Bryant BW9, Installation, Start-Up, And Operating Instructions Manual, Page: 23 / 52

E. Draft Inducer Temperature Safety Switch
The Draft Inducer Temperature Safety Switch is a disc thermostat (180°F setpoint) located on the induced draft fan outlet port. The switch protects
the inducer and vent pipe from a potential high temperature condition for the discharging flue gases. This condition would typically be a result
of higher aquastat setting or over-firing. The temperature safety switch automatically resets when the vent temperature decreases. (15°F switch
differential).
WARNING: Never run cold water into a hot empty boiler. The boiler will be damaged and/or serious bodily injury may
result.
F. Casting Temperature Safety Switch
In the event of lack of or loss of water in the boiler, the Casting Temperature Safety Switch (300°F setpoint) installed on the top of the aluminum
boiler section shuts off the boiler by shutting off power to the Integrated Boiler Control (IBC) and causes the Power Indicator Light to go out. This
fault requires manual reset of the casting temperature safety switch to restart the boiler. Verify that the boiler is properly filled with water before
resetting this switch.
G. Differential Pressure Air Proving Switch
The diaphragm type differential pressure switch is connected by vinyl tubing to the pressure signal hose adapters. The pressure switch monitors
air flow by sensing the diffential pressure measured in inches of water (in. w.c.). The factory settings on these switches are 1.00-in.w.c. for
BW9-100, 1.35-in. w.c. for BW9-75 and 1.55-in. w.c. for BW9-50. The contacts are normally open, and close when the draft inducer is running
and causing the differential pressure at the switch to exceed the setting. The closed switch proves there is adequate air flow for combustion. The
pressure switch shuts off the main burner if the differential pressure is inadequate due to a blocked vent pipe or a blocked air intake or blocked
boiler sections or blocked draft inducer. After 5 minutes of lack of adequate differential pressure, the IBC will lockout. The
″
PURGE
″
indicator
light will blink, indicating a failure to prove adequate combustion air flow or flue gas flow. The IBC is manually reset from lockout as described
in the Sequence of Operation section of this chapter.
H. Draft Inducer
The draft inducer (blower) provides a means for pulling combustion air into and through the mixer, the burner, the flue ways of the cast aluminum
boiler sections and the flue adapter before being discharged through the vent piping to the outdoors. See applicable sections for proper sizing and
installation of combustion air and vent piping in this manual.
I. 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 (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 return piping systems and boiler. The circulator pump is furnished in a
carton within the boiler cabinet for a single zone or zone valve controlled heating system and should be correctly located on the downstream (i.e.,
pumping away) side of the expansion tank. For a pump controlled system (where there is a circulator for each zone) the circulator provided with
the boiler can work for one zone. For more details on piping and circulators, see Near Boiler Piping section of this manual.
J. 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 3/4-in. tapping at the bottom of the front boiler section. 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.
K. ASME Rated Pressure Relief Valve
Each boiler must have a properly sized and installed ASME 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 properly 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 piping 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 ASME specifications.
WARNING: 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.
L. Flame Rollout Safety Shutoff
As required, this boiler is equipped with a manual reset flame rollout safety shutoff means, which shuts off main burner gas in the event that the
flow of combustion products through the flueways is reduced. In the event of blocked flueways, enough air will not be available to support
combustion, and the Integrated Boiler Control (IBC) will lockout due to loss of adequate air flow (after 3 trials for ignition). The
″
PURGE
″
diagnostic indicator lamp (lamp ’B’ on the IBC, see Fig. 21) will blink indicating the failure mode as a lack of adequate air flow. The IBC is
manually reset from lockout by either removing and re-establishing the thermostat’s call for heat, or by turning the service switch off, then back
on. If the boiler cannot be restored to normal operating condition by resetting the control, contact a qualified service agency to check heat
exchanger flueways for blockage.
M. (Optional) External Condensate Pump
For installations where there is no floor drain or other appropriate drainage receptacle available to receive net condensate overflow from the boiler,
an external float activated condensate pump with integral sump is required. This unit can be installed to pump the condensate 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 to raise boiler as required for proper installation.
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