and through both furnaces. (See
Fig. 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.
Fig. 4—Removing Bottom Closure Panel
A02098
Fig. 5—Location of Foam Strips
A02254
FOAM
STRIPS
FOR BACK-TO-BACK
APPLICATIONS, APPLY
FOAM STRIPS AT THIS
HEIGHT, ALONG BACK
OF FURNACE
—6—

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 Fig. 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 Fig. 4.)
a. Lay furnaces on back or sides.
b. Remove 2 screws from bottom front panel.
c. Rotate front panel downward to remove.
d. Remove bottom closure panel and discard.
e. Reinstall bottom front panel.
f. Stand furnaces upright.
4.
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 Fig. 2.)
WARNING: 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 in the downflow position, 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 Fig. 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 Fig. 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 Fig. 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. below discharge flange, from inside top of discharge opening and through both furnaces. (Similar
to Fig. 6.)
Drill two 1/8-in. holes, approximately 1 in. below return air flange, from inside top of return air opening and through both furnaces. (Similar
to Fig. 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.
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.
A02232
Fig. 6—Attaching Furnaces Together at Discharge Opening
A02219
Fig. 7—Attaching Furnaces Together at Return Air Opening
—7—
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13. Go to PROCEDURE 2A for Single Stage Furnaces or PROCEDURE 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 Fig. 8a.):
1. Construct a platform from ¾″(nominal plywood), extending out 30 inches 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.
For suspended installations (See Fig. 8b. Not recommended for wood trusses unless approved by the truss manufacturer or other approved
engineering methods):
1. Furnaces may be suspended using two (2) pieces of 1 ½”x1½”x¼”thick cold rolled angle iron underneath the furnaces and four (4)
3/8″diameter threaded rods.
2. Allow for at least nine (9) inches in front of each door for door removal.
3. Each piece of angle iron must be secured to the bottom of each furnace with at least two (2) #8 x ¾″sheet metal screws.
4. Maintain all clearances to combustibles per the furnace Installation, Start-up and Operating Instructions.
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.
Fig. 8a—Attic Installtion of Horizontal Back-to-Back Furnaces
A02241
30˝ Work Platform
Dripleg
Dripleg
Extension Harness
Gas Supply Shut-off
Gas Supply Shut-off
Gas Pipe Union
Gas Pipe Union
30˝ Work Platform
Sheet Metal
Same As Installation Instructions
22˝
12˝
43/4˝
1˝
173/4˝ over all 4 3/4˝ under door
1˝ under furnace
Extend out 12˝ from face
of door
3/8˝ Lock Washer
3/8˝ Flat Washer
3/8˝ Flat Washer
3/8˝ Lock Washer
3/8˝ Hex Nut
3/8˝ Hex Nut
3/8˝ Threaded Rod
1 1/2˝ x 1 1/2˝ x 1/4˝ Angle Iron
—8—

Refer to Fig. 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 Fig. 4.)
a. Lay furnaces on back or sides.
b. Remove 2 screws from bottom front panel.
c. Rotate front panel downward 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
Fig. 8b—Suspended Installation for Horizontal Furnaces Back-to-Back
A02200
Twinning Kit
Extension Harness
3/8” Threaded Rod
See detail
Secure angle Iron to bottom of furnace
with at least (2) #8 x 3/4” sheet metal
screws in each furnace
1 1/2” x 1 1/2” x 1/4” Angle Iron
9” minimum for door removal
on both sides of furnace
3/8˝ Lock Washer
3/8˝ Flat Washer
3/8˝ Flat Washer
3/8˝ Lock Washer
3/8˝ Hex Nut
3/8˝ Hex Nut
3/8˝ Threaded Rod
1 1/2˝ x 1 1/2˝ x 1/4˝ Angle Iron
—9—

4. For All Horizontal applications:
Return air can only be connected to bottom opening of furnace. (See Fig. 2.) A common return air plenum is required for proper auxiliary
limit switch operation.
WARNING: 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 or back of the furnace for return-air duct connections in the horizontal position, as limit cycling will occur.
5. Apply 2 factory-supplied foam strips to the back of each furnace. Locate strips equal distance from top and bottom as shown in Fig. 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 Fig. 3.)
7. Position furnaces back-to-back on attic platform or suspended supports. Adjust and shim each furnace to align both furnaces. Follow all
clearance to combustible material.
8. If furnaces are installed closer than 12 inches above a deck made from combustible material, provide roll-out protection as shown in the
furnace installation instructions. The bottom closure pan may be used for this purpose.
NOTE: DO NOT lay furnace down flat on the side that external extension harness is installed. Raise furnace up a minimum of 1½ inches above
deck so harness does not rub on casing or deck.
9. Drill two 1/8-in. holes, approximately 1 in. below discharge flange, from inside top of discharge opening and through both furnaces. (See
Fig. 6.) Drill two 1/8-in. holes, approximately 1 in. below return air flange, from inside top of return air opening and through both furnaces.
(Use Fig. 6 as an example)
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.
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 PROCEDURE 2A for Single Stage Furnaces or PROCEDURE 2B for Two Stage Furnaces.
D. Horizontal, Stacked Together
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 Fig 9a):
1. Construct a platform from ¾″(nominal plywood), extending out 30 inches 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.
For suspended installations (See Fig 9b. Not recommended for wood trusses unless approved by the truss manufacturer or other approved
engineering methods):
1. Furnaces may be suspended using two (2) pieces of 1 ½”x1½”x¼”thick cold rolled angle iron underneath the furnaces and four (4)
3/8″diameter threaded rods.
2. Allow for at least nine (9) inches in front of each door for door removal.
3. Each piece of angle iron must be secured to the bottom of each furnace with at least two (2) #8 x ¾″sheet metal screws.
4. Maintain all clearances to combustibles per the furnace Installation, Start-up and Operating Instructions.
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 Fig. 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 Fig. 4.)
a. Lay furnaces on back or sides.
—10—
→

b. Remove 2 screws from bottom front panel.
c. Rotate front panel downward 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 Fig. 5.
6. Remove 7/8-in. diameter accessory hole knockouts in blower compartment from mating sides of furnaces. (See Fig. 3.)
7. Insert a plastic snap bushing through the 7/8″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. below discharge flange, from inside top of discharge opening and through both furnaces. (See
Fig. 6.) Drill two 1/8-in. holes, approximately 1 in. above return air opening flange, from inside blower compartment and through both
furnaces. (See Fig. 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
2A. All Single-Stage Models: 58STA, 58STX, 58DLA, 58DLX, 310AAV, 310JAV, 311AAV, 311JAV, PG8MAA, AND PG8JAA Multipoise
Single-Speed Non-Condensing HSI Furnaces
WARNING: FIRE HAZARD
Failure to follow this warning can cause a 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.
See electrostatic discharge precaution on page 2.
Fig. 9a—Attic Installation of Horizontal Furnace Stacked Together
A02242
30˝ Work Platform
Two 2˝ x 4˝
or one 4˝ x 4˝
Sheet Metal
22˝
12 3/4˝
53/4˝
173/4˝ over all 4 3/4˝ under door
1˝ under furnace
Extend out 12˝ from face
of door
17 3/4˝
—11—

The twinning kit can be used for single-stage or 2-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 ½ inches of ½″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″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″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 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 control mounting bracket using 2 factory-supplied screws. (See Fig. 10A.)
NOTE: See Fig. 13 for Single Stage furnace Twinning Kit wiring diagram.
b. Connect TKR white wire labeled W from TKR to LH furnace control thermostat connection W.
Fig. 9b—Suspended Installation for Horizontal Furnaces Stacked Together
A02202
3/8” Threaded Rod
See detail 9” minimum for door removal
Secure angle iron to bottom of
furnace with at least (2) #8 x 3/4”
sheet metal screws
11/2” x 11/2” x 11/4”
Angle Iron
—12—

c. Connect TKR black wire labeled C from TKR to LH furnace control thermostat connection COM 24V.
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.
2. Install Auxillary Limit Switch (ALS-M) on L/H furnace:
a. Drill 1/8-in. hole in blower housing 12 in. below blower shelf. (See Fig. 11.)
b. Position ALS-M so reset button faces front of furnace.
c. Secure bracket to blower housing using a factory-supplied screw.
d. Disconnect red transformer wire from LH furnace control SEC-1 connection.
e. Connect red transformer wire connector to ALS-M wire connector PL7 labeled TRAN.
f. Connect orange ALS-M wire connector labeled DOOR SWITCH or SEC 1 to LH furnace control SEC-1 terminal.
g. If Extension Harness was used, connect 2-wire harness to Extension Harness
3. Install Secondary 4-wire harness on R/H furnace:
The Secondary Harness includes the Auxiliary Door Switch and Auxiliary Limit Switch. The harness is also tagged ″Secondary Furnace″near the
plug ends of the harness.
a. Connect red wire labeled R-Secondary to RH furnace control thermostat connection R.
b. Connect white wire labeled W-Secondary to RH furnace control thermostat connection W.
c. Connect black wire labeled C-Secondary to RH furnace control thermostat connection COM 24V.
d. Connect yellow wire labeled TEST SECONDARY from LH furnace control TEST terminal to RH furnace control TEST terminal.
e. If the furnaces are side-by-side, route loose ends of 4-wire harness from Secondary furnace to Main furnace through snap bushings
previously installed between furnaces. (See Fig. 4.)
f. Connect Secondary 4-wire harness into 4-wire Main harness.
g. If Extension Harness was installed, connect 4-wire Secondary Harness to the Extension Harness.
4. Install Auxiliary Limit Switch, ALS-S on Secondary furnace:
a. Drill 1/8-in. hole in blower housing 12 in. below blower shelf. (See Fig. 11.)
b. Position ALS-S with terminals facing front of furnace.
c. Secure bracket to blower housing using factory-supplied screw.
Fig. 10A—TKR Relay Secured with Factory-Supplied Screws on Single-Stage Unit
A02233
TKR Relay-Secure w/2
factory-supplied screws
—13—

5. Install Auxiliary Blower Door Interlock Switch, ILK-1 on Secondary furnace:
a. Measure along the left edge of the furnace casing, 5 inches down from blower shelf.
b. Drill a 3/16″clearance hole through front edge of furnace casing.
c. Insert blower door switch mounting tab behind front edge of furnace casing.
d. Secure blower door switch through casing with special flat head screw included with kit.
e. Secure auxiliary door switch ILK-1 using factory-supplied shallow head screw.
f. Connect 2-Wire Secondary Harness to 2-wire Main Harness that was routed through furnace casings.
g. If extension harness was installed, 2-wire Secondary Harness from Secondary to Main 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.
6. Select identical blower motor speed taps at control center motor connectors in both furnaces.
CAUTION: UNIT DAMAGE HAZARD
Failure to select identical blower speed taps in both furnaces can result in overheating of furnace components and possible loss of
furnace operation and damage to the furnaces.
7. Dress wires to ensure they do not contact sharp or moving parts nor interfere with blower operation, removal of filters, or operation of
switches.
8. Make all thermostat connections to LH furnace only. See Fig. 13.
Two-Stage Heat with 2-Stage Gas-Heat Thermostat (Field Supplied)
NOTE: ALL thermostat connections are to be made to LH furnace control ONLY. (See Fig. 14.)
NOTE: This application allows only the LH furnace to operate for first-stage heat mode or both furnaces to operate for second-stage heat mode
as determined by a 2-stage thermostat. See furnace Installation, Start-Up, and Operating Instructions for further details on this heating mode.
To operate furnaces in 2-stage heating mode when a 2-stage thermostat controls the staging, install twinning kit as described in Single-Stage Heat
with Single-Stage Gas Heat Thermostat, then modify TKR wiring as follows:
a. Disconnect TKR white wire labeled W from the LH furnace control thermostat connection W.
b. Cut off terminal of TKR white wire labeled W and strip 1/4 in.
c. Connect 2-stage thermostat W2 connection to TKR white wire labeled W.
Fig. 10B—Holes Drilled in Blower Housing
A02220
Align TKR Relay along edge of control
board. Mark holes in control board
mounting bracket and drill screw holes
using 1/8” drill bit. Secure relay to
control board mounting bracket using
factory-supplied screws.
—14—

CAUTION: UNIT DAMAGE HAZARD
Failure to follow this caution could result in intermitted furnace operation and unit damage.
Supply-air temperature will be uneven left-to-right when only main system is operating.
NOTE: ALL other 2-stage thermostat connections are to be made to LH furnace control ONLY. (See Fig. 14.)
2B. All Two-Stage Models: 58CTA, 58CTX, 312AAV, 312JAV Multipoise Two-Speed Non-Condensing HSI Furnaces with PSC Motors
WARNING: 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.
See electrostatic discharge precaution on page 4.
The twinning kit can be used for single-stage or 2-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 ½ inches of ½″flexible steel conduit
b. (2) 90° conduit connectors
c. (2) 4 wire polarized wiring harness
d. (2) 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 TKR relay harness from the outside of the furnace through
the 7/8″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″knockout in the casing
to the blower compartment.
d. Install the lock nuts on the 90° conduit connectors.
Fig. 11—Auxiliary Door Switch
A02251
—15—

Two-Stage Heat with Single-Stage Gas-Heat Thermostat (Field Supplied) (See Fig. 15.)
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 control mounting bracket using 2 factory-supplied screws. Two new screw holes
will have to be drilled using a 1/8-inch drill bit. See Fig. 10B for location of holes to be drilled.
b. Connect TKR white wire labeled W from TKR to LH furnace control thermostat connection W/W1.
c. Connect TKR black wire labeled C from TKR to LH furnace control thermostat connection COM 24V.
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.
f. Turn LHT set-up switch on L/H control board to “OFF.” (See Fig. 12.)
g. Turn LHT set-up switch on R/H control board to “ON.”
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.
2. Install Auxillary Limit Switch (ALS-M) on L/H furnace:
a. Drill 1/8-in. hole in blower housing 12 in. below blower shelf. (See Fig. 11.)
b. Position ALS-M so reset button faces front of furnace.
c. Secure bracket to blower housing using a factory-supplied screw.
d. Disconnect red transformer wire from LH furnace control SEC-1 connection.
e. Connect red transformer wire connector to ALS-M wire connector PL7 labeled TRAN.
f. Connect ALS-M orange wire connector labeled DOOR SWITCH or SEC 1 to LH furnace control SEC-1 terminal.
g. If Extension Harness was used, connect 2-wire harness to Extension Harness
3. Install Secondary 4-wire harness on R/H furnace:
The Secondary Harness includes the Auxiliary Door Switch and Auxiliary Limit Switch. The harness is also tagged “Secondary Furnace” near the
plug ends of the harness.
a. Connect red wire labeled R-Secondary to RH furnace control thermostat connection R.
b. Connect white wire labeled W-Secondary to RH furnace control thermostat connection W/W1.
c. Connect black wire labeled C-Secondary to RH furnace control thermostat connection COM 24V.
d. Connect yellow wire labeled TEST SECONDARY to RH furnace control TEST/TWIN terminal.
e. If the furnaces are side-by-side, route loose ends of 4-wire harness from Secondary furnace to Main furnace through snap bushings
previously installed between furnaces.
f. Connect Secondary 4-wire harness into 4-wire Main harness.
g. If Extension Harness was installed, connect 4-wire Secondary Harness to the Extension Harness.
4. Install Auxiliary Limit Switch, ALS-S on Secondary furnace:
a. Drill 1/8-in. hole in blower housing 12 in. below blower shelf. (See Fig. 11.)
b. Position ALS-S with terminals facing front of furnace.
c. Secure bracket to blower housing using factory-supplied screw.
5. Install Auxiliary Blower Door Interlock Switch, ILK-1 on Secondary furnace:
a. Measure along the left edge of the furnace casing, 5 inches down from blower shelf.
b. Drill a 3/16″clearance hole through front edge of furnace casing.
c. Insert blower door switch mounting tab behind front edge of furnace casing.
d. Secure blower door switch through casing with special flat head screw included with kit.
e. Secure auxiliary door switch ILK-1 using factory-supplied shallow head screw.
f. Connect 2-Wire Secondary Harness to 2-wire Main Harness that was routed from Secondary to Main furnace casings.
g. If extension harness was installed, 2-wire Secondary 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.
6. Select identical blower motor speed taps at control center motor connectors in both furnaces.
CAUTION: UNIT DAMAGE HAZARD
Failure to select identical blower speed taps in both furnaces can result in overheating of furnace components and possible loss of
furnace operation and damage to the furnaces.
—16—

7. Dress wires to ensure they do not contact sharp or moving parts nor interfere with blower operation, removal of filters, or operation of
switches.
8. Make all thermostat connections to LH furnace only.
Two-Stage Heat with 2-Stage Gas-Heat Thermostat (Field Supplied)
NOTE: ALL thermostat connections are to be made to LH furnace control ONLY. (See Fig. 15.)
NOTE: This application allows both furnaces to operate in low heat for first-stage heat mode or both furnaces to operate in high heat for
second-stage heat mode as determined by a 2-stage thermostat. See furnace Installation, Start-Up, and Operating Instructions for further details
on this heating mode.
To operate furnaces in 2-stage heating mode when a 2-stage thermostat controls the staging, install twinning kit as described in the two-stage heat
with single-stage gas heat thermostat:
a. Turn LHT set-up switch on L/H control board to “ON.”
b. Turn LHT set-up switch on R/H control board to “ON.”
NOTE: ALL other 2-stage thermostat connections are to be made to LH furnace control ONLY. (See Fig. 15.)
PROCEDURE 3—CONNECT ELECTRICAL COMPONENTS-COOLING
WARNING: FIRE HAZARD
Failure to follw 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. Failure to follow this
warning can cause a fire, personal injury, or death.
When installing twinned outdoor units with twinned gas furnaces, it is necessary to use a field-supplied 24-vac pilot-duty relay and a field-supplied
24/115-vac transformer as shown in Fig. 13, 14, or 15 to prevent overloading furnace 24/115-vac transformer.
PROCEDURE 4—VENTING
Refer to Installation, Start-Up, and Operating Instructions supplied with each furnace for venting information.
CAUTION: When common-venting twinned, Category I (negative-pressure venting), non-condensing furnaces, exces-
sive condensate may occur as a result of oversized vent systems. Dedicated vents and/or proper vent sizing, per the current
edition of the National Fuel Gas Code, will reduce the potential for condensation.
PROCEDURE 5—GAS SUPPLY PIPING
NOTE: All gas connections must be made through exposed outer side of each furnace. Do not common connect any connection other than supply-
and return-air ducts.
Furnaces are recommended to be provided with a single shutoff valve. However, individual shutoff valves may be required by local codes or
jurisdictions. Refer to Installation, Start-Up, and Operating Instructions provided with each furnace for additional gas supply information.
PROCEDURE 6—ELECTRICAL SUPPLY CONNECTIONS
NOTE: All electrical power connections must be made through exposed outer side of each furnace. Do not common connect any connection other
than supply- and return-air ducts.
1. Each furnace shall be connected to its own 115-vac power supply. The twinning kit installation interconnects the furnaces, allowing them
to operate as a single furnace. The L1 (black) connection to each furnace must be connected to circuit breakers connected to the same service
panel 115-vac phase leg.
On single-phase (residential) systems, each furnace circuit breaker should be located directly across from each other in service panel, or each
furnace circuit breaker should be located on the same side of service panel, but must skip 1 space to be connected to the same leg of the
1-phase power supply.
On 3-phase (commercial) systems, each furnace circuit breaker should be located directly across from each other in service panel, or each
furnace circuit breaker should be located on the same side of service panel, but must skip 2 spaces to be connected to the same leg of the
3-phase power supply.
The proper 115-vac phasing of furnace connections permits 24-vac transformer phasing as described below.
2. Phasing of the connected 24-vac transformer secondary circuits can be determined with the LED status of both furnaces. See furnace
Installation, Start-Up, and Operating Instructions and status code labels on blower doors. The furnaces’ transformers’ black leads should
be connected to PR1 connectors and white leads to PR2 connectors on controls. If 1 or both LEDs are rapidly flashing, disconnect lead at
TEST/TWIN terminal of LH furnace and observe LED at each furnace.
To verify that the furnaces are in phase, check from Main furnace L1 to Secondary furnace L1 with a voltmeter. If the furnaces are in phase,
the voltage between both furnaces will be ZERO.
Fig. 12—LHT Switch Settings
A02221
LHT
OFF
DLY
OFF
ON
1 2 3
Thermostat Type Left Hand Right Hand
LHT Switch 1 LHT Switch 1
Single Stage
Thermostat OFF ON
Two Stage
Thermostat ON ON
—17—

IF:
a. Both LEDs are on continuously:
System phasing is okay.
b. One or both LEDs are rapidly flashing:
(1.) Line voltage polarity is reversed
(2.) Reverse SEC-1 and SEC-2 in furnace with rapid flashing LED.
c. One LED is off, 1 LED is on continuously:
(1.) The 24-vac circuit is inoperative on furnace with LED light off.
(2.) Check transformers, auxiliary limits, and door switches in both furnaces and correct problem.
Fig. 13—Single Stage Furnace and A/C-Single Stage Thermostat
A02227
THERMOSTAT MAIN ( LH ) FURNACE
RELAY 1
PLC
ALS-M
PLA
NOTE #5
Y/Y2
G
W
R
COM
Y1
BLK
WHT
TEST/TWIN
TKR
BLU
SEC-2 SEC-1
TRAN WHT
BLK
L2
NOTE #2
PR1
BLK
WHT
RED
YEL
PLB
SECONDARY ( RH ) FURNACE
Y/Y2
G
W
R
COM
Y1
TEST/TWIN
BLU
SEC-2 SEC-1
BLK
WHT
RED
YEL
PLB RED
TRAN WHT
BLK
L2
NOTE #2
PR1
MAKE NO THERMOSTAT
CONNECTIONS TO
SECONDARY OR RH
FURNACE
1
2
ORN
BLU
RED
EXTENSION HARNESS
(IF USED)
PLA
1
2
ORN
BLU
ILK-1 ALS-S
NOTE #1
ORN
NOTE #3
24 VAC
TRANSFORMER (FIELD SUPPLIED) NOTE #4
115 VAC
CY
OUTDOOR UNIT
NO. 1
CY
OUTDOOR UNIT
NO. 2
LEGEND: NOTES:
Y
G
W
R
COM
NOTE #3
NOTE #6
327893-101 REV. A
1. ALS-S and ILK-1 are located in the SECONDARY or RH furnace
blower compartment.
2. Primary connections of transformer not shown; refer to furnace
wire label.
3. When extension harness is not required PLA and PLB must be
routed through holes in casings.
4. Transformer = 115 VAC primary / 24 VAC secondary / 40VA.
5. Relays = 24 VAC coils / pilot duty / normally open.
6. Y1 and DHUM terminal not available on "RED" LED control board.
NOTE #6
ALS-M MAIN AUX. LIMIT SW., OVERTEMP-MANUAL
RESET, SPST - (N.C.)
ALS-S SECONDARY AUX. LIMIT SW.,
OVERTEMP-MANUAL RESET, SPST - (N.C.)
ILK-1 SECONDARY AUX. BLOWER DOOR
INTERLOCK SWITCH, SPST - (N.O.)
PLA 2-CIRCUIT TWINNING KIT CONNECTOR
PLB 4 - CIRCUIT TWINNING KIT CONNECTOR
PLC 1 - CIRCUIT TWINNING KIT IN-LINE SPLICE
TEST/TWIN COMPONENT TEST & TWINNING TERMINAL
TKR TWINNING KIT RELAY, SPST - (N.O.)
TRAN TRANSFORMER - 115VAC / 24VAC
(PART OF FURNACE)
115 VOLT WIRING
TWINNING KIT EXTENSION HARNESS (REQUIRED)
FIELD WIRING
FACTORY WIRING (TWINNING KIT)
FIELD INSTALLED AIR CONDITIONING WIRING (WHEN REQUIRED)
SINGLE STAGE FURNACE & A/C-SINGLE STAGE THERMOSTAT
DHUM DHUM
4
1
3
2
4
1
3
2
FIELD
SUPPLIED
RELAY
—18—

d. One or both LEDs are dim or flickering.
Furnaces are on different phase legs. Disconnect TWIN/TEST lead. If both LEDs are on continuously when TWIN/TEST is
disconnected, furnace line voltage power supply is out of phase.
3. Reconnect lead at TWIN/TEST terminal of LH furnace and observe LED at each furnace. The LEDs will glow steady for proper phasing.
PROCEDURE 7—START-UP AND ADJUSTMENT
Refer to Installation, Start-Up, and Operating Instructions supplied with furnaces for detailed information.
1. Shut off all power and gas to both furnaces.
2. Position blower off delay switches on controls in BOTH furnaces to SAME desired gas heat blower off delay. (See Fig. 16 and 17.) See
furnace Installation, Start-Up, and Operating Instructions for further details.
3. Attach twinning connection wiring label above the existing furnace wiring label on the inside of the L/H furnace blower access door. Use
the following labels for the following applications:
Fig. 14—Single Stage Furnaces and A/C-Two Stage Thermostat
A02228
THERMOSTAT
RELAY 1
PLC
ALS-M
PLA
RELAY 2
NOTE #5
Y1
Y/Y2
G
W
R
COM
BLK
WHT
TEST/TWIN
TKR
BLU
SEC-2 SEC-1
TRAN WHT
BLK
L2
NOTE #2
PR1
BLK
WHT
RED
YEL
PLB
Y/Y2
G
W
R
COM
Y1
TEST/TWIN
BLU
SEC-2 SEC-1
BLK
WHT
RED
YEL
PLB RED
TRAN WHT
BLK
L2
NOTE #2
PR1
MAKE NO THERMOSTAT
CONNECTIONS TO
SECONDARY OR RH
FURNACE
1
2
ORN
BLU
RED
EXTENSION HARNESS
(IF USED)
PLA
1
2
ORN
BLU
ILK-1 ALS-S
NOTE #1
ORN
NOTE #3
24 VAC
TRANSFORMER (FIELD SUPPLIED) NOTE #4
115 VAC
C Y
OUTDOOR UNIT
NO. 1
C Y
OUTDOOR UNIT
NO. 2
LEGEND:
1. ALS-S and ILK-1 are located in the SECONDARY or RH furnace
blower compartment.
2. Primary connections of transformer not shown; refer to furnace
wire label.
3. When extension harness is not required PLA and PLB must be
routed through holes in casings.
4. Transformer = 115 VAC primary / 24 VAC secondary / 40VA.
5. Relays = 24 VAC coils / pilot duty / normally open.
6. Y1 and DHUM terminal not available on "RED" LED control board.
NOTES:
W2
Y1
G
W/W1
R
COM
Y/Y2
NOTE #3
327892-101 REV. A
NOTE #6 NOTE #6
DHUM DHUM
4
1
3
2
4
1
3
2
FIELD INSTALLED AIR CONDITIONING WIRING (WHEN REQUIRED)
SINGLE STAGE FURNACE & A/C-TWO STAGE THERMOSTAT
ALS-M MAIN AUX. LIMIT SW., OVERTEMP-MANUAL
RESET, SPST - (N.C.)
ALS-S SECONDARY AUX. LIMIT SW.,
OVERTEMP-MANUAL RESET, SPST - (N.C.)
ILK-1 SECONDARY AUX. BLOWER DOOR
INTERLOCK SWITCH, SPST - (N.O.)
PLA 2-CIRCUIT TWINNING KIT CONNECTOR
PLB 4 - CIRCUIT TWINNING KIT CONNECTOR
PLC 1 - CIRCUIT TWINNING KIT IN-LINE SPLICE
TEST/TWIN COMPONENT TEST & TWINNING TERMINAL
TKR TWINNING KIT RELAY, SPST - (N.O.)
TRAN TRANSFORMER - 115VAC / 24VAC
(PART OF FURNACE)
115 VOLT WIRING
TWINNING KIT EXTENSION HARNESS (REQUIRED)
FIELD WIRING
FACTORY WIRING (TWINNING KIT)
FIELD SUPPLIED RELAYS
MAIN ( LH ) FURNACE SECONDARY ( RH ) FURNACE
—19—

Single Stage furnaces with single-stage thermostat, 327893–101
Single Stage furnaces with two-stage thermostat, 327892–101
Two Stage furnaces with single-stage or 2-stage thermostat, 327891–101
4. Attach twinning reference label 327956–101 on outside of blower access door of RH furnace blower door.
5. Turn on power and gas to both furnaces.
6. Reinstall blower access doors on both furnaces.
7. Operate furnaces through 2 cycles in each mode to confirm correct operation by operating only thermostat.
a. Single-stage gas heating thermostat R-to-W operates both furnaces gas heat mode. First stage of a 2-stage thermostat causes LH furnace
to operate in gas-heat mode. Second stage of a 2-stage thermostat causes both furnaces to operate in gas heat mode.
b. Single stage thermostat operates first or second stage of a two stage furnace, based on the furnace control board algorithm. 2-stage
heating thermostat R-to-W/W1 will operate both furnaces in low heat mode. Thermostat R to W/W1 and-W2 causes both furnaces to
operate in high gas-heat mode.
c. Thermostat R-to-G for continuous fan or low-cooling blower.
Fig. 15—Two Stage Furnaces and 1 Stage A/C Unit-One or Two Stage Thermostat
A02229
THERMOSTAT
RELAY 1
PLC
ALS-M
PLA
RELAY 2
NOTE #5
W2
Y/Y2
G
W/W1
R
COM
Y1
BLK
WHT
TEST/TWIN
TKR
BLU
SEC-2 SEC-1
TRAN WHT
BLK
L2
NOTE #2
PR1
BLK
WHT
RED
YEL
PLB
W2
Y/Y2
G
W/W1
R
COM
Y1
TEST/TWIN
BLU
SEC-2 SEC-1
4
1
3
2
BLK
WHT
RED
YEL
PLB RED
TRAN WHT
BLK
L2
NOTE #2
PR1
MAKE NO THERMOSTAT
CONNECTIONS TO
SECONDARY OR RH
FURNACE
1
2
ORN
BLU
RED
EXTENSION HARNESS
(IF USED)
PLA
1
2
ORN
BLU
ILK-1 ALS-S
NOTE #1
ORN
NOTE #3
24 VAC
TRANSFORMER (FIELD SUPPLIED) NOTE #4
115 VAC
C Y
OUTDOOR UNIT
NO. 1
C Y
OUTDOOR UNIT
NO. 2
ACRDJ AIR CONDITIONING RELAY DISABLE JUMPER
ALS-M MAIN AUX. LIMIT SW., OVERTEMP-MANUAL
RESET, SPST - (N.C.)
ALS-S SECONDARY AUX. LIMIT SW.,
OVERTEMP-MANUAL RESET, SPST - (N.C.)
ILK-1 SECONDARY AUX. BLOWER DOOR
INTERLOCK SWITCH, SPST - (N.O.)
PLA 2-CIRCUIT TWINNING KIT CONNECTOR
PLB 4 - CIRCUIT TWINNING KIT CONNECTOR
PLC 1 - CIRCUIT TWINNING KIT IN-LINE SPLICE
TEST/TWIN COMPONENT TEST & TWINNING TERMINAL
TKR TWINNING KIT RELAY, SPST - (N.O.)
TRAN TRANSFORMER - 115VAC / 24VAC
(PART OF FURNACE)
115 VOLT WIRING
TWINNING KIT EXTENSION HARNESS (REQUIRED)
FIELD WIRING
FACTORY WIRING (TWINNING KIT)
LEGEND:
1. ALS-S and ILK-1 are located in the SECONDARY or RH furnace
blower compartment.
2. Primary connections of transformer not shown; refer to furnace wire
label.
3. When extension harness is not required PLA and PLB must be routed
through holes in casings.
4. Transformer = 115 VAC primary / 24 VAC secondary / 40VA.
5. Relays = 24 VAC coils / pilot duty / normally open.
6. Two-stage heating can be accomplished by one of the two methods:
a. Using one stage thermostat and letting the Main Furnace’s (LH)
algorithm control low and high-heat operation.
b. Using a two-stage thermostat to control low and high-heat
operation. (Apply "W2" Wire)
NOTES:
LHT
OFF
DLY
2
ON
OFF
THERMOSTAT
TYPE
LEFT HAND
LHT SWITCH 1
RIGHT HAND
LHT SWITCH 1
13
TWO STAGE
THERMOSTAT
ON ON
W2
Y1
G
DHUM
W/W1
R
COM
Y/Y2
327891-101 REV. A
NOTE #3
NOTE #6
4
1
3
2
DHUM
2 STG FURNACES / 1 STG A/C UNIT - TWO-STAGE OPERATION
FIELD SUPPLIED RELAYS
FIELD INSTALLED AIR CONDITIONING WIRING (WHEN REQUIRED)
OFF ON
DHUM
MAIN ( LH ) FURNACE SECONDARY ( RH ) FURNACE
ONE STAGE
THERMOSTAT
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