In article ,
dennis@home wrote:


"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.

Y es - it's a strange distance. Far more than needed to protect from a
picture hook nail.

Although most things you buy which are designed for screwing to a wall
come with screws which are far too short to make a really secure fixing.

--
*Bigamy is having one wife too many - monogamy is the same

Dave Plowman London SW
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