3.1 The Electrical Installation Certificate (EIC) & Schedules

What is an Electrical Installation Certificate (EIC)?

The Electrical Installation Certificate (EIC) is the documentation issued for a new electrical installation, or for an addition or alteration to an existing installation that requires the installation (or a distinct part of it) to be energised for the first time. It certifies that the design, construction, inspection, and testing of the work comply with BS 7671:2018+A4:2026 at the moment it is put into service.

The EIC is not a maintenance or condition report — it is a declaration of compliance from new. Once issued, it forms part of the installation's permanent records and is typically retained by the occupier or owner.

When an EIC is Required

An EIC must be issued for:

• A new installation (full first fix and second fix)
• A rewire of an existing installation
• The installation of a new circuit (any new circuit, regardless of size or load)
• A consumer unit or distribution board change
• Any addition or alteration extensive enough to require the whole installation (or a distinct part) to be re-energised and fully verified

For smaller jobs that do not require a new circuit, the Minor Electrical Installation Works Certificate (MEIWC) is used instead (covered in Section 3.2).

The Three Required Parts of an EIC

Per BS 7671 and GN3 10th Edition (2026), a valid EIC consists of three inseparable parts. All three must be present — a certificate on its own, without its schedules, is invalid and incomplete.

Who Signs the EIC?

The EIC requires signatures from three responsible parties:

1. Designer — responsible for the design, including conductor sizing, protective device selection, and disconnection time calculations
2. Installer — responsible for the construction and erection of the installation
3. Inspector — responsible for carrying out the inspection and testing

On small jobs, one person may hold all three roles, provided they are competent in each. However, for notifiable work (work notifiable to building control), best practice and GN3 recommend that the inspector should be impartial — ideally not the person who carried out the installation. This independence strengthens the validity of the verification.

Recorded Supply and Test Details

The certificate records the characteristics of the supply at the origin:

• External earth fault loop impedance (Ze) — measured at the incoming terminal
• Prospective fault current (PFC) — the higher of the prospective short-circuit current and the earth fault current
• Type of earthing (TN-C-S, TN-S, TT, or IT)
• Voltage and number of phases (typically 230 V single-phase or 400 V three-phase)
• Nature of supply parameters — the prospective earth fault current (PEFC) and the prospective short-circuit current (PSCC); the greater of the two is recorded as the prospective fault current (Ipf)

The schedule of test results records, for each circuit:

• Continuity of protective conductors and R1+R2 values
• Insulation resistance (line-to-line and line-to-earth)
• Polarity confirmation
• Earth fault loop impedance (Zs) measured at the furthest point of the circuit
• RCD/RCBO operation — tripping times at 1× and 5× rated residual current
• PFC at each circuit's distribution board

The schedule of inspections records the visual inspection items — conductor connections, presence of earthing and bonding, identification and labelling, access for maintenance, and IP ratings of enclosures. Each item on the schedule is ticked as satisfactory or noted as deficient. The schedule of inspections is completed before the schedule of test results, because visual inspection must precede any energised testing — testing a defective installation could create danger.

Relationship Between the Three Parts

The three parts work together as a single compliance package:

• The certificate provides the overall declaration and the supply-side data that contextualises every circuit.
• The schedule of test results provides the objective measured evidence that each circuit performs as designed.
• The schedule of inspections provides the visual confirmation that the installation is erected correctly and safe to energise.

If any one part is missing, the chain of evidence is broken. An inspector who signs a certificate without the supporting schedules has not demonstrated that the installation complies — they have only asserted it.

Scope and Extent Recorded on the EIC

The EIC must state the extent of the work covered. For a full new installation, this is the entire installation. For an addition or alteration, the certificate must clearly identify which part of the installation is covered and which pre-existing parts are excluded. This prevents ambiguity about what has been verified and what has not. The inspector must also record any limitations agreed before the inspection — for example, a circuit that could not be isolated and therefore could not be fully tested. Agreed limitations must be justified and clearly stated; they are not a substitute for testing.

Key Exam Point

The 2391-52 exam frequently tests the principle that all three parts must accompany an EIC. A common wrong answer suggests that "the schedule of inspections is optional for small jobs" — it is not. Without all three parts, the EIC is incomplete and the installation cannot be properly certified as compliant with BS 7671. Another common wrong answer suggests that the inspector can sign without recording Ze or PFC — these supply characteristics are mandatory because they contextually validate every Zs and disconnection time recorded on the schedule of test results.