Dunkirk Q90-50 - Page 41

DRAFT INDUCER TEMPERATURE SAFETY
SWITCH
Ifdraftinducertemperaturereachestemperature
safety switch set-point, safety switch contacts open
immediately, closing gaj.valve (light goes out).
T
I Draft inducer runs through 30 second post purge and Iswitches OFF.
I
I Circulator runs with thermostat on call for heat. I
I hen temperature safety switch contacts connect
before end of call for heat, control goes in normal
light-off sequence.
LOSS OF FLAME SIGNAL
Ifestablished flame signal is lost while control expects
burner is operating, control immediately de-energizes
gas valve.
Valve and flame li_lhts _1oout.
I Draft inducer runs through 30 second post purge. I
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.
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.
I Draft inducer runs through 30 second post purge. I
I !
IIf call f°r heat remains' IBC waits 5 minutes f°rairfl°Wltobe re-established,
If airflow does not re-establish control lockout problem
with combustion airflow.
Purge light blinks,
C0ntr01 aut0matically reset after 15 minutes.
CASTING TEMPERATURE SAFETY SWITCH
If burner operates when boiler has no water, I
aluminum boiler sections heat up rapidly,
I
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 liqht qoes out.
HIGH LIMIT CONTROL
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 I
purge and switch OFF.
I
Circulator runs as long as thermostat calls for I
heat.
J
When high limit contacts connect before end of I
call for heat - control goes into normal light-off
1
sequence.
CIRCULATOR PUMP
Circulator is energized as long as thermostat callsl
for heat during lockout.
I
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.