915SB: Installation, Start-up, Operating and Service and Maintenance Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
26
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
.
7. Attach furnace J-Box cover to mounting bracket with screws
supplied in loose parts bag. Do not pinch wires between cover and
.
BX Cable Installation in Furnace J-Box
1. Install J-Box mounting bracket to inside of furnace casing. See
.
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
6. Attach furnace J-Box cover to mounting bracket with screws
supplied in loose parts bag. Do not pinch wires between cover and
bracket.
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
could cause this fuse to blow. If fuse replacement is required, use ONLY
a 3-amp. fuse of identical size. See
Accessories
(See
.)
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.
.
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.
Power from an alternate power supply that
is non-sinusoidal may
damage the furnace electronics
or cause erratic operation.
Contact the alternate power supply manufacturer for specifications and
details.
A11157
Fig. 37 – Field-Supplied Isolation Relay for Humidifiers with
Internal Power Supply
A190023
Fig. 38 – Example of Single Stage Furnace Control
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
Coil
To Humidifier Leads
To Com/24V Screw Terminal
on Thermostat Strip
To HUM Terminal On
Furnace Control Board
To Humidifier Leads
24-V THERMOSTAT
TERMINALS
PL2
–
(115VAC) HOT SURFACE IGNITER &
INDUCER MOTOR 115V SUPPLY CONNECTOR
115-VAC (L2) NEUTRAL
CONNECTIONS
115-VAC (BL-1) BLOWER MOTOR LINE
VOLTAGE CONNECTION
EAC-1 TERMINAL
(115-VAC 1.0 AMP MAX.)
PL1
–
LOW VOLTAGE MAIN HARNESS
CONNECTOR
TRANSFORMER 24-VAC
CONNECTIONS
3-AMP FUSE
STATUS LED LIGHT
HEAT OFF-DELAY
HUMIDIFIER TERMINAL
(24-VAC 0.5 AMP MAX.)
BOARD PART NUMBER
LOCATION
COOLING SPEED
TAP
HEATING SPEED
TAP
PR-1
115-VAC (PR-1) TRANSFORMER
PRIMARY
J2 DEFEAT
JUMPER
TEST/TWIN
J2
HEAT OFF-DELAY
JUMPER SELECT
L1
PLT -FACTORY RUN TEST PORT
PRODUCTION USE ONLY
BL-1
115-VAC (L1) LINE VOLTAGE
CONNECTION
FAN SPEED TAP
J1