Earthing System & Tranny

Lectrician · 28 Jul 2010

Ok, not a quiz as such (well, ok it is), but what earthing system do you think this pole mounted tranny provides?

It is a single tranny feeding a single service head.

And, this sign probably means very little to us mortals - it just reads like bad english

Monkeh · 28 Jul 2010

TN-C-S?

LoveRocket · 28 Jul 2010

TN-C-S PNB?

RF Lighting · 28 Jul 2010

TN-C-S

Lectrician · 28 Jul 2010

Well the concensus is TN-C-S. This is what I thought too when I looked, which annoyed me as TN-S had been requested and confirmed.

I had a closer look....

TN-S at the head, but at the tranny they should have taken two conductors from the N terminal on the side of the tranny, one going down to the 'rod' in the ground (done) and the other for the neutral. The split concentric cable should of had the neutral on the neutral conductor and earth crimped onto the smaller conductor running down to the rod.

Can you spot another error?

GarethW · 28 Jul 2010

Phasing ??

Adam_151 · 28 Jul 2010

Anti-clockwise phasing?

RF Lighting · 28 Jul 2010

Have they just got the colours in the wrong order is is the actual phase rotation backwards too?

Are the DNO saying they have supplied a TN-S?

jaysean1 · 28 Jul 2010

the casing for the head is missing!!

plugwash · 28 Jul 2010

Given that it's present in the upper picture I presume he just took it off to figure out what was going on.

londonboy · 28 Jul 2010

I have never worked with split con before... do you not need to sleeve the bare CPC's?

Monkeh · 28 Jul 2010

londonboy said:
I have never worked with split con before... do you not need to sleeve the bare CPC's?

You would if installing under BS7671, but DNO's don't install to BS7671 afaik. As such they're too lazy to bother.

Lectrician · 28 Jul 2010

RF Lighting said:
Have they just got the colours in the wrong order is is the actual phase rotation backwards too?

Are the DNO saying they have supplied a TN-S?

Didn't have my phase rotator so could not check the rotation, and as they have taped the cores up the pole you cannot really tell from that. I will check at some point - it's not essential at the mo.

DNO have confirmed TN-S on paperwork but are sending an eng to check.....

LoveRocket · 29 Jul 2010

Nope. You can't tell the DNO how to configure their equipment.

If there's a separate earth and neutral conductor from the star point of the tranny (which is rodded down) then it's TN-S. End of story mate.

Spark123 · 29 Jul 2010

That's the point, the neutral and earth are being taken from the same conductor (star point to the earth rod conductor) part way down the pole hence neutral current will be flowing in the short length of cable between the join and the transformer star point.

What type of installation is it Lec? Caravan site / farm?

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Earthing System & Tranny

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