Checkout Procedure & Adjustments - UTICA BOILERS UB90-200 Installation, Operation & Maintenance Manual

Verify Proper Sequence Of Operation
The sequence can be followed via the diagnostic indicator lamps on the Integrated Boiler Control in Figure
#16 ( Section: Controls and Accessories). This is the normal sequence of operation. A more detailed sequence
of operation containing potential faults can be found in the service hints section.
SEQUENCE OF OPERATION
(1) Lamp A is illuminated, indicating that the integrated control is receiving 24 volts
and is in standby waiting for the thermostat to call for heat.
(2) Thermostat calls for heat, energizing the system circulator.
(3) Integrated boiler control performs self check of internal circuitry, lasting
approximately two seconds, and energizes the draft inducer.
(4) The draft inducer comes up to speed and establishes combustion airfl ow,
causing the normally open differential pressure air proving switch contacts to
close. When combustion airfl ow is proved, Lamp B is illuminated indicating
that the 15 second pre-purge cycle has begun.
(5) After the pre-purge has completed, Lamp B is extinguished and Lamp C is
illuminated, indicating power is being delivered to the hot surface igniter for
the 20 second igniter warm-up period. The bright yellow-orange glow of the hot
surface igniter can be observed through the observation port on the boiler.
(6) After the igniter warm-up period the integrated boiler control energizes the
gas valve, initiating a 6 second trial for ignition mode which is indicated by the
illumination of Lamp D. Two seconds later, Lamp C will extinguish when the
integrated boiler control stops sending power to the hot surface igniter.
(7) A low level illumination of Lamp E indicates the initiation of fl ame proving. During
the last 2 seconds of the trial for ignition mode, main burner fl ame is proven by
fl ame rectifi cation through the hot surface igniter, providing a fl ame signal that is
relayed to the integrated boiler control, fully illuminating Lamp E.
(8) The thermostat ends its call for heat, causing the integrated boiler control to
de-energize the gas valve and system circulator. Lamp D is extinguished while
the unit enters the 30 second post purge mode, indicated by the illumination
of Lamp B. Lamp E will remain illuminated as the remainder of the gas in the
blower is burned off (approximately 2 seconds). During post purge the blower
remains powered and clears out any residual products of combustion.
(9) After the post purge mode the draft inducer is de-energized and the unit goes
into standby mode until the next call for heat from the thermostat.
NOTE: The fi rst one or two cold starts may be rough due to the gas line not being completely purged
of air, causing low fi ring rate and high excess air levels
CHECKOUT PROCEDURE & ADJUSTMENTS
25
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DIAGNOSTIC
INDICATOR LAMPS
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E.
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