The official period of consultation on the first draft of the 18th Edition is now complete, and the IET and committees are currently writing the final draft, reflecting public comments made this summer, which will be published on 1st July 2018 and come into effect on 1st January 2019.
Below are 3 proposed changes which could have a significant impact on you.
Section 411 – Outdoor Circuit Protection
Currently, the use of an RCD as additional AC circuit protection on outdoor equipment is optional, and decided by a risk assessment. Our interpretation of the proposed changes indicates that after 1 st January 2019, there will be no exception made, and an RCD will be required for all outdoor circuits, including lighting, with a current rating not exceeding 32 A.
Many businesses have external signage lighting, shopfront or entrance lighting, and if this change is confirmed, there could be a significant cost impact.
For schools with an IT lab where interference affects RCD, it may be necessary to consider moving computers to spurs instead of sockets.
There has been a significant change proposed so that there is no longer an exception for the provision of RCDs for socket-outlets with a current rating not exceeding 32 A. There is no doubt that they are a very efficient protective device and, where practicable, they are a valuable addition to the electrical installation. This means that electrical installers will need to find alternative solutions to provide a power supply to equipment that is required to be on a non-RCD protected circuit, such as switch fused connection units.
Section 753 – Embedded electrical heating systems.
If you use embedded electrical heating systems, such as underfloor or in-wall heating in hotels or offices, swimming pools or spas, or for frost prevention or embedded de-icing controls – updates to this section will apply to you.
The updates cover the structure surrounding the embedded system, with a view to reducing penetration, overheating due to short-circuiting and damage to adjacent material(s) from overheating.
If you are renovating rooms in your hotel, building an extension or considering installation of embedded heating systems – you should familiarise yourself with the latest requirements and ensure that your designers can provide documentation regarding the use of approved substances.
The scope of Section 753 has been extended to apply to embedded electric heating systems for surface heating. They also apply to electric heating systems for de-icing or frost prevention or similar applications, and cover both indoor and outdoor systems. These include heating systems for non-hardened compacted areas (for example, football fields, lawns). Heating systems for industrial and commercial applications complying with IEC 60519 and IEC 62395 are not covered.
Consequently, Section 753 now includes additional requirements to cover wall heating, heating conductors and cables where laid in soil and concrete etc. Documentation is also covered. The designer will be required to provide appropriate information about approved substances in the surroundings of the heating units.
Regulation 753.424.101 requires that for wall heating systems the heating units shall be provided with a metal sheath or metal enclosure or fine mesh metallic grid. The metal sheath or metal enclosure or fine mesh metallic grid shall be connected to the protective conductor of the supply circuit.
Regulation 753.424.102 requires special care to be taken to prevent the heating elements creating high temperatures to adjacent material. This may be achieved by using heating units with temperature self-limiting functions or by separation with heat-resistant materials. Separation may be accomplished by placing on a metal sheet, in metal conduit or at a distance of at least 10 mm in air from the ignitable structure. A note adds that a larger separation distance may need to be considered depending on adjacent material.
Section 443 – Protection Against Overvoltages
Section 443 is likely to be significantly revised based on the recently published IEC and CENELEC standard. We expect to see the removal of AQ criteria as a means of establishing the need for protection against transient over voltage - often the result of a lightning strike.
Our interpretation of the new clause implies that the major factor in determining if over-voltage protection is needed, will move from the likelihood of it happening, to the impact if it did.
Depending on the nature of your business, lightning or other overvoltage protection may be required, and if you are unsure you will need to complete a risk assessment. If you don't complete a risk assessment, it will be assumed that you DO need protection.
Assuming BS 7671 follows the IEC and CENELEC standard the AQ criteria (conditions of external influence for lightning) for determining if protection against transient overvoltage is needed would no longer be included in BS 7671. Instead, protection against transient overvoltage would have to be provided where the consequence caused by overvoltage affects:
- human life, e.g. safety services, medical care facilities
- public services and cultural heritage, e.g. loss of public services, IT centres, museums; and
- commercial or industrial activity, e.g. hotels, banks, industries, commercial markets, farms.
For all other cases, a risk assessment would have to be performed in order to determine if protection against transient overvoltage is required. If the risk assessment is not performed, the electrical installation would have to be provided with protection against transient overvoltage.
However, an exception not to provide protection is included for single dwelling units where the total economic value of the electrical installation to be protected is less than 5 times the economic value of the SPD located at the origin of the installation.
Protection against switching overvoltages should still be considered.
Intersafe will continue to monitor the updates shared by the IET and provide commentary on situations most relevant to our customers.
Please note: This article only gives an overview of selected draft proposals, which may or may not be included in the 18th edition (BS 7671:2018) wiring regulations, depending on the decision of the national committee.