Your boiler is struggling to keep the flame lit while trying to heat your tap water, which usually means the system is cutting out during use.

DHW mode – burner error

What causes this fault?

This fault happens when the boiler successfully starts but cannot maintain a steady flame while heating your water, causing the system to shut down for safety. It is typically caused by a malfunctioning gas valve that isn't providing the right fuel mix or worn-out ignition parts that can no longer sense the flame correctly. In some cases, a damaged seal around the burner can also disrupt the combustion process and trigger this error.