LG 395CAV - Manual (Page 9)

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 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.
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. HUM terminal is energized with the gas valve. See
accessories in the Electrical Connections section.
e. Flame-sensing—When burner flame is sensed, the con-
trol 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.
NOTE: Ignition sequence will repeat 3 additional time before a
lockout occurs. Lockout automatically resets after 3 hrs, or can be
manually reset by turning 115v off (not at thermostat) for 3 sec
minimum, then on again.
f. Blower on delay—Forty sec after burner flame is proven,
the blower motor is energized on heating speed. Simul-
taneously, the humidifier and electronic air cleaner
terminals (HUM and Com for humidifier, EAC-1 and
EAC-2 for electronic air cleaner) are energized. If jumper
is on pin 6 and pin 9, blower on delay is 60 sec.
g. Blower off delay—When the thermostat is satisfied, the
circuit between R-W is broken, de-energizing the gas
valve stopping gas flow to the burners. The blower
motor 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.
h. Post-purge—The inducer motor remains energized 5 sec
after the burners are extinguished. If jumper is on pin 6
and pin 9, the post-purge period is 15 sec.
2. Cooling mode
When the thermostat "calls for cooling," R-G and R-Y
circuits close. The R-Y circuit starts the outdoor condensing
Fig. 9—Control Board
A93052
G
R
Y
W
3-AMP FUSE
Com
24V
HUMIDIFIER TERMINAL
(24-VAC 0.5 AMP MAX)
LED OPERATION &
DIAGNOSTIC LIGHT
HARNESS CONNECTOR
24V TRANSFORMER SEC-2
SPARE 1
SPARE 2
EAC 1 (BLACK)
EAC-ELECTRONIC AIR CLEANER
TERMINALS (115-VAC 1.5 AMP MAX)
EAC 2 (WHITE)
115-VAC (L2) NEUTRAL
CONNECTION
24V THERMOSTAT
TERMINALS
BLOWER SPEED
SELECTION TERMINALS
INDUCER MOTOR
CONNECTOR
115-VAC (L1)
POWER
SUPPLY
HOT SURFACE
IGNITOR
CONNECTOR
HEAT
COOL
BLOWER OFF DELAY
ADJUSTMENT SWITCH
SEC-1
TEST/TWIN
HUM
Fig. 10—EAC Terminals on Control Board
A93053
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