Your boiler is operating at its maximum heating capacity and has entered a temporary monitoring state, which is usually part of normal operation or a simple setting adjustment.

Max. heating output

What causes this fault?

This code appears when the boiler has reached its highest possible heat production and is working at full power to meet the demand you have set. It is often triggered if the thermostat is set very high or if the heating system is trying to warm up a very cold house quickly. It is considered a status message rather than a mechanical failure, indicating that the system is simply running at its limit.