High Lockout
Red | On permanently on Vokera Compact HE

Your boiler has become too hot and has shut itself down as a safety precaution to prevent damage.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

Appliance overheat

What causes this fault?

This fault occurs when the water inside the heat exchanger reaches an unsafe temperature, triggering a safety sensor to cut the power. The most common reasons are a failed pump that isn't moving water around the system or a blockage of sludge and debris restricting the flow. Sometimes, a faulty sensor can also trick the boiler into thinking it is overheating when it actually isn't.

This fault is more common in autumn when heating systems are switched back on after a long summer break, often causing internal pump components to seize.

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.

Find a Gas Safe engineer
Search the official register →

Related guides you might find useful

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →

Banging / kettling / whistling noise

Each noise points to a different fault.

Read →

Boiler won't turn on — 9-step checklist

Work through these before the call-out.

Read →