In article ,
"G&M" writes:

"Christian McArdle" wrote in message
. net...
Is there a "main earth bond" in such a system? If so where is it?
I'm concerned only because if there is a "main earth bond" then should
it be some proportion of the meter tail size (even on a TT system)?

TT doesn't need the large earth conductor sizes that TN-C-S (PME)
requires,
as the RCD ensures that any earth current flow is short lived and requires
only 100mA to trip, so earth loop impedence is not particularly relevent
(within reason).

However, it is a VERY good idea to install the TN-C-S recommended sizes,
as
it will enable you to upgrade to TN-C-S when it becomes available in your
area.

Why do you see PME as an improvement ?

You can design for improved circuit protection without either
having the whole house on one or two RCDs, or having to use lots
of RCBOs.

Where we are the PME earth is so
far above real earth you daren't trust it and have to convert back.

What sort of voltage difference are you talking about?
The supplier is required to ground the PEN (Protective earth and
neutral) conductor within some fairly short distance from your
house (like 60m, but can't recall for sure). Any significant
PEN to ground voltage would indicate a supply fault.

--
Andrew Gabriel