Amendment 2: changes to BS7671 Section 433 | Surge Protection Devices

Amendment 2: changes to BS7671 Section 433 | Surge Protection Devices

Kirsty Johnson, Technical Sales Director at Surge Protection Devices, discusses the proposed changes to BS7671 Section 433, and how this will affect the requirements for surge protection.

The 18th Edition regulations has provided quite a few proposed changes around surge protection. Another area which will see significant alterations is in section 433, which discusses the regulations surrounding the application of surge protection to different installations.

The ‘shall’ regs
The current edition of BS7671 has the following regulations under 443.4:

“Protection against transient overvoltages shall be provided where the consequence caused by over voltage could:

i. Result in serious injury to, or loss of, human life
ii. Result in interruption of public services and/or damage cultural heritage
iii. Result in interruption of commercial or industrial activity
iv. Affect a large number of co-located individuals”

Whereas the proposed amendment 2 would have this regulation read:

“Protection against transient overvoltages shall be provided where the consequence caused by over voltage could result in:

i. Serious injury or loss of human life
ii. Significant financial or data loss”

Note 3 includes electrical safety systems associated with safety services as defined in part 2 of BS7671. BS 7671 defines safety services as:

“An electrical system for electrical equipment provided to protect or warn persons in the event of a hazard, or essential to their evacuation from a location”

On the surface, those reading these changes may feel that this is a ‘back-track’ on the use of SPDs from the wiring regulations committee, but in reality, it doesn’t really change the installations that regulation 443.4 applies to.

The proposed Note 3 would mean that an installation with a safety service, i.e. a fire alarm panel, would need to be protected from overvoltage. Realistically, an installation that would require SPDs under the original version, is still likely to require SPDs under the proposed amendment. For instance, an installation that would fall under the original point of resulting in interruption of commercial or industrial activity, would likely still come under the regulation for significant financial loss and protecting safety services.

Under the new amendment, there is more emphasis on a discussion with the end user, which is explained in Note 4 (we’ll discuss this in more detail later in the article). So, under these proposed changes, an electrical designer would now only need decide if any of the circuits on the distribution board could cause injury or death or could lose the client money or data at an unreasonable amount for the client to accept, which could potentially make the decision a simpler and easier-to-remember process for the designer.

The risk assessment
There aren’t any significant changes under the proposed amendment 2 on the risk assessment. So, for all cases, other than covered under 443.4, the risk assessment shall be performed to calculate the risk of damage from an overvoltage from atmospheric origin.

Single dwellings are an exception to this (as covered later in the article), although it’s worth referring to the proposed regulation 443.4.2 at this point, as the risk assessment only calculated the risk of an overvoltage from an atmospheric origin, not from switching events.

Proposed regulation 443.4.2 states:

“Protection against overvoltages shall be considered in the case of equipment likely to produce switching overvoltages or disturbances exceeding the applicable rated impulse voltage of equipment”

Therefore, under the proposed amendment 2 of BS7671, if you do use the risk assessment method, consideration must be given to sensitive equipment, where overvoltage protection may be necessary.

SPD TrainingNote 4, as previously mentioned, encourages discussion between the electrical designer and the client to ensure that no unacceptable losses occur from overvoltage. This is where it would be recommended to ask about any specific sensitive equipment that you may not be aware of inside the installation.

“Note 4: A discussion will need to take place between the designer, installer and any other relevant parties such as the installation owner or end user, to determine what is considered to be intolerable, or in the case of single dwelling units, to determine the total value of loss.”

Single dwellings
For domestic installations, there’s a slight change in the wording around the installation of surge protection. The current edition reads:

“Protection against overvoltages is not required single dwelling units where the total value of the installation and equipment therein does not justify protection.”

The proposed statement also includes a note:

“Protection against transient overvoltages is not required for single dwelling units where the total value of loss therein does not justify such protection.”

“Note 5: In practice, most single dwelling units will have equipment rated to overvoltage category level i and/or ii connected to the fixed installation. This equipment, therefore, is potentially at risk from the effects of transient overvoltages.”

Under these proposed changes, although the regulation itself is largely unchanged, the appearance of Note 5 indicates that most domestic installations would benefit from the installation of an SPD. Again, referring back to Note 4, this should be discussed with the end user to evaluate if the risk of damage to equipment is acceptable for your client.

Obviously, we’re currently working with the ‘proposed’ changes and things may possibly change slightly by time of publication, which is due in March 2022.

In the meantime, if you’re interested in free CPD training on all things surge protection related, you can register directly through our training academy.

Register for Surge Protection Devices’ free CPD training by clicking here

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