Page 28 Part # MCOSM06 Rev 1 (11/03/08)
IGNITION SEQUENCE
First Stage – Trial For Pilot Ignition
On every call for heat (system start), the S86 performs an
internal safe-start check and shows that a ame-simulating
condition is present. During a normal start, the S86 opens the
pilot valve in the gas control. This allows gas to ow to the
pilot burner. Simultaneously the electronic spark generator
in the S86 produces a 30,000 volt pulse output. This voltage
produces a spark at the pilot burner igniter/sensor rod,
igniting the gas ow around the electrode. If the pilot ame
is not detected during the trial for pilot ignition, the S86H
contains a safety lockout timer (90 Seconds) to limit the
ignition period.
Second Stage – Main Burner Operation
When the Pilot ame is established, a ame rectication
circuit is complete to the burner ground. The S86 ame
sensing circuit detects the ame circuit and shuts the spark
generator o. At the same time the second operator (main
gas valve) is opened in the gas control, allowing gas ow
to the burners. This pilot ame ignites the main burner
conventionally.
Safety Lock Out Time.
The safety lockout timer circuit starts timing the moment the
trail for the pilot ignition starts. When the timing periods runs
out, the trial for ignition ends, and the control module goes
into lockout. Before another attempt to start can be made,
the S86 must be reset. Reset by adjusting the thermostat or
controller below room temperature, or to its "OFF" position.
An alternate method is to shut the system power "OFF". If
normal ignition does not occur, use the trouble shooting
table to determine the problem.
START
STAGE 1
TRIAL FOR
IGNITION
STAGE 2
MAIN BURNER
OPERATION
END
1. CONTROLLER CALLS FOR HEAT
2. SPARK GENERATOR POWERED
First valve (Pilot) operator opens
3. PILOT BURNER OPERATION
Pilot burner lights.
Module senses
ame current.
OR Pilot burner does not light.
After 90 seconds system
locks out: must be
manually reset.
4. FLAME CURRENT SENSED
• Spark generator o.
• Second valve operation (main) opens
POWER INTERRUPTION
System shuts o, restarts
when power is restored
PILOT FLAME FAILURE
Main valve closed.
Module start trail for ignition.
5. MAIN BURNER OPERATION
Module monitors pilot ame current
6. CONTROLLER SATISFIED
Valves close, pilot and main burners are o