Sequence of operation – Dunkirk Q90-200 Series II User Manual
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Sequence Of Operation Diagnostics
Follow sequence using the diagnostic indicator lamps on Integrated Boiler Control (IBC). See “Controls And Accessories”
on page 26 for normal sequence of operation. Detailed sequence of operation containing potential faults can be found in
service hints section.
SEQUENCE OF OPERATION
DIAGNOSTIC
INDICATOR LAMPS
(1) Lamp A is illuminated, indicating integrated control is receiving 24 volts and is in
standby waiting for thermostat call for heat.
(2) Thermostat calls for heat, energizing system circulator.
(3) Integrated boiler control performs self check of internal circuitry, approximately
two seconds, energizing draft inducer.
A.
B.
C.
D.
E.
(4) Draft inducer comes up to speed and establishes combustion airflow, causing
normally open differential pressure air proving switch contacts to close. When
combustion airflow is proved, Lamp B illuminates indicating 15 second pre-
purge cycle has begun.
A.
B.
C.
D.
E.
(5) After pre-purge completion, Lamp B is extinguished and Lamp C is illuminated,
indicating power is being delivered to hot surface igniter for 20 second igniter
warm-up period. Observe bright yellow-orange glow of hot surface igniter
through observation port on boiler.
A.
B.
C.
D.
E.
(6) After igniter warm-up period, integrated boiler control energizes gas valve,
initiating 6 second trial for ignition mode, indicated by illumination of Lamp
D. Lamp C extinguishes after 2 second delay. Integrated boiler control stops
sending power to hot surface igniter.
A.
B.
C.
D.
E.
(7) Low level illumination of Lamp E indicates initiation of flame proving. During
last 2 seconds of trial for ignition mode, main burner flame is proven by flame
rectification through hot surface igniter, providing flame signal is relayed to
integrated boiler control, fully illuminating Lamp E.
A.
B.
C.
D.
E.
(8) Thermostat ends its call for heat. Integrated boiler control de-energizes gas
valve and system circulator. Lamp D is extinguished while unit enters 30
second post purge mode, indicated by illumination of Lamp B. Lamp E will
remains illuminated as remainder of gas in blower is burned off (approximately
2 seconds). During post purge blower remains powered and clears out any
residual products of combustion.
A.
B.
C.
D.
E.
(9) After post purge mode draft inducer is de-energized. Unit goes into standby
mode until next call for heat from thermostat.
A.
B.
C.
D.
E.
NOTE: First one or two cold starts may be rough due to gas line not being completely purged of air,
causing low firing rate and high excess air levels.
13 - SEQUENCE OF OPERATION DIAGNOSTICS