Bradford White UPDX2-75T6FRN - Manual (Page 10)

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 shut down
and the blower will post purge for 15 seconds. The gas control LED flashes a short flash once every 4
seconds (idle) status code.
Pressure Switch / Blower Temperature Switch- If either switch opens the pilot valve and main valve are
shut down. The blower continues to run for 30 seconds attempting to close the circuit. The control LED
flashes 3 times followed by a 3 second pause.
Flame Sense- If flame is lost, the pilot & main valve are shut down and the blower runs for 15 seconds. The
gas control attempts to re-light the pilot 4 times. If unsuccessful, the blower is shut down 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.
9. Burner Off.
10. Blower Post-purge (15 seconds).
Sequence of Operation
Abnormal Operation
1. Flammable Vapor Sensor Fault:
a) If the Flammable Vapor Sensor 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
70,000 ohms after 30 seconds, the gas control proceeds to verify resistive delay for 2 minutes and flashes 7 times
followed by a 3 second pause. This process is repeated 5 times until the gas control either returns to normal
operation or proceeds to a lockout mode flashing 7 times followed by a 3 second pause.
b) If the Flammable Vapor Sensor Resistance is Below 3000 ohms - The gas control immediately turns off all
outputs and proceeds to flash 8 times then 1 time followed by a 3 second pause. The error self clears if the
resistance returns to the normal range for at least 15 seconds.
Normal Heating Sequence (continued)
2. Temperature Sensor Fault:
a) Temperature Sensor Detected Open Circuit - The gas control Immediately turns off all outputs and proceeds to
flash 8 times then 3 times followed by a 3 second pause. The error self clears if the fault clears for at least 15
seconds.
b) Temperature Sensors not Reading the Same Temperature Within ±5.5 °F - The gas control immediately turns
off all outputs and proceeds to flash 8 times then 3 times followed by a 3 second pause. The error self clears if the
fault clears for at least 15 seconds.
c) Water Temperature in Excess of ECO (Energy Cut Out) limit - The gas control immediately turns off the pilot
and main valve and proceeds to flash
4 times followed by a 3 second pause. Blower continues to run until the gas
control is reset. The set point knob should be turned to the minimum temperature setting for at least 6 seconds
and then turned clockwise by 45
o .
Page 10
UPDX Series
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