BS 7671 Amendment 4 (A4:2026) Study Guide

How to use this guide

Read one chapter at a time, then answer its questions before you look at the answers. The chapters follow the order of BS 7671 itself (Part 1 to Part 7, then the Appendices), so you can open the orange book at the same place.

Each chapter has three parts:

1. What it means: the change explained in plain English, and why it was made.
2. Examples: real jobs (a flat, a shop, a battery install) showing how the change affects what you do or write.
3. Questions and answers: test yourself. Cover the answer, say it out loud, then check.

Chapter 11 is a one-page site checklist, and Chapter 12 is a mixed revision quiz, the kind of questions an assessor asks.

⚠️ Safety note. This guide is our own study notes, built from the NICEIC The Wire webinars (Parts 1 to 4) and published summaries. It is not a copy of the standard, and it is not an NICEIC or IET publication. Before you rely on any value (Zs, Ze, sizes, distances) on a real job, check it in BS 7671:2018+A4:2026 and Guidance Note 3. The result on a certificate is always your own professional judgement.

Words used in this guide

Chapter 1 — What A4 is: dates, transition and the orange book

Since 15 October 2026, BS 7671:2018+A4:2026 is the only current edition of the Wiring Regulations. Every EICR from that date, and all new work designed from that date, must be done to A4.

What it means

An amendment does not replace the 18th Edition. It changes parts of it and re-issues the whole book. A4 has an orange cover, so people call it "the orange book". It brings in the 2023 Corrigendum and A3 (2024), so A4 is one complete book: you do not need A2 or A3 next to it.

Transition rule. Work designed before 15 October 2026 can still be finished and certified to A3 after that date. Check the contract: if it says "to the latest edition", A4 applies. If you certify to A3 after 15 October, tell the client it follows a withdrawn standard.

No exam. You keep your 18th Edition qualification. NICEIC expects you to know the changes and to keep CPD records (for example, your four The Wire certificates).

Reading the orange book

• Pages 12 to 14 summarise every change.
• A line in the margin (sidebar) marks a technical change. Editorial changes may not have one.
• Lists changed order: the first level is now (a), (b), (c) and the second level (i), (ii). It used to be the other way round.
• Style changes: cpc → CPC, rms → RMS, "comply with" → "conform to".
• Ring end-to-end tests are now written r₁-r₁, rₙ-rₙ, r₂-r₂ (they used to be L-L, N-N, cpc-cpc).
• "Shall" = a requirement. "Should" = a recommendation. Not following a recommendation is not a departure, but your installation must be equally safe.
• Form references: 18.4 on a form means A4; 18.3 means A3. Declarations say "BS 7671 2026" for A4 work.

Examples

Example 1 — the late job. You quoted and designed a kitchen rewire on 1 October 2026 and finish it on 20 October. You may certify it to A3, because it was designed before 15 October. Note on the EIC that it was designed to A3, and tell the client A3 is now withdrawn. If the client's contract says "latest edition", certify to A4 instead.

Example 2 — the EICR. A landlord books an EICR for 5 November 2026. It must be to A4. There is no choice, because a condition report checks the installation against the current standard on the day.

Example 3 — the old NOCS draft. You started an A3 EIC in NOCS on 10 October. You can still finish it in NOCS until 15 April 2027.

Questions and answers

Chapter 2 — Part 1: Scope, object and fundamental principles

Part 1 now covers stationary secondary batteries and Power over Ethernet, and the designer (not the installer) must agree to any equipment that has no standard.

What it means

Scope (110.1.1). Part 1 says what BS 7671 applies to. A4 adds two things to the list:

• Stationary secondary batteries: rechargeable batteries fixed in place that store energy for the installation, such as a home battery with solar PV. The new rules are in Chapter 57 (see Chapter 6 of this guide).
• Power over Ethernet (PoE): data cables that also carry DC power to cameras, Wi-Fi points and lights. The new rules are in Section 716 (see Chapter 9).

A4 also adds Section 545, functional earthing for ICT (IT and telecoms) equipment.

133.1.2 — equipment with no standard. Sometimes you fit equipment that no British or European standard covers. Before A4, the person ordering the work and the installer agreed it was safe. Now it is the person specifying the installation and the designer. The designer must be satisfied it gives the same level of safety. Record it as an agreed departure on the EIC.

133.1.3 — equipment used outside its standard. If you use equipment in a way its own standard does not cover, record it as a departure on the EIC.

"Comply with" becomes "conform to". This is a wording change across the book. It matches how BSI writes other standards. It does not change what you must do.

Examples

Example 1 — an imported light fitting. A client buys a designer pendant from abroad with no UKCA/CE marking or standard you can confirm. As designer, you check it is safe (construction, IP rating, earthing). If you and the client agree to fit it, write it on the EIC as a departure under 133.1.2, with the reason.

Example 2 — a battery job. A client wants a 10 kWh battery added to their PV. Before A4, BS 7671 had no specific rules for it. Now it is in scope: Chapter 57 applies, with its RCD, isolation and notice rules.

Example 3 — PoE in an office. An IT firm installs PoE cameras along a corridor. That cabling is now inside the scope of BS 7671 (Section 716), so it must meet its current and SELV/PELV rules.

Questions and answers

Chapter 3 — Part 2: Terms and definitions

Part 2 is renamed "Terms and definitions" and gains more than 40 new definitions. You don't need to memorise them all, but you must know the ones that appear on certificates and on site.

What it means

Related terms are now grouped. For example, "skilled person" and "instructed person" sit together under persons, and the battery types sit under battery. The 2023 Corrigendum terms (firefighting lobby, firefighting shaft, protected stairway) and A3's bidirectional and unidirectional protective device are built in.

Unidirectional and bidirectional devices. A unidirectional device is marked for which way power flows (line/load, in/out, or arrows). A bidirectional device has no such marking and works whichever way the power flows. Where power can flow both ways (PV, batteries, generators), use bidirectional devices.

Examples

Example 1 — is it PCE? A hybrid inverter that charges a battery from PV and feeds the house: yes, it is power conversion equipment. A plain isolator: no, it does not convert anything.

Example 2 — RDC-DD or RDC-PD? An EV charger's data sheet says it has "6 mA DC detection" that signals the charger's own contactor to open. That is an RDC-DD (detection, used with a switching device). A standalone device to BS IEC 62955 that detects and disconnects by itself is an RDC-PD.

Example 3 — the MCB marked line/load. On a board fed by a battery inverter, you find an MCB with "LINE" printed at the top. It is unidirectional. If power could flow back through it, replace it with a bidirectional device or follow the manufacturer's instructions.

Questions and answers

Chapter 4 — Part 3: Assessment of general characteristics (earthing systems)

A4 recognises TN-C-S (PNB) earthing for the first time, and the certificates now let you choose TN-C-S (PNB), TN-C and IT as well as TN-S, TN-C-S and TT.

What it means

Before you design or test, Part 3 asks you to find out about the supply: voltage, frequency, prospective fault current, Ze, and the type of earthing. The earthing type decides your disconnection times, bonding and what Zs values you can use.

The letters, quickly

• First letter, how the supply source is earthed: T = directly to earth; I = isolated from earth (or through a high impedance).
• Second letter, how your exposed metalwork is earthed: T = your own earth electrode; N = connected to the supply's earthed neutral.
• After the dash: S = separate neutral and earth conductors; C = combined neutral and earth (PEN).

PNB in detail. With PME, the DNO joins neutral and earth at many points along the network. With PNB, they are joined at only one point, close to the supply, with an earth electrode. It is shown in Figure 3.9B (PME is Figure 3.9A). DNOs have used PNB for years; A4 now names it.

How to recognise PNB (from ENA G12 Issue 5):

• 4 or fewer consumers on that supply, and
• the earth electrode is 40 m or less from the supply point.
• It may be labelled.

If in doubt, ask the DNO. The DNO must tell you the earthing type free of charge.

For you as an inspector: record what you find. On A4 forms, choose TN-C-S (PNB) when the DNO confirms it or the clues and label show it. The Ze limit to compare against is the same 0.35 Ω.

Examples

Example 1 — the farm cottage. Two cottages and a barn are fed from a pole transformer 25 m away, with an earth electrode at the pole. The cut-out has an earth terminal from the supply. Three consumers, electrode within 40 m: this is likely PNB. Check the label or ask the DNO, then tick TN-C-S (PNB). Measured Ze 0.21 Ω: below 0.35 Ω, fine.

Example 2 — the London terrace. A terrace in N12 with a PME label on the cut-out and a 100 A fuse. Many consumers on the street: this is ordinary TN-C-S (PME), not PNB.

Example 3 — the outbuilding. A garden office fed from the house is made TT with its own rod, because exporting PME to it isn't suitable. The house is TN-C-S; the outbuilding circuit is recorded with its own R_A.

Questions and answers

Chapter 5 — Part 4: Protection for safety

Part 4 has no big new rules, but it clarifies four things you meet every week: RCD Zs values, where AFDDs are required, cables in escape routes, and what surge protection does not cover.

What it means

411.4.204 — Zs for RCD-protected circuits. Table 41.5 gives maximum Zs values for circuits where an RCD gives fault protection. A4 makes clear they apply to both non-delayed (general) RCDs and S-type (time-delayed) RCDs. It is a clarification, not a new limit.

421.1.7 — AFDDs (arc fault detection devices, BS EN 62606). An AFDD detects the arcing from a loose terminal or damaged cable and switches off before a fire starts. They are required on single-phase socket-outlet circuits rated up to 32 A in:

• high-rise residential buildings (HRRBs): over 18 m tall or more than 6 storeys (the ground floor counts as a storey). A3 called these "higher risk residential buildings".
• houses in multiple occupation (HMOs)
• purpose-built student accommodation
• care homes

They are recommended everywhere else. They are not required on EV charge point circuits or battery storage circuits. Thatched buildings are dealt with under 422.4 (fire risk from construction), not 421.1.7.

Section 422 — escape routes (Corrigendum built in).

• No cables in firefighting shafts or protected stairways unless they serve fire safety systems there.
• Fire-resistant cables (422.2.1) are allowed in a protected corridor.
• 422.2.202: cables count as outside the escape route if they're in an enclosure with the same fire resistance as the route, or if the fire engineer specifies it.

The "3-metre rule" renamed. Where a cable is not protected against overload or fault at its start (for example, a short tail from the supply), it must be installed so a fault is very unlikely. A4 calls this "inherently short-circuit and earth-fault proof". 557.6.3 gives examples: single-core cables in insulated conduit or trunking, extra mechanical protection, or keeping a safe distance from other parts.

Section 443 — overvoltage. SPDs protect against surges from distant lightning and switching. Section 443 does not cover a direct or nearby lightning strike. That needs a lightning protection system (BS EN 62305).

Examples

Example 1 — the 7-storey block. You change a consumer unit in a flat on the 3rd floor of a 7-storey block. The building is HRRB (more than 6 storeys), so each 32 A socket ring needs an AFDD. Lighting circuits: recommended, not required.

Example 2 — the HMO. A 5-bedroom HMO in a 3-storey house. It is an HMO, so the socket circuits need AFDDs, even though it isn't tall.

Example 3 — the EV charger. You add a 32 A charge point circuit in the same HMO. No AFDD required on that circuit.

Example 4 — an S-type RCD. A TT installation has a 100 mA S-type RCD at the origin. You may use the Table 41.5 Zs values for circuits it protects, because A4 says the table covers S-type too.

Example 5 — the protected stair. A contractor wants to run a new data and lighting cable up a protected stairway in a block. Only cables for fire safety systems serving that stair may go there. Re-route or put them in an enclosure with equal fire resistance (422.2.202), or ask the fire engineer.

Questions and answers

Chapter 6 — Part 5: Selection and erection of equipment

Part 5 has the most practical changes in A4: a new colour for functional bonding, RCD type hierarchy, new Section 545 (functional earthing for ICT), new rules for generators and PV in parallel, and new Chapter 57 for batteries.

6.1 Identification, notices and wiring (Chapters 51 and 52)

Conductor colours (Table 51)

Never use green/yellow for a functional conductor, and green/yellow sleeved pink is not allowed. NICEIC: functional conductors should preferably be pink along their length, and must be identifiable as pink at the terminations.

514.9.1 — the domestic chart exemption. A circuit chart (a diagram or schedule at the board) is normally required. In a dwelling you don't need one if the client is given the certificate with its schedules. A4 extends this from EICs to EICRs as well, as long as the report and its guidance for recipients are given to the client.

Notices must be "clearly and durably marked": a sticky label that will peel off in a year isn't enough.

521.10.202 Note 5 — premature collapse. Cable supports must stop cables falling and trapping people in a fire. The note makes clear this is about safe evacuation and firefighter access, not about keeping the circuit working.

522.6.202 to 522.6.204 — cables in walls. The text is now a table. No technical change. A cable 50 mm or more deep in a wall that has no metal parts needs no additional protection. Shallower cables still need the safe zones plus 30 mA RCD protection, or mechanical protection.

522.8.10 — buried cables. "Equivalent protection" for a buried cable means a duct with an N750 impact rating.

Table 52.4 — conductor classes. Class 1 = solid, class 2 = stranded, class 5 = flexible, class 6 = very flexible. Choose terminations to suit the class and shape (for example, ferrules on class 5 in a screw terminal if the manufacturer requires them).

6.2 Protective devices and RCDs (Chapter 53)

RCD selectivity. If there is an S-type RCD upstream, the RCD downstream must switch all live conductors including the neutral.

Table 537.4 lists disconnectors and switch-disconnectors separately and adds the RDC-PD.

The RCD hierarchy ("blinding"). DC fault current can stop ("blind") an RCD that wasn't designed for it. An RCD does not block DC from passing to the one above it. So never put a less capable type upstream of a more capable one:

1. Type AC (AC only) — lowest
2. Type A (AC + pulsating DC)
3. Type F (A + mixed frequencies)
4. Type B (all of these + smooth DC) — highest

No AC upstream of A, F or B. No A upstream of F or B. No F upstream of B. The only exception: the manufacturer declares the combination suitable.

6.3 Section 545 — functional earthing for ICT (new)

This is the old "clean earth" idea for computer, telecoms and data equipment, now written down. It is for function (stable signals, EMC), not safety.

• One functional bonding conductor can go straight to the MET.
• Several conductors go to a main functional earthing terminal (MFET), then one conductor from the MFET to the MET.
• Large installations may use a bonding ring.

6.4 Generators and PV in parallel (Section 551)

• Don't connect a source on the load side of an RCD that also protects other circuits, unless that RCD switches the neutral.
• Generating sets, including batteries, connect on the supply side of all final-circuit protective devices.
• The board (busbar) rating must be at least one of these four: 1. the rating of the incoming overcurrent device; 2. a single overcurrent device that all supplies pass through; 3. the maximum current set by an import/export limitation scheme; 4. the total connected load with no diversity, including export, plus a warning label.

6.5 Chapter 57 — stationary secondary batteries (new)

Covers fixed rechargeable batteries that supply the installation. Not covered: batteries inside products, plug-in UPS, emergency lighting, fire alarm batteries, machinery.

Examples

Example 1 — the office comms room. An IT company wants a clean earth to its server rack and two telecom cabinets. Run each rack's pink "FB" conductor to an MFET, then one conductor to the MET. The telecom bonding is 16 mm² copper (BS EN 50310). Do not use green/yellow.

Example 2 — the RCBO board with a Type B. A client's board has a Type AC main RCD. You add a heat pump that needs Type B protection. The Type AC upstream could be blinded by DC. Change the main switch to a non-RCD switch, or use a Type B upstream, or a combination the manufacturer declares suitable.

Example 3 — the home battery. A 13.5 kWh battery with a hybrid inverter in a semi-detached house. Fit it outside on the wall if possible (PAS 63100). Use a Type B RCD unless the inverter's manual says its separation allows another type. Isolators on the AC and DC sides. Label the origin, meter, board and inverter: "Isolate both AC and DC sources". Connect it on the supply side of the final-circuit devices.

Example 4 — board rating. A 100 A supply, a 63 A board, and PV + battery able to add 32 A. Option 4 (total connected load, no diversity) gives a rating need above 63 A, so the board would be overloaded. Use option 1 (board rated 100 A), or an export/import limitation scheme set at 63 A (option 3).

Example 5 — the shallow cable. You chase a socket drop 30 mm deep in a plaster wall, outside the safe zone. It needs mechanical protection. At 50 mm or more deep with no metal in the wall, it would need none.

Questions and answers

Chapter 7 — Part 6: Inspection and testing

The biggest change for everyday work: under A4, only C1 and C2 make an EICR Unsatisfactory. FI (further investigation) no longer fails the report, and "without delay" has gone from its wording.

What it means

653.1 — you produce the EICR taking account of the notes in Appendix 6 (the model forms and their guidance).

653.2 — the wording now says observations "might impair safety" or "might give rise to danger"; it refers to Schedule(s) of Inspection (plural, for larger installations), and adds (g) guidance for recipients: the client must get the notes that explain the report.

Photos and thermal images can be attached to support observations. A thermal image must show its temperature scale bar, or it proves nothing.

The classification codes

To make this clear, the A4 EICR splits observations into two tables:

1. C1 and C2 observations — any entry here makes the report Unsatisfactory.
2. C3 and FI observations — these don't change the outcome.

Why FI changed. NICEIC said FI was being misused: inspectors coded FI when they simply couldn't see or test something, which failed reports unfairly. Now:

• If you could not inspect or test something, consider recording it as a limitation (with the reason) rather than an FI.
• Use FI when you found something that needs investigating, for example a reading that doesn't make sense, or evidence of a problem you can't trace in the time available.
• With no records at all, a survey may be needed first.
• If you find something dangerous while investigating, it becomes C1 or C2.

Limitations (Section D) must include reasons: "Loft not accessed — boarded and stored items, client declined removal." The A4 form's limitation boxes say "including the reasons".

Warn long-standing clients. A landlord used to A3 might see an FI and think the report passed when it didn't (or the reverse). Explain: an A3 FI failed the report; an A4 FI doesn't.

Examples

Example 1 — the hidden junction box. On an EICR you find the upstairs lighting circuit has an insulation reading of 0.8 MΩ L-E, but everything you can see looks fine. You can't find the cause in the time you have. Code it FI: "Low insulation resistance on circuit 3, cause not found — further investigation is advised." Under A4 the report can still be Satisfactory if nothing is C1/C2. Explain to the client it still needs investigating.

Example 2 — the locked cupboard. The landlord's meter cupboard is locked and no key is available. You cannot inspect the tails or the main switch. That is a limitation, not an FI: "Intake cupboard locked, no key available on the day."

Example 3 — the hot terminal. A thermal camera shows a neutral terminal at 78 °C on a 32 A RCBO with an 18 A load. Take the thermal image with its scale bar visible, attach it, and code it C2 (it's potentially dangerous). The report is Unsatisfactory.

Example 4 — only C3s and an FI. You record three C3s (no SPD, old-style labels, no RCD on a lighting circuit in a dwelling where it was not required at the time) and one FI. A4 outcome: Satisfactory. Under A3 the FI would have made it Unsatisfactory.

Example 5 — missing bonding. No main bonding to the incoming gas pipe. That is C2 on either edition. Unsatisfactory.

Questions and answers

Chapter 8 — The A4 certificates: EICR, EIC and Minor Works

All three model forms in Appendix 6 changed. Use the form version marked 18.4 (A4), and write "BS 7671:2018+A4:2026" as the edition.

8.1 EICR (condition report)

Overall assessment: Satisfactory if there are no C1 or C2 observations. FI and C3 don't change it.

8.2 EIC (new work)

• One EIC can now cover additions or alterations that add new circuits.
• Guidance for recipients is numbered.
• AFDD guidance: the client should press the AFDD test button every six months (like an RCD).
• 133.1.2 agreements (equipment with no standard) are recorded as departures.
• The same new supply boxes: PNB, TN-C, IT, breaking capacity.
• Bidirectional and unidirectional devices share one British Standard, so you record only the standard number.

8.3 Minor Works (MEIWC)

• "Parts" are now called "Sections".
• A 133.1.2 box (equipment with no standard) is added.
• PNB, TN-C and IT earthing choices are added.
• New fields: breaking capacity of the protective device, and RCD time delay (for S-type).
• Ring end-to-end labels change from L/L, N/N, cpc/cpc to r₁-r₁, rₙ-rₙ, r₂-r₂.
• There is no field for a bidirectional device: write it in the circuit comments box.
• A Minor Works certificate is not for a consumer unit change. Use an EIC.

Examples

Example 1 — Section I on a PNB cottage. Earthing: TN-C-S (PNB). Supply device: BS 88-3, 80 A, breaking capacity 16.5 kA (read it from the fuse marking; if you can't see it, ask the DNO). Ze measured 0.22 Ω.

Example 2 — Section J on a TT bungalow. You measure the rod with a loop tester (following the safe method in Guidance Note 3). Record "Z_e 64 Ω" and tick Z_e as the method, not R_A.

Example 3 — the consumer unit swap. A client asks for "just a Minor Works" for a new consumer unit. No: a consumer unit change needs an EIC, with a full schedule of test results for every circuit.

Example 4 — adding a socket spur. You add one socket to an existing ring. A Minor Works is right. Record the ring end-to-end readings as r₁-r₁ 0.42 Ω, rₙ-rₙ 0.42 Ω, r₂-r₂ 0.70 Ω.

Example 5 — three new circuits. A kitchen extension adds a cooker circuit, a ring and a lighting circuit to an existing board. One EIC can cover all three additions.

Questions and answers

Chapter 9 — Part 7: Special installations or locations

Part 7 gains a new Section 716 for Power over Ethernet and a much larger Section 710 for medical locations; pools, caravan parks, marinas, solar PV, outdoor lighting and EV charging also change.

What it means

Part 7 sections add to or replace the general rules for places with higher risk. The general rules still apply unless Part 7 says otherwise.

The locations PoE must not pass through: 701 bathrooms, 702 pools, 703 saunas, 706 restrictive conductive locations, 710 medical locations.

Examples

Example 1 — the garden hot tub. A client wants an outdoor hot tub on a PME supply. Section 702 may apply. The tub must be to BS EN 60335-2-60. Consider the PME risk: people are wet and barefoot, so think about making the hot tub supply TT or follow the manufacturer's earthing advice.

Example 2 — PoE cameras in a care home. Cameras are fine in corridors, but the PoE cable must not run through a bathroom (701). Route it another way.

Example 3 — the EV charger. A 7 kW charger with built-in 6 mA DC detection (RDC-DD) can go on a Type A RCBO. Without it, use a Type B RCD or an RDC-PD to BS IEC 62955. No AFDD needed.

Example 4 — the PV inverter. On a roof PV install, fix the label "Isolate both AC and DC sides before servicing" at the inverter. It is now a requirement. Use H1Z2Z2-K solar cable and keep it off the roof surface.

Example 5 — the car park bollards. Lighting bollards in a shop car park, reachable by the public: 30 mA RCD, unless they are SELV, out of reach, or in a locked IK08 enclosure.

Questions and answers

Chapter 10 — The Appendices

The two appendix changes you will use most are Appendix 4 (buried cable ratings now split into D1 and D2) and Appendix 6 (the new A4 model forms, covered in Chapter 8).

What it means

Appendix 1 — British Standards. Lists the 370+ standards BS 7671 refers to. BS 7671 combines about 43 harmonised documents and is maintained by the committee JPEL/64.

Appendix 4 — current-carrying capacity. For buried cables there are now two reference methods:

The tables have separate columns for cables suitable for burial. Pick the right column, because a cable in a duct (D1) runs warmer than one buried direct (D2), so its rating is usually lower.

Appendix 6 — model forms. The A4 EIC, EICR and Minor Works with their guidance for recipients (see Chapter 8). 653.1 says you produce the EICR taking account of these notes.

Part 8 and Appendix 17 (energy efficiency). These came in with A2:2022 and are still in A4. Some websites list energy efficiency as an A4 change; it isn't new.

Examples

Example 1 — the garden office. A 6 mm² SWA runs 30 m to a garden office, in a duct under the lawn. Use the D1 column. If it were laid direct in the trench, you'd use D2.

Example 2 — the car park column. A cable to a lighting column is pulled through a buried duct. D1, and the duct must meet N750 impact rating if it is the "equivalent protection" (522.8.10).

Questions and answers

Chapter 11 — On site: what to do differently under A4

Use this as a checklist on every job until it becomes habit.

Before you start

• Orange book (A4) in the van; Guidance Note 3 up to date
• Work designed after 15 Oct 2026 or an EICR? Use A4 forms (18.4)
• Check the earthing type: PME, PNB (4 or fewer consumers, electrode within 40 m, label), TN-S, TT. Ask the DNO if unsure
• Note the supply fuse type, rating and breaking capacity (kA)
• Check the building type: HRRB (over 18 m or more than 6 storeys), HMO, student accommodation, care home → AFDDs on socket circuits up to 32 A

Designing and installing

• RCD hierarchy: no AC above A/F/B, no A above F/B, no F above B (unless the manufacturer says so)
• Battery or PV? Supply side of final-circuit devices, Type B RCD by default, isolate AC and DC, PAS 63100 location, "Isolate both AC and DC sources" labels
• Board rating checked against the four options; option 4 needs a warning label
• Bidirectional devices where power can flow both ways
• Functional earthing/bonding in pink or "FE"/"FB", never green/yellow
• Cables in walls: 50 mm deep with no metal, or safe zones + RCD, or mechanical protection
• Buried cables: D1 or D2 rating; N750 duct for equivalent protection
• No general cables in firefighting shafts or protected stairways
• Consumer unit change → EIC, never a Minor Works
• Notices clearly and durably marked

Inspecting (EICR)

• Can't inspect it? Limitation with the reason (Section D), not FI
• FI = "further investigation is advised", only for real unexplained findings
• Only C1/C2 make it Unsatisfactory
• Record the electrode as R_A or Z_e
• Photos and thermal images attached, with the scale bar
• Give the client the report with its guidance for recipients (this also covers the domestic chart exemption, 514.9.1)
• Long-standing client? Explain the A3 vs A4 FI difference

After the job

• Tell the client to press the RCD and AFDD test buttons every six months
• Keep your CPD record of A4 learning

Chapter 12 — Final revision quiz

Thirty mixed questions. Aim for 27 or more. Answers are in the table after the questions, so cover it first.

Part A — quick-fire

1. When was A3 withdrawn?
2. Do you need an exam for A4?
3. What is the max Ze for PNB?
4. Two clues that a supply is PNB?
5. Define a high-rise residential building.
6. Colour of a functional bonding conductor?
7. Can a Type A RCD be upstream of a Type B?
8. Default RCD type for a battery system?
9. Several functional bonding conductors go where?
10. Which board-rating option needs a label?
11. Does an FI fail an A4 EICR?
12. What does Section D now record?
13. Can you use a Minor Works for a consumer unit change?
14. How often should an AFDD test button be pressed?
15. PoE max current per conductor?
16. PV inverter label wording?
17. Third DC protection option for EV charging?
18. D1 vs D2?

Part B — scenarios

19. You inspect a 2-bed flat in an 8-storey block. The ring circuits have no AFDDs. How do you code it on an EICR?
20. A client's battery inverter is in the loft. What do you advise?
21. An EICR has two C3s and one FI. What is the outcome under A4?
22. You can't access the bathroom ceiling void. How do you record it?
23. A supply to three houses comes from a pole transformer with an electrode 30 m away. Which earthing box do you tick?
24. A heat pump needing Type B protection is added below a Type AC main RCD. What's the problem?
25. A server rack needs a clean earth. What colour and size (copper, unprotected)?
26. A designer wants to fit equipment with no standard. Which regulation and where is it recorded?
27. You attach a thermal image to an observation. What must it show?
28. An HMO tenant asks for an EV charger. Does it need an AFDD?
29. A cable runs 50 mm deep in a timber-stud wall with no metal parts. Does it need extra protection?
30. A landlord's old A3 EICR failed on one FI. Your A4 EICR has the same FI and no C1/C2. What do you tell them?

Answers

For NICEIC contractors, also do: the NICEIC Let's Get Technical Plus workbook (22 questions, answers on page 45; webinar reflection pages 40 to 43). Find it in the NICEIC portal → Support and services → Technical guidance. Keep your four The Wire CPD certificates with your training records.

Sources

• NICEIC The Wire webinars on BS 7671:2018+A4:2026, Parts 1 to 4
• NICEIC — Understanding BS 7671:2018+A4:2026
• Eland Cables — BS 7671 Amendment 4 overview
• IET — A4 model EICR form
• IET — all A4 model forms
• PAS 63100 (BSI, free) and ENA G12 Issue 5 (free)

The worked examples are made up for learning. Always check values against the orange book and Guidance Note 3.