this is for electricians who, faced with the very rare situation
of this special form of supply need to know the bonding
requirements.
PNB can be recognised by the fact it is found mainly in rural
areas.
it is ALWAYS an overhead line, pole transformer, single phase
or multiphase type of supply.
the neutral earth is NORMALLY crimped at the point at which
the insulator bracket is fixed to a consumers external wall, but
in rare situations can be in the neutral block of the DNO service.
because PNB is non-statutory, the consumers bonding requirements
are less onerous than PME regulations.
while the ELI is expected to be low, (less than 0.5) as with all DNO
ELI parameters external to the installation, this cannot be guaranteed.
an ideal situation, particularly as these are mainly rural installations
would be to use the PNB connection as an earth path with RCCD/S.

Regards

Nonsense - try here for an example of PNB being offerd on a large (ish) supply. This example is SSE - see section 7.2

Regards

OMS

-------------------------
Failure is always an option

"It is ALWAYS an overhead line, pole transformer, single phase
or multiphase type of supply. "

No it's not I have seen plenty of PNB installations from transformers situated in basements in the next room to the LV panel.

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/

I think I`m just about getting my head around why PNB is TNS not TNC-S as we`ve always been taught.

If at the TX the conductor is earthed right after the N winding then that N conductor is taken any distance to the installation where it is split as N & E then it is a PEN and therefore TNC-S.

But if the N extends (unearthed) to the installation and then it is earthed at the installation then it is only a N conductor up to that point where it becomes earthed (in other words it is Tx star point right at the earth reference) thereby TNS.

Of course I might be wrong!

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik

How very dare you?

I am not Mr Cockburn!

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik

I reckon that means I am wrong or I have worded my question badly?

I am not Mr Cockburn though I promise you

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik

Wow that`s a relief, mind you I would not call anybody David Cockburn

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik

Except David Cockburn perhaps, Ebee -

OMS

-------------------------
Failure is always an option

OMS,
I so very nearly stated "Even if he is actually David Cockburn"

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik

LoL -

OMS

-------------------------
Failure is always an option

ebee, i've taken my post down , in the interests of keeping the peace.

Leaving it looking like Ebee is talking to himself, nothing being wrong with talking to yourself of course, so long as you don't start a argument!

I do sometimes argue with myself but I usually win

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik

How can you win an argument with yourself??
unless of course you win by winning and win by loosing, like whos round is it!!