Sequence Of Operation Flow Chart - American Water Heater Ultra Low NOx 104 Series Instruction Manual

Commercial gas water heaters
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Description of this flow chart can be found in the "SeqUeNCe OF OPerATION" section found on page 26.
Switch power on to unit
Thermostat calls for heat
UGB sends PWM signal to Blower to
start the blower at high purge speed
Blower engages Prover Switch
20 seconds later blower
runs at low igni on speed
After 30 seconds, Ignition
Control provides power to
Spark Igniter and opens Gas
Valve
Ignition Control maintains spark for up
to 4 seconds and monitors Flame
Sensor to determine if Burner is lit
Does Burner
light?
YES
Ignition Control changes Blower from
low speed to high speed after 5 seconds
Ignition Control monitors
flame signal
Loss of flame signal?
NO
Thermostat is satisfied
Blower – off; Blower Prover – opens
Ignition Control – off; Gas Valve – closes
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seQuenCe of operation flow Chart

NO
Gas Valve – off
YES
Gas Valve – off
figure 24.
27
NO
YES
Is this the third
ignition trial?
NO
YES
Is this the third loss
of flame signal?
Wait 15 minutes.
Blower runs at
low speed

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