Legislation & the Mains Position

01Statutory vs non-statutory

Two words come up all the time with legislation. Know the difference.

02The Building Regulations

• The Building Regulations 2010 apply in England and Wales (amended in England in 2013). Scotland and Northern Ireland have their own. Know the rules where you're working.
• Building work is defined in Regulation 3. It includes putting up or extending a building, installing or extending a controlled service or fitting, material alterations, cavity wall insulation, and underpinning foundations.
• The regulations are split into Parts, each with an Approved Document giving guidance. Part P is electrical safety in dwellings, but electrical work often touches other parts too. Chasing a wall or drilling a joist is Part A (structure). Going through a fire barrier is Part B (fire safety).

Electrician's Guide to the Building Regs · Building work, Regulation 3 and a list of regulations · pp.16–17 (new)

Electrician's Guide to the Building Regs · Table of all Parts and Approved Documents (A to S) · p.20 new · p.18 old The tutor said "highlight this table"

03Part P: scope and dwellings

Electrician's Guide to the Building Regs · 1.3.2 Scope of Part P · p.22 new Electrician's Guide to the Building Regs · Figure: scope of Part P (houses, flats, shop with shared or separate meter) · p.23 new · p.20 old

A skilled person doesn't have to hold a particular qualification. BS 7671 defines one as someone with adequate education, training and practical skills to see the risks and avoid the hazards. You prove it through qualifications, site experience, signed-off work and paperwork.

BS 7671 · Part 2 Definitions · "Skilled person" · p.44 new Key word: adequate

04Minor work vs notifiable work

Minor work doesn't involve a new circuit. It's an alteration or addition to an existing installation.

Electrician's Guide to the Building Regs · Notifiable work table · p.29 new · p.26 old "Highlight this table, this is important"

Electrician's Guide to the Building Regs · 1.6 Non-notifiable work (list) · p.30 new · p.27 old

Plugging in an extension lead isn't installation work, because it isn't fixed wiring. Replacing twin and earth with singles in conduit is a new circuit, so it's notifiable.

05Special locations and bathroom zones

BS 7671 Part 7 lists the special installations or locations. There are about 20, and the first is locations containing a bath or shower. Any room with a bath or shower, en-suites included, is a special location. A sink on its own doesn't count.

BS 7671 · Contents · Part 7 special installations or locations (701 = bath/shower) · p.3 new

Electrician's Guide to the Building Regs · Figure: extent of the special location in a bath or shower room (zones 0, 1, 2 and 600 mm) · next page after the notifiable table · p.30 new

Electrician's Guide to the Building Regs · Bathroom zone drawings: bath, shower tray, walk-in shower with no tray · pp.88–89 new · pp.82–83 old Electrician's Guide to the Building Regs · Swimming pool zones · p.93 new · p.87 old

06How to notify: the three routes

Notifiable work must be pre-notified to Local Authority Building Control (your local council) unless it's an emergency, or unless the person doing the work is in a competent person scheme. "Person" is a legal term meaning the firm or sole trader doing the work.

Electrician's Guide to the Building Regs · 1.4.1 Prior notification · 1.4.2 Competent person · 1.4.3 Registered third-party certifier · 1.4.4 Conditions of authorisation · pp.24–25 new · pp.21–22 old Electrician's Guide to the Building Regs · 1.4.5 Certification by a building control body · 1.4.6 Unregistered persons · p.27 new The tutor said to highlight 1.4.1 to 1.4.6. Exam questions ask about notification methods.

07Responsibility and penalties

• The primary responsibility for complying with the Building Regulations lies with the person carrying out the work (you, or your firm). Not the client.
• The installer, qualified or not, faces a fine of up to £5,000 plus £50 per day the non-compliance continues. That's the slide figure. The tutor said it's usually treated as unlimited, depending on how serious it is.
• The owner or person ordering the work may also face enforcement action requiring them to alter or remove work that doesn't comply.

08Approved Documents A, B, C, E, F, L, M

The tutor suggested writing your own summary of every Approved Document. It's good exam prep.

A: Structure (notches, holes and chases)

Electrician's Guide to the Building Regs · 10.1.1 Notches and holes in joists (table and figure) · p.166 new · p.168 old Electrician's Guide to the Building Regs · 10.1.2 Chases in walls · p.167 new On-Site Guide · Same joist and chase drawings with extra detail, including cables in walls buried at least 50 mm deep unless protected · pp.91–92 old edition

B: Fire safety

Fire barriers where cables pass through walls and floors, and smoke and heat alarm positions (including loft conversions). The tutor said she got smoke and heat alarm questions in her own Building Regs exam.

Electrician's Guide to the Building Regs · Section 10: Approved Document B, fire safety and smoke/heat alarms · from p.168 new

C · E · F · L

• C: site preparation and resistance to contaminants and moisture. Stop gas and water getting in where cables enter.
• E: resistance to the passage of sound. Cables running through sound insulation have a reduced current-carrying capacity. Take care with recessed downlights in ceilings that contain sound insulation.
• F: ventilation.
• L1: conservation of fuel and power in dwellings. Energy-efficient lighting and automatic control of outside lights.

M: Access to and use of buildings

• When rewiring or altering an existing circuit, you don't have to meet Part M. The finished installation just has to be no less accessible than it was before.
• When refurbishing or rewiring, it's fine to mount switches and sockets in keeping with the existing property.

Electrician's Guide to the Building Regs · Approved Document M: switch and socket heights figure · p.186 new · p.189 old The tutor said to highlight or tab this image

P: Permitted cable routes

Cables hidden in walls must run in the permitted zones: horizontally or vertically in line with an accessory, or near the wall's edges and corners. If a cable runs outside the zones, e.g. diagonally between two outlets, it needs extra protection, such as earthed metal conduit or RCD protection. Capping over cables in a chase is common, but it's extra mechanical protection rather than a requirement.

Electrician's Guide to the Building Regs · Permitted cable routes / zones figure (blue = OK, orange = needs extra protection) · p.43 new On-Site Guide · Similar permitted-zones figure

09EAWR 1989, BS 7671 and the On-Site Guide

EAWR 1989

The Electricity at Work Regulations 1989 came into force on 1 April 1990. They're a statutory instrument, so you can be prosecuted for breaking them. You mainly need Regulations 1–16, plus Regulation 29 (the defence). Get the free HSE guide HSR25 (search "HSR25"). NVQ assessors will expect you to know it.

BS 7671

The IET Wiring Regulations (the big orange book). Not a statutory instrument. Its fundamental principles cover protection for safety, design, selection of equipment, and erection, verification and inspection and testing.

On-Site Guide

A user-friendly, toolbox-sized handy reference from the IET. It's the book you'll carry every day. The big BS 7671 comes out when you're unsure.

ESQCR

The Electricity Safety, Quality and Continuity Regulations: the law the DNO (distribution network operator) follows for supplies and earthing.

BS 7671 Part 2 is the definitions section. In the exam, a definition sometimes sends you somewhere else. "Trunking" says see cable trunking, and "low voltage" is found under voltage. Practise using the book.

BS 7671 · Part 2 Definitions · pp.33–50 new BS 7671 · "Voltage": low voltage and extra-low voltage defined here · p.50 new

10The intake: from service head to circuits

• Adding a consumer unit (e.g. for a garage or EV charger): a Henley block (connector block) splits the tails after the meter. It's usually fitted by the DNO or supplier.
• Older consumer units used rewireable fuses (BS 3036), which have fuse wire in a carrier. You'll still find them.

11Earthing systems: TN-C-S, TN-S, TT

Reading the letters: T = Terra (earth) · N = Neutral · C = Combined · S = Separate.

Electrician's Guide to the Building Regs · Supply systems: expected maximum Ze values (TN-C-S 0.35 Ω, TN-S 0.8 Ω) · p.53 new · p.47 old Electrician's Guide to the Building Regs · Figure: cable sheath earth (TN-S), earthing and main bonding · p.55 new · p.49 old On-Site Guide · List of earth electrode types (rods, plates, etc.) for TT

The earth fault path

Suppose a line conductor comes loose and touches the metal case of a load. The fault current travels through the case, along the CPC to the MET, down the earthing conductor, back through the supply to the transformer star point, and round to the protective device, which trips. This is automatic disconnection of supply (ADS).

12Ze, R1 + R2 and Zs

Ze

External earth fault loop impedance: everything from the transformer, through the supply, up to the intake. Measured live with test equipment.

R1

Resistance of the circuit's line conductor.

R2

Resistance of the circuit's CPC (circuit protective conductor): the green/yellow cable from the consumer unit to every socket, light, spur and so on. (Rn is the neutral.)

R1 + R2

Found by a continuity test (method 1) on each final circuit, done dead.

Zs

Total earth fault loop impedance.

Zs = Ze + (R1 + R2)

Example (made-up figures, for practice):
TN-C-S supply, measured Ze = 0.30 Ω
Ring circuit continuity test, R1 + R2 = 0.52 Ω
Zs = 0.30 + 0.52 = 0.82 Ω
→ compare with the maximum permitted Zs for that protective device

The tutor said this will be covered again in more depth during the 18th Edition and inspection & testing modules. For now, just know what each term means.

13Protective devices

Consumer units contain devices that protect the final circuits (cable and equipment) against overloads, short circuits and earth faults.

OCPD = overcurrent protective device. It's the family name for CBs, RCBOs and fuses.

RCD rating IΔn = 30 mA
30% of 30 mA = 0.3 × 30 = 9 mA
→ keep total standing earth leakage on that RCD below ~9 mA

• Split-load board (CBs grouped under RCDs): if one circuit has an earth fault, the RCD trips every circuit on that side. An RCBO board trips only the faulty circuit. That costs more, but prices are coming down. A split-load board is still compliant, so you can't tell a client they must upgrade.
• Overload example: a 4-way extension lead full of 13 A appliances in one socket, or a kettle and a toaster on the same double socket. That causes overheating and melted accessories.

BEAMA guides (free online) · AFDDs and SPDs: where and why they're installed

Breaking capacity (Icn) is the largest fault current a device can safely break. A typical domestic CB or RCBO is 6 kA (6,000 A), and some are 10 kA or more. The DNO's main cut-out fuse is rated much higher, e.g. 33 kA.

14Circuit breaker types and fusing factor

On-Site Guide · Table 7.2.7: circuit-breaker types, tripping currents and applications · p.102 new · p.90 old "We use that quite a lot"

In is the device's rated current, e.g. 6 A or 32 A.

B6 lighting circuit (domestic lighting):
  current to trip within 0.4 s = 5 × In = 5 × 6 = 30 A

B32 ring final circuit (domestic sockets):
  current to trip within 0.4 s = 5 × 32 = 160 A

If there's also an RCD, it must trip within 300 ms (0.3 s)

A CB has two ways of tripping:

• A magnetic coil handles big fault currents fast.
• A bimetallic strip heats up and bends under overload, so it trips more slowly.

Circuit breakers have a fusing factor of 1.45
→ the bimetal starts its tripping action at 1.45 × In

B6:  6 × 1.45 = 8.7 A
So between 8.7 A and 30 A the B6 trips on a time curve;
at 30 A or more (5 × In) it trips within 0.4 s

For lighting, work out the circuit current from the lamps' power, e.g. 10 × 20 W = 200 W, then I = P ÷ V. Tomorrow's topics are earthing and bonding, circuit design, In, Ib, Iz and ring vs radial circuits.

15Fuses and ratings

Typical domestic circuits: 2 lighting (upstairs and downstairs), 2 socket circuits, cooker, shower, immersion heater, maybe a separate kitchen circuit. Smoke alarms are often taken off a lighting circuit. How many you can fit depends on the number of ways in the board, and RCDs take up ways too.

16All book references from Day 2

Tab these pages. "New" = green/orange editions, "old" = green/brown.

★ = the tutor specifically said to highlight or tab it. Page numbers are as given in the session. Check them against your own copy, because printings can differ slightly. BS 7671 amendments are organised by chapter and regulation number rather than page.

17Self-test

Unofficial student notes written from the Module 1 Day 2 webinar recordings (15/09/2026), shared free for fellow learners. Not produced or endorsed by the training provider. The afternoon recording starts partway through the session, so the service head and meter section is based on the slides shown. Always check against your course books, BS 7671 and your tutor. Spotted a mistake? Let us know so it can be fixed for everyone.

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