Intergas 21 Fault Code (Combi Compact HRE)

Safety disclaimer

Fault code summary

Manufacturer

Intergas

Fault code

21

Fault type

Temperature sensor, Central heating

Severity

Not specified

Reset

After the fault is rectified, press the reset key on the operating panel.

Applicable models

HRE 24/18, HRE 28/24, HRE 36/30, HRE 36/40

Quick answer

Sensor fault S2.

What does this fault code mean?

Sensor fault S2.

Common causes

• Broken wiring.
• S2 sensor fault.

Symptoms

• The fault LED flashes and the main display shows 21.

What can the homeowner safely check?

• Record the code and contact an authorised installer.

Boiler reset information

After the fault is rectified, press the reset key on the operating panel.

When should I call an engineer?

Contact a suitably qualified heating engineer when the fault persists, the boiler locks out, or the manufacturer instructions do not resolve it. For gas appliance work in the UK, use a Gas Safe registered engineer.

Engineer diagnosis

• Check S2 and its wiring.

Applicable boiler models

• HRE 24/18
• HRE 28/24
• HRE 36/30
• HRE 36/40

Related fault codes

• 0 — Combi Compact HRE

  Sensor fault after self-check.

  Read fault code
• 0.0 — Combi Compact HRE

  Low pressure.

  Read fault code
• 1 — Combi Compact HRE

  Temperature too high.

  Read fault code
• 10 — Combi Compact HRE

  Sensor fault S1.

  Read fault code
• 11 — Combi Compact HRE

  Sensor fault S1.

  Read fault code
• 12 — Combi Compact HRE

  Sensor fault S1.

  Read fault code
• 13 — Combi Compact HRE

  Sensor fault S1.

  Read fault code
• 14 — Combi Compact HRE

  Sensor fault S1.

  Read fault code

Manufacturer documentation

Section 11.1: Main display 20,21,22,23,24 — Sensor fault S2.

Last verified

2026-09-12

Frequently asked questions