High
Primary Overheat on Worcester Bosch 24CDi BF

Your boiler has automatically shut down because it has become too hot to operate safely and needs attention to restore central heating or hot water.

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

Boiler not fully water pressurised, air in system, pump failure, primary sensor not correctly fixed to pipe, or short circuit across contacts 5 & 6 (overheat thermostat fault).

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

No hot water but heating works

Almost always a stuck diverter valve on combis.

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 →