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Safety Control Operation
Temperature Limit Control – The temperature limit control interrupts burner operation when the supply water tempera-
ture exceeds the set point. Maximum allowable water temperature in a water boiler is 250F. The L4080D will reset itself
when the water temperature drops below the set point less the differential (typically 15F). The circulator will continue
to operate for as long as the thermostat or operating control calls for heat. If a vent damper is installed, it will close
when the high limit opens. Manual reset water limit controls, such as the Honeywell L4006E, must be manually reset.
For this reason, they should be set well above the operating limit control to avoid nuisance boiler shutdowns.
Blocked Vent Switch - The blocked vent switch automatically interrupts main burner operation when flue gas spillage,
caused by a complete vent blockage, occurs. The circulator continues to operate and the vent damper (if used) remains
open with a call for heat. If the blocked vent switch is activated, do not attempt to place the boiler in operation. Correct
the cause of the spillage and reset the blocked vent switch.
Flame Roll-out Switch - The flame roll-out switch automatically interrupts main burner operation when flames or
excessive heat are present in the vestibule. The circulator continues to operate and the vent damper (if used) remains
open with a call for heat. This control is a single use device. If the flame roll-out switch is activated, do not attempt to
place the boiler in operation. Correct the cause of the spillage and replace the flame roll-out switch.
Low Water Cut-off (by others) – Low water cut-offs interrupt burner operation if the water level in the boiler drops
below a safe level. See the manufacturer’s instructions for further details on the operation of this safety control.
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