valve handle appears to be in the closed position, the microswitch is still open). If the valve is fully closed, refer to the troubleshooting guide, TROUBLESHOOTING THE 24 VAC CIRCUIT.
Some typical causes of ignition failure in this category include a defective sensing wire in the ignitor assembly, a defective module, a defective ignition wire, and a defective ignitor.
Occasionally you may encounter an ignition failure situation in which all components appear to be serviceable and the microamp reading is within specification, but the unit nevertheless goes into ignition failure during operation. The probable cause in this case is an intermittent failure of an ignition module. When the unit is opened up for troubleshooting, the module cools down enough to operate correctly; however, when the unit is again closed up and placed back into service the module heats up and fails.
PROBLEMS RELATED TO THE GAS VALVE
If the problem is not in the 24 VAC circuit, it is most likely in the gas valve. Before replacing the gas valve, refer to TROUBLESHOOTING THE GAS VALVE.
1.7.2 Improper Burner Function
With problems in this category, the burner ignites but exhibits abnormal characteristics such as “popping,” dark spots on the burner ceramics, fluctuating flame intensity, and flames shooting out of the flue.
“Popping” indicates delayed ignition. In this condition, the main gas valve is opening but the burner is not immediately lighting. When ignition does take place, the excess gas “explodes” into flame, rather than smoothly igniting.
The primary causes of popping are:
•Incorrect or fluctuating gas pressure
•Defective or incorrectly adjusted combustion air blower
•Inadequate
•
•Cracked ignitor or broken ignition wire
•Defective ignition module
•Cracked burner tile (typically causes a very loud pop).
If popping occurs only during peak operating hours, the problem may be incorrect or fluctuating gas pressure. Verify that the incoming gas pressure (pressure to the gas valve) is in accordance with the appropriate CE or
If popping is consistent during all hours of operation, the most likely cause is an insufficient air supply. Check for “negative pressure” conditions in the kitchen area. If air is flowing into the kitchen area, this indicates that more air is being exhausted than is being replenished and the burners may be starved for air.
