Ignition Failure - A.O. Smith Cyclone XL 100 Series Service Handbook

Pettinr The Water Heater Back In Service
1. Lower the Operating Set Point to end the heating cycle. Use the Enable/Disable Switch located on the front of the water heater and put
the unit in disabled mode.
2. Close the main gas shutoff valve serving the water heater.
3. Disconnect manometer sensing tube.
4. Close the Supply Gas Pressure Test Port on the Gas Control Valve. Turn the needle valve slotted head clockwise until tight.
5. Open the main gas shutoff valve serving the water heater and check for leaks at the Gas Control Valve test ports.
6. Use the Enable/Disable Switch located on the front of the water heater and put the unit in enabled mode. Increase the Operating Set
Point if necessary to cause the water heater to have a call for heat.

2. IGNITION FAILURE

Ignition Failure
0 days 0 hrs 0 mins ago
Error Code:
Flame not detected. Clean flame
rod. Check gas supply.
Press the Advanced button for
more information
CHECK/ REPAIR
• Determine whether or not the burner is igniting by looking through sight glass. Because the control system will shut off the Gas
Control Valve if 2-3 seconds if ignition is not detected, you must look in the sight glass at the exact moment the Gas Control Valve
icon appears on the display screen.
TESTING FOR IGNITION )FLAME):
• Set the Set Point Temperature high enough so there is a call for heat.
• Recycle the unit off and back on by turning the Enable/Disable switch to Disable for one second and then back to Enable.
• The unit will begin an ignition cycle.
• When the Gas Control Valve icon appears on display screen, immediately look through the sight glass for a brief blue flame (if you
are getting an Ignition Failure error, the flame, if the burner ignites, will only be present for 2-3 seconds).
IGNITION FAILURE FOR NEW INSTALLATIONS:
If Ignition failure happens to new installations during initial startup, check the following items first:
1. Confirm that gas-supply line is fully purged all the way up to the gas valve.
2. Confirm that the gas-supply pressure at the gas-valve test port falls--but falls no more than 2"wc from static pressure when the gas
valve is energized (click sound can be heard when the gas valve is energized).
• If there's no change in gas pressure reading and/or the gas valve does not become energized during the ignition, check gas valve
wiring connections and 24 Vac at the wire plug.
• If the supply pressure falls significantly during the ignition, check the service regulator capacity and gas piping size to correct the
issue.
3. If you have confirmed Step 1 & Step 2, but NO flame is detected through the top-mounted combustion view-port, check the wiring
connections to the spark transformer and spark rod.
4. If you have confirmed Step 1 & Step 2, flame IS detected through the combustion view-port, BUT no flame icon displays on the UIM,
check flame rod and flame rod wiring connections.
5. If you have confirmed Step 1 & Step 2, the flame icon is displays on the UIM momentarily or you experience occasional ignition
failures, turn the gas valve throttle COUNTERCLOCKWISE 1/8 turn at a time.
If adjestinr the ras valve resolves the irnition issee, yoe mest ese a combestion analyzer to verify the followinr:
a. That the combustion is clean.
b. That the CO2 reading from the combustion flue is within 8.9% - 9.3% during running.
B
2-70
BACK ADVANCED
CAUSES:
• On an "Ignition Failure" error, either the burner is not
igniting or the burner is igniting, but the Flame Sensor is
not detecting ignition (flame).
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