Overvoltage Protection: the latest update | Electrium

Overvoltage Protection: the latest update | Electrium

Electrium provides a brief overview of one specific update in the Corrigendum: overvoltage protection.

It’s now well documented that the IET has updated certain requirements in Section 443 of BS 7671 Amendment 2. Those requirements relate to providing protection against transient overvoltages of an atmospheric origin or due to switching.

The revised requirements of Regulation 443.4.1 are as follows: 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.

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

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 and the completion certificate.

Owner responsibilities

While Regulation 443.4.1 takes account of circumstances where the owner of the installation could 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) the benefits of protection in any modern installation with its plethora of sensitive electronic equipment will far 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 and installers must use their own judgement. However, the types of premises that come to mind – hospitals, care homes, banks and financial institutions may well already have the subject covered in their electrical installation specifications.


The Wylex single module SPD is fully rated at 100 A and does not need MCB protection. It connects directly onto the busbar ( just like an MCB) in way number one. It uses fewer cable links than some alternative products and fits all Wylex consumer units & SP&N distributions boards. This Type 2 Surge Protection device includes a status indicator and volt-free contacts for remote monitoring as well as replaceable cartridges that 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.

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