Last edited 27 Jul 2021

Low voltage

According to Approved Document P - Electrical safetyDwellings: 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.’

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