AJJewsbury said:

That said, concentric cables run overhead are often considered to be equivalent to underground as the cable is self screening to some extent.

In the surge protection world, we are also concerned about L-Earth and N-Earth.

The Type 1 need, though, is about direct strike to overhead cable or pole-mounted transformer - more common with bare overhead, but can happen with insulated overheads especially pole-mounted transformer supply. By overheads to be clear I mean where there is a span (or catenary) between poles in the LV supply network to the property (or if looped as stated by Andy, nearby property).

People will be quick to point out that 443 does not address direct strokes (and is not intended to). This is perfectly correct, but I would draw attention to 543.1 which does introduce direct strokes, and the first para says the section focuses "mainly on 443, but also can eb used in conjunction with BS EN 62305 or otherwise stated."

In particular, though, with this issue, see NOTE to 534.4.1.1.

Adam Kuzack said:

Sourcing electrical switchgear from online retailers

Just be careful that you are not the "importer" from a legislation point of view. If you do end up with that role, you may well bear all the responsibilities of the manufacturer for the relevant legislation, such as: Electrical Equipment (Safety) Regulations, Electromagnetic Compatibility Regulations, Construction Products Regulation, etc.

In addition, Regulation Group 511 is important for your certification, If the product is not declared to a British or Harmonized Standard, you need to make a declaration on the relevant certification in accordance with Regulation 511.2.

(Yes, pedantically, this perhaps arguably extends to equipment such as crimps and ferrules, being termination preparation components in wiring systems ... see definition of electrical equipment in Part 2. Ferrules, for example being the subject of French, German or UL standards, but sadly not a British or Harmonized standard.)

Thank you for the comments on the type of cable that may be supplying the property. I will investigate further. What seems to be the  / opinion with regards to whether a type 1 spd will be required? What are the guiding factors that will determine whether it will be Type 2 or a Type 1+2 device - could do with some guidance on this question. 

Thanks 

Adam Kuzack said:

What are the guiding factors that will determine whether it will be Type 2 or a Type 1+2 device - could do with some guidance on this question. 

See NOTE to 534.4.1.1, and on top of that, "where required by BS EN 62305" for buildings with LPS (and therefore Section 443 of BS 7671 does not apply).

Which cable is the incomer (and which is the outgoer)? I don't like that cable which appears to have come adrift from its clips.

Graham, can we keep it simple please? :-)

Correct me if I am wrong, but a LPS would be fitted to e.g. a steel-framed factory and requires Type 1. In the absence of an LPS (and the risks which required it in the first place), Type 2 will do.

What I am unclear on is a lightning conductor which protects e.g. a church spire. If I remember my physics lessons correctly, the idea is to conduct the electricity in the sky to ground in order to prevent it building up and making lightning. Would such a lightning conductor amount to an LPS?

Chris Pearson said:

Would such a lightning conductor amount to an LPS?

Yes, although there are LPS to BS 6651 and LPS to BS EN 62305. BS 7671 no longer recognizes BS 6651 (because it's been withdrawn) ...

More to the point, is the question of whether the LPS is bonded to MET. This was not always done, but is usually now where BS EN 62305 applies - if it's done, then you probably need Type 1 - but that would be indicated by BS 62305 anyway (which you'd have to apply according to BS 7671).

Omitting Type 1 where BS EN 62305 says it should be provided can cause injury, fire, or extensive damage.

Overhead supplies are also subject to damage from direct strikes, and omitting Type 1 here can also cause extensive damage or injury.

Chris Pearson said:

Correct me if I am wrong, but a LPS would be fitted to e.g. a steel-framed factory and requires Type 1.

What are the driver here? There are small factories and large ones?  What's the nature of the supply, and what's the direct lightning stroke risk? (agree, increased if steel-framed large structure and not a lot else in the vicinity ... but again 443 leaves the decision to BS EN 62305).

So, the typical case where BS EN 62305 isn't directly involved, but Type 1 may be needed, is the domestic property, village shop, etc., where there's an overhead supply ... and the risk remains. I think everything else you're getting BS EN 62305 out for (and would you insurance cover you for making the decision on issues covered by that standard)?