"John Rumm" wrote in message
et...
Martin Carroll wrote:

What I meant to say was why should it be buried 50mm below surface?

To circumvent the 17th edition requirement that concealed cables have
"Additional protection" from a = 30mA trip RCD. (protecting the cable
(metal conduit etc), using shielded cable (SWA, Earthshield, MICC, etc),
and surface wiring being other ways.

IMO putting it 50 mm deep is a problem.
If you are putting something substantial up you will use screws that are
longer than 50 mm so it offers little protection.
It does make it harder to locate using a detector.
I expect its another of those "we haven't really thought this through but it
sounds like we are doing our job" things the IEE comes up with periodically.
I suppose they will try and ban screws longer than 50 mm to fix the problem.