Dunkirk Q90-200 Series II - Manual (Page 27)

27
Differential Pressure Switches
• Diaphragm type differential pressure switches are
connected by vinyl tubing to gas valve, air inlet
connection on negative side, and sight glass adapter
on positive side. Pressure switches monitor air flow
by sensing differential pressure measured in inches of
water (” w.c.).
• Switch factory settings are 0.5” w.c. on normally open
switch and 3.5” w.c. for normally closed switch.
• See pages 31-32, “Detailed Sequence of Operation,” for
details.
Blower
Blower provides means for pushing combustion air into
and through mixer, burner, and flue 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
pump.
• Circulating pump provides energy to move water
through closed loop supply, return piping systems,
terminal heating equipment (finned tube radiators, etc.)
and back through boiler for reheating.
• To provide required hot water flow rates, circulator
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
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
A.S.M.E. rated pressure relief valve.
• Water expands as it is heated by the burner/boiler
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.
10 - CONTROLS AND ACCESSORIES
• Pipe pressure relief valve discharge with same size as
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
described may cause water damage and/or serious
bodily injury.
Blocked Vent Safety Shutoff
• Boiler equipped with blocked vent safety shutoff, shuts
off main burner gas in event airflow of combustion
products through flue-way is reduced.
• Air will not be available to support combustion if flue-
way is blocked. IBC locks out due to loss of adequate
air flow.
• Pressure switches monitor air flow by sensing differential
pressure. Contacts normally open and close when draft
inducer is running causing differential pressure at switch
to exceed settings. Closed switch proves adequate air
flow for combustion.
• Pressure switch shuts off main burner if differential
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 26,
indicating failure to prove adequate combustion air
flow or flue gas flow. IBC automatically resets after 15
minutes or manually reset as noted see “C” page 26 .
Boiler cannot be restored to normal operating condition
by resetting control, contact qualified service agency to
check heat exchanger flue-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 firing. 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 specific
features.
External Condensate Pump (Optional)
Installations where no floor drain or other appropriate
drainage available, external float 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
to relieve strain on boiler and heating system from
increasing pressure.