Bradford White UPV75 Series Service Manual page 10

UPV75 Series - Sequence of Operations
Abnormal Operation
1. Simulated Resistive Device Fault:
a. If the resistance is greater than 70,000 Ohms – The gas control immediately turns off all
outputs. 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 once 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 once with three second pause. The status self clears if
the resistance returns to normal range for at least 15 seconds.
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 with 3 second pause. The status self
clears if the fault clears for at least 15 seconds.
b. Temperature sensor 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 twice with 3
second pause. The status 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 pilot & main valves and proceeds to flash 4 times with 3 second pause. Blower
continues to run until gas control is reset. To reset control, rotate knob of temperature
control to the minimum setting for at least 6 seconds before returning to desired temperature
setting.
3. Pressure Switch/Blower Temperature Fault:
a. Pressure switch closed at start of call for heat – The gas control waits 4 seconds then,
proceeds to flash 2 times with 3 second pause. The control waits 2 minutes and then turns
on blower for 30 seconds. The blower turns off after 30 seconds and the control waits for
pressure switch to open. Any time the pressure switch opens, the blower turns on (or stays
on) and the control proceeds to wait for pressure switch to close.
b. Pressure switch or blower temperature switch failed to close – The gas control runs the
blower for 30 seconds waiting for the pressure switch and/or blower temperature switch to
close. If either switch does not close in 30 seconds, the blower turns off and the control
flashes 3 times with 3 second pause. The gas control waits 2 minutes before turning on the
blower for another 30 seconds to see the circuit close. This cycle repeats as long as there is
a call for heat or until the circuit closes.
c. Pressure switch or blower temperature switch opens during burner operation – The
gas control turns off the pilot and main valve, runs blower for 15 seconds (inter-purge)
waiting for pressure switch and/or blower temperature switch to close. If either switch fails to
close, the control proceeds as described in 3b above, if the circuit closes again by the end of
the inter-purge, the recycle counter is incremented, if the recycle count has not reached its
limit (4), another trial for ignition begins. If the recycle count has been reached, the gas
control turns off the blower and flashes 6 times then 2 times with 3 second pause. The gas
control waits 5 minutes before repeating ignition sequence.
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