Bradford-White Corp U4TW50T*FRN, U4TW40T*FRN Sequence of Operation, Abnormal Operation cont’d

Sequence of Operation

Abnormal Operation (cont’d)

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 the 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 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 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 the 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 incre- mented, 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 a 3 second pause. The gas control waits 5 minutes before repeating ig- nition sequence.

4.Trial for Ignition Fault:

A)Pressure switch opens during trial: The gas control turns off the ig- niter 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 a trial for ignition starting at blower pre-purge.

B)Flame Not Sensed: The gas control energizes the spark igniter at- tempting to light the pilot and prove flame. If flame is not sensed within 90 seconds, the spark igniter turns off, the pilot valve is closed. The gas control LED flashes 6 times then 1 time with 3 sec- ond pause. The control waits 5 minutes before repeating the ignition sequence.

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