Earthing Sockets

[SgtTrojan]

During an NICEIC annual inspection of work to assess the company's integrity it was declared by the inspector that it was not a requirement to earth any accessory backbox (as long as it had one fixed lug, as stated above).

I also agree with the comments about other trades removing live covers to do a better job and the need for them to be earthed.[/u]

 

[radweld]

Having seen the state of various accessory wiring* it always strikes me as bad engineering to cram in unnecessary additional bits of copper in to the backbox.

* I am sure everybody reading this perfectly dresses the cable in the backbox, fully sleeve all earths and ensure all wires are securely terminated, of course.

 

[Spark123]

During an NICEIC annual inspection of work to assess the company's integrity it was declared by the inspector that it was not a requirement to earth any accessory backbox (as long as it had one fixed lug, as stated above).

I'll disagree with this comment, it depends on what it is. If the back box is accessible then it must be earthed using fixed wiring - not rely on a fixing screw.
Similarly, where the accessory doesn't have an earth terminal such as a bog standard plastic light switch the back box must be earthed.

 

[SgtTrojan]

Oh don't worry, I am all for connecting an cpc to where ever there is a terminal for it but an NICEIC inspector may not pull that up as a non-conformance.

 

[Chri5]

Oh don't worry, I am all for connecting an cpc to where ever there is a terminal for it but an NICEIC inspector may not pull that up as a non-conformance.

So in summary, for the 15 seconds it takes to run a flylead it's accepted that it is a good thing to do- Its not a requirement to do provided the back box has 1 x fixed lug, is fixed with metal face plate screws and the box is in the wall.

If the box is surface, if the box is fixed with plastic screws or if the box had no fixed lugs it is essential.

So would it not be best to do as I and 50% + of the posters do and simply provide a earth to the box every time.



I buy 100m of 1.5mm gy single core every year or two. 15cm flylead = approx. 660 flyleads at a crippling cost of 2.5p each

 

[SgtTrojan]

OOohh you are venturing into the realms of supplementary bonding and the minimum size of conductor for exposed conductive part to exposed conductive part.

 

[dingbat]

OOohh you are venturing into the realms of supplementary bonding and the minimum size of conductor for exposed conductive part to exposed conductive part.

If you're wanting to go down that diversionary, off-topic route, the best universally unknown size is the second of the group; exposed to extraneous.

 

[SgtTrojan]

It's on topic. Exposed to exposed. Socket earth terminal to socket back box. What is the minimum size permitted?

 

[dingbat]

It's on topic. Exposed to exposed. Socket earth terminal to socket back box. What is the minimum size permitted?

The topic is earthing, not supplementary bonding.

 

[SgtTrojan]

Uhmmm

I know you don't need me to tell you but there are four conductors classified under the term "earthing". What is the extra link cable called if classified under "earthing"?

 

[dingbat]

I know you don't need me to tell you but there are four conductors classified under the term "earthing".

I think you'll find that's incorrect. Only numbers 1 & 3 are doing the job of earthing. 2 & 4 are bonding. But they are all called 'protective conductors'.

What is the extra link cable called if classified under "earthing"?

Well, have a look on page 32 and work it out.

(Of course you'd also need to acquaint yourself with Ch 54 and the definitions and then have a think about what your point is.
And you may want to check out how the Wiring Regulations National Committee refer to the topic. )

 

[SgtTrojan]

Ok, thank you, protective conductors, not earthing but conductor 4 links two exposed conductive parts and is classified as supplementary bonding.

So is the link classified as supplementary bonding and governed by the size restrictions in Table 4.3 p30 of OSG?

(I love earthing debates - Does that make me wierd?)

 

[dingbat]

Ok, thank you, protective conductors, not earthing but conductor 4 links two exposed conductive parts and is classified as supplementary bonding.

But notice that in that diagram the exposed conductive parts belong to two different circuits. In a single circuit the cpc does the job all by itself - see Reg 544.2.4

So is the link classified as supplementary bonding and governed by the size restrictions in Table 4.3 p30 of OSG?

The wiring committee don't think so; they refer to the subject under debate as the earthing of flush metal accessory boxes and have determined that flush metal accessory boxes should be considered to be exposed-conductive-parts and connected to the main earthing terminal by means of a circuit protective conductor. Then, of course, they go on to say that this can be satisfactorily achieved by using the fixing screws as long as one of the lugs is fixed...

Of course, if you have reason to believe that this would not be satisfactory due to external influences, etc, then you do whatever you believe you need to do to make it satisfactory.

(I love earthing debates - Does that make me wierd?)

No.

Completely normal.

Like me.

 

[Spark123]

It's on topic. Exposed to exposed. Socket earth terminal to socket back box. What is the minimum size permitted?

Regulation 543.1.3, S=sqrt I²t / K
For a 32A circuit 1.5mm² usually suffices.

 

[Spark123]

Oh don't worry, I am all for connecting an cpc to where ever there is a terminal for it but an NICEIC inspector may not pull that up as a non-conformance.

I hope he would haul you over the coals if you didn't connect a flylead from socket front to backbox in a metal clad socket (or any other metal type with the backbox exposed.)