722 Boiler Fault Code: What It Means on Every Brand

The 722 fault code appears on 2 brands — Ariston and Chaffoteaux — 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 722 means	Severity	DIY?
AAriston	Fault code 722 on Ariston boilers has two distinct meanings depending on which model you own — always check the data plate on your boiler before drawing any conclusions. Full guide →	Lockout — engineer likely	No
CChaffoteaux	Fault code 722 appears on Chaffoteaux multizone boilers — such as the Niagara Delta range — when the control board detects that the water temperature in Zone 2 has climbed beyond its safe… Full guide →	Engineer may be needed	No

722 brand by brand

Ariston 722

Fault code 722 on Ariston boilers has two distinct meanings depending on which model you own — always check the data plate on your boiler before drawing any conclusions. On most multi-zone and SenSys-type Ariston systems, code 722 signals that the water temperature in heating Zone 2 has climbed above the safe operating threshold, causing the boiler's safety system to shut the appliance down in a protective lockout. On Clas One, Clas Net One, E-Combi, and E-System models, the same code instead points to a defective or disconnected return temperature sensor on Zone 2 — the boiler cannot read a valid temperature signal from that zone and locks out as a precaution. In both cases the boiler will stop heating until the underlying fault is resolved and the unit is reset.

Causes, fixes & costs for Ariston 722 → · All Ariston codes

Chaffoteaux 722

Fault code 722 appears on Chaffoteaux multizone boilers — such as the Niagara Delta range — when the control board detects that the water temperature in Zone 2 has climbed beyond its safe operating threshold. The boiler triggers a protective shutdown to prevent damage, and the fault code is displayed to alert you to the problem. In essence, hot water in Zone 2 is not circulating properly, causing heat to build up rather than being distributed around the heating circuit. For reference, fault code 723 signals the same overheating condition but in Zone 3, confirming that Chaffoteaux monitors each zone independently.

Causes, fixes & costs for Chaffoteaux 722 → · All Chaffoteaux codes

Frequently asked questions

Is the 722 fault code the same on every boiler?

No. 722 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 722 fault myself?

Not usually. On every brand listed, 722 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 722 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.