Mastering EICR Classification Codes: C1, C2, C3 and FI Explained

Accurate observation coding on an Electrical Installation Condition Report (EICR) is critical. Incorrectly assigning a Code C2 where a Code C3 belongs can cost property owners thousands of pounds in unnecessary remedial work, while under-coding a Code C1 hazard leaves occupiers at risk of shock or fire.

In this guide, we analyze the official classification criteria from IET Guidance Note 3 (Section 3) and BS 7671:2018+A4:2026.

The Four EICR Classification Codes

Code C1: Danger Present

Definition: Risk of injury is present. Immediate remedial action is required. The inspector must issue an immediate Notice of Unsafe Situation to the person ordering the report.

Real-world C1 Examples:

• Exposed live 230V terminals accessible without the use of a tool or key.
• Conductive metal enclosure energised due to a dead short.
• Missing enclosure cover exposing live busbars in a accessible consumer unit.

Code C2: Potentially Dangerous

Definition: Urgent remedial action required. While not presenting immediate danger at the time of inspection, a failure mechanism or logical fault could become dangerous under secondary conditions.

Real-world C2 Examples:

• Absence of main protective earthing or main protective bonding to gas/water services.
• Earth fault loop impedance ($Z_s$) exceeding the maximum tabulated limit in BS 7671 where automatic disconnection (ADS) is not guaranteed.
• Absence of 30mA RCD protection for socket-outlets used by ordinary persons where required by Regulation 411.3.3.
• Thermal damage, severe scorching, or melted insulation on terminals.

Code C3: Improvement Recommended

Definition: Non-compliance with BS 7671 that does not present immediate or potential danger, but improvement would enhance safety or bring the installation up to modern standards.

Real-world C3 Examples:

• Absence of circuit identification diagrams or schedule at the consumer unit.
• Wiring colors matching older pre-harmonized BS 7671 standards (e.g. Red/Black) without warning label.
• Non-fire-rated plastic consumer unit in a domestic dwelling (where no damage or overheating exists).

Code FI: Further Investigation Required

Definition: An observation that cannot be fully determined during inspection without further investigation, or where access limitations prevent verifying safety.

Real-world FI Examples:

• Unidentified sub-main cables with unknown protective device rating at source.
• Circuits showing unacceptably low insulation resistance where the cause cannot be pinpointed without invasive tracing.

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Impact on Overall EICR Outcome

Observations Present	Overall Assessment Outcome
Any Code C1 present	UNSATISFACTORY
Any Code C2 present	UNSATISFACTORY
Any Code FI present	UNSATISFACTORY
Only Code C3 or no defects	SATISFACTORY

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