32
Figure 20: Schematic W
iring Diagram, Standard Control Set w/Optional L
WCO 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 burne
r.
The burner will operate in the following sequence:
Prepurge for the
fi
rst 10 seconds;
fi
re until the thermostat is satis
fi
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 satis
fi
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 l
imit 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 bur
ner 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-of
f (L
WCO) control, if probe senses a low water condition, power to the L7
248C control is de-energized. When water level is
replenished, L
WCO will automatically re-energize sending power to the L7248C control.
BOILER SEQUENCE OF OPERA
TION
Summary of Contents for MPO Series
Page 6: ...6 Figure 1 MPO 84 Thru MPO 231 Water Boiler ...
Page 22: ...22 Figure 13A Water Boiler Piping for Circulator Zoned Heating System Supply Side Circulator ...
Page 38: ...38 Figure 27 L1 L2 and V1 Head Electrode Positioning and Gun Setting Beckett AFG ...
Page 49: ...49 SERVICE RECORD DATE SERVICE PERFORMED ...
Page 50: ...50 Bare Boiler Assembly ...
Page 52: ...52 Bare Boiler Assembly ...
Page 54: ...54 Jacket Assembly ...
Page 56: ...56 MPO84 Thru MPO231 Water Boilers Trim and Controls ...
Page 58: ...58 Beckett AFG Burner ...
Page 61: ...61 Figure A2 LWCO Location ...