BoilerFaultCodesWhat the manual says
Manufacturer manualTest function for the safety temperature limiter (STL): The burner is switched on with maximum output, the temperature controller is switched off
What causes this fault?
This is a routine safety procedure rather than a mechanical failure. The boiler intentionally runs at maximum power to verify that the high-limit sensor can correctly detect an overheat scenario and shut the system down safely. Once the software confirms the safety limit works, the boiler will return to its normal heating mode.
DIY fix possible
Wait for the test to complete automaticallyDo not turn off the power while the test is runningMonitor the display to ensure it returns to normal operation once finished
Avoid the next call-out bill
A cover plan would handle faults like P.5: no call-out fees, no surprise bills.
Affiliate links. We may earn a commission at no extra cost to you.
Related fault codes
All 71 fault codes on the ecoTEC exclusive
Seeing a different code? Every code this model can display, in one place.