Burner locks out with code indicating pre-purge or post-purge timing error

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Faulty fan motor not reaching speed, Incorrect wiring of fan to control box, Defective control box timing circuit, Blocked fan causing slow start

Safety: Disconnect power before working on the fan or wiring.

Steps:

Check fan start-up: Call for heat and observe (from a safe distance) whether the fan starts promptly. If it hesitates or hums, the motor or capacitor may be failing.
Inspect wiring: Confirm that the fan motor is wired to the correct terminals on the Riello control box as per the wiring diagram.
Clean fan: Remove dust and debris from the fan wheel and housing to reduce load.

If purge timing remains incorrect, the control box likely requires replacement.

Hard 4/5

Combustion Fan Motor

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