21
Differential Pressure Switches
Diaphragm type differential pressure switches are
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connected by vinyl tubing to gas valve, air inlet
connection on negative side, and sight glass adapter
on positive side. Pressure switches monitor air fl ow
by sensing differential pressure measured in inches of
water (” w.c.).
Switch factory settings are 0.5” w.c. on normally open
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switch and 3.5” w.c. for normally closed switch.
See pages 25-27,
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“Detailed Sequence of Operation,” for
details.
Blower
Blower provides means for pushing combustion air into
and through mixer, burner, and fl ue ways of cast aluminum
boiler section before being discharged through vent piping
to outdoors.
Circulator Pump
Forced hot water system requires at least one circulating
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pump.
Circulating pump provides energy to move water
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through closed loop supply, return piping systems,
terminal heating equipment (fi nned tube radiators, etc.)
and back through boiler for reheating.
To provide required hot water fl ow rates, circulator
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pump must be properly sized to overcome frictional
losses (usually measured in feet of water, also referred
to as “pump head loss”) of supply and return piping
systems and boiler.
Circulator pump is furnished in a carton within boiler
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cabinet. Locate circulator(s) on downstream (i.e.,
“pumping away”) side of expansion tank.
Drain Valve
Manual drain valve is means of draining water in heating
system, including boiler, hot water supply and return piping
systems installed above drain valve.
Install drain valve in ¾” tapping at bottom of boiler.
Piping installed below drain valve elevation requires
additional drain valves installed at low points in piping
systems to drain entire system.
WARNING
Burn and scald hazard. Safety relief valve could
discharge steam or hot water during operation.
Install discharge piping per these instructions.
!
A.S.M.E. Rated Pressure Relief Valve
Each boiler must have properly sized and installed
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A.S.M.E. rated pressure relief valve.
Water expands as it is heated by the burner/boiler
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sections. If no place for water to expand its volume,
(i.e., properly sized functioning expansion tank)
pressure inside of boiler and heating system increases.
9 - CONTROLS AND ACCESSORIES
Pipe pressure relief valve discharge with same size as
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valve discharge opening to open drain, tub or sink, or
other suitable drainage point. Do not subject to freezing,
in accordance with A.S.M.E.
Failure to provide pressure relief valve with piping as
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described may cause water damage and/or serious
bodily injury.
Blocked Vent Safety Shutoff
Boiler equipped with blocked vent safety shutoff, shuts
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off main burner gas in event airfl ow of combustion
products through fl ue-way is reduced.
Air will not be available to support combustion if fl ueway
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is blocked. IBC locks out due to loss of adequate air
fl ow.
Pressure switches monitor air fl ow by sensing differential
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pressure. Contacts normally open and close when draft
inducer is running causing differential pressure at switch
to exceed settings. Closed switch proves adequate air
fl ow for combustion.
Pressure switch shuts off main burner if differential
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pressure is inadequate due to blocked vent pipe, blocked
air intake, blocked boiler section, or blocked air inducer.
After 5 minutes of inadequate differential pressure, IBC
will lock out.
“Purge” indicator lamp blinks, see Figure 19, Page 20,
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indicating failure to prove adequate combustion air
fl ow or fl ue gas fl ow. IBC automatically resets after
15 minutes or manually reset as noted “Hot Surface
Igniter” on page 20
.
Boiler cannot be restored to
normal operating condition by resetting control, contact
qualifi ed service agency to check heat exchanger fl ue-
ways for blockage.
High Limit /Low Water Cut Off
Unit equipped with high limit low water cut off control,
protects against over temperature and dry fi ring. Control
provides burner cut off if unsafe water loss, which can
result from broken or leaking radiator, pipe, or boiler. Use
water/glycol mixture 50% with low water cut off.
Refer to manufacturer provided literature for specifi c
features.
External Condensate Pump (Optional)
Installations where no fl oor drain or other appropriate
drainage available, external fl oat activated condensate pump
with integral sump (not supplied) is required.
May pipe condensate pump to remote tie in point to
sanitary sewer system. For this application, boiler must be
installed so proper pitch of piping to external condensate
reservoir (sump) can be accomplished. Use wood frame or
blocks to raise boiler as required for proper installation.
Furnished relief valve automatically opens at 30 psi
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to relieve strain on boiler and heating system from
increasing pressure.