Controls And Accessories; Integrated Boiler Control (Ibc); Gas Control Valve; Hot Surface Igniter - Dunkirk Quantrum 90-50 Installation Manual

This section provides a brief description of the key controls
and accessories found in this boiler.
See the Troubleshooting section of the Service Hints chapter
of this installation manual for detailed sequences of operation
and troubleshooting procedures. See the Repair Parts chapter
of this manual for locations of all control components and ac-
cessories described.
A. Integrated Boiler Control (IBC)
The Integrated Boiler Control (IBC) is a microprocessor based
controller for a high efficiency gas boiler that monitors all
safety controls and which controls the operation of the com-
bustion air blower, circulator pump, burner, and a combination
hot surface igniter/flame sensor. This controller is not intended
for use with a vent damper. This controller is mounted on the
control panel inside of the boiler and contains five (5) diagnos-
tic indicator lights.
B. Gas Control Valve
The electrically controlled 24 Volt Honeywell Model VR8205
Combination Gas Control Valve is designed to meet the re-
quirements for use with hot surface ignition systems found in
this boiler. The valve is piped to the gas/air mixer.
C. Hot Surface Igniter
The 120 Volt Hot Surface Igniter heats up to 1800 °F to initiate
combustion of the gas in the burner. The igniter is mounted
next to the burner through the gas/air mixer. The igniter also
serves as a means for proving the main burner flame by flame
rectification. In the event of a lack of flame signal on three
(3) consecutive trials for ignition, the IBC will lockout. The
"VALVE" and "FLAME" diagnostic indicator lamps (lamp "D"
and "E" on the IBC, See Figure #16) will blink indicating the
failure mode as a lack of flame signal. The IBC is manually
reset from lockout by either removing and reestablishing the
thermostat's call for heat, or by turning the service switch off,
then back on.
D. High Limit Aquastat Control
The High Limit Aquastat Control determines the maximum
boiler water temperature and also provides a means for
protecting the boiler and heating system from unsafe operat-
ing conditions which could damage the boiler. The aquastat
is mounted in the ½" NPT control well and ¾"x½" bushing
on the top of the front boiler section at the hot water outlet.
The aquastat is tied in with the IBC and is factory set at 180 °F
water temperature. The high limit setpoint is field adjustable

CONTROLS AND ACCESSORIES

and may be set anywhere between 100 °F and 200 °F. The field
setpoint adjustment for each installation depends on heating
system requirements. The aquastat automatically resets when
the boiler water temperature decreases (5-30 °F adjustable
differential). The differential can be adjusted with the (white)
Differential Adjustment Wheel on the aquastat and gives the
flexibility for boiler operation. The larger the differential, the
longer the run cycle of the boiler.
NOTE: The maximum setpoint of the Aquastat must not
exceed 200 °F.
E. Draft Inducer Temperature Safety Switch
The Draft Inducer Temperature Safety Switch is a disc thermo-
stat (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 higher aquastat setting or over
firing. The temperature safety switch automatically resets when
the vent temperature decreases. (15 °F switch differential).
F. Casting Temperature Safety Switch
In the event of lack of or loss of water in the boiler, the Cast-
ing 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. WARNING-Never run cold water
into a hot empty boiler.
G. Differential Pressure Air Proving Switch/Blocked
Vent Safety Shutoff
All 90 Series Hot Water Boilers come equipped with either one
(100 Series) or two (200 Series) diaphragm-type differential
pressure switches. The differential pressure switch monitors air
flow by sensing the differential pressure measured in inches
of water (" w.c.). The pressure switch contacts close when the
draft inducer is running. 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, a blocked air intake, blocked boiler sec-
tions, or a blocked draft inducer. After five (5) minutes of lack
of adequate differential pressure, the IBC will lock out and the
"Purge" indicator light will blink, indicating a failure to prove
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