Your boiler's internal memory chip has developed a communication fault, meaning the control board can no longer read its essential settings.

Parameter storage unit (PSU) error.

What causes this fault?

This fault occurs when the small plug-in memory chip on the main control board fails or loses its connection. It is usually caused by an electrical glitch or internal wear and tear that prevents the boiler from identifying its own model and safety settings. Without these specific instructions, the boiler shuts down immediately as a safety precaution.