High Lockout
P0.5-0.9 bar on Potterton Powermax HE

Your boiler has detected that the water pressure is too low, which prevents the system from running safely and efficiently.

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

Water pressure in CH system low

What causes this fault?

This fault occurs when there is not enough water in your heating system to maintain the required pressure for operation. The most common reason is a slow leak from a radiator valve or pipework, though it can also happen if air was recently bled from your radiators without the system being topped back up.

This issue is more frequent in autumn when homeowners turn their heating back on for the first time and discover that 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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