Electrical work in South Africa is tightly regulated, for good reason. This guide is not a wiring manual: it explains the Certificate of Compliance that every installation needs, and the parts of SANS 10142-1, the wiring code, that affect how much cable a job takes and what size it must be. The wiring itself must be done or checked by a registered electrician.
The Certificate of Compliance
SANS 10142-1 notes that in South Africa it is a statutory requirement for every user or lessor of an electrical installation to have a valid Certificate of Compliance (CoC) for it. A CoC is issued by a competent person, someone authorised by the relevant body to test an installation, issue a test report and certify it, and it is only valid with a test report in the format the standard sets out. The standard asks for the tests to be done, and a test report completed, for each distribution board and supply.
For a builder this means: price the electrician’s inspection, testing and CoC into the quote, and don’t hand over a job until the CoC is issued.
Voltage drop
Current flowing through a long cable loses a little voltage on the way. SANS 10142-1 6.2.7.1 says the voltage drop from the point of supply to any outlet may not exceed 5% of the standard voltage. For 230/400 V supplies that is 11.5 V on single-phase and 20 V on three-phase.
Voltage drop matters most on long runs: an outbuilding, a borehole pump, a gate motor or a garden light far from the distribution board. The drop rises with the current and the length, and falls with a bigger cable.
Worked example: a 30 A single-phase load 30 m away on 6 mm² copper cable drops about 6.75 V, which is 2.93%, comfortably within 5%. The same load on a much longer run, or a smaller cable, can easily go over. The voltage drop calculator works this out and shows the smallest copper or aluminium size that stays within your limit. It checks voltage drop only: the cable must also carry the current safely, which the electrician checks.
Cable sizes for plug and light circuits
SANS 10142-1 table 6.27 limits the protection on small PVC-insulated conductors: 10 A on 1 mm², 16 A on 1.5 mm² and 25 A on 2.5 mm². So 2.5 mm² Surfix suits a 20 A plug circuit, and 1.5 mm² suits a 10 A or 16 A light circuit.
The standard doesn’t limit how many points a circuit may have, but a plug circuit’s anticipated load may not exceed 5 kW (6.15.2.2), and only circuits protected at 20 A or less may mix plugs, lights and fixed appliances (6.15.4.2). Each new plug point needs at least one socket-outlet to SANS 164-2 (6.15.1.1.1).
Surfix twin and earth is sold in 10, 50 and 100 m lengths. The plug points and Surfix cable calculator estimates how much of each size to buy from the number of points and the average run to each.
Ohm’s law on site
Many quick checks come down to Ohm’s law: current = power ÷ voltage. A 2 kW heater on 230 V draws about 8.7 A. Adding up the appliances on a circuit shows whether it is near the 5 kW plug-circuit limit. The Ohm’s law calculator handles these sums.
For the builder
- Plan points with the client early; chasing walls after plastering costs time and money.
- Keep stoves, geysers and aircons on their own circuits sized for them.
- Leave a clear route for cables in roofs and walls before ceilings close.
- Keep the CoC with the house documents and give a copy to the client.
This guide is general information for estimating. It is not engineering, legal or tax advice. Check SANS 10400 (the National Building Regulations) and your local municipality’s building control officer for your project.