18
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WARNING
Never run cold water into a hot, empty boiler.
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 pres-
sure switches monitor air flow by sensing the differ-
ential pressure measured in inches of water (” w.c.).
The factory settings on these switches are 0.5” w.c.
on the normally open switch and 3.5” w.c. for the nor-
mally closed switch. See Section XVI,
“Detailed Se-
quence of Operation,”
for details on the operation of
the differential pressure switches.
BLOWER
The blower provides a means for pushing combus-
tion air into and through the mixer, the burner, the flue
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, ter-
minal heating equipment (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. 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 in-
stalled above the drain valve. This drain valve is in-
stalled 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 in-
stalled 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) pres-
sure on the inside of the boiler and heating system
will increase. The furnished relief valve will automati-
cally 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. specifications. Failure to provide the
pressure relief valve with piping as herein described
may cause water damage and/or serious bodily in-
jury. 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 airflow of combustion products through
the flue-way is reduced. In the event of a blocked
flue-way, enough air will not be available to support
combustion and the IBC will lock out due to loss of
adequate air flow. Pressure switches monitor air flow
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 flow for combustion. The pres-
sure 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 dif-
ferential pressure, the IBC will lock out. The “Purge”
indicator lamp (see Figure 16) will blink, indicating
a failure to prove adequate combustion air flow or
flue gas flow. The IBC will automatically reset after
15 minutes or can be manually reset as noted in the
section titled
“Hot Surface Igniter.”
If the boiler cannot
be restored to normal operating condition by reset-
ting the control, contact a qualified service agency to
check the heat exchanger flue-ways for blockage.
LOW WATER CUT OFF
This unit is equipped with a low water cut off control
that protects against dry firing. 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% concentra-
tion may be used with the low water cut off.
EXTERNAL CONDENSATE PUMP (OPTIONAL)
For installations where there is no floor drain or other
appropriate drainage available to receive conden-
