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)
Socket outlet on a distribution circuit
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you would need to have an RCD at the house end or use an RCD socket.
Normally it is not; that's why SWA is used.
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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.
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?
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
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
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
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:
... and then ...
Kind Regards, John
You ignited my curiosity so a quick google found this - essentially SRCD not listed in 7671 may have been an error
https://communities.theiet.org/discussions/viewtopic/1037/25173
https://communities.theiet.org/discussions/viewtopic/1037/25173
Yes, I think we discussed that ('possible oversight') at the time. However, as I've just written it seems that BS7288 may be 'the problem'.
Kind Regards, John
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