"mitchd" wrote in message
...
Tim S wrote:
mitchd wrote:

..

Just out of interest, how far do you consider it reasonable to export a
TN-S
earth - I'd be interested for when I have to do it?

Cheers

Tim

Hi don't think distance is relevant, a decent earth loop reading is the
thing i would look for.

Calculate the cable size needed needed using
http://www.tlc-direct.co.uk/Technica...ltageDrop.html
and table 54G of the 16th edition for the CPC if there is no main bonding
required in the outbuilding

and another thing......
if you decided to put in a new pme supply from local electricity supplier
to said garage there would be no need for an earth rod. My point is all
customers really on electricity supplier for an earth point unless their a
tt system.
I have had issues with tn-s supplies, first thing to check is earth loop
had quite a few with high readings, they were simply converted to tnc-s by
local electricity supplier, but the house had been without an effective
earth for who knows how long.

It is more likely that you will see a TT supply converted to a TN-C-S
without the main earth connection being made as the bonding on the
installation was not up to TN-C-S standards and so the installation is left
as a TT.

Adam