How to Fix Worcester Bosch E9-224 Fault Code (UK)
Worcester Bosch showing E9-224 — Primary overheat. UK diagnosis, likely spare (primary flow NTC) and step-by-step reset.
What the code means
E9-224 on a Worcester Bosch indicates primary overheat. The boiler locks out to protect the heat exchanger and, on gas faults, to comply with the Gas Safety (Installation and Use) Regulations. Always reset to confirm the code is live, not historical.
Likely spare
The most common fix is the primary flow NTC. Check the exploded diagram against the GC number on the data plate before ordering — Worcester Bosch revised parts on Worcester Bosch units mid-production.
Fix procedure
Bleed system, check pump running, replace NTC if reads open.
Log the fault and reset. If the code returns within 24 hours, escalate to full electrical diagnosis with a manometer and multimeter.
Frequently asked questions
- Can I reset E9-224 myself?
- You can press the reset button up to 3 times. If E9-224 returns, the boiler needs a Gas Safe engineer — it is illegal to repair gas components without registration.
- Is the part covered under warranty?
- Worcester Bosch standard warranty is 2–10 years depending on model. Registered installations get the full term. Check the sticker inside the case.
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