The £1300 AFDD consumer unit

davezawadi (David Stone):

Whilst in some cases surge protection may be useful Graham, the regulations take this to being a requirement and specifically state that this is lightning protection. The specification for its fitting is entirely based on lightning strikes.

Absolute nonsense. BS 7671 says nothing of the sort. In fact, see 2nd para of 443.1.1

This section does not specify requirements for protection against transient overvoltages due to direct or nearby lightning strokes on the structure.

The overvoltages covered by BS 7671 are atmospheric origin or due to switching. As I inferred in my previous response, the former being either cloud-cloud or remote (in which case impedance comes into play).

 

Were your devices suffering from such spikes or other causes? I know and have measured many mains spikes, but the cause is usually other things, so why not come clean and simply say surge protection may be useful in some circumstances?

Definitely the types of "spikes" inferred in 443.1.1, and in the places concerned, it's a mixture of both ... in reality, not in a dream or a speculation.

 

The cost-benefit analysis should be up to the consumer, not some remote manufacturer or regulation committee who have no idea of the likelihood or cost of any damage. It might well be a good idea for a data centre, but for Mrs Bloggs who has two LED lights, probably not worthwhile. The energy from switching spikes and similar is very low compared with lightning, and may often be entirely satisfactorily removed with very simple and cheap VDRs. Live conductor to Earth protection is rather different to L-N protection, simpler and effective for preventing damage to connected semiconductors, particularly in with the mains supply impedance being raised with some small series inductors, except in extreme cases. The regulations seem to have a fascination with the line-Earth voltage which is only seen by any attached EMC suppression components. I don't doubt that some equipment is occasionally damaged, or at least fails, but deciding the exact cause is often very difficult.

We are now at a point where the cost-benefit analysis is perhaps moving in favour of fitting them, as I said in my previous e-mail. I agree that, say 15 years ago, my view would have been wholly different, but I'm totally sold on the cost-benefit based solely on the cost of equipment I've had damaged by cloud-cloud strikes alone over the past 20 years, in an urban area (although by the coast). And I know I'm not alone.

 

davezawadi (David Stone):

Whilst in some cases surge protection may be useful Graham, the regulations take this to being a requirement and specifically state that this is lightning protection. The specification for its fitting is entirely based on lightning strikes.

Absolute nonsense. BS 7671 says nothing of the sort. In fact, see 2nd para of 443.1.1

This section does not specify requirements for protection against transient overvoltages due to direct or nearby lightning strokes on the structure.

The overvoltages covered by BS 7671 are atmospheric origin or due to switching. As I inferred in my previous response, the former being either cloud-cloud or remote (in which case impedance comes into play).

 

Were your devices suffering from such spikes or other causes? I know and have measured many mains spikes, but the cause is usually other things, so why not come clean and simply say surge protection may be useful in some circumstances?

Definitely the types of "spikes" inferred in 443.1.1, and in the places concerned, it's a mixture of both ... in reality, not in a dream or a speculation.

 

The cost-benefit analysis should be up to the consumer, not some remote manufacturer or regulation committee who have no idea of the likelihood or cost of any damage. It might well be a good idea for a data centre, but for Mrs Bloggs who has two LED lights, probably not worthwhile. The energy from switching spikes and similar is very low compared with lightning, and may often be entirely satisfactorily removed with very simple and cheap VDRs. Live conductor to Earth protection is rather different to L-N protection, simpler and effective for preventing damage to connected semiconductors, particularly in with the mains supply impedance being raised with some small series inductors, except in extreme cases. The regulations seem to have a fascination with the line-Earth voltage which is only seen by any attached EMC suppression components. I don't doubt that some equipment is occasionally damaged, or at least fails, but deciding the exact cause is often very difficult.

We are now at a point where the cost-benefit analysis is perhaps moving in favour of fitting them, as I said in my previous e-mail. I agree that, say 15 years ago, my view would have been wholly different, but I'm totally sold on the cost-benefit based solely on the cost of equipment I've had damaged by cloud-cloud strikes alone over the past 20 years, in an urban area (although by the coast). And I know I'm not alone.