Your boiler has shut down because it has overheated or detected a lack of water flow through the system.

Burner in fault state. Temperature limiter has responded. Cause: Check the heating system water level. Check the circulation pump. Vent the heating system. Check the temperature limiter and leads. Press E.

What causes this fault?

This fault occurs when the boiler's internal temperature reaches a dangerously high level, triggering a safety shutdown to prevent damage. The most common reasons are a pump failure that stops water from moving or a buildup of air and sludge that creates a blockage in the heat exchanger. Essentially, the burner is creating heat, but the system cannot move that heat away quickly enough.