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I have a length of 3core SWA cable and some existing outdoor sockets on the side of the house.
my thinking is to put the SWA straight in to the existing double socket, run it down the garden (digging in) and in to a junction box to supply the sockets. The lighting could also be plugged in to the sockets if it made it simpler.
only likely to be running the odd power tool, radio, lamps or other such stuff, fairly light use.
Does this sound ok?
However the earth at the load end may or may not be taken from the armour, it may instead be that the armour is insulated, and earth taken from a local electrode, depending if it is better to create a TT island for the load - examples where it is better to have a local earth rod and not use the suppliers earth at the load end, when the suppliers earth is PME /TNC-s include for car charging points, swimming pools, areas with earth floors and livestock, caravan pitches, and a few other situations. Examples where you would use the house earth are if it has a dry wooden floor and all the electrical items are domestic, and essentially indoors.
Between those extremes lies a large area requiring some thought.
The interesting thing is that virtually all, if not all, of the defects have been revealed on inspection rather than testing.
The cable did not have the armour earthed, well it was not even connected.
1) how are the existing sockets supplied - own circuit, or spurred off the house ring, or just hung off the back of the light switch ? You need to know, and to be sure they are in fact supplied correctly to begin with, i.e. from a circuit that can take the load, and the supply cable is co-ordinated with the rating of the fuse or breaker, and there is RCD protection.
If they are spurred off an existing ring, it is a very good idea to add a fused spur or RCD spur with a switch inside the house to protect just the outdoor bit, than you can isolate it when you go on hols or if water gets in.
2) This SWA - what is it's copper cross section? - for sockets over that distance I'd expect at least 2.5mmsq if the circuit fuse or breaker was 20A or less. Perhaps 4mmsq. Again, the cable size needs to co-ordinate for the rating of rest of the circuit. Look up how to terminate the IP rated glands unless you already know what you are doing.
3)Digging in - if it is not under a concrete path, I'd suggest aim for half meter down or more, in case the garden gets dug at some point.
4) Earthing. How is your house earth, TT, TNS or TNC-s . Also is the shed floor timber and dry, or cement or earth or possibly damp, and is it possible you may plug something in and take it outside ?
Please confirm all these things, as it affects what is recommended for the earthing at the shed end of thing
5) Using a fused spur off the power cct. for the light switch at the shed end may be OK - but you do need to think about what happens if lights all trip off due to a faulty appliance - emergency lights or any critical loads.
So in summary it may well be OK, but it depends.