Carrier 58PAV - Manual (Page 8)

Category I Fan-Assisted Furnaces. The horizontal portion of the
venting system shall maintain a minimum of 1/4-in. upward slope
per linear ft and it shall be rigidly supported every 5 ft or less with
hangers or straps to ensure that there is no movement after
installation.
Step 8—Start-up, Adjustment, and Safety Check
GENERAL — The furnace must have a 115-v power supply
properly connected and grounded. Proper polarity must be main­
tained for correct operation. Thermostat wire connections at R, W,
C, and Y must be made at the 24-v terminal block on the control
board. The gas service pressure must not exceed 0.5 psig (14-in.
wc), but must be no less than 0.16 psig (4.5-in. wc).
A CAUTION
This furnace is equipped with a manual reset limit switch in
the gas control area. The switch opens and shuts off power to
the gas valve if a flame rollout or over heating condition
occurs in the gas control area. DO NOT bypass the switch.
Correct inadequate combustion air supply problem and reset
the switch.
Before operating the furnace, check each manual reset switch for
continuity. If necessary, press the button to reset the switch.
The blower compartment door must be in place to complete the
115-v circuit to the furnace.
SEQUENCE OF OPERATION — Using the schematic diagram
shown in Fig. 10, follow the sequence of operation through the
different modes. Read and follow the wiring diagram very care­
fully.
NOTE: If there is a power interruption, and any thermostat call,
the control initiates a 90-sec blower only on period before starting
another cycle.
1. Heating mode
When the wall thermostat "calls for heat," the R-W circuit
closes. The furnace control performs a self-check, verifies the
pressure switch contacts are open, and starts the inducer
motor.
a. Prepurge period — As the inducer motor comes up to speed,
the pressure switch contacts close to begin a 15-sec
prepurge period.
b. Ignitor warm-up—At the end of the prepurge period, the
ignitor is energized for a 17-sec ignitor warm-up period. If
ignition is not established during the first cycle, the next
warm-up period is increased to 45 sec. All subsequent
Ignition cycles will be 45 sec, or until the 115-v power
supply is interrupted. By interrupting the 115-v power
supply, the warm-up period is automatically reset to 17 sec.
c. Ignition sequence—When the ignitor warm-up period is
completed, the gas valve opens, permitting gas flow to the
burners where it is ignited. After 5 sec, the ignitor is
de-energized and a 2-sec flame-sensing period begins.
d. Flame-sensing—When burner flame is sensed, the control
begins the blower on delay period and continues holding
the gas valve open. If burner flame is not sensed, the
control closes the gas valve, and repeats ignition cycle.
e. Blower on delay — Forty sec after burner flame is proven,
the blower motor is energized on heating speed. Simulta­
neously, the humidifier and EAC terminals (HUM-1 and C
for humidifier, EAC-1 and EAC-2 for electronic air
cleaner) are energized. Jumper JW9 should not be cut. If
jumper JW9 has been cut, the blower on delay is 60 sec.
f. Blower off delay—When the thermostat is satisfied, the
circuit between R-W is broken, de-energizing the gas valve
and stopping gas flow to the burners. The'blower motor,
humidifier, and EAC remain energized 90,135,180, or 225
sec (depending on the blower off-time selection). The
furnace is factory set for a 135-sec blower off delay.
g. Post-purge—The inducer motor remains energized 5 sec
after the burners are extinguished. Jumper JW9 should not
be cut. If jumper JW9 has been cut, the post-purge period
is 15 sec.
2. Cooling mode
When the thermostat "calls for cooling" R-Y circuit closes.
The R-Y circuit starts the outdoor condensing unit and the
furnace blower motor on cooling speed. The EAC terminals
are energized with 115v when the blower is operating on
cooling speed. HUM-1 terminal is not energized.
When the thermostat is satisfied, R-Y circuit is broken. The
condensing unit stops and the furnace blower continues
operating on cooling speed for an additional 90 sec.
3. Continuous blower mode
When the R-G circuit is made, the blower motor operates on
heating speed. During a call for heat, the blower stops,
allowing the furnace heat exchangers to heat up more quickly,
then restarts at the end of the 40-sec blower on delay period.
Jumper JW9 should not be cut. If jumper JW9 has been cut,
the blower on delay is 60 sec.
The blower reverts to continuous operation after the heating
cycle is completed.
When the thermostat "calls for cooling," the blower operates
on cooling speed. When the thermostat is satisfied, the blower
operates an additional 90 sec before reverting back to con­
tinuous operation on heating speed. EAC and HUM-1 termi­
nals are energized.
4. Heat pump mode
When installed with a heat pump, the furnace control auto­
matically changes the timing sequence to avoid long blower
off time during demand de&ost cycles. When the W-Y or
W-Y-G thermostat inputs are received at the same time, the
control changes the blower to heating speed, or starts the
blower if it was off and begins a heating cycle. The blower
remains on until the end of the purge period, then shuts off
until the end of the ignition warm-up and trial for ignition
periods (a total of 24 sec). The blower then comes back on at
heating speed.
When the W input signal disappears, the control begins the
normal inducer post-purge period and the blower changes to
cooling speed after a 1-sec delay. If the W-Y-G signals should
disappear at the same time, the blower remains on for the
selected heating blower off delay period, and the inducer goes
through its normal post-purge period. If the W-Y inputs
should disappear, leaving the G signal input, the control goes
into continuous blower mode and the inducer remains on for
the normal post-purge period.
While in heat pump mode, the control uses only the 17-sec
ignition warm-up period and does not use the 45-sec period at
all. Any time the control senses false flame, the control locks
out of the heating mode. This occurs because the control
cannot sense the W input due to the false flame signal and, as
a result, sees only the Y input and goes into cooling mode
blower off delay. All other control functions remain in
standard format. EAC terminals are energized during blower
operation. HUM-] is energized only during gas heat or defrost
operation.