After proper wiring and piping of boiler system is complete, testing of
controls can start. Before testing controls, it is recommended that
all contactor fusing be removed. This is to prevent possible element
failure under test conditions.
A. OPERATING AND TESTING THE McDONNELL &
MILLER LOW WATER CUTOFF CONTROL.
1. Be sure all valves from incoming water supply are fully open.
Turn boiler switch to “ON” position, pump or solenoid
valve will energize, allowing boiler to fill with water. Proper
water level is automatically reached with level control sup-
plied. Pump or solenoid feed will shut off at proper water level.
Contactor(s) will energize, supplying power voltage to ele-
ments.
2. Checking operation of pump switch. (Figure 1) With water
level visible in sight glass, partially open drain valve at bottom
of boiler. If automatic blowdown supplied, push manual blow-
down switch until valve open light is on, hold for few seconds.
Water level will fall, allowing float to trip pump switch to
“ON” position. Close drain valve or release manual blowdown
switch.
Pump motor or solenoid valve will energize and water level
will resume to normal level in sight glass.
3. Checking low water cutout switch operation, open drain
valve completely. If automatic blowdown supplied, push in
and hold manual blowdown switch until water level falls
enough to trip cutout switch. Close drain valve or release man-
ual blowdown switch. If low water cutout is automatic reset,
pump or solenoid will return water level to normal. If low
water cutout is manual reset, then manual reset button on
McDonnell & Miller low water cutoff control must be pushed
to complete circuit. Turn off boiler. Reinstall contactor
fuses.
WARNING: Be sure all electrical connections are tight
before energizing boiler. Reset all manual reset con-
trols by pushing reset buttons on: (1) high limit control
located on top of boiler and (2) McDonnell & Miller
located on the side of boiler.
Diagram 14
Typical Export Boiler
TYPICAL WIRING DIAGRAMS
