In message ,
(Dale Shuttleworth) wrote:

Hi,

Sparks ) wrote:

[...]

: Phone the electricity co and ask to be converted to PME. You must not do
: this work yourself. Legally, it is the elec co's cable. Technically, they
: must confirm that their neutral is continuous back to the substation and
: suitable for PME use. Commonsensically, it involves opening up the incomer
: and exposing the incoming cable before the service fuse.
:
: Okay, I did think this would be the case here
: I was wondering if i could use the neutral after the meter, so to avoid
: having to call them out, but i see it needs confirmation from them, so
: better leave it to them!
:
: Do you think they charge for this?

Probably, on the basis that there's no real need for the change so far
as they are concerned and it costs them money to send a man round... I
can't see any real justification for you to change from what sounds like
a TN-S system (earth return via sheath) to a TN-C-S system (PME - earth
return via neutral) - you'll still need the earth rod for operation from
the generator in either case.

[...]

[...]

I read back to the start of the thread, and as far as I can tell it
seems as if there is a TN-S system in place, and the sole area of
concern is the "small size" of the earth wire from the cable sheath to
the consumer unit. To see if this is inadequate will require knowledge
of the wire's actual CSA and some calculations involving your circuits
and the "fault loop impedance" of the installation and the supply, but
if you want to be sure there should be no problem installing a thicker
earth wire even if, as is probably the case, this is not really
neccessary.

In itself I don't think this is really a case for upgrading to TN-C-S
with all its attendant bonding stringencies (and the supply may not be
capable of giving you TN-C-S), but it *is* a case for calling up the
supply company and asking if they can attach a thicker earth wire which
you will provide. To cover possible future TN-C-S use this earth wire
should be at least half the size of the "meter tails" which generally
these days means 16mm2 for 25mm2 tails.

You may even find the company doesn't charge for this. I'm in the middle
of a rewire at the moment and, somewhat similarly, wanted to upgrade the
earth. The situation is slightly different in that the supply was
already TN-C-S (PME) and marked as such, but the installation was TT. My
big problem was that I couldn't find an earth rod anywhere!

I called SWaLEC who put me on to Western Power Distribution who
(eventually) came out and attached my 16mm2 earth to the neutral block
on their incoming. They even upgraded the main fuse from 60A to 80A, and
all without charge, though the engineer did say that as far as he was
aware this was about the only thing they didn't charge for doing - I
think he meant the earthing and that I got the fuse as a "by product"
:-)

The meter was already rated 80A so they didn't have to change that when
they installed the new fuse.

Does this shed any light on the matter?

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Don't fight technology, live with it: http://www.livtech.co.uk/
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