UTICA BOILERS UB90-200 Installation, Operation & Maintenance Manual page 21

Differential Pressure Switches
The diaphragm type differential pressure switches are
connected by vinyl tubing to the gas valve and the air
inlet connection on the negative side and the sight glass
adapter on the positive side. The pressure switches monitor
air fl ow by sensing the differential pressure measured in
inches of water (" w.c.). The factory settings on these
switches are 0.5" w.c. on normally open switch and 3.5"
w.c. for normally closed switch. See pages 30-32, "Detailed
Sequence of Operation," for details on operation of
differential pressure switches.
Blower
The blower provides a means for pushing combustion air
into and through the mixer, the burner, the fl ue ways of
the cast aluminum boiler section before being discharged
through the vent piping to the outdoors.
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 (fi nned tube radiators, etc.) and back through
the boiler for reheating. To provide the required hot water
fl ow 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. The
circulator(s) should always be located on the downstream
(i.e., "pumping away") side of the expansion tank.
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 ¾" tapping
at the bottom of the boiler. 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.
A.S.M.E. Rated Pressure Relief Valve
Each boiler must have a properly sized and installed
A.S.M.E. rated pressure relief valve. Water expands as it is
heated by the burner/boiler sections. If there is no place
for the water to expand its volume, (i.e., a properly sized
and functioning expansion tank) pressure on the inside of
the boiler and heating system will increase. The furnished
relief valve will automatically open at 30 psig pressure to
relieve the strain on the boiler and heating system from
the increasing pressure. The pressure relief valve discharge
must be piped with the same size as the valve discharge
opening to an open drain, tub or sink, or other suitable
drainage point not subject to freezing, in accordance with
A.S.M.E. specifi cations.
CONTROLS AND ACCESSORIES
Failure to provide the pressure relief valve with piping as
herein described may cause water damage and/or serious
bodily injury. The boiler manufacturer is not responsible for
any water damage or personal injury.
Blocked Vent Safety Shutoff
The boiler is equipped with a blocked vent safety shutoff
which shuts off the main burner gas in the event that the
airfl ow of combustion products through the fl ue-way is
reduced. In the event of a blocked fl ue-way, enough air
will not be available to support combustion and the IBC will
lock out due to loss of adequate air fl ow.
Pressure switches monitor air fl ow by sensing differential
pressure. The contacts are normally open and close when
the draft inducer is running and causing the differential
pressure at the switch to exceed its setting. The closed
switch proves there is adequate air fl ow for combustion.
The pressure switch shuts off the main burner if the
differential pressure is inadequate due to a blocked vent
pipe, a blocked air intake, a blocked boiler section, or
a blocked air inducer. After 5 minutes of inadequate
differential pressure, the IBC will lock out.
The "Purge" indicator lamp (see Figure #16) will blink,
indicating a failure to prove adequate combustion air fl ow
or fl ue gas fl ow. The IBC will automatically reset after 15
minutes or can be manually reset as noted on page 20 of
this manual, "Hot Surface Igniter." If the boiler cannot be
restored to normal operating condition by resetting the
control, contact a qualifi ed service agency to check the
heat exchanger fl ue-ways for blockage.
Low Water Cut Off
This unit is equipped with a low water cut off control that
protects against dry fi ring. This control provides burner cut
off if there is an unsafe water loss, which can result from
a broken or leaking radiator, pipe, or boiler. A water/glycol
mixture up to 50% concentration may be used with the low
water cut off.
External Condensate Pump (Optional)
For installations where there is no fl oor drain or other
appropriate drainage available to receive condensate from
the boiler, an external fl oat activated condensate pump with
integral sump (supplied by others) is required.
The condensate pump can be piped to a remote tie in point
to a sanitary sewer system. For this application, the boiler
must be installed so that proper pitch of piping to the
external condensate reservoir (sump) can be accomplished.
Use wood frame or blocks (not factory supplied) to raise
boiler as required for proper installation.
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