Low voltage
According to Approved Document P - Electrical safety – Dwellings: Low voltage is, ‘a voltage exceeding extra-low voltage, but not exceeding 1,000 V ac or 1,500 V dc between conductors, or 600 V ac or 900 V dc between conductors and earth.’ Where extra-low voltage is, ‘A voltage not exceeding 50 V ac or 120 V ripple-free dc, whether between conductors or to earth.’
The Illustrated Guide to Electrical Building Services, Third Edition (BG 31/2017), by David Bleicher & Peter Tse, published by BSRIA in 2014, suggests that: ‘Low voltage is a term used to describe 400 V three-phase and 230 V single-phase supplies. These are nominal voltages - the actual voltage may vary up to 10%. The intake to buildings that have a low voltage supply is usually provided by the electricity supplier in the form of an underground cable that emerges at a suitable point within the building. The cable is connected directly to the electricity supplier’s cut-out. Also known as a service head, this is a fused unit that protects the supplier’s infrastructure.’
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
Welsh and Scottish 2026 elections
Manifestos for the built environment for upcoming same May day elections.
Advancing BIM education with a competency framework
“We don’t need people who can just draw in 3D. We need people who can think in data.”
Guidance notes to prepare for April ERA changes
From the Electrical Contractors' Association Employee Relations team.
Significant changes to be seen from the new ERA in 2026 and 2027, starting on 6 April 2026.
First aid in the modern workplace with St John Ambulance.
Ireland's National Residential Retrofit Plan
Staged initiatives introduced step by step.
Solar panels, pitched roofs and risk of fire spread
60% increase in solar panel fires prompts tests and installation warnings.
Modernising heat networks with Heat interface unit
Why HIUs hold the key to efficiency upgrades.
Reflecting on the work of the CIOB Academy
Looking back on 2025 and where it's going next.
Procurement in construction: Knowledge hub
Brief, overview, key articles and over 1000 more covering procurement.
Sir John Betjeman’s love of Victorian church architecture.
Exchange for Change for UK deposit return scheme
The UK Deposit Management Organisation established to deliver Deposit Return Scheme unveils trading name.
A guide to integrating heat pumps
As the Future Homes Standard approaches Future Homes Hub publishes hints and tips for Architects and Architectural Technologists.
BSR as a standalone body; statements, key roles, context
Statements from key figures in key and changing roles.
Resident engagement as the key to successful retrofits
Retrofit is about people, not just buildings, from early starts to beyond handover.