Bradford White UPDX2-75T6FRN - Manual (Page 11)

Sequence of Operation
Abnormal Operation (cont.)
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 followed by a 3 second pause. The gas control waits 2 minutes and then turns on the blower for 30
seconds. The blower turns off after 30 seconds and the gas control waits for the pressure switch to open. Any time
the pressure switch opens, the blower turns on (or stays on) and the control proceeds to waiting for the pressure
switch to close.
b) Pressure Switch or Blower Temperature Switch Failed Open - 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 followed by a 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 the blower for 15 seconds (inter-purge) waiting for the pressure switch and/or blower
temperature switch to close. If either switch fails to close, the gas 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 control
turns off the blower and flashes 6 times then 2 times followed by a 3 second pause. The gas control waits 5
minutes before repeating ignition sequence.
4. Trial For Ignition Fault:
a) Pressure Switch Opens During Trial - The gas control turns off the igniter and pilot valve. The gas control
proceeds as described in 3b above. If the pressure switch closes within 30 seconds, the gas control will continue
with trial for ignition starting at blower pre-purge.
b) Flame Not Sensed - The gas control energizes the spark igniter attempting to light the pilot and prove flame. If
flame is not sensed within 90 seconds, the igniter turns off, the pilot valve is closed and the gas control runs the
blower through post purge and flashes 6 times then once followed by a 3 second pause. The control waits 5
minutes before repeating the ignition sequence.
5. Flame Sensing Fault:
a) Flame Lost During Run - The gas control turns off the pilot and main valves and runs the blower for 15 seconds
(inter-purge). The gas control increments the recycle count, 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 3 times followed by a 3 second pause. The control waits 5 minutes before repeating the
ignition sequence.
b) Flame Sensed Out of Sequence - the gas control only looks for pilot flame when the blower is running. If a flame
is present when the pilot valve is not open the control proceeds to wait for flame loss and flashes 5 times followed
by a 3 second pause. This continues until flame is lost, once the flame signal is lost, the gas control flashes 6
times then 4 times followed by a 3 second pause. The gas control waits 5 minutes before repeating the ignition
sequence.
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UPDX Series
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