A.O. Smith 104 Series, Instruction Manual

Page: 24 / 56

24
SEQUENCE OF OPERATION FLOW CHART
Des F ription of this À ow F hart F an be found in the ³ SEQUENCE OF OPERATION ´ se F tion found on page 25
FLOWCHART 1.
START
THERMOSTAT
CALLS FOR HEAT.
IF FLAME IS LOST, S89 CLOSES
GAS CONTROL, THEN RESTARTS
SAFE START CHECK AND TRIAL
FOR IGNITION.
IF FLAME CURRENT IS ABSENT,
WEAK, OR UNSTEADY, S89
LOCKS OUT AND SHUTS DOWN
SYSTEM. MUST BE RESET.
IF NO SPARK, S89 LOCKS OUT
AND SHUTS DOWN SYSTEM.
MUST BE RESET.
IF FLAME SIMULATION
CONDITION IS PRESENT,
SYSTEM WILL NOT START.
POWER INTERUPTION.
SYSTEM SHUTS OFF. RESTARTS
WHEN POWER IS RESTORED.
SAFE START
CHECK
VALVE-ON DELAY
30S PREPURGE
COMBUSTION
AIR BLOWER STARTS.
SPARK GENERATOR
POWERED, IGNITION
BEGINS AND GAS
CONTROL OPENS.
BURNER LIGHTS.
IGNITION STOPS
AND FLAME
CURRENT IS
SENSED.
BURNER RUNS
S89 MONITORS
FLAME CURRENT.
THERMOSTAT
SATISFIED. GAS
CONTROL CLOSES,
BURNER GOES OFF.
SAFE
START
CHECK
VALVE-ON DELAY
(S89F ONLY)
TRIAL FOR
IGNITION
BURNER
OPERATION
END