Externally mounted Electric meter box - Consumer unit

Discussion in 'Electricians' Talk' started by DannyDoLittle, Sep 1, 2017.

  1. Coloumb

    Coloumb Screwfix Select

    @unphased Did the technical guys say you needed to fit a switch fuse? Please don't tell me they quoted that reg at you?
     
  2. leesparkykent

    leesparkykent Well-Known Member

    TBTH column isn't an electrician and unphased isn't a time served electrician either.....so any one who reads this thread and previous threads on the same subject can make their own mind up ;)....
     
    Risteard likes this.
  3. Coloumb

    Coloumb Screwfix Select

    I doesn't mater though does it? In our context it's simple. Why put two switch fuses of the same rating within three meters of each other? Being time served really makes not odds, or even being an electrician. The question is academic. So it's a really pointless argument to make unless you can state the reasons why. According to you it's written in the dcusa doc I posted, but you won't tell me where.
     
  4. leesparkykent

    leesparkykent Well-Known Member

    But you are not an electrician so whats the point as you clearly won't understand!
     
  5. Coloumb

    Coloumb Screwfix Select

    You mean I don't understand having two switch fuses of the same rating within three meters of each other? If I don't get it then wouldn't the best thing to do to be to explain, with reference to the dcusa link?
     
  6. leesparkykent

    leesparkykent Well-Known Member

    You've come out with the same rating thing etc not me...A 100A bs361 type 2 or bs88-3 (what ever you want to call it) will discriminate fully with a 63A fuse of the same kind...

    Answer this question...is the main fuse part of the distributors equipment?
     
  7. Coloumb

    Coloumb Screwfix Select

    Sigh, that's not the point though is it? You are convinced some how that it is a requirement to fit a switch fuse, potentially of the same rating as the cutout, within three meters of it. Ergo, two fuses of the same rating within three meters of each other. Your argument is based on the fact that it is a contractual requirement between the meter operator and the supplier yet you refuse to actually produce any evidence to suggest this has any kind of basis.
     
  8. leesparkykent

    leesparkykent Well-Known Member

    No you come out with the bit about the same rating etc not me..... 100A DNO fuse and I have a 63A fuse in my switch fuse...who's fuse goes 1st when there's a fault on the distribution circuit that comes off the load side of the switch fuse?
     
  9. Bazza-spark

    Bazza-spark Screwfix Select

    All this assumes the supply is TN. What happens where the supply is TT? With the requirement for a metal CU the prospective earth fault current on a TT system may well be too low to blow any fuse if a fault occurs on the tails from the CU to the meter, hence the whole earthing system has the potential to become live as the fault is the wrong side of any RCD's in the system.
     
  10. Coloumb

    Coloumb Screwfix Select

    So don't tell me you would be happy to NOT fit a switch fuse of the same rating as the cut out if the meter tails > 3m?

    And please don't tell me you would fit a 30a s/f for a 60a c/o.
     
  11. leesparkykent

    leesparkykent Well-Known Member

    Why would I have to fit one of the same rating or type? So back to the question...who's goes 1st?
     
  12. JP.

    JP. Screwfix Select

    I always thought that after the meter you fit a 100 amp dp isolator in enclosure, and from the enclosure you go to the db - the length of the tails from the enclosure can be 3 or 4 meters (depending on DNO) and then anything over that needs other stuff doing (not going to say what) TT may need other considerations to be factored in.
     
  13. leesparkykent

    leesparkykent Well-Known Member

    Well you would design a compliment installation with selectivity and earth fault protection taken into account...I don't really get your point?
     
  14. Coloumb

    Coloumb Screwfix Select

    I actually think your just trolling now but hey.

    You go to a job, it's a complete re-wire. The customer wants the CU in the kitchen which is 10m away from the cut out which is rated at 60a. You check the Ze and find 16mm SWA three core will have a low enough Zdb to pop the fuse in the cut out. Do you

    A) fit a switch fuse of 30a within 3m of the cut out.
    B) fit a switch fuse of 60a within 3m of the cut out.
    C) Do nothing, the cut fuse is good enough.

    ?
     
  15. leesparkykent

    leesparkykent Well-Known Member

    No you install a switch fuse of course. The DNO's fuse could be upgraded if necessary.....So for the 3rd or 4th time of asking..Who's fuse goes 1st?
     
  16. Coloumb

    Coloumb Screwfix Select

    Yes but which one, a or b?

    In the case of a 100a cut out -> 63a s/f the 63a goes first. We've already had this discussion a few posts back so it's a bit of a waste of time, so I hope this post will put it to bed so we can get back on topic.
     
  17. Bazza-spark

    Bazza-spark Screwfix Select

    My point is that you are stating the DNO or meter operators stipulate the requirement for a switchfuse. This is assuming it is a TN system. What is their stipulation where the supply is TT?
     
    Coloumb likes this.
  18. leesparkykent

    leesparkykent Well-Known Member

    Neither if can be helped as it's prudent to provide discrimination.
     
  19. leesparkykent

    leesparkykent Well-Known Member

    Yeah what if the earthing arrangement is TT? If you install a distribution circuit because the tails are over 3meters then you design a complient circuit that has earth fault protetion of course....:eek:
     
  20. Coloumb

    Coloumb Screwfix Select

    So if your actually saying you don't need a s/f if the cut out provides protection?
     

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