resideo S8910U3000 Manuel D'installation page 18

S8910U3000
4. The ignition module cannot be repaired. If it mal-
functions, replace it.
5. Only trained, experienced service technicians
should service hot surface ignition systems.
6. After servicing, verify proper system operation.
Perform the checkout steps in the Startup and Checkout
section as the first step in troubleshooting. Then check the
troubleshooting sequence (Fig. 7) to determine the exact
the cause of the problem.
After troubleshooting, perform the checkout procedure
again to be sure the system is operating normally.
Status LED Used to Troubleshoot
The LED can be used to check the appliance status. A
description of the LED signals follows. Refer to Table 6 on
page 19 for a complete list of LED codes.
IMPORTANT
The LED displays system status for the current call
for heat. When the call for heat is interrupted
(thermostat satisfied or system power switched
off), the LED goes off and the status information is
lost.
• A steady green LED indicates the normal operating
mode during a call for heat (24 V terminal is powered).
The system can be in any of the normal operating
modes including prepurge, warmup, ignition trial,
between trial purge, or normal run.
• An intermittant red flash, and two, three, or four yellow
flashes indicate a lockout mode. Refer to Table 6 for a
complete list of LED codes. The most probable cause is
the main burner failing to light or failure to detect the
flame. Run the appliance through a call for heat and if
the burner does not light, check the:
— gas supply
— input voltage
— hot surface igniter
— gas control
— wiring
If the main burner lights, but goes out at the end of
ignition trial, check the:
— igniter/sensor
— flame rod
— burner ground connections
— wiring
• Intermittant green flashes indicates the flame
rectification signal is weak. The most probable causes
are:
— contaminated or mislocated igniter/sensor or
flame rod
— poor flame sense leadwire insulation or connec-
tions
— poor gas pressure
If the flame rectification signal is strong when the
appliance lights, but weak while heat is being delivered,
check for overheating of the igniter/sensor, flame rod
ceramic or flame sense leadwires.
• Four yellow flashes indicate an internal error. The most
probable cause is an S8910U logic failure. Start a new
call for heat and if the four-flash signal returns wait 1 to
2 hours and repeat the last step. If the four-flash signal
returns again, replace the S8910U.
34-00008EFS—03
• A steady red LED indicates a device lockout due to a
detected welded gas valve relay. Replace the control.
Ignition System Checks
Step 1: Check igniter wire harness.
Make sure:
a. Ignition cable does not run in contact with any
metal surfaces.
b. Connections to the ignition module and to the
igniter or igniter-sensor are clean and tight.
c. Ignition cable provides good electrical continu-
ity.
Step 2: Check ignition system grounding. Nuisance
shutdowns are often caused by a poor or erratic ground.
a. A common ground is required for the module,
igniter, flame sensor and main burner.
•Check for good metal-to-metal contact between the
igniter bracket and the main burner.
•Check the ground path from the GND (BURNER)
terminal on the module to the main burner. Make
sure connections are clean and tight. If the wire is
damaged or deteriorated, replace it by following
the appliance manufacturer instructions. A
temporary leadwire connection between the GND
(BURNER) terminal and the main burner can help
confirm a ground path problem.
•Check the temperature at the igniter ceramic or
flame sensor insulator. Excessive temperature
permits leakage to ground. Contact the appliance
manufacturer if the temperature exceeds rating
of igniter or sensor.
•If flame sensor or bracket is bent out of position,
restore to the correct position.
•Replace the igniter and sensor or igniter-sensor
with an identical unit if the insulator is cracked.
Step 3: Check the flame sensing circuit.
a. Make sure the burner flame is capable of provid-
ing a good rectification signal. See Fig. 5.
b. Make sure about 3/4 to 1 in. of the flame sensor
or igniter-sensor is continuously immersed in
the flame for the best flame signal. See Fig. 5.
c. Check for excessive (above 1000 °F [538 °C])
temperature at the ceramic insulator on the
flame sensor. Excessive temperature can cause a
short to ground.
d. Check for cracked igniter-sensor or sensor
ceramic insulator, which can cause short to
ground, and replace unit if necessary.
•Make sure electrical connections are clean and
tight. Replace damaged wire with moisture-
resistant No. 18 wire rated for continuous duty up
to 221 °F (105 °C).
e. If the igniter is other than a Norton 201 or 271,
make sure it meets the following specifications:
•Igniter must reach 1832 °F (1000 °C) within the
selected warm up time of 7, 17, 34 or 45 seconds
with 102 Vac applied.
•Igniter must maintain at least 500M ohm insulation
resistance between the igniter leadwires and the
igniter mounting bracket.
•Igniter must not develop an insulating layer on its
surface (over time) that would prevent flame
sensing.
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