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

S

sivoodoo

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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.
 
A

AlanDavies

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  • #2
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:
S

sivoodoo

  • Thread Starter Thread Starter
  • #3
Brilliant!!!
Thank you so much.
 
S

Spudnik

  • Thread Starter Thread Starter
  • #4
This info is in the BRB.
Somewhere.
 
S

sivoodoo

  • Thread Starter Thread Starter
  • #5
thanks, ive been looking in the big red one and i cant find it yet?
 
A

AlanDavies

  • Thread Starter Thread Starter
  • #6
On Site Guide - appendix 9 - page 166
 
S

sivoodoo

  • Thread Starter Thread Starter
  • #8
Thank you all

How accurate is this measurment, some of the results I have seen dont add up?
 
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Des 56

-
Arms
Esteemed
Thank you all

How accurate is this measurment, some of the results I have seen dont add up?

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
 
T

trebor

  • Thread Starter Thread Starter
  • #10
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.

exacto mondo 0.4 x 1000/ 19.51 = 20.5 metres

all the figures for resitance of conductors are in the OSG or GN3
 
B

bigal

  • Thread Starter Thread Starter
  • #11
Forgotten how good this site is. Thanks for the reminder.
bigal
 
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