Free learning

EICR codes explained: C1, C2, C3 and FI

An Electrical Installation Condition Report (EICR) gives each observation a classification code. The code tells the person responsible for the installation how urgent the remedial action is. (A4 EICR, Section K)

Below: what each code means, how FI differs from C3 under BS 7671:2018+A4:2026, five worked examples from our book EICR Coding for Electricians, and common mistakes. Sources are listed at the end.

What each code means

C1: danger present

C1 means danger present, with a risk of injury: immediate remedial action is necessary. (A4 EICR, Section K)

The people using the installation are at immediate risk. The person ordering the report should be advised to act without delay, and the inspector should not wait for the full report to give this advice. (ESF BPG4, p.12)

C2: potentially dangerous

C2 means potentially dangerous: urgent remedial action is necessary. (A4 EICR, Section K)

It is for something that is not dangerous at the time of the inspection, but would become an immediate danger if a fault or other foreseeable event occurred. (ESF BPG4, p.12)

C3: improvement recommended

C3 means improvement recommended. (A4 EICR, Section K)

It is for something that is not a source of immediate or potential danger, where improvement would still make the installation safer. (ESF BPG4, p.13)

FI: further investigation is advised

FI means further investigation is advised. (A4 EICR, Section K)

It is for a potential issue, found by the inspection and testing, that the inspector cannot give a code until it has been investigated further. (ESF BPG4, p.13)

Terms that are not codes

  • Observations (Obs) are items worth noting that are not non-compliances with BS 7671 and do not warrant a code. (ESF BPG4, p.12)
  • NC only is a non-conformity that does not give rise to danger and is not required to be recorded on an EICR. (ESF BPG4, p.12)
  • Myths are items that are not non-compliances with BS 7671 and do not need reporting. (ESF BPG4, p.12)

FI or C3: what A4 changed

Section K of the A4 EICR has two tables. The C1 and C2 table affects the overall assessment of the report; the C3 and FI table does not. (A4 EICR, Section K)

Section E of the form says an observation coded C3 or FI is advisory and does not affect the overall assessment, but should be given due consideration. An unsatisfactory assessment means C1 and/or C2 conditions have been identified. (A4 EICR, Section E)

So FI does not by itself make a report unsatisfactory, as Wiring Matters 110 and ESF's A4 pocket guide both confirm. (Wiring Matters 110; ESF pocket guide, p.11)

The FI wording changed too. Before A4, further investigation was required without delay; now it is advised. (Wiring Matters 110)

FI is rare in homes

In a domestic or similar installation, it should generally be possible to code each observation without further investigation. BPG4 gives no domestic FI examples. (ESF BPG4, p.13)

Periodic inspection is not a fault-finding exercise. Where an observation can be given a code, further investigation is not needed to complete the report. (ESF BPG4, p.13)

Wiring Matters 110 says it should not be necessary to use FI in the majority of circumstances. (Wiring Matters 110)

In short: FI is only for a potential issue you found but cannot verify because of the extent and limitations; a part you could not inspect is a limitation. (ESF BPG4, p.13; A4 EICR, notes 9 and 14)

Five worked examples from the book

Each scenario below is quoted from the book, with its question number, the code the book gives and its source. Codes depend on the inspector’s own assessment of what they actually find.

Q23 and Q24: a loose blank, with and without a lockable lid

“The consumer unit has no lockable lid. A plastic blank at way 9 is loose and drops out when you touch it.”

Code C2. On a consumer unit without a lockable lid, BPG4 codes a blank that is not suitably secured or durable, with potential access to live parts, as C2. (ESF BPG4, p.20)

“In a holiday let the board sits behind a lid with a working key lock. Behind the lid, a spare way has been closed off with a strip of electrical tape.”

Code C3. With a lockable lid, BPG4 codes the same kind of blank as C3. (ESF BPG4, p.23)

Q11: lighting with no RCD

“In a 1990s house the lighting circuits have no RCD protection. Nothing else is wrong with them.”

Code C3. BPG4 codes the absence of additional protection by RCD for AC final circuits supplying luminaires in domestic premises as C3. (ESF BPG4, p.22)

Q22: a low insulation resistance reading

“Insulation resistance on the garage radial, live conductors joined and tested to earth: 0.3 MΩ.”

Code C2, not FI. BPG4 codes insulation resistance below 1 MΩ between live conductors connected together and Earth as C2. Wiring Matters 110 calls FI here a wrong use of the code: finding the reason is fault-finding. (ESF BPG4, p.19; Wiring Matters 110)

Q39: a circuit you cannot trace

“Way 6 in a 1990s board is live and loaded, but after switching it off nothing you can find in the house has gone dead. Your colleague suggests putting FI.”

Code C3, not FI. BPG4 codes the absence of appropriate identification of circuits as C3. Wiring Matters 110 gives an unidentified circuit as a common wrong use of FI: identifying it is remedial work. (ESF BPG4, p.24; Wiring Matters 110)

The wiring you could not trace is also a limitation. It may not be possible to readily trace an individual circuit, and a limitation, agreed or operational, should be recorded on the report. (ESF BPG4, p.9)

Q93: a burning smell under a floor you agreed not to lift

“Before the inspection the client agreed that the fitted hardwood floor in the lounge would not be lifted. During testing you notice a burning smell near the floor, but every circuit tests satisfactorily. The lighting has no RCD.”

The smell gets FI: it is an issue the inspector is unable to verify because of the extent and limitations. (A4 EICR, note 14)

The floor is an agreed limitation, recorded in Section D with the reasons and the name of the person it was agreed with. (A4 EICR, Section D)

The lighting is C3, as in Q11. With only C3 and FI on the report, the overall assessment is satisfactory, because both are advisory. (ESF BPG4, p.22; A4 EICR, Section E)

Tell the client the floor area should be investigated as soon as possible. Visible evidence of excessive heat, such as charring, would be C2 and make the report unsatisfactory. (ESF BPG4, pp.13, 21; A4 EICR, Section E)

The book marks this answer as a judgement call rather than a guide example.

Common coding mistakes

  • Calling a report unsatisfactory because of C3s or FIs. If no observation is coded C1 or C2, it would not be reasonable to report the installation as unsatisfactory. (ESF BPG4, p.15)
  • Writing FI for a part you did not inspect. That is a limitation: record it in Section D as agreed or operational, with the reasons. (A4 EICR, Section D)
  • Coding every socket without RCD as C2. BPG4 gives C2 where it is likely to supply mobile equipment outdoors; one that is unlikely to, does not serve a bath or shower room and is not otherwise judged dangerous is C3. (ESF BPG4, pp.18, 22)
  • Reporting myths. Unbonded metal sinks that are not extraneous-conductive-parts, BS 3871 circuit-breakers and socket-outlets without switches are not defects: BPG4 lists them as myths. (ESF BPG4, p.26)

Practise coding

Our book EICR Coding for Electricians (A4 PDF, 85 pages) has 138 graded scenarios and 150 worked observations, with the code, the reasoning and the source for every answer.

Or try Inspection and Testing Calculations first: Read a free sample on Amazon.

Sources

This page summarises published guidance in our own words. It does not reproduce BS 7671. Always check your own copy of the current book.