Earthing System & Tranny

[Adam_151]

I'm not convinced that the way its been connected makes it TNCS (and even if it did, surely not PME)

If you think of a standard TNS setup, 4 conductors from the transformer to the substation fuseboard, where the neutral is tied down to earth and the neutral and earths of the outgoing supplies are attached. Or as often encountered on reasonably sized commerial/industrial sites... PNB, where the 4 transformer unloading tails come into the customers main panel along with the means of staking down... not sure this situation is massivly different, the star point of teh transformer is just dropped a few feet down the pole before being referenced to earth and feeding the customer supply

In my book its TNS if its separate from the point of the DNO earth tie down in the vicinity of the transformer, and TNCS if its not

 

[johno12345]

Id call that TN-S

if there were a n-e link in the cutout then PNB but BS7671 doesnt seem to recognise PNB anymore, if ever

 

[1john]

TN-S surely, i was under the impression that TN-C-S meant that the earth and neutralhad to be seperated at the origin of the installation, ie the cut out, not at the pole connection? Saying that I thought all new supplies were TN-C-S

 

[LoveRocket]

Hmmmm, I see what you're getting at. With N & E combined for a few feet it could be argued that it's TN-C-S. But the DNO guy will just say it's TN-S and tell you to wind your neck in.

 

[Lectrician]

I am more than happy to call it TN-S, and I would certainly not call this TN-C-S.

I was meerly pointing out that it was difficult to tell.

However, neutrals are always the crimps/line taps that corrode, and if that joint on the neutral up the pole corrodes it would not be a great outcome. The N/E is meant to split on the actual terminal of the tranny, not down the pole, but what ever the DNO have done is nothing to do with me. The post was more for refference really.

I actually rang to check it was TN-S before I removed the service head cover, I would not have bothered otherwise.

The site is actually just a field that is let out for various events - camping for 28days a year, open air market once a week, car boots, weddings and parties etc. There is often portacabins and steel container type shower facilities on site.

 

[Lectrician]

TN-S surely, i was under the impression that TN-C-S meant that the earth and neutralhad to be seperated at the origin of the installation, ie the cut out, not at the pole connection? Saying that I thought all new supplies were TN-C-S

Our DNO will usually provide TN-S as standard when you end up with your own tranny. Especially so on installs like this.