Kenmore K90-150 Owner's Manual page 18

,_ WARNING
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 flow by sensing the
differential 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 normally closed switch. See Section XVI,
"Detailed Sequence of Operation," for details on
the operation of the diferential pressure switches.
The blower provides a means for pushing combus-
tion air into and through the mixer, the bumer, the flue
ways of the cast aluminum boiler section before being
discharged through the vent piping to the outdoors.
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, termi-
nal 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 retum piping
systems and boiler. The circulator pump is fumished
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.
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 in-
stalled 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.
Each boiler must have a properly sized and installed
American Society of Mechanical Engineers rated pres-
sure 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 prop-
erly functioning expansion tank) pressure on the inside
of the boiler and heating system will increase. The fur-
nished relief valve will automatically open at 30 psig
pressure te relieve the strain on the boiler and heating
system from the increasing pressure. The pressure re-
lief 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 injury. The boiler manufacturer is net re-
sponsible for any water damage or personal injury.
This boiler is equipped with a blocked vent safety shutoff
means, which shuts off the main bumer gas in the event
that the flow of combustion products through the flue-
ways is reduced. The Integrated Boiler Control will have
to be manually reset in the event of three consecutive
attempts for ignition that are halted by a blocked vent.
In the event of blocked vent, enough air will not be avail-
able to support combustion, and the boiler control will
lockout due to loss of adequate air flow (arcer 3 trials
for ignition). The "Purge" diagnostic indicator lamp (lamp
"B" in Figure 16) will blink indicating the failure mode as
a lack of adequate air flow. The IBC is manually reset
from lockout by either removing and reestablishing the
thermostat's caUfor heat, or by tuming the service switch
off, then back on. If the boiler cannot be restored to nor-
mal operating condition by resetting the control, contact
a qualified service agency to check heat exchanger
flueways for blockage.
This unit is equipped with a Low Water Cut Off con-
trol that protects against dry firing. This control pro-
vides 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% con-
centration may be used with the Low Water Cut Off.
For installations where there is no floor drain or other
appropriate drainage available to receive condensate
from the boiler, an extemal float 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 extemal condensate reservoir (sump) can be ac-
complished. Use wood frame or blocks (not factory sup-
plied) to raise boiler as required for proper installation.