High
90 on Worcester Bosch 537i

Your boiler has detected that it is not operating according to its expected energy settings, which typically indicates an issue with the internal electronics or the gas-to-air ratio setup.

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

Heat output 27.2 kW / Heat input 27.5 kW (RD532i L.P.G) or Heat output 33.4 kW / Heat input 33.8 kW (RD537i L.P.G)

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

Pilot light keeps going out

Older boilers — thermocouple, draught, gas supply.

Read →

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →