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higher aquastat setting or over firing. The temperature safety switch automatically resets when the
vent temperature decreases. (15 °F switch differential).
F. CASTING TEMPERATURE SAFETY SWITCH
In the event of lack of or loss of water in the boiler, the Casting Temperature Safety Switch (300 °F
setpoint) installed on the top of the aluminum boiler section shuts offthe boiler by shutting off
power to the Integrated Boiler Control (IBC) and causes the Power Indicator Light to go out. This
fault requires manual reset of the casting temperature safety switch to restart the boiler. Verify that
the boiler is properly filled with water before resetting this switch. WARNING- Never run cold water
into a hot empty boiler.
G. DIFFERENTIAL PRESSURE AIR PROVING SWITCH
The diaphragm type differential pressure switch is connected by vinyl tubing to the pressure signal
hose adapters. The pressure switch monitors air flow by sensing the diffential pressure measured in
inches of water (" w.c.). The factory settings on these switches are 1.17 "w.c. for K90-100, 1.35
"w.c. for K90-75 and 1.55 "w.c. for K90-50. The contacts are normally open, and close when the
draft inducer is running and causing the diffential pressure at the switch to exceed the setting. The
closed switch proves there is adequate air flow for combustion. The pressure switch shuts off the
main burner if the differential pressure is inadequate due to a blocked vent pipe or a blocked air
intake or blocked boiler sections or blocked draft inducer. After five (5) minutes of lack of the
adequate differential pressure, the IBC will lockout. The "PURGE" indicator light will blink,
indicating a failure to prove adequate combustion air flow or flue gas flow. The IBC is manually
reset from lockout as described in the Sequence of Operation section of this chapter.
H. DRAFT INDUCER
The draft inducer (blower) provides a means for pulling combustion air into and through the mixer,
the burner, the flue ways of the cast aluminum boiler sections and the flue adapter before being
discharged through the vent piping to the outdoors. See applicable sections for proper sizing and
installation of combustion air and vent piping in this manual.
I. CIRCULATOR PUMP
Every forced hot water system requires at least one circulating pump. The circulating pump imparts
the necessary energy to move the water through the closed loop supply and return piping systems,
terminal heating equipment (i.e. finned tube radiators, etc.) and back through the boiler for reheating.
To provide the required hot water flow rates, the circulator pump must be properly sized to overcome
frictional losses (usually measured in feet of water, also referred to as "pump head loss") of the
supply and return piping systems and boiler. The circulator pump is furnished in a carton within the
boiler cabinet for a single zone or zone valve controlled heating system and should be correctly
located on the downstream (i.e., pumping away) side of the expansion tank. For a pump controlled
system (where there is a circulator for each zone) the circulator provided with the boiler can work for
one zone. For more details on piping and circulators, see Near Boiler Piping section of this manual.
J. DRAIN VALVE
The manual drain valve provides a means of draining the water in the heating system, including the
boiler and hot water supply and return piping systems installed above the drain valve. This drain
valve is installed in the 3A"tapping at the bottom of the front boiler section. Any piping installed
below the elevation of this drain valve will require additional drain valves to be installed at low
points in the piping systems in order to drain the entire system.
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