See Section I, Procedure 2 for furnace and kit components used.
1. The 2-stage thermostat causes the furnaces to operate in first-stage heat (LH furnace operates in heat while RH furnace blower operates but
RH furnace is not heating) or causes the furnaces to operate in second-stage heat (both furnaces operate in heat), depending on whether 1
or 2 thermostat stages are calling for heat.
2. Operation in ALL modes is the same for twinned furnaces as for an individual furnace. See furnace Installation, Start-Up, and Operating
Instructions for more information on sequence of operation.
SECTION II: SINGLE-SPEED AND TWO-SPEED MULTIPOISE CONDENSING HSI FURNACE MODELS
SINGLE STAGE SINGLE STAGE TWO-STAGE
Model Series Model Series Model Series
58MCA 170 and later series 340MAV H and later series 58MTA 110 and later series
58MXA 160 and later series 350MAV G and later series 58MTB 100 and later series
58MCB 100 and later series PG9MAA E and later series 352MAV B and later series
58MXB 100 and later series 340AAV A and later series 352AAV A and later series
58MSA 140 and later series 350AAV A and later series
34MAV E and later series PG9MAB A and later series
PROCEDURE 1—INSTALL FURNACES
NOTE: Multipoise units can be installed in UPFLOW, DOWNFLOW, or HORIZONTAL configurations.
A. Upflow, Downflow, Side-By-Side Configuration
Refer to Fig. 20 for appearance and dimensional drawing of twinned furnaces and their connection locations.
1. Select 2 identical heating and airflow furnaces. (See Table 3.)
2. Remove bottom closure panels from both furnaces. (See Fig. 22.)
a. Remove main and blower access doors.
b. Remove 2 screws from front filler panel.
c. Rotate front filler panel downward to remove.
Fig. 17—Two-Stage Furnace Control
A02017
LHT
OFF
DLY
ON
OFF
W2
BLW
24-V-THERMOSTAT
TERMINALS
SETUP SWITCHES
LOW-HEAT ONLY AND
BLOWER OFF-DELAY
TWINNING AND/OR
COMPONENT TEST
TERMINAL
ACRDJ - AIR CONDITIONING
RELAY DISABLE JUMPER
TRANSFORMER 24-VAC
CONNECTIONS
PL1 - LOW VOLTAGE MAIN
HARNESS CONNECTOR
PL3 -ICM CONTROL
HARNESS CONNECTOR
HUMIDIFIER TERMINAL
(24-VAC 0.5 AMP MAX.)
3-AMP FUSE
LED OPERATION &
DIAGNOSTIC LIGHT
115-VAC (L2) NEUTRAL
CONNECTIONS
PL2 - HOT SURFACE
IGNITER & INDUCER
MOTOR CONNECTOR
115-VAC (L1) LINE
VOLTAGE CONNECTION
EAC-1 TERMINAL
(115-VAC 1.0 AMP MAX.)
BLOWER SPEED
SELECTION TERMINALS
HI HEAT
LO HEAT
SPARE-1
SPARE-2
COOL
Y1 DHUM G COM
24V
WW1 Y/Y2 R
TEST/TWIN
HUM
1 2 3
PLT
ACRDJ
0.5-AMP024 VAC
FUSE 3-AMP
SEC-1 SEC-2
PL1
NEUTRAL-L2
1
EAC-2
BHT/CLRBHI/LOR
PL3 1
BLWR
COOL
SPARE-1 SPARE-2
1-AMP@115 VAC
EAC-1 PR-1
IDR
HSIR
IDM
IHI/LOR
PL2
1
HSI HI LO
S
T
A
T
U
S
C
O
D
E
L
E
D
HI HEAT LO HEAT
L1
—22—
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