E48 Boiler Fault Code: What It Means on Every Brand

The E48 fault code appears on 2 brands — Andrews and Warmflow — and it does not mean the same thing on each. The same two or three characters can signal a pressure problem on one boiler and an ignition fault on another, so identify your brand first and use the table below to jump to the right page.

Up to: Lockout — engineer likely 2 brands use this code Meaning differs by brand

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 E48 means	Severity	DIY?
AAndrews	The E48 fault code on Andrews boilers (which share the Warmflow platform and fault code table) indicates that the boiler has detected water pressure in the sealed heating system has… Full guide →	Lockout — engineer likely	Some checks
WWarmflow	The E48 code appears on Warmflow Agentis series boilers when the internal pressure sensor detects that the water pressure in your central heating system has climbed above the safe upper… Full guide →	Engineer may be needed	Some checks

E48 brand by brand

Andrews E48

The E48 fault code on Andrews boilers (which share the Warmflow platform and fault code table) indicates that the boiler has detected water pressure in the sealed heating system has climbed above the safe upper limit. As a safety measure, the boiler shuts itself down and will not restart until the pressure is brought back within the normal operating range. On a healthy system, cold pressure should sit between 1 and 1.5 bar; anything significantly above 2 bar is cause for concern and will typically trigger E48. Note that Andrews combi boilers share their control platform with the Warmflow Agentis series, so this code applies equally across both ranges.

Causes, fixes & costs for Andrews E48 → · All Andrews codes

Warmflow E48

The E48 code appears on Warmflow Agentis series boilers when the internal pressure sensor detects that the water pressure in your central heating system has climbed above the safe upper limit — typically beyond around 2.5–3 bar. As a protective measure, the boiler shuts itself down and will not restart until the pressure is brought back into the normal operating range of 1.0–1.5 bar (shown in the green zone on the pressure gauge). It is worth noting that on certain Warmflow oil boiler models — notably the Eternal GU145 — E48 can instead signal a burner lockout after repeated failed ignition attempts, which points to a different set of causes such as oil supply blockages or airlocks rather than a pressure issue. Always check your specific model's manual to confirm which interpretation applies to your boiler.

Causes, fixes & costs for Warmflow E48 → · All Warmflow codes

Frequently asked questions

Is the E48 fault code the same on every boiler?

No. E48 means different things on different brands — see the table above. Always identify your boiler's brand (it is printed on the front casing) before acting on any advice about the code.

Can I fix a E48 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 E48 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.