E117 Boiler Fault Code: What It Means on Every Brand

The E117 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 E117 means	Severity	DIY?
BBaxi	The E117 code appears on Baxi boilers when the water pressure inside the central heating system climbs above approximately 2.9 bar — well beyond the safe operating window. Full guide →	Lockout — engineer likely	Some checks
PPotterton	The E117 code appears on Potterton boilers when the system water pressure has climbed above approximately 2.9 bar — well beyond the safe operating range. Full guide →	Lockout — engineer likely	Some checks

E117 brand by brand

Baxi E117

The E117 code appears on Baxi boilers when the water pressure inside the central heating system climbs above approximately 2.9 bar — well beyond the safe operating window. At that level the boiler locks itself out as a protective measure, refusing to fire until the pressure is brought back into the normal cold-system range of 1.0–1.5 bar. Note: a small number of engineers and at least one trade source suggest that on certain Baxi models E117 can also relate to a circulation-detection issue rather than overpressure. If your pressure gauge reads within the normal range but the code keeps returning, mention this to your engineer so they can investigate the circulation side as well.

Causes, fixes & costs for Baxi E117 → · All Baxi codes

Potterton E117

The E117 code appears on Potterton boilers when the system water pressure has climbed above approximately 2.9 bar — well beyond the safe operating range. As a protective measure, the boiler shuts itself down and refuses to fire until the pressure is brought back within limits and the fault is cleared. Under normal conditions a cold heating system should sit between 1.0 and 1.5 bar, rising slightly to around 1.5–2.0 bar when fully warmed up. When pressure consistently exceeds that upper threshold and reaches the 2.9 bar trigger point, the boiler interprets this as a risk to internal components such as seals, pipework, and the heat exchanger, and locks out accordingly.

Causes, fixes & costs for Potterton E117 → · All Potterton codes

Frequently asked questions

Is the E117 fault code the same on every boiler?

Broadly, yes — on Baxi and Potterton the E117 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 E117 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 E117 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.