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GFCI *breaker* failure modes?

** It is generally the case.
You stupid, context shifting, Google Groups troll.

No context shifting - you asserted something that I disagreed with.

It is hard to find relative numbers, but in general old properties have TN-S earthing and new properties (last thirty years or so) have TN-C-S / PME.

Electricity suppliers certainly think that they mostly install TN-C-S / PME..

See for example:
http://www.westernpower.co.uk/Connections/Information-for-Electrical-Installers.aspx

They state:
We provide PME (protective multiple earthing) facilities as standard at thevast majority of new electricity connections. In some cases we can also install a PME earthing terminal at existing non-PME installations, although this does depend on the design of our electricity system and on the type ofinstallation.

In case you think I am cherry-picking just one power supplier, here is a quotation from an engineering design standard (EDS 06-0017) used by another large supplier:

Protective Multiple Earthing (PME) is the most common form of earthing provided at new installations. A single conductor for neutral and earthing functions is utilised and an earth terminal is provided at the customer’s installation. The customer’s earthing may be connected to this terminal providing the relevant requirements in BS 7671 are satisfied. In some cases it is not appropriate to provide a PME earth terminal, either due to the nature of the distribution system or due to the type of installation itself.

As for using google groups for posting - sorry about that - I'll get round to using a proper usenet service sometime.

John
 
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