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Worcester Bosch Boiler E9 / E9 224 Error Code

Overheat limiter tripped on Worcester Bosch boilers.

Worcester Bosch All Worcester Bosch boiler codes

E9 / E9 224

May need a pro

A safety temperature limiter on the heating flow has cut in because the water inside the boiler got too hot. The CDi Classic engineer's booklet blames low water or low pressure, a seized pump, a tripped flue or heating limiter, a wiring or fuse fault, or the PCB. Water that can't get away, such as every radiator valve shut, can push the temperature up too.

Compatible models

Listed as E9224 in the GB162 V2 operating instructions; Greenstar CDi Classic combi, system and regular boilers and the HighFlow 440CDi and 550CDi ErP show E9. Check your manual for other Greenstar ranges.

Also shown as

Greenstar CDi Classic and HighFlow CDi models show this as E9 alone and treat it as a locking fault that needs a reset. The GB162 V2 commercial manual lists E9224 as thermostat temperature too high.

Difficulty

Try the basic checks, but the usual fix is a technician's job.

How to fix
When to call a pro
Parts
FAQ

Not sure you are reading the code right? See how to read Worcester Bosch boiler codes.

Safety first: never take the casing off a gas boiler. If you smell gas, open windows, don't use light switches, turn the gas off at the meter if you can and call your gas emergency number from outside. A carbon monoxide alarm going off means the same: switch the boiler off, get fresh air and call.

How to fix Worcester Bosch E9 / E9 224

Check the pressure
Low water is the first cause on Worcester's list. If the gauge reads under 1 bar, top up as your user manual explains.
Open up the radiators
Make sure radiator valves and thermostatic valves aren't all turned off, and bleed any radiator that's cold at the top. Worcester's GB162 manual suggests both for E9 224.
Reset once after it cools
Give the boiler time to cool down, then reset it the way your manual describes. If E9 comes back, stop there.

When to call a technician

A repeat overheat lockout points at the pump, a sensor or the controls inside the casing, all of which need a Gas Safe engineer. Keep resetting it and you're running a boiler that's tripping on its last line of protection.

Parts linked to E9 / E9 224

These are the parts an engineer usually checks for this code. They sit inside the sealed casing, so leave them to a Gas Safe registered engineer.

Frequently asked questions

Which Worcester Bosch models show the E9 / E9 224 code?

Can I fix Worcester Bosch E9 / E9 224 myself?

Only the outside checks above. If they don't clear E9 / E9 224, the fix is inside the boiler and needs a Gas Safe registered engineer.

Other Worcester Bosch boiler codes

Last reviewed 2026-10-21. Codes and steps can vary by model; check your owner's manual.

Sources we checked