Meter Isolator with SPD

gap_gap · Feb 9, 2022

Hi
We are looking to get an EV charger installed, and I asked for an SPD to be on the new CU that will be required for that.
The electrician has suggested that instead of having an SPD in the new CU, could replace the incoming isolator in the meter cupboard with one that has an SPD incorporated - something like this:

100A DP Electricity Meter Isolator Switch with T1+2 Combined Surge Protection

proteusswitchgear.com

It seems like a great way to cover the whole home, but I can't seem to find much information about these in practice, with most SPD being installed in the CUs. Are there any gotchas with this approach, and also I take it that it will need the main fuse pulling so will need the electrician to contact the DNO?

Many thanks for any advice!

littlespark · Feb 9, 2022

What I would say is, that an SPD is a sacrificial element, which will need replaced if it gets too many surges... (not sure of average lifetime)

That would be easier to replace, if it was past the service isolator... If it was in the enclosure with the isolator, the seals would need to be cut on the fuse, and the isolator housing to get it out.

It could be in a separate enclosure, if not in the consumer unit.

gap_gap · Feb 9, 2022

littlespark said:
What I would say is, that an SPD is a sacrificial element, which will need replaced if it gets too many surges... (not sure of average lifetime)

That would be easier to replace, if it was past the service isolator... If it was in the enclosure with the isolator, the seals would need to be cut on the fuse, and the isolator housing to get it out.

It could be in a separate enclosure, if not in the consumer unit.

That is a really good point thanks! Hadnt thought about replacing and needing to get the fuse out - I read somewhere that 5 years was an approx life on these, so not ideal to need to take out! In terms of a separate enclosure, can a single one be used to cover 2 CUs, or would it need to be in front of the Henley blocks to achieve that?

littlespark · Feb 9, 2022

Its just one to cover the whole installation, whether that's 1, 2 or more consumer units.
The ones that come fitted in CU's normally have maybe a 40A MCB before it.
The SPD in one consumer unit will protect the other CU's as long as the first mainswitch isnt turned off.

There is also the decision of type 1 or type 2, so not just a case of "shove that one in, its cheaper!"

gap_gap · Feb 9, 2022

littlespark said:
Its just one to cover the whole installation, whether that's 1, 2 or more consumer units.
The ones that come fitted in CU's normally have maybe a 40A MCB before it.
The SPD in one consumer unit will protect the other CU's as long as the first mainswitch isnt turned off.

There is also the decision of type 1 or type 2, so not just a case of "shove that one in, its cheaper!"

Amazing, thanks so much for the advice and guidance, will go back to the installer as think having the SPD just in the new CU will make things much simpler. Thanks again!

richy3333 · Feb 9, 2022

Depending upon the electrical installation more than one SPD could be required if you have more than 1 CU. Needs proper consideration

timhoward · Feb 9, 2022

littlespark said:
What I would say is, that an SPD is a sacrificial element, which will need replaced if it gets too many surges... (not sure of average lifetime)

That would be easier to replace, if it was past the service isolator... If it was in the enclosure with the isolator, the seals would need to be cut on the fuse, and the isolator housing to get it out.

Are you sure it works like that? Most of the SPD modules I’ve come across allow you to just pull the front off and change the sacrificial part without even opening the CU / enclosure.

catdog1121 · Feb 9, 2022

littlespark said:
What I would say is, that an SPD is a sacrificial element, which will need replaced if it gets too many surges... (not sure of average lifetime)

That would be easier to replace, if it was past the service isolator... If it was in the enclosure with the isolator, the seals would need to be cut on the fuse, and the isolator housing to get it out.

It could be in a separate enclosure, if not in the consumer unit.

Those enclosures come with two parts, a bigger one covering the isolator and then a smaller one that will cover one side of the terminals.. The idea is you need to take the larger part off first, this allows you to get to the outgoing terminals while the smaller part covers the incoming still live terminals.. This would also allow you to service the SPD, if a DNO has put on seals on the consumer side of the isolator then these can be cut..

gap_gap · Feb 10, 2022

Discussed with our electrician and the Wylex unit allows the SPD to be exchanged without taking off the cover - so sounds good!

I suppose the main thing is installing this will mean pulling the main fuse and so would need the DNO to be notified?