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:
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2 multipoise, 33.3 inch, single-speed, non-condensing furnaces (See Fig. 1, 2, and Table 2.)
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2 multipoise, 33.3 inch, 2-stage, non-condensing furnaces (See Fig. 1, 12, and Table 2.)
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2 upflow, 40 inch, single-speed, condensing furnaces (See Fig. 20, 21, and Table 3 or 4.)
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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
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Single-Stage Heat with Single-Stage Gas-Heat Thermostat
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Two-Stage Heat with 2-Stage Gas-Heat Thermostat
Models 58CTA, 58CTX, 312AAV, and 312JAV, Multipoise 2-Stage Non-Condensing HSI Furnaces
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Two-Stage Heat with Single-Stage Gas-Heat Thermostat
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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
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Single-Stage Heat with Single-Stage Gas-Heat Thermostat
SECTION III: Models 58MTA, 58MTB, 352MAV and 352AAV Upflow 2-Stage Condensing HSI Furnaces
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Two-Stage Heat with Single-Stage Gas-Heat Thermostat
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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:
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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.
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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.
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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.
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