American Water Heater 381T1546NOX Water Heater User Manual


 
16
Servicing should only be performed by a Qualied Service Technician
SEQUENCE OF OPERATION – FLOW CHART
Thermostat calls for heat
Switch power on to unit
Blower engages Prover Switch
AŌer 30 seconds, IgniƟon
Control provides power to
Spark Igniter and opens Gas
Valve
IgniƟon Control maintains spark for up
to 4 seconds and monitors Flame
Sensor to determine if Burner is lit
Does Burner
light?
IgniƟon Control changes Blower from
low speed to high speed aŌer 5 seconds
IgniƟon Control monitors
flame signal
Thermostat is saƟsfied
Blower – off; Blower Prover – opens
IgniƟon Control – off; Gas Valve – closes
Wait 15 minutes.
Blower runs at
low speed
Is this the third loss
of flame signal?
Is this the third
igniƟon trial?
Loss of flame signal?
YES
YES
NO
NO
Gas Valve–off
Gas Valve–off
NO
NO
YES
YES
UGB sends PWM signal to Blower to
start the blower at high purge speed
20 seconds later blower