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SERVICE & MAINTENANCE SUGGESTIONS (CONT'D)
TRIAL FOR IGNITION
Pilot Ignition
Following call for heat (system start on S8600H), the module
energizes the first main valve operator. The first main valve opens,
which allows gas to flow to the pilot burner. At the same time, the
electronic spark generator in the module produces a 13,000 volt
spark pulse output (at 25 pf load). The voltage generates a spark
at the igniter-sensor that lights the pilot.
If the pilot does not light, or the pilot flame current is not at least 1.0
uA and steady, the module will not energize the second main valve
and the main burner will not light.
Safety Lockout
S8600H provides 100 percent shutoff, or safety lockout. A timer
starts timing the moment the trial for ignition starts. Ignition spark
continues only until the timed trial for ignition period ends. Then
the module goes into safety lockout. Lockout de-energizes the
STAGE 1
TRIAL FOR IGNITION
37403-5-0620
S8600H NORMAL OPERATING SEQUENCE
IF FLAME CURRENT SENSED
*SPARK GENERATOR OFF
*SECOND VALVE OPERATOR (MAIN) OPENS
first main valve operator and closes the first main valve in the gas
control, stopping pilot gas flow. The control system must be reset
by turning the valve off for one minute or by turning off power to the
module for one minute.
Main Burner Operation
When the pilot flame is established, a flame rectification circuit
is completed between the sensor and burner ground. The flame
sensing circuit in the module detects the flame current, shuts off
the spark generator and energizes the second main valve operator.
The second main valve opens and gas flows to the main burner,
where it is ignited by the pilot burner. The flame current also holds
the safety lockout timer in the reset (normal) operating condition.
When the call for heat ends, both main valve operators are de-
energized, and both main valves in the gas control close.
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