711 Boiler Fault Code: What It Means on Every Brand

The 711 fault code appears on 2 boiler brands — Ariston and Chaffoteaux — 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 711 means	Severity	DIY?
AAriston	Ariston fault code 711 (shown on the display as '7 11') indicates a problem with the Zone 1 return temperature sensor — the NTC thermistor that monitors the temperature of water flowing… Full guide →	Lockout — engineer likely	No
CChaffoteaux	Fault code 711 appears on multi-zone Chaffoteaux boilers and indicates that the control board has detected a problem with the return pipe temperature sensor (NTC probe) on Heating Zone 1. Full guide →	Lockout — engineer likely	No

711 brand by brand

Ariston 711

Ariston fault code 711 (shown on the display as '7 11') indicates a problem with the Zone 1 return temperature sensor — the NTC thermistor that monitors the temperature of water flowing back into the boiler from the heating circuit. When the boiler's control board detects an abnormal or absent signal from this sensor, it locks out and displays 711 to protect the system. On single-zone models this is simply the heating return sensor; on multi-zone or Sensys-controlled systems it refers specifically to the Zone 1 return sensor.

Causes, fixes & costs for Ariston 711 → · All Ariston codes

Chaffoteaux 711

Fault code 711 appears on multi-zone Chaffoteaux boilers and indicates that the control board has detected a problem with the return pipe temperature sensor (NTC probe) on Heating Zone 1. The boiler cannot obtain a valid temperature reading from that sensor — because it is reading open-circuit, short-circuit, or outside its expected resistance range — and has locked out to protect the system. The 711 code is part of the 700-series zone probe family used on the Expert Control platform: 701/711 relate to Zone 1, 702/712 to Zone 2, and 703/713 to Zone 3. The x01–x03 variants cover flow (send) probes, while the x11–x13 variants (including 711) specifically target return probes. If your display shows 711, the fault is isolated to the Zone 1 return sensor circuit.

Causes, fixes & costs for Chaffoteaux 711 → · All Chaffoteaux codes

Frequently asked questions

Is the 711 fault code the same on every boiler?

Broadly, yes — on Ariston and Chaffoteaux the 711 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 711 fault myself?

Not usually. On every brand listed, 711 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 711 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.