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  1. spark 68

    Old mem mcb type

    Actually this is not strictly true, the types B,C and D have a range of magnetic trip currents, which extend to the letter below, Type B = 3 to 5 X In, Type C = 5 to 10 X In, and Type D = 10 to 20 X In, just we use the highest number multiplier as the worst case. The older standard has a...
  2. spark 68

    Old mem mcb type

    No they are not the same at all Type 1 are X4 In, Type B are X5 In Type 2 are X7 In, Type C are X10 In Type 3 are X10 In Type D are X20 In Type 4 can be various depending on manufacturer If anything Type 3 are roughly equivalent to type C
  3. spark 68

    Caravan hook ups

    I am wondering if you might possibly have a N-E fault on the TT side somewhere, this would give you that type of reading, might be worth checking, although as everything should be RCD'd on this side anyway this might not be likely. Remember the N is effectively joined to the TNC-S E via the CNE...
  4. spark 68

    Split Concentric as a submain

    You might be better off using the cable manufacturers data for the cable you are planning on using, this often gives more favourable results than the generic tables in 7671.
  5. spark 68

    Split Concentric as a submain

    It is unlikely you would be able to get full discrimination in domestic anyway, partial at best, I have seen a faulty cable on a table lamp fitted with a 5A plug fuse trip out the 32A MCB supplying the RFC.
  6. spark 68

    Split Concentric as a submain

    True, but we are not trying to discriminate here, it is only to satisfy the DNO, they don't like you relying on their service fuse past about 3m, I believe it is also so they can guarantee their Ze figure, they have to draw the line somewhere as to what they will accept, the 3m rule seems to be...
  7. spark 68

    Split Concentric as a submain

    Why are you limiting your available supply to 63A ? Your SF needs to be within 3m of the incomer/meter, this is to satisfy the DNO by not relying on their service fuse, you can use an 80A SF to fulfil this requirement, a 63A SF won't discriminate with the DNOs 80A fuse anyway.
  8. spark 68

    Socket Breaker

    That was partly my point, I can give him max Zs values, but without a known Ze it is a bit pointless unless they are maybe using an upfront RCD as per caravans which would give a lot more leeway, I could also give him max circuit lengths for a given csa/MCB combination, but without knowing the...
  9. spark 68

    Socket Breaker

    Which was precisely why I asked for more information ie. circuit length and installation method etc., if this is to be *fully* certified for UK use then by rights it will need to take voltage drop into account too. Sure we can give him standard circuit data/layout for basic radial S/Os MCB and...
  10. spark 68

    Socket Breaker

    I said that last night lol :)
  11. spark 68

    Socket Breaker

    Some of this we cannot predict without a lot more information, the Ze (external Earth loop impedance) is beyond our control so more information is needed here, what type of cabling is used, how it is installed and length of circuit all has a bearing on current carrying capacity, R1+R2...
  12. spark 68

    Fire Brigade advice

    No!, lol :) it means we are all engineers now yay :conehead: :hurray:
  13. spark 68

    Downlights in a thatched house

    Exactly what I was thinking .
  14. spark 68

    Design of consumer units for amendment 3

    It is entirely the fault of the IET for this half-arsed badly thought out reg. On one hand they were saying this amd was to harmonise with other international standards and Europe, okay so far if that was what is meant... Then they ignore one international standard completely (glow wire test)...
  15. spark 68

    Earthing cable running through kitchen cupboards

    Don't need it as presumably it is >= 4mm, I would have ran it behind all the same though.
  16. spark 68

    Socket Breaker

    It might help us a bit better to help you, if you explain what exactly you are trying to achieve and exactly what you want to know.
  17. spark 68

    Socket Breaker

    Do you have access to BS7671 Gardner ? If you do then have a look at appendix 15 :)
  18. spark 68

    Socket Breaker

    Both are actually quite sweeping and broad statements ;) For instance a look at table 7.1 in the OSG for max circuit length and allowed installation methods, where only OCPD (no RCD) is present then Zs is the limiting factor first, when an RCD is thrown into the mix then SC becomes the limiting...
  19. spark 68

    Socket Breaker

    As the E connection is usually derived by way of the starpoint N, it is generally given that if an OCPD will comply L-E, then it will also comply L-N.
  20. spark 68

    Socket Breaker

    Yes I know Spin, the OP he asked about selection for general use S/O, I am aware he is from the US, but as far as I can gather he is certifying a product for Europe/UK, a type B gives a reasonable compromise for max Zs V inrush requirements, unless he has something specific in mind which may...

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