Abnormal Operation - Bradford White D4403S*F(BN Service Manual

Sequence of Operation
Normal Heating Sequence (cont'd)
7. Steady State Operation: During steady state operation, the gas control monitors:
Thermostat Temperature Sensor: When the setpoint temperature is satisfied, the
gas control is shutdown, and the damper is powered closed. The gas control LED
flashes a short flash once every 4 seconds (Idle status code).
Damper Position: If the damper position is altered during a call for heat, the pilot
and main valves are shutdown. The damper is powered open attempting to close
the damper safety circuit. The gas control LED flashes 3 times with a 3 second
pause.
Flame Sensor: If flame is lost, the pilot and main valves are shutdown. The damper
is powered open. The gas control attempts to re-light the pilot 4 times. If unsuc-
cessful, the damper is closed, and the gas control proceeds to a 5 minute lockout.
The gas control re-attempts to light the pilot starting at Normal Heating Sequence
#2.
8. Thermostat Satisfies: Gas control LED flashes once every 4 seconds.
9. Burner Off
10. Damper Powered Closed (15 seconds)

Abnormal Operation

1. Flammable Vapor Sensor Fault:
A) If the resistance is greater than 70,000 ohms: The gas control immediately turns
off all outputs. The gas control waits and monitors resistance for 30 seconds. If the
resistance is greater than 65,000 ohms after 30 seconds, the gas control proceeds
to verify resistive delay for 2 minutes and flashes 7 times then 1 time with a three
second pause. This process is repeated 5 times until the control either returns to
normal operation or proceeds to flammable vapor lockout.
B) If the resistance is below 3000 ohms: The gas control immediately turns off all
outputs and proceeds to flash 8 times then 1 time with a three second pause. The
error self clears if the resistance returns to normal range for at least 15 seconds.
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