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DETAILED SEQUENCE OF OPERATION
SAFETY SEQUENCES DURING OPERATION
DRAFT INDUCER TEMPERATURE SAFETY SWITCH
IF DRAFT INDUCER TEMPERATURE REACHES
TEMPERATURE SAFETY SWITCH SETPOINT,
SAFETY SWITCH CONTACTS OPEN IMMEDIATELY,
CLOSING GAS VALVE (LIGHT GOES OUT).
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, CON-
TROL GOES INTO 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 WILL BE DE-ENER-
GIZED.
VALVE AND FLAME LIGHTS GO OUT.
DRAFT INDUCER RUNS THROUGH 30 SECOND
POST PURGE.
IF CALL FOR HEAT REMAINS, IBC WAITS 5 MIN-
UTES FOR AIRFLOW TO BE RE-ESTABLISHED.
IF AIRFLOW DOES NOT RE-ESTABLISH CON-
TROL LOCKOUT - PROBLEM WITH COMBUSTION
AIRFLOW.
PURGE LIGHT BLINKS.
CONTROL WILL
AUTOMATICALLY RESET AFTER 15 MINUTES.
LOSS OF FLAME SIGNAL
IF AN ESTABLISHED FLAME SIGNAL IS LOST WHILE
CONTROL EXPECTS THAT THE BURNER IS OPERAT-
ING, CONTROL WILL IMMEDIATELY DE-ENERGIZE
GAS VALVE.
VALVE AND FLAME LIGHTS GO OUT.
DRAFT INDUCER RUNS THROUGH 30 SECOND
POST PURGE.
CONTROL WILL ATTEMPT TO RELIGHT BOILER
3 TIMES. IF FLAME IS NOT PROVEN, CONTROL
LOCKOUT - PROBLEM ESTABLISHING A FLAME
SIGNAL.
VALVE LIGHT IS BLINKING.
CONTROL
WILL AUTOMATICALLY RESET AFTER 1 HOUR.
HIGH LIMIT CONTROL
IF BOILER WATER TEMPERATURE REACHES
HIGH LIMIT (AQUASTAT) 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 REMAKE BEFORE
END OF CALL FOR HEAT - CONTROL GOES INTO
A NORMAL LIGHT-OFF SEQUENCE.
CASTING TEMPERATURE SAFETY SWITCH
IF BURNER OPERATES WHEN BOILER HAS NO WA-
TER, ALUMINUM BOILER SECTIONS HEAT UP RAPIDLY.
CASTING TEMPERATURE SAFETY SWITCH CON-
TACTS WILL OPEN, BREAKING 24 VOLT POWER
TO IBC. POWER INDICATOR LIGHT GOES OUT.
REQUIRES MANUAL RESET TO RECLOSE CON-
TACTS.
POWER LIGHT GOES OUT.
CIRCULATOR PUMP
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;
OR (B) WAITING FOR THE CONTROL TO
AUTOMATICALLY RESET AFTER 15 MINUTES
FOR LOSS OF COMBUSTION AIRFLOW OR
ONE HOUR FOR LOSS OF FLAME.
