A surge protection device (SPD) that meets an insurer’s requirements can still leave an installation exposed to surge damage. With some South African insurers now refusing surge-related claims where no SPD is fitted, electricians and consulting engineers need to check whether the policy specification suits the site they’re working on.

“Many policies take a one-size-fits-all approach, typically requiring the same type of SPD regardless of a property’s location, use case or level of exposure,” says Dr Andrew Dickson, engineering executive at CBi-electric: low voltage. “That blanket approach can fall short of protecting the very assets the policy is designed to cover.”

In his experience, insurers specify a Type 2 (Class II) device in the distribution board, often with a 40kA rating. Yet the same requirement may be applied to a suburban home supplied by underground reticulation and a remote farmhouse fed by long overhead lines in an area with high lightning ground flash density, despite the vastly different risk profiles.

Matching the SPD type to the risk

Not all surges are the same, and neither are the devices designed to protect against them. Each SPD type is designed for a particular kind of surge:

Type 1 (Class I) SPDs are designed to divert the high-energy currents associated with direct lightning strikes. Installed at the service entrance, they are often required at properties where lightning protection systems are fitted or where installations are exposed to direct lightning strikes, including some remote sites and those supplied by overhead lines.

Type 2 (Class II) SPDs, the most common in residential distribution boards, protect against induced surges from indirect lightning and switching transients caused by power interruptions, supply restoration and network faults.

Type 3 (Class III) SPDs provide an additional layer of protection for sensitive electronics at the point of use, typically working alongside upstream Type 2 protection.

Dr Dickson recommends a coordinated approach, using different SPD types where the site assessment calls for them. A single Type 2 device at the board may be sufficient to protect the installation; however, it may not meet the requirement of the policy. In the same manner, an installation with many pieces of sensitive electronic devices in it may benefit from the inclusion of coordinated point-of-use protection.

Looking beyond the 40kA rating

The kA rating indicates a device’s peak surge current-handling capability under specific test conditions, but it does not, on its own, determine how effectively the device will protect an installation.

“A higher kA rating doesn’t mean better protection,” notes Dr Dickson. “What matters is whether the device has been selected for the expected surge exposure, the equipment being protected and the environment being employed in. Specifying a higher rating for its own sake is like using a 10-pound hammer to drive in a 10mm nail. It might work, but that doesn't mean it's the right tool for the job.”

Over time, repeated exposure to switching transients and other surges can gradually degrade an SPD, even if individual events fall below its maximum discharge current rating.

For this reason, Dr Dickson suggests evaluating factors such as voltage protection level, discharge current ratings, and the potential surge exposure, while incorporating regular status checks into maintenance schedules.

Start with the installation

“The starting point should always be the installation itself,” he says. “Contractors need to understand where surges are likely to originate, how they could enter the electrical system and what equipment needs protection before deciding which devices to specify.”

While national standards provide a framework for selecting and installing appropriate surge protection, effective implementation requires an assessment of the individual site.

Where that assessment identifies a need for protection beyond the insurer’s minimum requirements, documenting the technical reasoning gives the client a clear record of why additional measures have been specified. Contractors should also ensure that any alternative or supplementary protection continues to satisfy the applicable policy conditions.

Dr Dickson would like to see insurers draw on that same technical expertise when setting their requirements. “Insurers have an important role to play in encouraging better surge protection, but their requirements need to reflect the risks involved. Working more closely with electrical engineers could help ensure that the protection they require is appropriate for each installation.”

Purpose-built surge protection

CBi-electric: low voltage manufactures voltage-limiting surge protection devices for residential and industrial applications in accordance with SANS 61643. Available in a DIN-mount version and a dual-mount version that clips onto both DIN rail and CBi mini rail, the devices can be fitted to new and existing distribution boards. They feature an LED status indicator to show when replacement is required, as well as a built-in thermal disconnect.