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Ross Trician

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Hello all,

I went to look at a job today that I have been asked to price for but I am abit confused at the way the c.u is fed.

The job is a bowling green club house thats being extended, the cu tho is fed from the meter of the tennis courts, about 40m away.
it is run in 2 core swa that look to be maybe 16mm max. they have used the armourings as the cpc.

the main cutout is 100A,

would I be right in saying the supply cable needs to be suitably rated to match the cut out fuse?

also is it allowed, (whether morally or not) to use the armourings as the cpc to supply the c.u?

been looking in the big red book but cant seem to see the obvious if its there..

I am thinking it wants the cable changing to 3 core and25mm, Subject to the volts/amps drop etc for the distance.

thanks, Ross.
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  • Thread Starter Thread Starter
  • #2
You can still use the armour as the cpc as long as it is correctly terminated.
Had a friend who failed an NIC visit for not running a separate CPC and only relied on the armouring! Don't know where it is stated in the reg tho.


  • Thread Starter Thread Starter
  • #4
Agree with dazza.
Better to use 3rd core for cpc and armouring(earthed) as protection.
Better safe than sorry.



  • Thread Starter Thread Starter
  • #5

You can absolutely use the armour as a CPC providing the CSA value is large enough and continuity can be absolutely assured. P131 ol'red.

Got to be honest though I never do, always use 3core for single phase ar install seperate conductor for 3 phase.


Ross Trician

  • Thread Starter Thread Starter
  • #6
Hello folks,,,thanks forthe replys...

My understanding is that I need to install a fused isolator, (rated for the swa cable) at the meter. earth the armourings at the supply end, and then create a TT system at the Bowling Green pavilion.
the problem with using a third core for the earth is if this was to get broken you would then make the earth a phase...

isnt it something to do with exporting the earth in a tncs,(pme) system???

wouldnt it be nice if things were simple, clear and

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