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  1. J

    A MCB 1200+ amps tripped .. help is needed urgent

    As above, it's likely to be a MCCB (or ACB/OCB...) and not a MCB. These all have a wide range of protection applied to them, so the type of protection fitted is important in order to analyse the problem. Most offer additional earth fault protection, so it could be a relatively small leakage...
  2. J

    Zs values recorded results.

    The reason is that ADS is all designed around protection of the individual in the event of contact (nail into a cable shorting to earth/cpc sort of thing) this determines the duration of fault (and to some extent the voltage - which should be less than 2/3 × 230V [due to the higher cross...
  3. J

    Zs values recorded results.

    Look at the regulations, Zs is defined as the earth loop path so essentially R1 + R2 (+ Re). It has nothing to do with the neutral path. ADS is always related to the earth route. Actually there is no specific disconnection time within the regulations for line to neutral faults - only that...
  4. J

    Zs values recorded results.

    You say recording the values - why are you recording the values? If it is to confirm ADS - this is particularly the earth path, so just lit Zs relates specifically to the earth path if you are confirming ADS, then you measure Zs and not the L - N path.
  5. J

    Bosch Professional or Makita

    I like that, tends to get expensive for a few tools though! I am thinking of phasing the older tools out as their batteries fail. With luck I will just about convert everything to the latest lithium ion in time for them to move on to the next range - and hence repeating the process.....
  6. J

    Bosch Professional or Makita

    Bit late to the party, but for me it isn't really about the drill itself, but the range of tools you use. You want the same make/series across; drill, driver, multitool, saw, chaser..... whatever, so go for whichever range has all the tools you want (need + desire) - all sharing the same...
  7. J

    BS 7671 18th edition amd 2 question?

    I believe the question dates from pre 2013, there was only one value given in the table (extract above), and the answer of 1.04 would have been correct at that time. Tbh there are several websites out there which have old questions relating to previous editions, it can be counterproductive to...
  8. Screenshot_20230804-172155_Brave.jpg

    Screenshot_20230804-172155_Brave.jpg

    • Julie.
    • Media item
    • Comments: 0
    • Category: Professional Electrician
  9. J

    BS 7671 18th edition amd 2 question?

    OK, could be, I am not near my book at the moment, the tables changed around 2013 so I may be thinking of the older ones. If the 1.04 ohm does line up with the old version and not the new, then it may be an outdated question applicable to an older version of the regs. Your question about...
  10. J

    BS 7671 18th edition amd 2 question?

    I don't have the latest table to hand, but from memory there is only one option, it is a final circuit on a TN system, so you know the max operating time is 0.4s. I think there is only one line for bs88 fuses (especially at 0.4s) at 32A, which from memory should be around 1.04 ohm so their...
  11. J

    How bespoke is this? Is there an alternative?

    You are correct, the uppercase letter (D, Y, Z, V, etc) refers to the primary winding, the lowercase letters refer to secondary winding(s) The number(s) 0, 1, 11, 6 etc refer to the phase shift between windings (referred to the primary) There could also be a n which indicates a star point...
  12. J

    Question about earthing the armour of SWA

    The problem isn't necessarily the loop impedance for the remote end, but what happens if the SWA is punctured shorting line to armour? Will that cause sufficient current to operate in a suitable time? I have seen situations where the remote supply (sub board, large load etc) has a suitable Zs...
  13. J

    UK AC At Home Anyone?

    We put a couple of Panasonic units in (living room and main bedroom) they have been OK for years. Basically we run the copper pipe, silver soldered it where required and pressurised it for a numer of days, since it held pressure long term, we then evacuated the pipework (~£20 vacuum pump), and...
  14. J

    Ze readings >2000Mohms

    Just thought I might add some other boring information. So if you short a generator directly, theoretically the current in each phase would be like this: Thus, the peak current could be over 2.8 (2 x sqrt(2)) the steady state value, in practice slightly less, and the decay rate changes...
  15. IEC_60909_Figure2.png

    IEC_60909_Figure2.png

    • Julie.
    • Media item
    • Comments: 0
    • Category: Professional Electrician
  16. 20230617_125741-01.jpeg

    20230617_125741-01.jpeg

    • Julie.
    • Media item
    • Comments: 0
    • Category: Professional Electrician
  17. 20230617_130210-01.jpeg

    20230617_130210-01.jpeg

    • Julie.
    • Media item
    • Comments: 0
    • Category: Professional Electrician
  18. J

    Ze readings >2000Mohms

    Ok, there is much to unwrap here – and I am struggling to do so! Let’s try talking it through – why do we want the Zs - there are two reasons, and let’s apply them to a domestic situation then industrial, then generation. Firstly We need to find out the MINIMUM fault level so we can...
  19. J

    Lucien Nunes Electrical Engineer Extraordinaire

    Sad, sad news. A great loss.
  20. J

    Electricity supply - Maximum Capacity of Connection 18 kVA

    The standard connection is up to 100A single phase or up to 100A per phase on three-phase. However in rural locations this could be limited to 32A (or 32A per phase) and in non-rural locations is normally limited by a fuse to 80A as a maximum (could be 45A, 60A, 63A.....) To calculate Amps...

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