Lennox LGT150H - Page 24

Page 24
D-GAS HEAT COMPONENTS
1-Control Box Components A3, A55, T3,
K13
WARNING
Shock hazard. Spark related compo
nents contain high voltage which can
cause personal injury or death. Discon
nect power before servicing. Control is
not field repairable. Unsafe operation
will result. If control is inoperable, sim
ply replace the entire control.
Burner Ignition Control A3
The ignition controls are located in the heat section areas
below the compressors. The controls are manufactured
UTEC. See table 6 for LED codes.
The ignition control provides three main functions: gas
valve control, ignition and flame sensing. The unit will usu
ally ignite on the first attempt; however, the ignition attempt
sequence provides three trials for ignition before locking
out. The lockout time for the control is 5 minutes. After lock
out, the ignition control automatically resets and provides
three more attempts at ignition. Manual reset after lockout
requires breaking and remaking power to the ignition con
trol. See figure 11 for a normal ignition sequence and figure
12 for the ignition attempt sequence with retrials (nominal
timings given for simplicity). Specific timings for the ignition
controls are shown in figure 13.
TABLE 6
UTEC
LED
Flashes
Indicates
Slow Flash Control ok, no call for heat
Fast Flash Control ok, call for heat present.
Steady Off Internal control fault or no power
Steady On
Failure
Control internal failure
1 Flash Rollout switch open
2 Flashes
Limit open or lockout from to many tries
during a single heat demand
3 Flashes
Pressure switch open with inducer on/
open during 5 minute inducer off time.
4 Flashes
Ignition lockout from no flame detected or
from too many flame losses.
5 Flashes Flame sensed out of sequence
6 Flashes Pressure switch closed with inducer off
7 Flashes Gas valve relay failure
8 Flashes
Lockout due to too many pressure switch
openings during one heat demand
ÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉ
ÉÉÉ
ÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉ
ÉÉ
ÉÉ
ÉÉÉÉÉÉÉÉÉÉ
NORMAL IGNITION SEQUENCE - TIMINGS NOMINAL
THERMOSTAT DEMAND
COMBUSTION AIR BLOWER
GAS VALVE
IGNITION SPARK
BLOWER
IGNITION TRIAL
SECONDS 0 30 35 0 110
ON / CLOSED
OFF / OPEN
END OF
DEMAND
1
ÉÉÉÉÉÉÉÉÉÉÉÉÉ
COMBUSTION AIR PROVE SWITCH
5 570
FIGURE 11
FIGURE 12
RETRIALS - IGNITION ATTEMPT SEQUENCE - TIMINGS NOMINAL
ÉÉÉ
ÉÉ
ÉÉ
ÉÉ
ÉÉ
THERMOSTAT DEMAND
COMBUSTION AIR BLOWER
GAS VALVE
IGNITION SPARK
BLOWER
IGNITION TRIAL
SECONDS 0 30 35 70
ON
OFF
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉ
ÉÉ
ÉÉ
ÉÉ
ÉÉ
ÉÉ
ÉÉ
ÉÉ
65 100 105
WATCHGUARD
LOCKOUT
COMBUSTION AIR PROVE SWITCH
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
5