The £1300 AFDD consumer unit

Chris Pearson:

gkenyon:

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.

I thought that this thread was about AFDD, but as for SPD, I agree. FWIW, I think that the whole business of lightning stroke/strike in BS7671 is far too complicated and I find it difficult to see why a new build would not have SPD. I have never had any damage personally, but when I install a new CU it will have it. It isn't that the benefit has increased, it is that the cost has decreased. ?

I agree with you on the new build ... part of the difficulty with BS 7671 is that it applies not only to homes, offices and shops, but other installations, some of which (say if it's just resistive heating loads, or contains loads with in-built surge protection) may not require SPDs.


In addition, there are existing properties with which it may be difficult to adopt a blanket mandate, although those difficulties are there already. For example:

• a new circuit is added to existing house, say for a traditional resistive element oven. The oven's circuit is not SPD protected - the choice needs to be there as in this case, perhaps the omission of the SPD won't do too much damage.

• an existing building has LPS to BS 6651. You are asked to rewire a floor on the building for an office as part of a refit. There is no surge protection ... what do you do? In this case, the cost of not having the surge protection could well be large, BUT the cost of providing the surge protection might include a re-assessment (and perhaps improvement) of the existing lightning protection system to BS EN 62305 series, and then provision of a hierarchy of SPDs to BS EN 62305-4.

What about if the load were an electric vehicle at say £30K+ - would you recommend SPDs are fitted? I'm sure most charging points are installed without them.

Chris Pearson:

gkenyon:

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.

I thought that this thread was about AFDD, but as for SPD, I agree. FWIW, I think that the whole business of lightning stroke/strike in BS7671 is far too complicated and I find it difficult to see why a new build would not have SPD. I have never had any damage personally, but when I install a new CU it will have it. It isn't that the benefit has increased, it is that the cost has decreased. ?

I agree with you on the new build ... part of the difficulty with BS 7671 is that it applies not only to homes, offices and shops, but other installations, some of which (say if it's just resistive heating loads, or contains loads with in-built surge protection) may not require SPDs.


In addition, there are existing properties with which it may be difficult to adopt a blanket mandate, although those difficulties are there already. For example:

• a new circuit is added to existing house, say for a traditional resistive element oven. The oven's circuit is not SPD protected - the choice needs to be there as in this case, perhaps the omission of the SPD won't do too much damage.

• an existing building has LPS to BS 6651. You are asked to rewire a floor on the building for an office as part of a refit. There is no surge protection ... what do you do? In this case, the cost of not having the surge protection could well be large, BUT the cost of providing the surge protection might include a re-assessment (and perhaps improvement) of the existing lightning protection system to BS EN 62305 series, and then provision of a hierarchy of SPDs to BS EN 62305-4.

What about if the load were an electric vehicle at say £30K+ - would you recommend SPDs are fitted? I'm sure most charging points are installed without them.