Carrier 59SE5A Installation, Start-Up, Operating And Service And Maintenance Instructions page 75

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 in Fig. 65, 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 108-sec blower-only ON period two sec
after power is restored, if the thermostat is still calling for gas
heating. The Green LED light will flash Code 1+2 during the
108-sec period, after which the LED will be flashing a heartbeat,
as long as no faults are detected. After the 108-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
See Fig. 36 for thermostat connections.
The wall thermostat "calls for heat," closing the R-to-W
circuit. The furnace control performs a self-check, verifies
the pressure switch contacts LPS and HPS are open, and
starts the inducer motor IDM.
a. Inducer Prepurge Period- As the inducer motor IDM
comes up to speed, the HUM terminal is energized at 220v,
and the low pressure switch contacts LPS close to begin
an 18 second prepurge period, and 24 vac is supplied for
a field installed humidifier at the HUM 24 vac terminal.
The high pressure switch contacts HPS are ignored until
one nfinute after the gas valve is energized.
b. Igniter Warm-Up- At the end of the prepurge period, the
Hot-Surface igniter HSI is energized for a 20-sec 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 pernfits gas flow to the
burners where it is ignited by the HSI. Five sec after the
GVR closes, a 2-sec flame proving period begins. The HSI
igniter will remain energized until the flame is sensed or
until the 2-sec 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 sec, the control CPU will close the gas
valve GV, and the control CPU will repeat the ignition se-
quence for up to three more Trials-For-Ignition before go-
ing to Ignition-Lockout. Lockout will be reset automatic-
ally after 3-1/2 hours or by momentarily interrupting 220
vac power to the furnace, or by interrupting 24 vac power
at 24VAC or COM 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.
e. Blower-On Delay- If the burner flame is proven, the
blower motor is energized on HEAT speed 30 sec after the
gas valve GV is energized.
Sinmltaneously, the electronic air cleaner ternfinal EAC is
energized and remains energized as long as the blower mo-
tor 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 hu-
midifier terminal HUM 24 VAC. The inducer motor IDM,
and HUM ternfinal will remain energized for an 18-sec
post-purge period. The blower motor BLWM and air
cleaner ternfinal EAC will remain energized for 108, 144,
180, or 216 sec (depending on the heat-OFF delay selec-
tion). Note board selections are shown as 90, 120, 150,
180. The furnace control CPU is factory-set for a 144-sec
heat-OFF delay.
2. Cooling Mode
The thermostat "calls for cooling." See Fig. 36 for thermo-
stat connections
The thermostat closes the R-to-G-and-Y circuits. The
R-to-Y circuit starts the outdoor unit, and the
R-to-G-and-Y circuits start the furnace blower motor
BLWM on COOL speed.
The electronic air cleaner ternfinal EAC is energized with
220 vac when the blower motor BLWM is operating. When
the thermostat is satisfied, the R-to-G-and-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 108 sec. Jumper J2 can be cut to reduce
the cooling-OFF delay to 6 seconds.
3. Continuous Blower Mode
When the R-to-G circuit is closed by the thermostat, the
blower motor BLWM will operate on HEAT speed and
EAC ternfinal is energized as long as the blower motor
BLWM is energized.. During a call for heat, the blower
BLWM will stop during igniter warm-up (20 sec), ignition
(8 sec), and blower-ON delay (30 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.
In heating, the furnace control CPU will continue running
the blower motor BLWM at HEAT speed after the selected
blower-OFF delay period is completed.
When the thermostat "calls for cooling", the blower motor
BLWM will operate at COOL speed. When the thermostat
is satisfied, the blower motor BLWM will operate an addi-
tional 108 sec on COOL speed before reverting back to
continuous-blower speed.
When the R-to-G circuit is opened, the blower motor
BLWM will continue operating for an additional 6 sec, if no
other function requires blower motor BLWM operation.
4. Heat Pump Mode
Change Heat Pump to: HEAT PUMP MODE. When in-
stalled with a heat pump, the furnace control automatically
changes the tinting sequence to avoid long blower off times
during demand defrost cycles. When the R-to-W and-Y or
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 selec-
ted blower-OFF delay period. If the R-to-W-and-Y sig-
nals disappear, leaving the G signal, the blower motor
BLWM will continue running the blower motor BLWM at
HEAT speed after the selected blower-OFF delay period is
completed.
Component
Self-Test
Refer to page 66 for instructions.
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