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FIGURE 19: WIRING DIAGRAM, INTERMITTENT IGNITION AND McDONNELL & MILLER MODEL
#67 LOW WATER CUTOFF
Blocked Vent (“Spill”) Switch - Automatically interrupts burner operation in the event that flue gas spills 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. If the blocked vent switch opens, the cause of the venting 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 burner 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.
22
TH
TR
+
ROBERTSHAW
7000DERHC
GASVALVE
(BSI379)
HONEYWELL
VR8204/VR8304
SERIESGASVALVES
(BSI069-345)
VENTDAMPER(NOTE2)
NOTE3
2.VENTDAMPERREQUIREDONBSI069-BSI276,OPTIONALONBSI310-BSI379
3.ONBOILERSLESSVENTDAMPER,DAMPERHARNESSISNOTUSED.REDAND
BLUELEADSSHOWN AREJUMPEDTOGETHERUSINGREDJUMPERWIRE.
LESSVENT
DAMPER