NORMAL IGNITION SEQUENCE - TIMINGS NOMINAL
THERMOSTAT DEMAND
COMBUSTION AIR BLOWER
GAS VALVE
IGNITION SPARK
BLOWER
IGNITION TRIAL
011053030SDNOCES
ON / CLOSED
OFF / OPEN
END OF
DEMAND
1
COMBUSTION AIR PROVE SWITCH
5 570
FIGURE 15
RETRIALS - IGNITION ATTEMPT SEQUENCE - TIMINGS NOMINAL
THERMOSTAT DEMAND
COMBUSTION AIR BLOWER
GAS VALVE
IGNITION SPARK
BLOWER
IGNITION TRIAL
SECONDS0 30 35 70
ON
OFF
65 100 105
WATCHGUARD
LOCKOUT
COMBUSTION AIR PROVE SWITCH
5
FIGURE 16
THERMOSTAT DEMAND
COMBUSTION AIR BLOWER
GAS VALVE
IGNITION SPARK
BLOWER
IGNITION TRIAL
SECONDS0 30
ON
OFF
30
30
HEATING
CYCLE
6 (+3.4, -2.0) SEC.
END OF
THERMOSTAT
DEMAND
123
FIGURE 17
immediately restart the ignition sequence and then lock
out if ignition is not gained after the third trial. See System
a power failure. Upon restoration of gas and power, the
control will restart the ignition sequence and continue until
On a heating demand, the ignition control is energized by
the A55 Unit Controller. The ignition control then allows
30 to 40 seconds for the combustion air blower to vent
exhaust gases
from the burners. When the combustion air blower is purg-
ing the exhaust gases, the combustion air prove switch is
closing proving that the combustion air blower is operat-
ing before allowing the ignition control to energize. When
the combustion air prove switch is closed and the delay
is over, the ignition control activates gas valve, the spark
blower continues to operate throughout the heating de-
ignition control will attempt to ignite the burners up to two
more times. If ignition cannot be obtained after the third
attempt, the control will lock out. The ignition control is not
adjustable.
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