Electrical Safety Flashcards

What is the legal requirement for inspection and testing of temporary electrical installations on construction sites under BS 7671?

Answer: Periodic inspection and testing must be carried out at intervals not exceeding 3 months for construction site installations

BS 7671 Table 3A recommends a maximum interval of 3 months between periodic inspections and tests for construction site installations. This accounts for the harsh conditions, frequent modifications, and high risk of damage. An Electrical Installation Condition Report (EICR) must be produced after each inspection.

What is the danger of using a 230V supply for portable equipment on a construction site instead of 110V CTE?

Answer: The maximum voltage to earth is 230V rather than 55V, greatly increasing the risk of fatal electrocution particularly in wet or damp conditions

With a 230V supply, the full 230V appears between any live conductor and earth. With 110V CTE, the maximum voltage to earth is only 55V. The IET and HSE confirm that 55V is unlikely to cause a fatal shock even in adverse conditions, whereas 230V can kill instantly. This is why HSE guidance and BS 7671 mandate 110V CTE for portable construction site equipment.

What precautions are required when routing temporary electrical cables underground on a construction site?

Answer: Cables must be suitable for direct burial, laid at a minimum depth of 500mm, protected by cable covers or ducts, and marked with warning tape above

BS 7671 requires underground cables to be suitable for direct burial (SWA or equivalent), laid at a minimum depth of 500mm, mechanically protected by covers or ducts, and identified by warning tape or markers positioned above the cable. The route must be recorded on site plans to prevent future accidental damage during excavation.

Under PUWER 1998, what training must an operative receive before using electrical power tools on a construction site?

Answer: Adequate training in the safe use of the specific equipment, including pre-use checks, correct operation, and emergency procedures

The Provision and Use of Work Equipment Regulations 1998 (PUWER) require that anyone using work equipment receives adequate training covering the risks, correct methods of use, pre-use inspections, and actions to take in an emergency. This applies to all electrical power tools regardless of voltage. Training records must be maintained.

What should be done with an electrical tool that has failed its PAT test on a construction site?

Answer: It must be immediately withdrawn from service, labelled as defective, and either repaired by a competent person and retested, or disposed of

Equipment that fails a PAT test must be immediately removed from service and clearly labelled or tagged as defective to prevent anyone else using it. Under the Electricity at Work Regulations 1989 and PUWER 1998, it must then be repaired by a competent person and pass a retest before being returned to service, or be disposed of.

What is the significance of the IP rating 'IP65' on a construction site distribution board?

Answer: It means the enclosure is dust-tight (6) and protected against water jets (5) from any direction, making it suitable for harsh outdoor construction environments

The IP (Ingress Protection) rating system defined in BS EN 60529 uses two digits: the first (6) indicates complete protection against dust ingress, and the second (5) indicates protection against water jets from any direction. IP65 is suitable for outdoor construction site use where boards are exposed to dust, rain, and wash-down. BS 7671 requires equipment to be suitable for its environment.