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CONSUMERS TAILS IN THE OSG

John Peckham
I have just been having a scan read of the latest edition of the OSG. On page 20 it says in respect of consumers tails, " Polarity should be indicated by the colour of the insulation and the minimum cable size should be 25mm".


Alongside this statement is a reference to 514.3.1. I am OK with the requirement in 514.3.1 for the colour of the insulation but where  does the requirement come from for the CSA to be 25mm?


I do know some DNOs representatives may require a minimum CSA of 25mm but I suspect that this is a personal preference. My thinking is this is one of the myths and legends of electrical installation work that has been repeated so often that it has become fact. My view is the tails need to be sized to take the maximum load and they also need to be co-coordinated with the supply fuse. In addition some older consumer unit terminals will not take a 25mm tail.


Can anyone direct me to a reference source that requires the minimum CSA of meter tails to be 25mm?


  • 0

    Sparkingchip:

    A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.


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    ?



    Z.

  • 0
    All this because an unnecessary guidance book prints a something which is not true.


    It also contains:
    "While the author, publisher and contributors believe that the information and guidance given in

    this work are correct, all parties must rely upon their own skill and judgement when making use of

    them. The author, publisher and contributors do not assume any liabifity to anyone for any loss or

    damage caused by any error or omission in the work, whether such an error or omission is the result

    of negligence or any other cause. Where reference is made to legislation it is not to be considered

    as legal advice. Any and all such liability is disclaimed."



    I also used to object to having to buy a copy in order to pass the scheme annual assessment.



  • 0
    It is also a good idea to increase the size of tails to 35mmsq if you have a continuous rating of 90amp+ ( supply permitting) This is particularly useful if you have high storage heater loads and water heating.


    They don't tell you that in the on-site guide.

    Regards, UKPN.

  • 0
    I have to admit to being flummoxed as to what the OSG is actually FOR, I have a copy of the regs in the car, and colleague keeps his in the van, in the megger case, to be exact.... so why would we need yet another book?
  • 0

    UKPN:



    It is also a good idea to increase the size of tails to 35mmsq if you have a continuous rating of 90amp+ ( supply permitting) This is particularly useful if you have high storage heater loads and water heating.


    They don't tell you that in the on-site guide.

    Regards, UKPN.

     

     




    Because tails on the consumer side of the meter carry less current than on the DNO side?


    Andy B.

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