Bryant GAS-FIRED INDUCED-COMBUSTION FURNACES 383KAV Installation, Start-Up, And Operating Instructions Manual Download Page 12

Page: 12 / 20

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

pressure switch contacts close to begin a 15-sec prepurge
period.

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

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

c. Ignition sequence—When igniter warm-up period is

completed, 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.

d. HUM terminal is energized with gas valve. See acces-

sories in the Electrical Connections section.

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

trol 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 stop-
ping gas flow to burners. The blower motor and EAC
remain energized for 135 sec.

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 termi-
nal 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.

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 oper-
ates on cooling speed. When the thermostat is satisfied, the
blower operates an additional 90 sec before reverting back
to continuous operation on heating speed.

4. Heat pump mode

When installed with a heat pump, the furnace control
automatically 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 re-
mains 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.

NOTE:

EAC-1 terminal is energized whenever blower operates.

HUM terminal is only energized when gas valve is energized

Start-up Procedures

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

purge the lines and check for leaks.

WARNING:

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 compo-

nents, 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 (adjacent to diagnostic light) and the C

-24V

terminal on furnace thermostat connection block for ap-
proximately 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

-24V terminals until

LED goes off.

b. LED will display previous status 4 times.

c. Inducer motor starts and continues to run for entire

component test.