Socket outlet on a distribution circuit

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Hi I need to supply power /DB2 to a shed AKA summer house at 35M from house which is straight forward enough, however the customer also wants a twin s/o in the garden halfway. Rather than bring a cable back from DB2 (or another cable /circuit from DB1) I am considering putting the socket midway within the distribution supply cable (6mm2 swa clipped direct ) . The OCPD would be 40A. I can’t see any reason why not to but as slightly unconventional? wondering if I’ve missed anything ( I’ve taken into account VD, cable current carrying capacity, , max Zs etc and earthing considerations)
 
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Yes good point because it means less selectivity on the (2) final circuits but that’s acceptable in this case and arguably better to have additional protection on the SWA than just ADS
 
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Under what circumstances is additional protection of an SWA cable by a 30mA not preferable to ADS ? (Ignoring selectivity as outlined above )
 
It is usually not desirable for a distribution circuit to be RCD 'protected' because then all the circuits connected to it will be lost with one fault.

One of the ways to avoid having to have an RCD on a cable is 'an earthed metallic covering' - so, conversely, if you have an RCD you don't need SWA.
 
Yes agreed. Anyway back to the original question is there anything wrong with the design which would effectively be a radial socket circuit with a DB at the end feeding a 20A radial and 6A lighting cct in the outbuilding?
 
Yes agreed. Anyway back to the original question is there anything wrong with the design which would effectively be a radial socket circuit with a DB at the end feeding a 20A radial and 6A lighting cct in the outbuilding?
For what it's worth, nothing wrong that I can think of, provided that, as discussed, the socket on the distribution cable is somehow provided with RCD protection.

Kind Regards, John
 
you would need to have an RCD at the house end or use an RCD socket.
Am I dreaming it, or did someone not fairly recently suggest that (for some reason I don't recall) an RCD socket is, strictly speaking, not an acceptable/compliant solution (despite being a common practice)??

Kind Regards, John
 
Never heard that before John ? My only Thought is they meant where the cables supplying the socket are concealed in walls less than 50 mil not otherwise protected etc ?
 
Never heard that before John ? My only Thought is they meant where the cables supplying the socket are concealed in walls less than 50 mil not otherwise protected etc ?
No, it wasn't that - the potential need for RCD protection of the cables is a separate issue.

The suggestion came as a total surprise to me (seemingly essentially rendering RCD sockets useless!) and, as I said, I can't remember anything about the alleged reasoning/explanation - so I'll see if I can find it!

Kind Regards, John
 
Never heard that before John ? ...
Found it :)

The suggestion (from flameport) was that the Standard for RCD sockets appears to require that there is also additional upstream RCD protection (which, as he says, would essentially make nonsense of RCD sockets). He wrote:
RCD sockets make no sense at all, as the standard for them requires that they have upstream RCD protection.
... and then ...
Scope from BS7288:2016
Fault protection (MCB/fuse) and additional protection (RCD) required upstream of the RCD socket outlet.
Not intended for isolation either.
View attachment 227617
That part is included in the preview at https://shop.bsigroup.com/ProductDetail/?pid=000000000030337151

Kind Regards, John
 

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