Construction site assembly
An enclosed assembly of switchgear and controlgear built for use on a construction site, either transportable or mobile. BS EN 61439-4 is the product standard, and it shortens the name to ACS. BS 7671's Section 704 covers the site's own supplies, while site offices, canteens, cloakrooms and toilets stay under its general rules.
Using Construction site assembly in context
Reviewed
A distinction worth remembering
A centre-tapped reduced-voltage supply limits voltage to earth compared with a conventional mains arrangement. It does not make damaged tools, wet connections or unsuitable cables acceptable. Site selection and inspection still matter.
Questions to take further
- How can I revise Construction site assembly beyond the definition?
- Explain what Construction site assembly describes, compare it with a related term and use it in a topic question. State any assumptions and what evidence you would need before applying the idea to real work.
Sources
- HSE: electricity on construction sites — Reduced-voltage site supplies and the continuing need for safe equipment.
- HSE: Electrical safety on construction sites (HSG141, second edition, 2023) — Voltage choice, 230 V precautions, user checks, leads, RCD bypass and sump pump cases, PME, and distribution system inspection.
- HSE: Health and safety in construction (HSG150) — What cordless and 110 V centre-tapped supplies do for the risk, and where mains equipment fits.
- HSE: work using electrically powered equipment — Suggested initial inspection intervals for 110 V and 230 V construction equipment.
- HSE: examples of reportable incidents — How RIDDOR treats a struck cable on a 110 V centre-tapped supply.
- NAPIT in Professional Electrician: temporary electrical installations on construction sites (2020) — Site distribution units, BS EN 60309-2 keying and 110 V outlet ratings.
- legislation.gov.uk: Electricity at Work Regulations 1989, regulation 4 — The Great Britain duty to maintain systems, so far as is reasonably practicable, to prevent danger.
- legislation.gov.uk: Electricity at Work Regulations (Northern Ireland) 1991 — Northern Ireland's own electricity at work regulations.
Where Construction site assembly fits in the learning path
The Special Locations section covers these units:
- Wet locations
- Sites, farms and shows
- Moving and temporary
- Heating, lighting and the outdoors
Curriculum mapping: C&G 2382-26 (BS 7671 Part 7).
See this section in the full curriculum
This section is on the Plus path. Lesson availability depends on content review and your learning path.
Read, practise, return
1. Read it in context
- 110 V Site Power ToolsSparks Basics
2. Try recalling, then explore practice
Use the memory prompt below to connect the vocabulary.
Follow a topic above to explore how the term is used, then use the learning entry below to find your path.
3. Return to the meaning
After reading or practising, explain the idea in your own words, then check what you remembered.
Recall a related term
Which term fits this definition? Say it to yourself, then reveal it. This is a memory prompt, with no score or saved result.
A site supply arrangement that lowers the voltage available to a person touching one live conductor and earth. A common 110 V centre-tapped transformer has an earthed midpoint, leaving about 55 V from either line to earth. Contact between both lines can still expose someone to 110 V, so damaged tools remain unsafe.
Reduced low voltage
Read the Reduced low voltage entryCompare related terms
Open a meaning to compare its role with Construction site assembly, or follow its full entry.
Reduced low voltage
A site supply arrangement that lowers the voltage available to a person touching one live conductor and earth. A common 110 V centre-tapped transformer has an earthed midpoint, leaving about 55 V from either line to earth. Contact between both lines can still expose someone to 110 V, so damaged tools remain unsafe.
Read the Reduced low voltage entryRCD — Residual Current Device
A protective device that detects an imbalance between the currents in the live conductors passing through it. In a single-phase circuit this usually means comparing line and neutral current. It disconnects when the residual current meets its operating conditions. A 30 mA RCD can provide additional shock protection, but it does not prevent every kind of electric shock or replace safe isolation.
Read the RCD entrySpecial location
A place or type of installation where the risks are higher or different, so BS 7671's Part 7 adds to or changes its general rules. Bathrooms, swimming pools, construction sites, caravan parks and EV charging all have their own section there. Read that section before designing or testing, because the general parts still apply unless it changes them.
Read the Special location entryA definition is a start. Using it in a real question is where it sticks.