Frymaster FBR18 Series manual Improper Burner Functioning, Incoming Gas Pressures

tion failure situation may be encountered 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, but 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 itself, but before replac- ing the gas valve, refer to the troubleshooting guide TROUBLESHOOTING THE GAS VALVE.

6.7.2 Improper Burner Functioning

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:

zIncorrect or fluctuating gas pressure

zA defective, dirty, or incorrectly adjusted combustion air blower

zInadequate make-up air

zHeat damage to the controller or ignition module

zA cracked ignitor or broken/loose ignition wire

zA defective ignition module

zA cracked burner tile.

If popping occurs only during peak operating hours, the problem is most likely incorrect or fluctuat- ing gas pressure. Verify that the incoming gas pressure (pressure to the gas valve) is in accordance with the following table, and that the pressure remains constant throughout all hours of usage.

Incoming Gas Pressures

Gas	Minimum	Maximum
	6" W.C.	14" W.C.
Natural	1.49 kPa	3.48 kPa
	14.93 mbar	34.84 mbar
	11" W.C.	14" W.C.
LP	2.74 kPa	3.48 kPa
	27.37 mbar	34.84 mbar

Refer to Check Burner Manifold Pressure in the Semi-Annual Checks and Services section of Chapter 4 for the procedure for checking the gas pressure supplied to the burner.

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