Dunkirk Q90-200 Series II - Manual (Page 31)

31
DRAFT INDUCER TEMPERATURE SAFETY
SWITCH
Draft inducer runs through 30 second post purge and
switches OFF.
Circulator runs with thermostat on call for heat.
When temperature safety switch contacts connect
before end of call for heat, control goes in normal
light-off sequence.
LOSS OF COMBUSTION AIRFLOW
If combustion airflow is lost while burner is firing
(Differential air pressure switch contacts open) gas
valve is de-energized.
Valve and flame lights go out.
Draft inducer runs through 30 second post purge.
If call for heat remains, IBC waits 5 minutes for airflow
to be re-established.
If airflow does not re-establish control lockout problem
with combustion airflow.
Purge light blinks
.
Control automatically reset after 15 minutes.
LOSS OF FLAME SIGNAL
If established flame signal is lost while control expects
burner is operating, control immediately de-energizes
gas valve.
Valve and flame lights go out.
Draft inducer runs through 30 second post purge.
Control attempts to light boiler 3 times. If flame is not
proven, control lockout problem establishing flame
signal.
Valve light is blinking
.
Control automatically resets after 1 hour.
HIGH LIMIT CONTROL
[REFER TO PAGE 37 FOR MORE INFO]
If boiler water temperature reaches high
limit setpoint, high limit n.c. contacts open
immediately, closing gas valve.
Valve and flame lights go out.
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 connect before end of
call for heat - control goes into normal light-off
sequence.
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.
Power light goes out.
CIRCULATOR PUMP
Circulator is energized as long as thermostat calls
for heat during lockout.
Recovery from any lockout requires reset, which
can be accomplished by:
(a) Removing and re-establishing thermostat’s
call for heat or turning service switch off
and back on;
or
(b) Waiting for control to automatically reset after
15 minutes for loss of combustion airflow or one
hour for loss of flame.
12 - DETAILED SEQUENCE OF OPERATION
If draft inducer temperature reaches temperature
safety switch set-point, safety switch contacts open
immediately, closing gas valve
(light goes out)
.