Earthing Metal Back Box?

[Damian30]

All,

Thanks for the feeback - all sorted now.

Looks like he already used the earth in the back box for the grid plus switch, so why he didn't do it for the joint box I don't know.

Thanks again,

Damian

 

[333rocky333]

I don't see why he didn't use the earth terminal in the back box to join the CPC's

surely, it wouldnt then be a ring circuit if he had

 

[JohnW2]

I don't see why he didn't use the earth terminal in the back box to join the CPC's

surely, it wouldnt then be a ring circuit if he had

It surely doesn't matter where the CPCs of a ring circuit are joined, so long as they are joined, does it? ... they can be joined at a back box terminal, in a bit of connector block, a Wago, in a JB, at an accessory or wherever, can't they?

Kind Regards, John

 

[sparkwright]

I think the point Rocky was trying to make is that in this case, where the ring has been extended, all the earths shouldn't just be simply joined together.

An old earth and new earth get joined.

The remaining old earth and the remaining new earth get joined.

As I'm sure you know, it would be the done thing to join all four earths together.

It wouldn't have hurt to join one set of the earths to that metal box earth terminal, or used a fly-lead between.

Possibly a fly-lead is best if the back box has a dodgy earth terminal, as some often do, but now I'm starting to complicate things.

 

[JohnW2]

I think the point Rocky was trying to make is that in this case, where the ring has been extended, all the earths shouldn't just be simply joined together.

Fair enough.

An old earth and new earth get joined. ... The remaining old earth and the remaining new earth get joined. ... As I'm sure you know, it would be the done thing to join all four earths together.

I presume you mean wouldn't. Although it's not 'the done thing' (and I wouldn't do it), and could confuse testing, ironically it would, electrically, be arguably "safer"!

Kind Regards, John

 

[endecotp]

Interesting...

So what exactly would the disadvantage be to joining all the earths together in a case like this?

It seems to me that adding additional redundancy to the path for the earth back to the CU can only be a good thing.

 

[JohnW2]

Interesting... So what exactly would the disadvantage be to joining all the earths together in a case like this? It seems to me that adding additional redundancy to the path for the earth back to the CU can only be a good thing.

That's what I meant when I said that, electrically speaking, it (redundant and 'parallel' CPCs) is arguably safer. It could cause confusion as regards testing because it could result in the 'end-to-end' resistance of the CPC of 'the ring' being less than it "ought" to be - again, I don't see that as an electrical problem, but it could result in some head scratching!

Kind Regards, John

 

[sparkwright]

I think the point Rocky was trying to make is that in this case, where the ring has been extended, all the earths shouldn't just be simply joined together.

Fair enough.

An old earth and new earth get joined. ... The remaining old earth and the remaining new earth get joined. ... As I'm sure you know, it would be the done thing to join all four earths together.

I presume you mean wouldn't. Although it's not 'the done thing' (and I wouldn't do it), and could confuse testing, ironically it would, electrically, be arguably "safer"!

Kind Regards, John

I did indeed mean WOULDN'T.