Crown Boiler AWR070 Installation Instructions Manual page 37

utes before the ignition sequence is retried.
10) Once the ignition module detects the presence of a pilot flame, voltage is applied across the main valve (terminals MV and
MV/PV on the valve), opening the valve and establishing main flame.
11) If the water temperature climbs above the high limit setting during the call for heat, the burner will shut down, and the vent
damper close, while the Heating Circulator continues to operate. The ignition sequence will restart (from Step 4) when the
water temperature falls to the high limit setting (HL) minus the high limit differential (HdF).
12) A call for DHW results in a sequence of operation that is identical to that described above except for omission of the thermal
purge function described in (3).
Blocked Vent Switch - Automatically interrupts main burner operation in the event that a blocked vent causes flue gas to spill
from the draft diverter opening. This switch is equipped with a reset button which must be pressed to restore normal burner
operation. An open blocked vent switch is indicative of a problem with the vent system and/or the combustion air supply. If the
blocked vent switch opens, the cause of this problem must be found and corrected by a qualified gas service technician before the
blocked vent switch is reset.
Flame Roll-out Switch - Automatically interrupts boiler operation when flames or excessive heat are present in vestibule. The
flame roll-out switch is a single use device which must be replaced by an identical switch in order to restore normal operation.
An open flame roll-out switch is usually indicative of a plugged heat exchanger. The cause of the flame roll-out must be found
and corrected by a qualified gas service technician, and the switch replaced with an identical one, before the boiler is returned to
operation.
E. Safety Control Operation
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