John Wood Commercial - AJWSC - Manual (Page 23)

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CALL FOR
HEAT ACTIVE
(Temperature low)
POWER INTERRUPTION System
shuts off
OR
PILOT FLAME FAILURE Valves close,
after recycle delay system recycles. If
recycles exceed maximum, timed
lockout is entered.
1
PILOT BURNER OPERATION
Pilot burner does not light. After retry delay system
retries. If retries exceed maximum, timed lockout is entered.
OR
Pilot burner lights. Ignition module senses flame current
and continues.
4
Damper energized. 2
STAGE 1
PREPURGE
STAGE 2
TRIAL FOR IGNITION
STAGE 3
MAIN BURNER OPERATION
STAGE 4
POSTPURGE
END
START
SPARK GENERATOR
POWERED
Pilot valve opens.
3
FLAME CURRENT
SENSED
Spark generator off,
Main Valve opens.
5
MAIN BURNER
OPERATION
Ignition module monitors pilot
flame current.
6
CALL FOR HEAT
INACTIVE
(Temperature at setpoint) Valves
close
7
Damper de-energized. 8
Figure 22 Sequence of Operation