Surge Protection Devices for domestic - what do you think?

a-z electrics · Apr 27, 2019

Evening all,
Just attended elex exeter and see there's a big push on these SPDs coming as standard now in domestic consumer units. Hager, Lewden and Contactum to name just 3.
I have had at least 2 clients in the last few months whose appliances have been damaged by apparently surges on the supply when power has been lost/switched back on, one was an ASHP and the other an Aga oven controller.
Disregarding what it says in the Green book, the additional cost of these when fitting/changing a board is not that great and they appear easy to fit retrospectively if there's a spare way for one. or even in a separate enclosure so I personally think there's a case for recommending them to customers..
What do people think, anyone else had any experiences?

pc1966 · Jun 13, 2022

As a general point, type 1 (or 1+2 which are more useful) SPD are always going to be far more expensive than type 2 due to the larger devices needed to absorb the energy. Typically the energy of the "standard" direct strike waveform (10us/350us) is an order of magnitude larger than the standard induced strike (8us/20us) waveform for a given peak current. Also within type 1 SPD you get different protection levels based on energy, and of course a cost for the beefier ones.

But there are 3rd party SPD manufacturers you can use as they typically are cabled in and not busbar mounted. For example:

SY12325KA2P - Type 1+2+3, 25ka, single phase, with window indication - Surge Devices

Lightning protection Level 3, 25kA 10/350μs. Fully compliant to BSEN62305, BS61643-11 & BS7671. Combined arrester Type 1+2+3 can handle direct lightning strikes and protect sensitive electronic equipment. Suitable for all installation types (TT, TNC-S & TN-S). Low let through voltage <1.3kV...

www.surgedevices.co.uk

Not cheap, but less eye-watering than most!

As a final point you will see some SPD describes as suitable for TT or for TN, that is kind of determined by the arrangement of protective devices with the usual TT configuration having a MOV from L-N, and a GDT from N-E. Realistically they are fine for most TN systems as well (as above example is described).