UTICA BOILERS UB90-200 Installation, Operation & Maintenance Manual page 31

DRAFT INDUCER TEMPERATURE SAFETY SWITCH
if draft inducer temperature reaches temperature safety switch
set-point, safety switch contacts open immediately, closing gas
(light goes out)
valve .
Draft inducer runs through 30 second post purge and switches
OFF.
Circulator runs with thermostat on call for heat.
When temperature safety switch contacts remake before end of
call for heat, control goes into normal light-off sequence.
LOSS OF FLAME SIGNAL
if an established fl ame signal is lost while control expects that
the burner is operating, control will immediately de-energize
Valve and fl ame lights go out.
gas valve.
Draft inducer runs through 30 second post purge.
Control will attempt to relight boiler 3 times. if fl ame is not
proven, control lockout - problem establishing a fl ame signal.
Valve light is blinking
. Control will automatically reset
aft er 1 hour.
LOSS OF COMBUSTION AIRFLOW
If combustion airfl ow is lost while burner is fi ring (Diff erential
air pressure switch contacts open) gas valve will be de-
Valve and fl ame lights go out.
energized.
Draft inducer runs through 30 second post purge.
If call for heat remains, IBC waits 5 minutes for airfl ow to be
re-established.
If airfl ow does not re-establish control lockout - problem with
Purge light blinks
combustion airfl ow.
automatically reset aft er 15 minutes.
DETAILED SEQUENCE OF OPERATION
if boiler water temperature reaches high limit (aquastat)
setpoint, high limit n.c. contacts open immediately, closing gas
valve.
Draft inducer continues to run for 30 second post purge and
switch OFF.
Circulator runs as long as thermostat calls for heat.
When high limit contacts remake before end of call for heat -
control goes into a normal light-off sequence.
Circulator will be energized as long as thermostat calls for heat
during lockout.
Recovery from any lockout requires reset, which can be
accomplished by:
(a) Removing and reestablishing the thermostat's call for heat
or turning the service switch off and back on;
(b) Waiting for the control to automatically reset aft er 15
minutes for loss of combustion airfl ow or one hour for loss of
fl ame.
. Control will
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CASTING TEMPERATURE SAFETY SWITCH
If burner operates when boiler has no water, aluminum boiler
sections heat up rapidly.
Casting temperature safety switch contacts will open, breaking
24 volt power to ibc. power indicator light goes out. Requires
manual reset to re-close contacts.
HIGH LIMIT CONTROL
Valve and fl ame lights go out.
CIRCULATOR PUMP
or
Power light goes out.