Limits and boundaries when working on electrical installations

Extra-low voltage is normally not exceeding 50 V a.c. (or 120 V ripple-free d.c.). Above that, up to 1000 V a.c., is low voltage. 120 V is the d.c. ELV limit, a common mix-up.

Source: BS 7671:2018+A4:2026 (Part 2, definitions: voltage bands (paraphrased))

Low voltage is above extra-low voltage (50 V a.c.) and up to 1000 V a.c. The figures 120 V and 1500 V are the d.c. limits for ELV and LV, a common mix-up with the a.c. values. Normal 230 V and 400 V supplies are therefore low voltage. BS 7671, Part 2, definitions.

Source: BS 7671:2018+A4:2026 (Part 2, definitions: voltage bands (paraphrased))

Work outside your competence and job scope should not be attempted, but you should not ignore danger either. Keep others away if you can do so without risk, and report it straight away to the person in control of the premises so a competent person can deal with it. EAWR 1989, regulation 16, and HSWA 1974, section 7.

Source: Electricity at Work Regulations 1989 (Regulation 16); Health and Safety at Work etc. Act 1974 (Section 7, duties of employees)

Low voltage stops at 1000 V a.c., and any voltage above low voltage is high voltage, so 11 kV is HV. Reduced low voltage is the 110 V system used for site tools, and ELV is 50 V a.c. or below. Electricity Safety, Quality and Continuity Regulations 2002, regulation 1.

Source: Electricity Safety, Quality and Continuity Regulations 2002 (Regulation 1(5), interpretation: 'high voltage' and 'low voltage'); BS 7671:2018+A4:2026 (Part 2, definitions: voltage bands (paraphrased))

Adding a socket outlet is installation work that needs the knowledge and experience to do it safely, including testing before use. If you lack that, you must not take it on, even when a client asks. Politely decline and recommend a competent electrician. Having it checked later does not make unsafe work safe in the meantime. EAWR 1989, regulation 16.

Source: Electricity at Work Regulations 1989 (Regulation 16)