High
E9 on Worcester Bosch Greenstar 30HE

Your boiler has switched itself off because it has detected that it is getting far too hot inside.

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.

What the manual says

Manufacturer manual

Safety temp. limiter in CH flow has tripped.

From this model's manual
Verified against the Worcester Bosch Greenstar 30he installation & service manual, page 45.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This fault occurs when the water temperature inside your boiler exceeds a safe limit, causing the safety sensor to shut the system down to prevent damage. The most common reasons are a failed internal pump that isn't moving water away quickly enough or a buildup of sludge and limescale that is restricting flow through the heat exchanger.

This fault is more common in the autumn when heating systems are switched back on after a long summer break, as internal pumps can seize up due to inactivity.

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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