69-0845—2
12
S8910U UNIVERSAL HOT SURFACE IGNITION MODULE
Step 4:
Reset the ignition module.
a. Turn the thermostat or controller to the lowest
setting.
b. Turn on the system power.
c. Wait one minute.
As you do Steps 5 and 6, watch for points where operation
deviates from normal. Refer to Troubleshooting section to
correct problem.
Step 5:
Check safety lockout operation.
a. Turn off the gas supply.
b. Set the thermostat or controller above the room
temperature to call for heat.
c. Watch for igniter warmup following prepurge. Igniter
starts to glow several seconds after it is powered.
d. Time the length of time the gas control is energized;
measure the time by connecting a voltmeter across
the gas valve terminals:
Selection tabs A and B—4 seconds.
Selection tabs C and D—7 seconds.
e. When using a three-trial ignition selection tab (tabs
B or D), watch for the start of 96-second between-
trial purge, followed by 34-second igniter warmup
and second try for ignition. After a third purge,
warmup and trial for ignition sequence, the S8910U
should lock out. LED goes into one flash mode after
lockout.
f. Open the manual gas control knob and make sure
no gas is flowing to the burner.
g. Set the thermostat below the room temperature and
wait one minute before continuing.
Step 6:
Check normal operation.
a. Set the thermostat or controller above the room
temperature to call for heat.
b. Observe the lightoff sequence and make sure the
main burner lights smoothly without flashback.
c. Make sure the burner operates smoothly without
floating, lifting, or flame rollout to the furnace
vestibule or heat buildup in the vestibule.
d. Test for a gas leak downstream of the gas control if
piping has been disturbed.
GAS LEAK TEST: Paint the gas control gasket edges and
all pipe connections downstream of the gas control with a
rich soap and water solution. Bubbles indicate a gas leak.
Tighten the joints and screws or replace component to
stop a gas leak. Recheck with soap and water solution.
e. Check the burner flame condition. The igniter-sensor
or sensor must be constantly immersed in flame.
Check the burner flame condition as shown in Fig. 6.
Do not relocate the hot surface igniter or flame rod.
f. Turn the thermostat or controller below the room
temperature. Make sure the main burner and pilot
flames go out.
WARNING
FIRE OR EXPLOSION HAZARD
CAN CAUSE PROPERTY DAMAGE,
SEVERE INJURY, OR DEATH.
Improper location of the 120 Vac hot surface
igniter or any flame sensing rod can result in
appliance malfunction.
1. Never attempt to relocate the 120 Vac hot
surface igniter or the flame sensing rod from the
original position established by the appliance
manufacturer.
2. Be sure the 120 Vac hot surface igniter or the
flame sensing rod is replaced in exactly the
original position after removal for inspection,
service or replacement.
Fig. 6. Check burner flame condition.
OPERATION
The S8910U is a direct ignition control used with a
120 Vac timed warmup hot surface igniter. The control
provides operating control and shuts off all gas flow on
ignition failure or loss of main burner flame in central heat
furnaces and other heating appliances.
Module operation is in three phases—prepurge/igniter
warmup, trial for ignition and burner operation. The
S8910U provides one or three trials for ignition, depending
on which selection tab is installed. Fig. 7 shows the normal
operating sequence.
CHECK BURNER FLAME CONDITION
NOISY
LIFTING
FLAME
BURNER
WAVING
FLAME
SMALL
BLUE
FLAME
LAZY
YELLOW
FLAME
GOOD
RECTIFYING
FLAME
3/4 TO 1 IN. (19 TO 25 MM)
1/4 TO 1/2 IN. (6 TO 13 MM)
M8446
CHECK FOR:
• HIGH GAS PRESSURE
• EXCESS PRIMARY AIR
OR DRAFT
CHECK FOR:
• POOR DRAFT
• EXCESS DRAFT
• HIGH VELOCITY OR
SECONDARY AIR
INSTALL SHIELD IF NECESSARY
CHECK FOR:
• CLOGGED PORTS OR
ORIFICE FILTER
• WRONG SIZE ORIFICE
CHECK FOR LACK OF
AIR FROM:
• DIRTY PRIMARY
AIR OPENING
• LARGE PORTS
OR ORIFICES