Specifications

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Figure 20: Schematic Wiring Diagram, Standard Control Set w/Optional LWCO and/or High Limit Accessory Kit
A call for heat by the thermostat energizes the L7248C control which in turn energizes the primary control to turn on the burner. The burner will operate in the following sequence: Prepurge for the fi rst 10 seconds; fi re until the thermostat is satisfi ed or the limit setting on the operating (high) limit is reached; post-purge for the last 10 seconds. The circulator will
operate as long as the thermostat is calling for heat. If the thermostat is not satisfi ed and the operating (high) limit is reached, the circulator will continue to operate, and the burner will stop until the operating (high) limit is closed by a 15°F drop in boiler water temperature. On water boiler equipped with Optional L4080B Auxiliary High Limit Control, if boiler water temperature exceeds the operating limit setting and reaches the high limit setting, the circulator will continue to operate, and the burner will stop until the high limit is closed by an 8°F drop in boiler water temperature. On burner start, if the cad cell does not see fl ame within approximately 15 seconds, primary control will shut burner down and enter into a recycle mode, after 60 seconds burner will restart
and repeat trial for ignition. If after three (3) trials for ignition, fl ame is not detected, control will enter into restricted mode and must be reset manually before burner can be restarted. On water boiler equipped with optional low water cut-off (LWCO) control, if probe senses a low water condition, power to the L7248C control is de-energized. When water level is replenished, LWCO will automatically re-energize sending power to the L7248C control.
BOILER SEQUENCE OF OPERATION