Carrier 58PAV Operations Instructions download pdf (Page 12)

1. Heating mode

When wall thermostat "calls for heat," R-W circuit closes. The

furnace control performs a self-check, verifies pressure switch

contacts are open, and starts inducer motor.

a. Prepurge period—As inducer motor comes up to speed,

pressure switch contacts close to begin a 15-sec prepurge

period.

b. HUM terminal is energized through the pressure switch

circuit. See accessories in the Electrical Connections sec-

tion.

c. Igniter warm-up—At the end of prepurge period, igniter is

energized for a 17-sec igniter warm-up period.

d. Ignition sequence—When igniter warm-up period is com-

pleted, gas valve opens, permitting gas flow to the burners

where it is ignited. After 5 sec, igniter is de-energized and

a 2-sec flame-sensing period begins.

e. Flame-sensing—When burner flame is sensed, the control

begins blower on delay period and continues holding gas

valve open. If burner flame is not sensed, the control closes

gas valve and repeats ignition sequence.

NOTE: Ignition sequence will repeat 3 additional times before a

lockout occurs. Lockout automatically resets after 3 hr, or can be

manually reset by turning 115v off (not at thermostat) for 3 sec

minimum, then on again.

f. Blower on delay—Forty-five sec after burner flame is

proven, blower motor is energized on heating speed.

Simultaneously, electronic air cleaner terminals EAC-1 and

EAC-2 are energized.

g. Blower off delay—When thermostat is satisfied, circuit

between R-W is broken, de-energizing gas valve stopping

gas flow to burners. The blower motor and EAC remain

energized for selected OFF delay.

h. Post-purge—Inducer motor remains energized 5 sec after

burners are extinguished.

2. Cooling mode

When the thermostat "calls for cooling," R-G and R-Y circuits

close. The R-Y circuit starts the outdoor condensing unit and

the combined R-Y and R-G circuits start the furnace blower

motor on cooling speed. The EAC-1 terminal is energized

with 115v when the blower is operating on cooling speed.

When the thermostat is satisfied, R-G and R-Y circuits are

broken. The furnace blower and EAC continue operating on

cooling speed for an additional 90 sec. Cooling OFF delay can

be set to 3 sec by cutting jumper J2. See figure 10.

3. Continuous blower mode

NOTE: EAC-1 terminal is energized with 115v whenever blower

operates.

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 45-sec blower on delay period.

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 for the cooling off-delay before reverting back to

continuous operation on heating speed.

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 defrost 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 prepurge period, then shuts off

until the end of the hot surface igniter 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

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 and the inducer remains on for the

normal post-purge period.

Anytime 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.

START-UP PROCEDURES

1. Purge gas lines—After all connections have been made, purge

the lines and check for leaks.

Never purge a gas line into a combustion chamber. Never use

matches, candles, flame, or other sources of ignition for the

purpose of checking leakage. Use a soap-and-water solution

to check for leakage. Failure to follow this warning can cause

fire, explosion, personal injury, or death.

2. Component test—The furnace control allows all components,

except gas valve, to be run for a short period of time.

This feature helps diagnose a system problem in case of a

component failure. To initiate component test procedure, short

(jumper) the TEST 3/16-in. quick connect terminal on control

(behind the Y terminal) and the C

OM-24V terminal on furnace

thermostat connection block for approximately 2 sec. (See Fig.

10.)

NOTE: Component test feature will not operate if any thermostat

signal is present at control.

Component test sequence is as follows.

a. Momentarily jumper TEST and C

OM-24V terminals until

LED goes off.

b. LED will display previous status 4 times.

c. Inducer motor starts and continues to run for entire com-

ponent test.

d. Hot surface igniter is energized for 15 sec, then de-

energized.

e. Blower motor operates on HEAT speed for 10 sec, then

stops.

f. Blower motor operates on COOL speed for 10 sec, then

stops.

g. Inducer motor stops.

3. To operate furnace, follow procedures on operating instruc-

tions label attached to furnace.

4. With furnace operating, set thermostat below room tempera-

ture and observe that furnace goes off. Set thermostat above

room temperature and observe that furnace restarts.

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Carrier 58PAV Operations Instructions Page 12

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