I am a bit confused about what the regs require and what is good practise when connecting the earth wires as they come into a metal back box, especially when using metal sockets and switches.

I had always been told you connect the two earth wires from your ring wires as they emerge into the box into the terminal IN THE BOX. Then you connect a wire (all sleeved green/yellow of course - or whatever newfangled colour is current) from the box terminal to the switch/socket earth terminal.

That always seemed daft to me because if the socket casing became live, I would have thought it better to have a more direct path from the touchable cover of the socket to the earth wires in the ring main by connecting the two earths from the wiring DIRECTLY to the socket. The box could then be earthed by a wire from the sockets earth terminal to the terminal on the back box. The socket would be directly earthed to the ring through only ONE connection and the box would be earthed through two connections.

Or does it make any difference which way you do it.???

Now to my big question....I have a similar dilema with the wiring of a 45 Amp double pole stainless steel cooker switch (which is the type that incorporates a 13 Amp socket). I am using 10mm cable (some of you may remember a previous post discussing which to use) and have a 47mm box, slightly recessed. all of which means I have to be very tidy in the box to fit everything in....made a bit more challenging because I am using one of those trendy flat flush front switches which go back deeper into the box.

So in this case do I connect both 10mm earth cables that emerge from the wall into the terminal in the back box??? ... which isn't really big enough to take TWO 10mm cables .....And then run an earth wire from that terminal to the switch.

That does not make sense as there are TWO earth terminals on the switch that look as though they are designed to take the cable, easily accomodating 10mm...and common sense would say its better to have the socket casing directly connected to the earth wires. Then I guess i just connect a sleeved wire from one of the switch terminals to the terminal on the back box.

I even wonder what the point of connecting the switch earth to the back box earthing terminal since they will be screwed together anyway. Ok I suppose it protects someone if they unscrewed the socket from the wall while the electricity was on and there was a bridge from the live wire to the box as it entered the box....so it would trip out and not make the box live.

Enough rambling...any comments from the pros??? ... and once again thanks in advance for the super response that this discussion board provides. Well done folk!! ( I was going to say "chaps" .. but there must be some lady electricians out there )

[quote author=braychurchmouse  link=1109977002/0#0 date=1109977002]I had always been told you connect the two earth wires from your ring wires as they emerge into the box into the terminal IN THE BOX. Then you connect a wire (all sleeved green/yellow of course - or whatever newfangled colour is current) from the box terminal to the switch/socket earth terminal. [/quote]
Nonononono.

For sockets, FCUs, flex outlets, cooker isolators etc - anything in fact that has an earth terminal to supply an earth to the connected appliance, you absolutely must connect the circuit cable(s) to the accessory earth terminal, and then run a flylead to the earth terminal of the box.  Only when the accessory doesn't have an earth terminal of its own (e.g. a light switch) do you connect the circuit cpc to the box.

If the accessory has a metal faceplate, then you should also run a flylead to its local earth terminal.

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That cleared that up nicely  8)

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I assume you kept the T+E sheath as little as possible, e.g. only 20mm into back of box, then it's easier to do, saying that I hate pattress altogether, worked with too much PVC to like pattress now

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I wouldn't want to upset anyone  

Afterall, we don't want to get into another debate altogether  

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Yea me too, anyway it's not possible to take it to back box first in most cases as terminal is too small

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All metal boxes, surface or flush, should be earthed, either trough one of the fixed lug's and the screw trough the earth bar, or via an additional earth fly lead..

Boxes with 2 removable lugs require earthing via a fly lead

I agree lecc

I was naive once and thought that this box was most likely one with a fixed lug, when I went back to do inspection's, both the lug's were removable, therefor it's safer to fly lead to the back box

Apparantly it can sway reading's when it comes to testing and inspection, but I'm yet to see how that work's out  

Well you wouldn't get solid core down small conduit, I think there's a lot to be said for using 25mm conduit

 

If you say so, all depends how many bends/set's or other forms you have, also how many interconecting boxes,/terminal boxes you have, how long the run etc

I assume you have installed these in a conduit system to know it will work?  

Strange, was just trying to envisage what you meant, was the backbox on the outside then?  

weird thing is that water has such a high resistance compared to copper, how can you be getting good/better z's just because there is an earth path trough some water on the wall to the ground, compared to the Zs trough all the copper cables

Less than an ohm??

hmmmmm  

Nah I meant the water, water has a high resistance  

Yikes, where you been PW!  

oh yea, so in short you're thinking exactly what I'm thinking  

lol, dunno.. don't care