The four codes
Every observation recorded on an Electrical Installation Condition Report carries a classification code. There are four, and they come from BS 7671 Appendix 6.
| Code | Meaning | Action required |
|---|---|---|
| C1 | Danger present, risk of injury | Immediate remedial action required |
| C2 | Potentially dangerous | Urgent remedial action required |
| C3 | Improvement recommended | Advisory |
| FI | Further investigation advised | Advisory |
The question that decides the code
Almost every coding decision comes down to one distinction:
Is the danger present now, or is it potential?
- If a person could be hurt by the condition as it stands today, without anything else having to fail first, it is a C1.
- If the condition means a person could be hurt when something else fails — a fault develops, a protective device is called on and cannot do its job — it is a C2.
- If the installation is safe as it is, but falls short of what the current edition would require, it is a C3.
That is why exposed live conductors at a damaged socket are a C1 — the hazard exists right now, with no further failure needed. It is also why the absence of RCD protection where the current edition requires it is a C2 rather than a C1: nothing is currently exposed and no fault currently exists, but if one develops it will not be cleared quickly enough.
C1 — danger present
The condition presents an immediate risk of injury. The person ordering the report must be told immediately, and in practice the circuit should be made safe on discovery rather than left as it was found.
Typical C1 observations:
- bare exposed live conductors accessible to touch
- a main protective earthing conductor found disconnected
- a protective device bypassed with fuse wire, with the cable already showing signs of overheating
- live parts accessible when a fuse or MCB is removed
- an extraneous-conductive-part being used as the sole earth path
C2 — potentially dangerous
No danger exists at the moment of inspection, but the installation is not in a safe condition for a fault. Urgent remedial action is required.
Typical C2 observations:
- no RCD protection where the current edition requires it
- insulation resistance below the minimum acceptable value, showing deteriorated insulation
- inadequate main protective bonding to gas or water services
- a circuit wired in cable undersized for its protective device and load
- a metallic consumer unit enclosure without an effective earth connection
C3 — improvement recommended
The installation is safe, but would be better if improved. Very often this is where an older installation that complied with the edition in force when it was built sits today.
Typical C3 observations:
- no RCD protection on a circuit where the current edition would require it but the installation is otherwise sound and the circuit is not in a location that demands it
- absence of a warning notice that the current edition would require
- older cable colours in use, correctly identified and safe
- a consumer unit in a location that is acceptable but not ideal
A C3 never makes a report unsatisfactory. If you find yourself wanting to code something C3 and mark the report unsatisfactory because of it, the code is probably wrong.
FI — further investigation
FI is not a severity. It means the inspection could not reach a conclusion, and something needs looking into further, without delay.
Use it when you have found evidence of a problem you cannot resolve on the day — an unexplained reading, a circuit you cannot trace, signs of previous overheating with no obvious cause. What you must not do is use FI to avoid making a decision you have enough information to make.
How the codes drive the overall assessment
This is the rule the 2391-52 examines most often:
The overall assessment is unsatisfactory only where a C1 or a C2 is recorded. C3 and FI are advisory and do not affect it — though they should be given due consideration.
Two consequences follow:
- A report with a dozen C3 observations and nothing worse is still satisfactory.
- A report with a single C2 is unsatisfactory, however good the rest of the installation is.
An FI does not by itself make a report unsatisfactory. But if the investigation it triggers turns up a C1 or C2, the assessment changes.
Working the judgement, not the definition
Reciting the four definitions is the easy part. What the exam actually tests is whether you can apply them to an observation you have never seen phrased that way before.
The fault coding trainer puts real EICR observations in front of you and asks you to classify them, then shows the reasoning behind the correct code — which is the part worth learning.
Common exam mistakes
- Coding something C1 because it looks alarming, when nothing is currently dangerous. Severity is about present danger, not appearance.
- Coding an older installation C2 purely for being built to an earlier edition.
- Treating FI as sitting between C2 and C3 in severity.
- Marking a report unsatisfactory on the strength of C3 observations.
- Using FI to defer a judgement the inspection already supports.