E430 Boiler Fault Code: What It Means on Every Brand

The E430 fault code appears on 2 boiler brands — Baxi and Potterton — 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 E430 means	Severity	DIY?
BBaxi	The E430 code relates to Baxi's internal water pressure self-check routine. Full guide →	Lockout — engineer likely	Some checks
PPotterton	The E430 code on a Potterton boiler relates to the boiler's internal water pressure test routine. Full guide →	Lockout — engineer likely	Some checks

E430 brand by brand

Baxi E430

The E430 code relates to Baxi's internal water pressure self-check routine. When E430 appears on its own, the boiler is mid-way through a temporary pressure test — it has not yet completed its assessment. When E430 appears alongside a crossed-out flame symbol, the test has definitively failed, meaning the boiler cannot confirm that system pressure is within a safe operating range. In either case, the boiler will typically lock out until the underlying pressure issue is resolved. This code is sometimes cross-referenced alongside code 166 in Baxi documentation, and both relate to the same pressure-monitoring function.

Causes, fixes & costs for Baxi E430 → · All Baxi codes

Potterton E430

The E430 code on a Potterton boiler relates to the boiler's internal water pressure test routine. When E430 appears on its own, the boiler is actively running a pressure self-check. When E430 is shown alongside a crossed-out flame symbol, the pressure test has failed and the boiler has locked out. In practical terms, the boiler's diagnostics have detected that system water pressure is either too low or behaving abnormally, and the boiler is refusing to fire until the underlying issue is resolved. This code is seen across several Potterton ranges including the Promax, Assure, and Gold/Titanium series, though the exact display can differ slightly between models — always cross-reference with your specific manual if unsure.

Causes, fixes & costs for Potterton E430 → · All Potterton codes

Frequently asked questions

Is the E430 fault code the same on every boiler?

Broadly, yes — on Baxi and Potterton the E430 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 E430 fault myself?

On some brands there are safe homeowner checks first — typically system pressure, the condensate pipe in cold weather, and a single reset. The underlying repair usually needs a registered engineer. Never open the boiler casing yourself.

Who should I call about a E430 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.