Shared 'earth' cabling with sub-mains

[JohnW2]

OK, this is hopefully a straightforward question which shouln't result in a long thread ....

Can anyone see any problem with having the 'earth' (not sure whether one should call it that, CPC or what) accompanying sub-mains (i.e. from MET to the 'distant' CU/DB) partially shared by two sub-mains/DBs - in other words, a cable which goes from MET to one 'distant' DB, then on from there to a second one?

The only issues I can think of would relate to testing, and they can presumably addressed by adequate labelling of the cables.

Kind Regards, John.

 

[viewer]

Why not use an 'earth block' just before CU1 the separate cables to each CU? This way testing, changes etc can be done to either without completely removing protection. Reduces cables in CU and tightening/checking is easier.

 

[JohnW2]

Why not use an 'earth block' just before CU1 the separate cables to each CU? This way testing, changes etc can be done to either without completely removing protection. Reduces cables in CU and tightening/checking is easier.

If when you say 'CU1' you mean the first of the 'remote' (i.e.served by sub-main) CUs, then that is precisely the arrangement I am talking about.

Kind Regards, John.

 

[viewer]

Hi John,
From your wording, I thought that you meant the that the cable from the MET went to the earth connection within CU1 (yes, that nearest the MET/meter) and then continued to CU2. This would mean that to work on CU1, you may have to disable the earthing to CU2. With an earth block at the side of CU1 (not the MET which is at the start of the sub main), then one CPC cable would go to MET, one to CU1 and another to CU2 thus providing an earth. Hope this makes sense.
Regards
V

 

[JohnW2]

Hi John,
From your wording, I thought that you meant the that the cable from the MET went to the earth connection within CU1 (yes, that nearest the MET/meter) and then continued to CU2. This would mean that to work on CU1, you may have to disable the earthing to CU2.

No, I didn't mean that. Sorry if I was not clear.

With an earth block at the side of CU1 (not the MET which is at the start of the sub main), then one CPC cable would go to MET, one to CU1 and another to CU2 thus providing an earth. Hope this makes sense.

Sure, not only does that make sense, but it's the very arrangement I was trying to describe . I therefore take it that, as I had assumed, there is no problem in CU1 and CU2 sharing the same connection back to the MET?

Kind Regards, John

 

[viewer]

Sorry, misunderstood first post. No legal/regulation problems as far as I know and I've this arrangement in my own house so that circuits can be changed as the house is rebuilt bit by bit.
Regards
V

 

[JohnW2]

Sorry, misunderstood first post. No legal/regulation problems as far as I know and I've this arrangement in my own house so that circuits can be changed as the house is rebuilt bit by bit.

Thanks for confirming.

Kind Regards, John.