High Lockout
A1 on Worcester Bosch Greenstar 30HE

Your boiler has detected that there is not enough water circulating through the system to operate safely.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

pump has run dry

What causes this fault?

This fault occurs when the boiler's internal sensors detect air pockets or a significant drop in water pressure, preventing the pump from moving water around. The most common cause is a leak in the system or radiators that have recently been bled, leaving the boiler with insufficient water to operate safely. Without enough water to act as a lubricant and coolant, the pump 'runs dry' and the system shuts down to prevent heat damage.

This issue is frequently seen in autumn when homeowners turn their heating back on for the first time and discover pressure has dropped over the summer months.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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