Honeywell Premix pilot burner Q358B2040B

This is a premix pilot burner from the Honeywell Q358 series (second generation). It is designed for gas boilers and water heaters. The burner has a target-type flame directed at the thermocouple, which is compatible with the Honeywell Q309A thermocouple. Flame sensing is by ionisation electrode (flame current). The reset type is mechanical and the burner operates on a premix air supply.

Parts of this type are selected by the burner series they are shaped for, the gas type (natural gas or LPG), and the required pilot flame output. The pilot burner includes an integrated electrode assembly, typically combining ignition and ionisation functions, so the electrode gap, ceramic insulator length, and mounting flange geometry must match the original component. Before ordering a replacement, verify that the gas orifice size and the air mixing setup correspond to the appliance design; an incorrect mixture leads to ignition failure or sooting.

Common failure modes for pilot burners of this type include a cracked ceramic insulator, erosion of the electrode tip, and a spark gap that has drifted out of specification. These issues can cause delayed ignition or loss of flame signal. In operation, the pilot flame may not light, lift from the nozzle, burn unevenly, or produce soot.