Overvoltage Protection AM2 Update


1 2

The IET have updated certain requirements in Section 443 of BS7671 Amendment 2. Those requirements relate to providing protection against transient over-voltages of an atmospheric origin or due to switching. The revised requirements are:

Protection against transient over-voltages shall be provided where the consequence caused by the overvoltage could result in:

  • Serious injury to, or loss of, human life

  • Significant financial or data loss

  • And in all other cases protection against transient over-voltages shall be provided unless the owner of the installation declares it’s not required

All Other Cases

Ironically the clearest part of Regulation 443.4.1 is item 3 which says that overvoltage protection is required in all other cases. This catch all scenario requires the installer and the installation owner to have a conversation on the basis that overvoltage protection is automatically included in the design, and if after that conversation an owner says “no thanks” then the contractor should record that decision on a departure note & the completion certificate.

Owners Responsibilities

While Regulation 443.4.1 does take account of circumstances where the owner of the installation may choose to declare that overvoltage protection is not required. Which may be because any loss or damage is considered tolerable and the owner is willing to accept all risks of damage to equipment and any consequential losses. However, the benefits of protection in any modern installation with its plethora of electronic equipment will outweigh any up-front SPD costs.

Specific Situations

Although Regulation 443.4.1 refers to some specific situations it does not provide any guidance as to which types of premises are considered as ones where overvoltage can cause “serious injury to, or loss of, human life”. Nor does it advise which types of installation are susceptible to “significant financial or data loss” from an overvoltage fault. Designers & installers must use their own judgement. However, the types of premises that come to mind, Hospitals, Care Homes, Banks & Financial institutions may well already have the subject covered in their electrical installation specifications.

Previous references to over-voltages causing the failure of a safety service, as defined in Part 2 has been removed by the revised wording to Regulation 443.4.1.

Wylex Single Module SPD

The Wylex single module SPD is fully rated at 100A and does not need MCB protection. It connects directly onto the busbar (just like an MCB) in way number one. It needs cable links than alternative products and fits all Wylex consumer units. This Type 2 Surge Protection device includes a status indicator and volt free contacts for remote monitoring. Secure replaceable cartridges are securely locked into place and cannot be removed without use of a tool. Wylex single module SPDs are designed, manufactured & tested to BSEN61643-11 and certified as compliant by Intertek. www.electrium.co.uk/wylex

Corrigendum Effective Date

The new requirements have been published by the IET and come into effect immediately (May 2023)

For more information on the Corrigendum -BS 7671:2018, please visit: www.theiet.org/updates.