9.1 Temporary Electrical Installations, Distribution Boards & SANS 10142 (CR 24)
Key Takeaways
Construction Regulation 24 applies in addition to the Electrical Installation Regulations 2009 and the Electrical Machinery Regulations 1988, and lists five duties, (a) to (e), with no subregulations.
CR 24(c) requires control of all temporary electrical installations to be designated to a competent person appointed in writing, and CR 24(d) requires those installations to be inspected at least weekly with findings recorded in a register.
CR 24(e) requires all electrical machinery to be inspected daily by the authorised operator or user, using a checklist, with findings recorded in a site register.
Under the Electrical Installation Regulations, installation work is done by registered persons for registered electrical contractors, and a certificate of compliance is issued for completed or altered installations.
Socket outlet and portable equipment circuits need earth leakage protection of not more than 30 mA (SANS 10142-1), and overhead lines need the owner's safe distance, exclusion zones and goalposts with height limiters.
1. The Statutory Framework for Electricity on Site
Temporary electrical reticulation on construction sites faces rain, mud, mechanical damage from plant, repeated extension and alteration, and heavy use of hand tools. Three sets of rules apply together:
- Construction Regulation 24 (electrical installations and machinery on construction sites), which applies in addition to the Electrical Installation Regulations, 2009 and the Electrical Machinery Regulations, 1988.
- The Electrical Installation Regulations, 2009 (EIR), which govern who may do electrical installation work and require a certificate of compliance (CoC) for installations, issued by a registered person.
- The Electrical Machinery Regulations, 1988 (EMR), which govern electrical machinery, including work on or near live equipment and safety clearances from overhead power lines.
The technical standard with which low-voltage installations, including temporary site installations, must comply is SANS 10142-1 (The wiring of premises – Low-voltage installations).
2. What Construction Regulation 24 Requires
CR 24 has no subregulations; it lists five duties, (a) to (e). A contractor must ensure that:
- (a) before construction starts and while it progresses, adequate steps are taken to ascertain the presence of, and guard against danger from, any electrical cable or apparatus under, over or on the site;
- (b) all parts of electrical installations and machinery are of adequate strength to withstand construction site conditions;
- (c) the control of all temporary electrical installations is designated to a competent person appointed in writing;
- (d) all temporary electrical installations are inspected at least once a week by a competent person, with the findings recorded in a register kept on site; and
- (e) all electrical machinery is inspected by the authorised operator or user daily, using a relevant checklist before use, with the findings recorded in a register kept on site.
Exam traps: the weekly inspection in (d) covers the installation (boards, cables, connections, earth leakage units); the daily check in (e) covers machinery (tools, mixers, saws) and is done by the user. CR 24 does not itself prescribe monthly tool tests, IP ratings or board heights; those come from SANS 10142-1, manufacturers and client specifications.
3. Who May Do the Work and Certification
Under the EIR, electrical installation work must be done by, or under the general control of, a registered person (electrical tester for single phase, installation electrician, or master installation electrician, depending on the work) working for a registered electrical contractor. A registered person must issue a certificate of compliance when an installation is completed or altered, backed by a test report. On a construction site, that means a CoC for the temporary supply and further test reports or CoCs as the temporary network is extended to new areas, tower cranes, hoists or batching plants. The CHSM should keep copies in the health and safety file with the CR 24(c) appointment.
4. Distribution Boards and Earth Leakage Protection
Good practice for site distribution boards, drawn from SANS 10142-1 and typical client specifications:
- Enclosure: robust, weatherproof and suitable for outdoor use (an ingress protection rating appropriate to dust and water jets is commonly specified), with intact gland plates and socket covers.
- Position: mounted on a stand or wall, off the ground and out of standing water, with clear access.
- Security: lockable, with keys held by the competent person and authorised electricians.
- Earth leakage protection: socket outlets and portable equipment circuits protected by earth leakage devices with a rated residual operating current not exceeding 30 mA; devices of 100 mA or more protect against fire, not against fatal shock.
- Testing: users press the test button before use, and the competent person's weekly inspection (CR 24(d)) includes the earth leakage units, with instrument trip tests at the frequency the electrical contractor specifies.
- Labelling: voltage warnings, circuit identification and the name and contact details of the competent person.
5. Site Cables and Portable Equipment
- Cable selection and routing: armoured cable for fixed sub-mains; flexible cords only where flexibility is needed, kept short and off wet ground. Buried cables should be at a suitable depth, marked and protected; overhead runs should be supported at heights that keep them clear of vehicles and plant. Road crossings use cable protectors or ducts.
- Damaged cords: taped joints, cut sheaths and broken plugs mean immediate withdrawal; repairs must be done by a competent person with proper connectors.
- Reduced-voltage and double-insulated tools: 110 V centre-tapped-earth supplies limit the voltage to earth to about 55 V, and Class II (double-insulated) tools reduce dependence on the earth conductor; both still need earth leakage protection on the supply.
- Daily checks and records: under CR 24(e), the operator or user inspects electrical machinery daily against a checklist and records it. Many sites add a periodic tagging inspection of portable tools by a competent person.
6. Overhead Power Lines and Buried Cables
CR 24(a) requires the presence of cables and apparatus on, under or over the site to be established and guarded against. In practice:
- Overhead lines: obtain the line owner's (Eskom's or the municipality's) written safe working distance for each line, because the EMR clearance requirements increase with voltage; mark exclusion zones; erect goalposts with height limiters on both sides of every crossing point; and plan crane, concrete-pump and tipper movements so that booms and loads cannot enter the exclusion zone, allowing for swing and conductor sag.
- Buried cables: treat drawings as indicative, scan with a cable avoidance tool and signal generator, expose cables by hand or vacuum excavation before mechanical digging near them (see Section 8.1 and CR 13(2)(g)), and use the cable owner's permit system for work near live cables.
7. Summary Matrix
| Topic | Source | Requirement |
|---|---|---|
| Locate and guard against cables and apparatus | CR 24(a) | Before and during construction |
| Equipment robust enough for site conditions | CR 24(b) | Construction-grade installations and machinery |
| Control of temporary installations | CR 24(c) | Competent person appointed in writing |
| Inspection of temporary installations | CR 24(d) | At least weekly; register on site |
| Inspection of electrical machinery | CR 24(e) | Daily by operator or user; checklist; register |
| Installation work and CoC | EIR 2009 | Registered person and registered electrical contractor; CoC for completed or altered installations |
| Shock protection | SANS 10142-1 | Earth leakage devices of not more than 30 mA on socket and portable equipment circuits |
| Overhead lines | EMR 1988; line owner | Safe distance by voltage; goalposts and height limiters |
8. The CHSM's Electrical Checks
The CHS Manager verifies the CR 24(c) appointment and the CoC, reads the weekly CR 24(d) register and samples the CR 24(e) daily checklists, tests that earth leakage units trip, looks for damaged or taped cords, and checks that every crossing under an overhead line has goalposts and a recorded safe distance.
A principal contractor on a commercial construction project installs a temporary main site distribution board (DB) fed from a 400V municipal bulk supply point. The site distribution board is placed directly on the ground in an unpaved laydown area, fitted with a standard 100 mA earth leakage circuit breaker, and kept unlocked to allow artisans quick access. During a statutory compliance audit, how must the Construction Health and Safety Manager evaluate this installation under Construction Regulation 24 and SANS 10142-1?
The installation is acceptable during the structural civil phase provided the distribution board is retrofitted with a 30 mA earth leakage unit before internal electrical reticulation begins.
The installation complies because the 100 mA tripping sensitivity is legally permitted for industrial construction sites to prevent nuisance tripping caused by heavy plant.
The installation complies with CR 24 provided that the main circuit breaker is rated above 60A and the supply transformer is registered with the local municipal supply authority.
Unsafe: the board must be weatherproof, lockable and raised, sockets need 30 mA earth leakage protection, and CR 24(c)-(d) require control and weekly inspection.
An earthworks contractor operates a 30-tonne articulated dump truck and a 25-tonne mobile crane on a site intersected by an active 11 kV overhead powerline. The site supervisor plans to route construction traffic directly under the conductors without physical clearance controls, asserting that crane booms will remain lowered while traveling. Under the Electrical Machinery Regulations (EMR 15) and Construction Regulation 24, what mandatory statutory clearance and physical control measures must be enforced?
Get the line owner's safe working distance, keep plant outside it, and erect goalposts and warning signs on every approach.
A minimum clearance of 5.5 meters must be maintained, but physical goalposts are only required if line voltages exceed 132 kV.
A clearance of 1.5 meters is enough for any distribution line, and warning flags tied directly to the conductors are sufficient.
Clearance restrictions do not apply to mobile machinery during transit provided travel speeds do not exceed 15 km/h and hazard lights are illuminated.
During a routine site inspection, the CHS Manager inspects the masonry subcontractor's portable electrical tools. The inspection reveals two 230V handheld angle grinders with cracked outer casings, power leads joined with PVC electrical insulation tape, and no inspection tags attached. The subcontractor foreman claims the tools are only six weeks old and argues that portable tools only require formal inspection every six months. Under Construction Regulation 24(2), what is the correct legal standard and required action?
Withdraw the tools: CR 24(e) requires daily recorded user inspection, and damaged casings and taped cords must be properly repaired or the tools scrapped.
The tools may continue in service until the end of the weekly shift provided the taped joints are elevated off the concrete slab and wrapped with self-amalgamating waterproof tape.
The tools are acceptable under the OHS Act provided the subcontractor maintains a valid Letter of Good Standing under COIDA and workers wear heavy-duty rubber gloves.
The tools may remain on site if connected to an isolating transformer, and six-month inspection intervals are legally compliant for tools purchased new within the same financial year.
Sections you finish are checked off in the contents.