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SPDs AMD 2

Chris Pearson
Well, I'll kick off the debate on SPDs. Once again, the emphasis seems to be on domestic (we all, or virtually all of us live in a home of one sort or another) so are the proposals an improvement or not?
  • 0
    wallywombat:

    They seem to have converted the existing confusing criteria into a new set of completely bewildering criteria. If I am reading the draft 443.4.1 correctly, it summarises as:
    • Must protect if could result in risk of injury/life or financial / data loss.

    • Except single dwellings, if intolerable (as decided by all parties), do risk assessment to decide if protection required.

    • Protection not required for single dwellings with not much to lose (except it notes that most will have much to lose).


    So they don't actually state what you should do for single dwellings with valuable electronics. It certainly doesn't state that you need SPDs, nor that you need to a risk assessment.


    That is pretty much exactly as I see it.


  • 0
    DaveZ nails it - this is all about the industry lobby groups on the Wiring Regs Committee dreaming up new illusory risks to which they have the magic bullet answer - but it'll cost ya! SPDs, along with AFDDs are snake oil products which promise the earth but deliver only a handful of soil where it isn't needed nor wanted.

    There are that many ifs buts and maybes in the regs these days that you might as well write your own, or at least stick to the safe physics evidence instead.
  • 0
    Chris Pearson:

    So do we do risk assessments for single dwelling units or not?

     




    "Except for single dwelling units ..."

     



    (I have raised a comment on the apparent typo.)




    "Stroke" is 100 % correct, and aligns with BS EN 62305-series.

     


  • 0
    I have to disagree Graham.


    The term "lightning stroke" is surely an incorrect translation of the German. I have never heard of a lightning stroke, and neither has Grammarly which tries to change it to strike! This term is a noun (lightning) and a verb (to strike). The verb of stroke (Oxford dictionary) is to rub or gently move one's hand over. What is in some other standard is irrelevant to the correct use of English in BS7671. The term "strokes of lightning" has been used in a literary manner, as of brush stroke in the sky, but this is only correct in strict context, and with the addition of "OF", and lightning stroke is not this case. Copying a strange term from one place to another without checking is simply very poor proofreading. I expect Chris agrees.


    Of course, this could be because English is no longer taught properly in Schools. It is a sign of the times that proper use of English is no longer thought to be important. In my opinion, it is the most important thing about any written or spoken communication. The meaning is otherwise unclear or even lost.
  • 0
    gkenyon:
    Chris Pearson:

    So do we do risk assessments for single dwelling units or not?


    "Except for single dwelling units ..."

     



    (I have raised a comment on the apparent typo.)

    "Stroke" is 100 % correct, and aligns with BS EN 62305-series.


    Graham, thank you. Every day is a learning day in this forum. ?


    IMHO the proposed 443.4.1 would be clearer if the exception for single dwelling units were removed. As it stands, if the risks are considered to be tolerable, no further action is required. Note 4 refers to determining the total value of loss in dwellings and then it is up to the occupier to compare the cost of SPD with the possible loss, i.e. to make a judgement as to whether the risks are tolerable. What does not seem logical is to exclude dwellings from the risk assessment because it may show that SPD is not justified. (Of course there is nothing to stop an occupier or his electrician doing a risk assessment in any case.)


    I also think that the difference between suburban and urban should be clarified though I struggle to determine where the boundary lies within this borough.


    I would also add that the more I think about it, the more I feel inclined to install SPD at home.


  • 0
    David,


    Your assertion that no-one has checked could perhaps be turned around. Just have a quick internet search on lighting protection products and the theory behind lightning and you will see it's pretty much the current usage.


    Technical English is not necessarily UK English (OED standard), and is certainly not where used in international standards.


    Unfortunately, things change over time, including language, and the English I use at work now, and the English my kids are being taught at school, has a number of differences to the English I was taught at school. Instead of railing against it, I had a look at how quickly some parts of language actually changes ... and also how some things change rather more slowly.


    A good example of the latter is a well-known four-letter expletive which, contrary to popular myth, does not have its roots in labelling of shipping containers of fertilizer (Store High In Transit) but comes to us almost unaltered from the Anglo-Saxon verb for taking a number two.
  • 0
    davezawadi (David Stone):

    I expect Chris agrees.


    Er, no! OED does have an entry for lightning stroke. Rather than cuddling the cat, it may be better think of a golf stroke. I must admit that I was surprised.


  • 0
    Chris Pearson:

    Graham, thank you. Every day is a learning day in this forum. ?


    IMHO the proposed 443.4.1 would be clearer if the exception for single dwelling units were removed. As it stands, if the risks are considered to be tolerable, no further action is required. Note 4 refers to determining the total value of loss in dwellings and then it is up to the occupier to compare the cost of SPD with the possible loss, i.e. to make a judgement as to whether the risks are tolerable. What does not seem logical is to exclude dwellings from the risk assessment because it may show that SPD is not justified. (Of course there is nothing to stop an occupier or his electrician doing a risk assessment in any case.)


    I also think that the difference between suburban and urban should be clarified though I struggle to determine where the boundary lies within this borough.


    I would also add that the more I think about it, the more I feel inclined to install SPD at home.




    I can't disagree with you here Chris. I think the real turning point will come when insurers don't pay out for an event simply because SPDs weren't fitted.


    Don't forget, though, telephone master sockets may not have SPDs in them any more - so if you've got wired network devices and haven't got FTTP, you might want to surge protect your phone/broadband line too.


  • 0
    I must say I dislike the term "risk assessment" in the context of SPDs. For me this phrase conjures up the idea of balancing the probability of an event against the likely level of harm of such an event. But for SPDs it's only the first part. I think something like "transient likelihood assessment" is a better description.


    I also dislike the abrupt 10-fold change in fenv between urban and suburban/rural. Since for many properties the distinction between urban and suburban is vague and highly subjective, it means that mostly the yes/no result of the risk assessment is dictated by that vague choice. I'd prefer something like a number from 0..10 based on the roughly estimated percentage of open space in the 1km square surrounding the property (parks, fields etc) - assuming of course that that's what the urban/suburban/rural disctinction is supposed to be about.
  • 0
    I'd prefer something like a number from 0..10 based on the roughly estimated percentage of open space in the 1km square surrounding the property (parks, fields etc) - assuming of course that that's what the urban/suburban/rural disctinction is supposed to be about.

    I've been pondering the same thing - I couldn't figure out why an urban area was 10x safer - it's not like thunderstorms avoid city centres (as far as I know). Similarly I'm confused by the criteria about the length of line between the consumer and substation - surely any distribution cable downstream of the consumer's tap off point will be just as an effective 'aerial' as that upstream.


    I did wonder if the urban thing wasn't down to the lightning, but the number of other installations that were effectively in parallel with our own, so if each took a 'share' of the surge, any one installation would end up with a smaller share. I could perhaps be persuaded that there was 10x the amount of wiring per km² in urban areas than in suburban/rural ones. Complete conjecture of course.


       - Andy.

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