Your boiler has failed while running a specific test used for commissioning or high-power performance checks.

Maximum load test program error

What causes this fault?

This fault occurs when the boiler's internal diagnostic program fails to complete its high-performance test correctly. It is usually triggered manually by an engineer during a service or installation, and the error suggests that the system couldn't maintain the required heat output to finish the check. The most common reason is a sensor reading an unexpected temperature or the test being interrupted before the sequence was finished.