What constitues an alteration to an existing installation.

[murdock]

In my opinion, putting a screw or pop rivet into the steel frame would constitute a violation of 6.12.1.3 'A wireway shall not be used as an earth continuity conductor'.
What do you think?

then lets look at how most installation worked in the past...as mentioned in another thread work...the steel frame of the socket outlet (crabtree and the old lumex plugs are a good examples) were screwed to the 4x4 /4x2 flush box which was passed for many years...i have noticed on some of the new installations the engineer has insisted that a link be put in between the 4x4/4x2 flush metal box and the frame of the socket outlet

most old domestic installations used the conduit and 4x4 or 4x2 steel box as the earth...ie when you removed the plug it was no longer earthed...just one example...in a situation like this i have come across a fair amount of so called elctricians (if they have ntc 3 they regard themselves as electricans...ntc 6 master elctricians) who remove the old metal framed socket and replace it with the new plastic sockets...becuas emost of them only own a couple of screwdrivers and a pair of pliers they cant test the plug to check for earth...the fact that there is no earth wire to connect to the socket just means that it doesnt need one...yeah i know you ar eshaking your head...what is really scary is when you confront the owner of the company who sent out the bright spark to replace the socket...says no problem just pull in an earth wire and send me the bill...i take out my plug tester and find they have replaced 14 socket outlets in the duplex...not one has an earth...i pack up my tools and advise the customer to contact the company who replaced the plugs.

[murdock]

Depends if you're using the actual wireway as the earth or you're just earth bonding the wireway as an extraneous item. In my sketch above the backbox and steel conduit in the wall are bonded, they're not used to actually carry the earth.

the older installations used the piping and metal boxes as the earth...there were only 2 wires in the electrical installation...red and black...no earth...the piping above the db would be bonded with a bonding strap and water pipes etc...including the electrical piping and earth wire from the overhead supply cable...all connected to one point...the problem however...over the years the pipes in coastal areas have rusted creating a higher resistance...deeming the earthing inadequate...so back to connecting an earth wire from the plastic socket or even replacing the metal one with another metal one...personally i would run a new earth wire back to a point were i can connect in to the incoming earth wire...be it an overhead line wher ethe earth wire would be running across the roof sapce or to the DB in the case of an underground armoured cable treminated at the DB

[Leecatt]

Depends if you're using the actual wireway as the earth or you're just earth bonding the wireway as an extraneous item. In my sketch above the backbox and steel conduit in the wall are bonded, they're not used to actually carry the earth.

Thanks for your reply Andy, I really do appreciate the input on this subject.
However in this case that Murdoch mentioned the cojute pipe is being used to connect the earth pin of the socket outlet to the earth wire bonded to the top of the same conjute.
My stance however, is that I feel that the replacement of a socket outlet, or light switch, DOES constitute an alteration to an existing installation, and therefore new rules have to be applied to the existing installation. I have heard voices from well qualified sources deny this.

[Leecatt]

the older installations used the piping and metal boxes as the earth...there were only 2 wires in the electrical installation...red and black...no earth...the piping above the db would be bonded with a bonding strap and water pipes etc...including the electrical piping and earth wire from the overhead supply cable...all connected to one point...the problem however...over the years the pipes in coastal areas have rusted creating a higher resistance...deeming the earthing inadequate...so back to connecting an earth wire from the plastic socket or even replacing the metal one with another metal one...personally i would run a new earth wire back to a point were i can connect in to the incoming earth wire...be it an overhead line wher ethe earth wire would be running across the roof sapce or to the DB in the case of an underground armoured cable treminated at the DB

I never took coastal conditions into account as I am inland , but a very valid point.