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58SC0B/58SC1B: Installation, Start–Up, Operating and Service and Maintenance Instructions
WARNING
!
FIRE OR EXPLOSION HAZARD
Failure to follow this warning could result in personal injury, death
and/or property damage.
Never purge a gas line into a combustion chamber. Never test for gas
leaks with an open flame. Use a commercially available soap solution
made specifically for the detection of leaks to check all connections.
19. Check for gas leaks.
20. Replace outer access door.
SEQUENCE OF OPERATION
NOTE: Furnace control must be grounded for proper operation or
control will lock out. Control is grounded through green/yellow wire
routed to gas valve and manifold bracket screw.
Using the schematic diagram, follow the sequence of operation through
the different modes. Read and follow the wiring diagram very carefully.
NOTE: If a power interruption occurs during a call for heat (W), the
control will start a 90-sec blower-only ON period two seconds after
power is restored, if the thermostat is still calling for gas heating. The
amber LED light will flash code 12 and display will show (12.1) during
the 90-sec period, after which the LED will be ON continuous, as long as
no faults are detected. After the 90-sec period, the furnace will respond
to the thermostat normally.
The blower door must be installed for power to be conducted through the
blower door interlock switch ILK to the furnace control CPU,
transformer TRAN, inducer motor IDM, blower motor BLWM,
hot-surface igniter HSI, and gas valve GV.
1. Heating
The wall thermostat "calls for heat," closing the R-to-W circuit.
The furnace control performs a self-check, verifies the pressure
switch contacts PRS are open, and starts the inducer motor IDM.
a. Inducer Prepurge Period – As the inducer motor IDM comes
up to speed, the pressure switch contacts PRS close, 24 VAC
power is supplied for a field installed humidifier at the HUM
terminal and the control begins a 15-sec prepurge period.
b. Igniter Warm-Up – At the end of the prepurge period, the
Hot-Surface igniter HSI is energized for a 17-second igniter
warm-up period.
c. Trial-for-Ignition Sequence – When the igniter warm-up period
is completed, the main gas valve relay contacts GVR close to
energize the gas valve GV, the gas valve opens, The gas valve
GV permits gas flow to the burners where it is ignited by the
HSI. Five seconds after the GVR closes, a 2-second flame
proving period begins. The HSI igniter will remain energized
until the flame is sensed or until the 2-second flame proving
period begins.
d. Flame-Proving – When the burner flame is proved at the
flame-proving sensor electrode FSE, the furnace control CPU
begins the blower-ON delay period and continues to hold the gas
valve GV open. If the burner flame is not proved within two
seconds, the control CPU will close the gas valve GV, and the
control CPU will repeat the ignition sequence for up to three
more Trials-For-Ignition before going to Ignition-Lockout.
Lockout will be reset automatically after three hours or by
momentarily interrupting 115 VAC power to the furnace, or by
interrupting 24 VAC power at SEC1 or SEC2 to the furnace
control CPU (not at W, G, R, etc.) If flame is proved when flame
should not be present, the furnace control CPU will lock out of
Gas-Heating mode and operate the inducer motor IDM until
flame is no longer proved.
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
e. Blower-ON Delay – If the burner flame is proven, the blower
motor is turned on at HEAT speed 25 sec after the gas valve GV
is energized.
Simultaneously, the electronic air cleaner terminal EAC-1 is
energized and remains energized as long as the blower motor
BLWM is energized.
f. Heat-OFF Delay – When the thermostat is satisfied, the R-to-W
circuit is opened, de-energizing the gas valve GV, stopping gas
flow to the burners, and de-energizing the 24-V humidifier
terminal 24VAC HUM. The inducer motor IDM will remain ON
for a 5-second post-purge period. Then turn off the inducer motor
and HUM (115-V) humidifier terminal. The blower motor
BLWM and air cleaner terminal EAC 1 will remain energized for
90, 120, 150, or 180 seconds (depending on the HEAT-OFF delay
selection). The furnace control CPU is factory-set for a
120-second Heat-Off Delay.
2. Cooling Mode
(See
Fig. 29
for thermostat connections.) The thermostat closes the
R-to-Y circuits. The R-to-Y circuit starts the outdoor unit, and the
R-to-Y circuits start the furnace blower motor BLWM on COOL
speed. The electronic air cleaner terminal EAC-1 is energized with
115 VAC when the blower motor BLWM is operating. When the
thermostat is satisfied, the R-to-Y circuits are opened. The outdoor
unit will stop, and the furnace blower motor BLWM will continue
operating on the COOL speed for an additional 5, 30, or 90 seconds
(depending on the cooling blower-OFF delay selection). The
furnace CPU is factory set for a 90 second cooling blower-OFF
delay (see
Fig.
28).
3. Continuous Fan Mode
When the R-to-G circuit is closed by the thermostat, the blower
motor BLWM will operate at the continuous-blower speed selected.
Terminal EAC-1 is energized as long as the blower motor BLWM is
ON.
During a call for heat, the blower BLWM will stop during igniter
warm-up (17 sec), ignition, and blower-ON delay (25 sec), allowing
the furnace heat exchangers to heat up more quickly, then restarts at
the end of the blower-ON delay period at HEAT speed.
When the thermostat "calls for cooling", the blower motor BLWM
will continue to operate at COOL speed. When the thermostat is
satisfied, the blower motor BLWM will continue to operate on
COOL speed based on the cooling blower-OFF delay setting before
reverting back to continuous fan speed.
When the R-to-G circuit is opened, the blower motor BLWM will
continue operating for an additional 5 sec, if no other function
requires blower motor BLWM operation.
4. Heat Pump
When installed with a heat pump, the furnace control automatically
changes the timing sequence to avoid long blower off times during
demand
defrost
cycles.
R-to-W-and-Y-and-G circuits are energized the furnace control
CPU will continue to turn on the blower motor BLWM at HEAT
speed, and begin a heating cycle. The blower motor BLWM will
remain on until the end of the prepurge period, then shut off for 24
sec then come back on at HEAT speed. When the W input signal
disappears, the furnace control begins a normal inducer post-purge
period and the blower switches to COOL speed after a 3 sec delay.
If the R-to-W-and-Y-and-G signals disappear at the same time, the
blower motor BLWM will remain on for the selected blower- OFF
delay period. If the R-to-W-and-Y signals disappear, leaving the G
signal, the blower motor BLWM will continue running the blower
motor at CONTINUOUS FAN speed after the selected heating
blower-OFF delay period is completed.
Wiring Diagram
Fig. 46
shows a schematic for the furnace wiring diagram.
40
When
the
R-to-W-and-Y
or
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