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call for heat.
❏ Make sure pilot lights smoothly when gas reaches the
pilot burner.
❏ Make sure main burner lights smoothly without flash-
back.
❏ Make sure burner operates smoothly without floating,
lifting, or flame rollout to the furnace vestibule or heat
buildup in the vestibule.
❏ If gas line has been disturbed, complete gas leak test.
GAS LEAK TEST: Paint gas control gasket edges and all
pipe connections downstream of gas control, including pilot
tubing connections, with rich soap and water solution.
Bubbles indicate gas leaks. Tighten joints and screws or
replace component to stop gas leak. Recheck with soap
and water.
❏ Turn thermostat or controller below room temperature.
Make sure main burner and pilot flames go out.
12
OPERATION
Module operation can be conveniently divided into two
phases for S8600, S8610 and three for S8660, S8670. The
phases are
• Prepurge (S8660, S8670 only)
• Trial for ignition (all models)
• Main burner operation (all models)
Figs. 11 and 12 summarize the normal operating se-
quences of the modules.
Fig. 11—S8600, S8610 normal operating sequence.
PREPURGE (S8660,S8670 ONLY)
When the S8660 is used in a fan-assisted combustion
system, the combustion air blower starts on a call for heat.
On proof of airflow, the air proving switch closes and
energizes the S8660, S8670. When the module is used in
an atmospheric system, the call for heat energizes the
module.
In either case, the module first initiates a 45 sec. delay
to allow system prepurge. After prepurge, the module starts
the pilot ignition sequence.
START
THERMOSTAT (CONTROLLER)
CALLS FOR HEAT
SPARK GENERATOR POWERED
First valve (pilot) operator opens
PILOT BURNER OPERATION
Pilot burner lights.
Module senses
flame current.
Pilot burner does not light.
Module Response
Shutoff/lockout timing is stamped on module
a
Ignition spark continues, pilot
valve remains open until system
is reset
S8600A,F
S8610A,F
S8600B,H
S8610B,H
a
STAGE 1
TRIAL FOR
IGNIITION
STAGE 2
MAIN BURNER
OPERATION
END
MAIN BURNER OPERATION
Module monitors pilot flame
current.
THERMOSTAT (CONTROLLER)
SATISFIED
Valves close, pilot and main
burners are off.
POWER INTERRUPTION
System shuts off, restarts when power is
restored.
PILOT FLAME FAILURE
Main valve closes.
Module starts trial for ignition.
1
FLAME CURRENT SENSED
Spark generator off.
Second valve operator (main)
opens.
2
3
4
5
6
1
OR
After 15 or 90 sec system
locks out; must be
manually reset.
After 90 sec. system shuts off;
after 5 minutes min. (6 minutes
nom.), module restarts trial for
ignition; ignition trial, shutoff, wait
sequence repeats until pilot lights
or call for heat ends.
a
S8600M
M1172B