IET Wiring Regulations, 17th Edition - Amendment 3

Craig Smith, Associate Director of Rolton Group, has studied and summarised the latest amendments the IET Wiring Regulations, 17th Edition below to help others get to grips with the changes.

On the 1st January 2015, the 17th Edition Wiring Regulations BS7671 were updated under the new title ‘IET Wiring Regulations 17th Edition Amendment 3’; this new edition and accompanying ‘On Site Guide’ are now issued under a yellow cover. The new regulations came into effect on 1st July 2015 and the main headline changes / effects on electrical installations are as follows:-

• All projects / installations that are designed from 1st July 2015 shall comply with this new edition.
• Electrical Installation Condition Report (EICR) of installations from 1st July 2015 should demonstrate compliance with these new regulations.
• Any projects, design work or installation complete prior to the end of June 2015 may follow either Amendment 2 or Amendment 3.
• New requirements do not apply to domestic style consumer units until 1st January 2016.

As always with changes in regulations, there are a number of minor tweaks to regulations, clauses, and text, though more often than not these changes are to realign with industry or to clarify and further enhance the content of the regulation. Amendment 3 does contain a number of fundamental changes, however, that as an industry we all need to be fully aware of.

First, regulations coming from Europe CENELEC standards now have a 100 series reference and UK standards now have a 200 series reference; older regulations remain unaffected but will be revised in the next edition. The term ‘Competent Person’ has also been changed to a revised title ‘Skilled Person (Electrically)’, and ‘Instructed Person (Electrically) has replaced ‘Instructed Person’.

Earth Loop Impedance (ELI) Zs values are now subject to a correction factor known as Cmin of 0.95. In essence this has been done to take account of supply voltage levels, which often fluctuate. This will obviously reduce the tabulated values of Zs by 5%. Part 4 of Amendment 3 details these changes and tables 41.2, 41.3, 41.4 and 41.6 have been revised to suit.

All sockets with a rating of up to and including 20A must be RCD protected under the new regulations. There are only two exceptions to the rule and these are in cases where, other than for installations in a domestic dwelling, a documented risk assessment determines that an RCD is not necessary, and for a specifically labelled or otherwise suitably identified socket outlet provided for the connection of a particular item of equipment. All sockets up to and including 32A that could be used to supply portable equipment outside (externally) must now be RCD protected via a 30mA device. For all installations in commercial premises that omit RCD protection, the designer of the installation must obtain a documented risk assessment stating that RCD protection is not required. This risk assessment must accompany the Electrical Installation Certificate.

Domestic style consumer units now have to be constructed from a non-combustible or not readily combustible material when fitted in domestic premises, though commercial premises are not affected by this new regulation. The consumer unit can be enclosed within a non-combustible or not readily combustible cabinet. Whilst steel is footnoted, this is not meant to exclude the consideration or use of non-combustible plastic.

In the past a number of cases have been sighted where firefighters have become entangled in cabling that has collapsed from high level to block escape routes with resultant loss of life. As such the new regulations call for all cabling and containment systems in escape routes to be supported such that they will not be liable to premature collapse in the event of fire. All containment and cabling systems must now be affixed using metal support systems including metal cable ties or held within metal containment.

Where cables are held within non-metallic containment systems the cabling must be retained with metal clips or cleats. With respect to cables in metal studwork walls, the exception for installations under the control of skilled persons has been removed and now unprotected cables run in metal studwork walls will require 30mA RCD protection irrespective of the cable depth from the surface. There is a new exception if the cables can be mechanically protected during the construction process, though this may be difficult to implement in practice.

There is a new definition for an auxiliary circuit in Part 2 of the regulations, ‘Circuit for transmission of signals intended for control, detection, supervision or measurement of the function status of a circuit’. Part 5 of the regulations set out the requirement. These auxiliary circuits do not include fire detection and alarm, emergency lighting or other control circuits.

Special Locations 714 and 715 are new and replace the requirements for outdoor lighting and low voltage lighting that used to be in Part 5. Within bathrooms, any circuits passing through Zones 1 or 2 must be RCD protected by 30mA device. The Electrical Installation Certificate has been revised and the old inspection form replaced with a more meaningful inspection checklist form similar to the Electrical Installation Condition Report. There is a new tick box to indicate the attachment of a risk assessment for the omission of RCD protection on sockets.

The Minor Electrical Installation Works Certificate has been changed to include the exception for RCD protection on sockets and to record the x5 test results for RCDs. The Electrical Installation Condition Report has also been modified slightly in the wording for limitations, which now require the inspection of items in accessible loft spaces. The inspection form has been modified to remove the separate column for ‘Further Investigation’, and a new ‘FI’ code, if applicable, is to be identified in the Classification column.

The above is only an outline of the key changes implemented by Amendment 3. Designers and Contractors should obtain a copy of the latest BS7671 and associated On Site Guide and familiarise themselves with the updates as soon as possible as this Amendment is now ‘live’, pardon the pun!