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Discuss length of circuit calculation - head scratching stuff! in the Periodic Inspection Reporting & Certification area at ElectrciansForums.co.uk.

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  1. sivoodoo
    Offline

    sivoodoo Guest

    Hi all,

    How do I work out the length of a circuit?


    I have these figures

    R1+R2 = 0.40

    The circuit is wired in 2.5mm/1.5mm T&E

    I take it I need to know the resistance of the T&E (where do I find this?)

    Could someone give me the formula or point me in the right direction

    Thank you.
     
  2. AlanDavies
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    AlanDavies Guest

    I got the data from here:Untitled

    1.5mm = 12.10 mOhms/m
    2.5mm = 7.41 mOhms/m

    12.10 + 7.41 = 19.51

    19.51 mOhms/1000 = 0.01951Ohms/metre

    0.4 / 0.01951 = 20.5m

    I think, can someone else check my maths.
     
    Last edited by a moderator: Feb 12, 2009
  3. sivoodoo
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    sivoodoo Guest

    Brilliant!!!
    Thank you so much.
     
  4. JASON
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    JASON Electrician's Arms

    Location:
    Button Pressing
    This info is in the BRB.
    Somewhere.
     
  5. sivoodoo
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    sivoodoo Guest

    thanks, ive been looking in the big red one and i cant find it yet?
     
  6. AlanDavies
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    AlanDavies Guest

    On Site Guide - appendix 9 - page 166
     
  7. JASON
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    JASON Electrician's Arms

    Location:
    Button Pressing
    Sorry, yes, the little red book!
     
  8. sivoodoo
    Offline

    sivoodoo Guest

    Thank you all

    How accurate is this measurment, some of the results I have seen dont add up?
     
    Last edited by a moderator: Feb 13, 2009
  9. Des 56
    Offline

    Des 56 Trusted Advisor

    Location:
    Gliese 581C

    Very accurate indeed

    Varying readings could be a number of factors
    Parallel earth paths when recording the R1+R2
    Loose or bad connections at outlets
    If its a ring
    Spurs giving an higher reading because of the extra lenghth
    Be sure that the Rn and R1 of the ring are exactly equal
    Interconnections on the ring
     
  10. trebor
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    trebor Guest


    exacto mondo 0.4 x 1000/ 19.51 = 20.5 metres

    all the figures for resitance of conductors are in the OSG or GN3
     
  11. bigal
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    bigal Guest

    Forgotten how good this site is. Thanks for the reminder.
    bigal
     
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