Ask the experts/Technical
N
Fully charged Main equipotential bonding in a block of flats
Snags & Solutions A practical guide to everyday electrical problems, now updated to Amendment No 1 of BS 7671 Snag 16
Main equipotential bonding must be provided in each flat in a block of flats.
‘Snags & Solutions’, NICEIC’s problem solving book, is available in three parts, which cover many commonly-encountered electrical installation problems. All parts have now been updated, where appropriate, to take account of the requirements of Amendment No 1 to BS 7671: 2008 (17th Edition of the IET Wiring Regulations), which was published on 1 July 2011 and came into full effect on 1 January 2012. Part 1 of Snags & Solutions addresses 53 problems relating to earthing and bonding, Part 2 covers 55 problems relating to wiring systems, and Part 3 covers 52 problems relating to inspection and testing. The books are available from NICEIC Direct. To give an indication of the value of these books, a snag and solution is being covered in each issue of Connections. This issue addresses a snag from Part 1 – Earthing and bonding, relating to the main protective bonding arrangements applicable in a block of flats.
snags and solutions A PRACTICAL GUIDE TO EVERYDAY ELECTRICAL PROBLEMS
Part 3
inspection and testing
COMPLIES WITH
50
Winter 2011-12 NICEIC Connections
50_51_technical 2 snags.FINAL.indd Sec1:50
NICEIC is occasionally asked whether main equipotential bonding should be provided for every flat in a block and, additionally, at the intake position.
Solution In each installation main protective bonding conductors must connect all the extraneous-conductive-parts to the Main Earthing Terminal (MET). (Regulation 411.3.1.2 refers). The requirements apply individually to each flat which has its own supply of electricity given in accordance with the Electricity Safety, Quality and Continuity Regulations: 2002 (ESQCR). This is because the consumer’s electrical equipment of each such separately-supplied unit (for example, the consumer unit, wiring system and accessories) is an ‘electrical installation’ as defined in Part 2 of BS 7671. Therefore, main bonding conductors complying with Section 544 are required to connect all the extraneous-conductive-parts within the flat to the MET. The main bonding connections to extraneous-conductive-parts such as gas, water, oil or other services need to be made as near as practicable to their points of entry to the respective flat, in accordance with the detailed requirements of Regulation 544.1.2. The same requirements that apply to the installation of each separately-supplied flat also apply to the electrical installation in the common parts of the multi-occupancy premises (eg the landlord’s areas). The extraneous-conductive-parts within such areas must be connected to the MET of that particular installation. The supply arrangements may vary from those shown in the figure in a number of ways. For example, the meter operator’s metering equipment may be grouped together at a common location, and/or the supplies may not be PME. The principles of application of Regulation 411.3.1.2, however, remain the same. The electricity distributor may have particular requirements for main bonding, above and beyond those of BS 7671, especially where PME conditions apply. Most electricity distributors publish notes of guidance and/or drawings to explain any such requirements.
www.niceic.com
20/1/12 10:04:50