Prepare for the South African wireman's licence by practising applied decisions under SANS 10142-1: coordinating cables with protective devices, separating earthing, bonding and earth leakage functions, and completing Certificate of Compliance test records in a defensible order.
What the licence authorises versus what a COC signature commits you to
The wireman's licence relates to authorised electrical installation work in South Africa; a Certificate of Compliance signature is a separate professional act attesting that an installation conforms to the wiring code.
Keep these two ideas separate in your notes. Authorisation to work on installations is an administrative and legal status, while a COC is a technical declaration with your name attached to specific stated items. A useful drill for any short case description you study is to answer in two layers: what the person may lawfully do, and what that person is formally attesting when signing. Write each layer as a single sentence until the separation is automatic.
Because registration and permit details are administrative matters, verify current categories, forms and processes directly with the Department of Employment and Labour rather than relying on older course notes. For study purposes, focus on the concept that signing a compliance certificate is a statement about conformity you can justify with test results, not a formality that follows the physical work. This framing shapes how you answer scenario questions about responsibility.
- Authorisation: the legal capacity to perform or supervise installation work
- COC: a documented conformity declaration tied to specific inspection and test results
- Practical habit: before signing anything, identify which items on the certificate your evidence actually covers
Earthing, bonding and earth leakage are three different protections
Earthing connects exposed metalwork to earth, equipotential bonding connects metalwork together, and earth leakage protection detects residual current and disconnects. Conflating them produces wrong answers in both theory and inspection questions.
Earthing gives fault current a low-impedance return path so that a protective device operates; bonding limits touch voltage differences between conductive parts; earth leakage protection senses imbalance between live and neutral currents and trips independently of fault path impedance. Each has a different conductor, a different test and a different failure mode. Write the three functions as a table in your notes with the verification test for each, so that when you practise a scenario you can trace a described symptom to the protective function it threatens before choosing a remedy.
Consider a metal sink pipework next to a socket circuit. Adding an earth electrode under the sink does nothing for touch voltage between the pipe and the circuit; bonding the pipework to the main earthing terminal is the relevant measure. Conversely, a broken protective conductor to an appliance frame may still let the earth leakage device stay quiet until someone touches the frame under certain conditions. Trace each symptom to the function it threatens before choosing a remedy.
- Earth fault path: relies on continuity of the protective conductor
- Bonding: controls potential differences between accessible metalwork
- Residual current protection: disconnects on current imbalance, complementing rather than replacing the other two
Worked scenario: breaker sized to the appliance, not the cable
Protection must be coordinated with the cable's current-carrying capacity under its installation conditions. A scenario where the breaker protects the appliance but overloads the cable tests whether you apply coordination, not component knowledge.
Scenario: a cooker circuit is run in 6 mm² cable partly buried in insulated wall material, and the electrician installs a 40 A breaker because the hob manufacturer specifies a 40 A supply. The mistake is treating the appliance requirement as the protection decision. Cable current-carrying capacity falls with grouping, ambient temperature and thermal insulation, so a 6 mm² cable in adverse conditions may not safely carry 40 A even though the same cable size elsewhere could. The correct decision is to check the cable's derated capacity against the proposed breaker first, and only then reconcile with the appliance requirement — for example by upsizing the cable, rerouting it out of the insulation, or confirming the appliance accepts a lower-rated protective device.
This matters because the failure mode is invisible: the installation works normally for years while the cable runs hot during sustained loads. In an exam answer, state the chain explicitly: installation conditions, correction factors, derated capacity, then protection rating, then appliance compatibility. Write the same chain for a socket outlet circuit on a common residual current device so you practise it in both directions — from cable up to protection, and from a chosen device back down to whether the cable survives.
- Mistake: selecting the protective device from the appliance nameplate alone
- Better decision: derate the cable for its actual installation conditions, then match protection to the cable
- Why it matters: overload damage to concealed cable develops without visible warning
Reading the wiring code as decision rules rather than isolated clauses
SANS 10142-1 is best studied as a network of conditions: each requirement answers a question about the installation. Rebuild clauses as if-then decisions so you can apply them to unfamiliar scenarios in the exam.
Pick a small set of themes — conductor selection, protection coordination, earthing and bonding, isolation and switching, and special locations — and for each theme write the code requirement as a decision with its trigger condition. For example, instead of memorising a bonding conductor size in isolation, note what it connects to and what it must be compatible with. This transforms revision from recall of numbers into reconstruction of reasoning, which is what scenario-based practice demands when the exact clause is not quoted for you.
Voltage drop, maximum demand and diversity are the themes where decision-rule study pays off most. Practise stating, in one sentence each, why maximum demand is estimated before conductor sizing, why diversity assumptions differ between a dwelling and a small workshop, and how a voltage drop calculation closes the loop after a cable size is chosen. If you can articulate the order of these decisions and what each one protects, you can handle a question that changes the building type without needing a memorised example to match.
- Rewrite each studied clause as: trigger condition, required decision, reason
- Practise the decision order: demand estimate, cable size, voltage drop check, protection coordination
- Test yourself by changing one variable (building type, route length, load) and re-running the chain
Worked scenario: a distribution board replacement and incomplete test evidence
Replacing a distribution board is a compliance event requiring verified continuity, earth leakage operation and recorded results. The plausible mistake is signing a certificate where test documentation does not support every stated item.
Scenario: an old board with defective, non-compliant wiring is replaced; the electrician re-terminates existing circuits, fits new residual current protection, and the installation works. Before issuing the compliance documentation, the mistake would be to record only that the board was replaced, without continuity readings for each circuit's protective conductor, insulation resistance results, and confirmation that each residual current device operates under test. The better decision is a defined test sequence: verify protective conductor continuity circuit by circuit, test insulation resistance, confirm earth loop impedance is consistent with the protection used, and operate each residual current device, recording values against identified circuits.
Why it matters: a re-terminated old circuit may look correct at the board while its protective conductor is broken mid-run, and only a continuity test reveals it. In the exam, answers that list tests in a logical order — continuity first, then insulation, then earth fault loop, then device operation — demonstrate understanding of why the order exists: you must confirm the safety path before energising for further tests. Build this sequence into your notes as a fixed template you can quote and justify.
- Mistake: documenting the replacement without per-circuit test evidence
- Better decision: run the standard test sequence on every affected circuit and record readings against circuit identifiers
- Why it matters: a defective protective conductor is invisible at the board and only continuity testing exposes it
Exercise: mock inspection of a written installation description
Use a written description of a small domestic installation and audit it against a checklist, scoring yourself on observation, reasoning and documentation. Repeat with changed variables until your rubric scores are stable.
Write or obtain a half-page description of a dwelling: supply, distribution board, a socket circuit, a lighting circuit, a geyser circuit, external metalwork and an outbuilding supply. Audit it as if preparing a compliance certificate. Expected observations include: identification of each protective device and the cable it protects, presence of bonding to relevant metalwork, residual current protection coverage for socket circuits, and whether any circuit's load, length or route raises a voltage drop or derating question. Deliberately plant one coordination fault and one documentation gap in your written description so you have known targets to find.
Score yourself against this rubric, three points per item: (1) did you trace each cable to its protective device and check coordination; (2) did you separate earthing, bonding and residual current findings rather than merging them; (3) did you list the test sequence with a purpose stated for each test; (4) did you identify what the certificate would and would not cover; (5) did you flag any item needing verification rather than guessing. A stable score of 13 or more out of 15 across two different installations is a reasonable learning milestone — it measures your audit discipline, not a predicted exam result. Rotate in a workshop or outbuilding description to vary diversity and bonding questions.
- Plant one cable-protection mismatch and one missing record in your practice description
- Score three points each on coordination tracing, function separation, test sequence, certificate scope, and verification honesty
- Repeat with a different building type until scores stabilise
A phased preparation sequence and concrete readiness checks
Sequence preparation in four phases: rebuild the code themes as decision rules, drill calculation chains, run mock inspections, then simulate full scenario answers under time. Finish only when readiness checks pass consistently.
Phase one, over your first stretch of study: convert each SANS 10142-1 theme into decision rules as described above, keeping a running list of triggers and reasons. Phase two: drill the calculation chains — maximum demand with diversity, cable sizing with correction factors, voltage drop, and protection coordination — on paper, one chain per sitting, until the order is automatic. Phase three: run the mock inspection exercise with several different installation descriptions. Phase four: write full answers to scenario questions under time, forcing yourself to state the decision chain and its justification in prose.
Treat these as readiness checks rather than predictions: you can recite the earthing, bonding and residual current distinction with the correct test for each; you can complete a coordination chain in both directions without notes; you can list the test sequence for a board replacement with a reason per test; and your mock inspection rubric scores are stable across two building types. For administrative questions about registration categories, application processes and current requirements, rely on the Department of Employment and Labour as the authoritative source rather than secondary summaries, since those details change and sit outside the technical syllabus.
- Phase 1: themes to decision rules; Phase 2: calculation chains; Phase 3: mock inspections; Phase 4: timed scenario answers
- Readiness check: three-function distinction with matching tests, stated from memory
- Readiness check: stable self-audit rubric scores across varied installation descriptions
| Protective measure | What it controls | Typical verification | Common confusion to avoid |
|---|---|---|---|
| Earthing (fault path) | Enables fault current to flow so overcurrent protection operates | Protective conductor continuity | Assuming an earth electrode substitutes for circuit protective conductor continuity |
| Equipotential bonding | Limits voltage differences between accessible conductive parts | Continuity of bonding conductors to the earthing terminal | Treating bonding and circuit earthing as the same conductor with the same purpose |
| Earth leakage (residual current) protection | Disconnects on current imbalance indicating leakage to earth | Device operation test with recorded response | Believing residual current protection removes the need for a sound earth fault path |
| Overcurrent protection coordination | Ensures the cable, not just the load, is protected | Comparison of derated cable capacity with device rating | Sizing the breaker from the appliance nameplate instead of the cable conditions |
References and further reading
Use these references to explore the concepts and check the latest information from the relevant organizations.
Continue your preparation
Interactive circuit lab
Use the schematic as the electrical model, rotate the PCB view to recognise physical components, then vary the live simulator to test how resistance changes current. The PCB view is a learning representation and is not a substitute for the schematic or installation drawing.
Source, load, and measurement path
A source supplies a series resistor and lamp, with a meter used to observe the circuit response.