EC Boiler Fault Code: What It Means on Every Brand

The EC fault code appears on 2 boiler brands — Viessmann and Worcester Bosch — and on all of them it points to the same kind of problem. The details still differ by brand (thresholds, sub-codes, reset procedure), so use the table below to jump to the page for your boiler.

Lockout — engineer likely 2 brands use this code

Which brand is your boiler?

The brand is printed on the front casing. Tap your brand for the full causes, fixes and repair costs.

Brand	What EC means	Severity	DIY?
VViessmann	The EC fault code appears on older Viessmann boiler models and signals a circulation-related burner lockout. Full guide →	Lockout — engineer likely	No
WBWorcester Bosch	If your Worcester Bosch boiler is showing what looks like an 'EC' fault code, it is almost certainly displaying 'EA' — the segment display on many Greenstar models can make an 'A' look… Full guide →	Lockout — engineer likely	No

EC brand by brand

Viessmann EC

The EC fault code appears on older Viessmann boiler models and signals a circulation-related burner lockout. In plain terms, the boiler has detected that water is not moving around the system at the required rate. To protect itself from overheating, it shuts the burner down and displays the EC code. The root cause is usually somewhere in the circulation circuit — the pump, the pipework, or the system condition — rather than the burner itself.

Causes, fixes & costs for Viessmann EC → · All Viessmann codes

Worcester Bosch EC

If your Worcester Bosch boiler is showing what looks like an 'EC' fault code, it is almost certainly displaying 'EA' — the segment display on many Greenstar models can make an 'A' look like a 'C' depending on viewing angle or screen font. The EA fault code means the boiler's PCB has failed to confirm a stable flame after multiple ignition attempts and has locked the boiler out as a safety precaution. In plain terms: your boiler tried to light the burner, could not verify a flame was present, and shut itself down to prevent any risk. Both heating and hot water will be unavailable until the underlying cause is resolved and the boiler is reset. Many Worcester Bosch models show a numeric sub-code alongside EA to give a more precise diagnosis — for example, EA 227 (ignition electrode or lead fault), EA 229 (flame sensor or ionisation signal issue), and EA 234 (gas valve or gas supply fault). If you can see a number after the EA on your display, note it down before calling an engineer, as it will help them identify the faulty component faster.

Causes, fixes & costs for Worcester Bosch EC → · All Worcester Bosch codes

Frequently asked questions

Is the EC fault code the same on every boiler?

Broadly, yes — on Viessmann and Worcester Bosch the EC code points to the same class of fault, and the recommended response is similar. Model-specific details such as sub-codes and reset procedures still vary, so follow the page for your own brand.

Can I fix a EC fault myself?

Not usually. On every brand listed, EC points to a fault that needs a suitably registered engineer to diagnose and repair. A single reset to rule out a transient glitch is reasonable; repeated resets are not.

Who should I call about a EC fault?

For gas boilers, a Gas Safe registered engineer — it is a legal requirement for any work on the appliance. If you smell gas at any point, leave the property and call the National Gas Emergency line on 0800 111 999.

General guidance only — not a substitute for professional advice, and not certified by a registered engineer. Any work on a gas appliance must be carried out by a Gas Safe registered engineer. If you smell gas, call 0800 111 999.