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912SD: Installation, Start-up, Operating and Service and Maintenance Instructions
6. Pull the ground wire of the field line voltage wiring through the
strain-relief bushing into the furnace casing.
7. Install the green ground screw to the J-Box bracket and attach both
ground wires to the green ground screw.
8. Connect any code required external disconnect(s) to field power
wiring.
9. Connect field power and neutral leads to furnace power leads inside
the external electrical box as shown in
Power Cord Installation in Furnace J-Box
NOTE: Power cords must be able to handle the electrical requirements
listed in
Table
10. Refer to power cord manufacturer's listings.
1. Install J-Box mounting bracket to inside of furnace casing. See
Fig.
35.
2. Route listed power cord through 7/8-in. (22 mm) diameter hole in
casing and J-Box bracket.
3. Secure power cord to J-Box bracket with a strain relief bushing or a
connector approved for the type of cord used.
4. Pull furnace power wires through 1/2-in. (12 mm) diameter hole in
J-Box. If necessary, loosen power wires from strain—relief wire-tie
on furnace wiring harness.
5. Connect field ground wire and factory ground wire to green ground
screw on J-Box mounting bracket as shown in
6. Connect power cord power and neutral leads to furnace power leads
as shown in
Fig.
33.
7. Attach furnace J-Box cover to mounting bracket with screws
supplied in loose parts bag. Do not pinch wires between cover and
bracket. See
Fig.
35.
BX Cable Installation in Furnace J-Box
1. Install J-Box mounting bracket to inside of furnace casing. See
Fig.
35.
2. Route BX connector through 7/8-in. (22 mm) diameter hole in
casing and J-Box bracket.
3. Secure BX cable to J-Box bracket with connectors approved for the
type of cable used.
4. Connect field ground wire and factory ground wire to green ground
screw on J-Box mounting bracket as shown in
5. Connect field power and neutral leads to furnace power leads. as
shown in
Fig.
33.
6. Attach furnace J-Box cover to mounting bracket with screws
supplied in loose parts bag. Do not pinch wires between cover and
bracket.
WARNING
!
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.
Do not drill into blower shelf of furnace to route control wiring. Route
any control or accessory wiring to the blower compartment through
external knockouts on the casing.
24-V Wiring
Make field 24-v connections at the 24-v terminal strip. See
Connect terminal Y as shown in
Use only AWG No. 18, color-coded, copper thermostat wire.
NOTE: Use AWG No. 18 color-coded copper thermostat wire for
lengths up to 100 ft. (31 M). For wire lengths over 100 ft., use AWG No.
16 wire.
The 24-v circuit contains an automotive-type, 3-amp. fuse located on the
control. Any direct shorts during installation, service, or maintenance
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
Fig.
34.
Fig.
35.
Fig.
35.
Fig.
Fig. 33
for proper cooling operation.
could cause this fuse to blow. If fuse replacement is required, use ONLY
a 3-amp. fuse of identical size. See
Accessories
(See
Fig. 38
and
Fig.
37)
1. Electronic Air Cleaner (EAC)
Connect an accessory Electronic Air Cleaner (if used) using 1/4-in.
female quick connect terminals to the two male 1/4-in.
quick-connect terminals on the control board marked EAC-1 and
EAC-2. The terminals are rated for 115VAC, 1.0 amps maximum
and are energized during blower motor operation.
2. Humidifier (HUM)
The HUM terminal is a 24 VAC output, energized when the gas valve
relay is operating during a call for heat.
Connect an accessory 24 VAC, 0.5 amp. maximum humidifier (if used)
to the ¼-in. male quick-connect HUM terminal and COM-24V screw
terminal on the control board thermostat strip.
NOTE: If the humidifier has its own 24 VAC power supply, an isolation
relay may be required. Connect the 24 VAC coil of the isolation relay to
the HUM and COM/24V screw terminal on the control board thermostat
strip. See
Fig.
38.
Alternate Power Supplies
This furnace is designed to operate on utility generated power which has
a smooth sinusoidal waveform. If the furnace is to be operated on a
generator or other alternate power supply, the alternate power supply
must produce a smooth sinusoidal waveform for compatibility with the
furnace electronics. The alternate power supply must generate the same
voltage, phase, and frequency (Hz) as shown in
rating plate.
Contact the alternate power supply manufacturer for specifications and
details.
Power from an alternate power supply that is non-sinusoidal may
damage the furnace electronics or cause erratic operation.
J2
24-V THERMOSTAT
TERMINALS
3-AMP FUSE
TRANSFORMER 24-VAC
CONNECTIONS
STATUS LED LIGHT
HEATING SPEED
TAP
COOLING SPEED
TAP
FAN SPEED TAP
115-VAC (L2) NEUTRAL
CONNECTIONS
EAC-1 TERMINAL
(115-VAC 1.0 AMP MAX.)
37.
Fig. 37 – Example of Single Stage Furnace Control
27
Fig.
37.
Table 10
HEAT OFF-DELAY
J2 DEFEAT
JUMPER SELECT
JUMPER
HEAT OFF-DELAY
J1
TEST/TWIN
PR-1
BL-1
L1
PL2 – (115VAC) HOT SURFACE IGNITER &
INDUCER MOTOR 115V SUPPLY CONNECTOR
or the furnace
PLT -FACTORY RUN TEST PORT
PRODUCTION USE ONLY
HUMIDIFIER TERMINAL
(24-VAC 0.5 AMP MAX.)
BOARD PART NUMBER
LOCATION
PL1 – LOW VOLTAGE MAIN HARNESS
CONNECTOR
115-VAC (PR-1) TRANSFORMER
PRIMARY
115-VAC (BL-1) BLOWER MOTOR LINE
VOLTAGE CONNECTION
115-VAC (L1) LINE VOLTAGE
CONNECTION
A190023
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