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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?
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.
The cable did not have the armour earthed, well it was not even connected.
The interesting thing is that virtually all, if not all, of the defects have been revealed on inspection rather than testing.
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 best way to have this done is to make he connection straight from your distribution board the the SWA if there was space in there and if there was a lay the cable on the outside wall. Then protect it with 16 or 32Amp MCB depending on what loads you want in the shed.
Connecting the SWA in to the existing socket is not the best practice as you might over load that particular socket
- Radial from main consumer unit wired with 4mm2 (earth is also 4mm2) to outdoor junction box at rear of house (This is where I would like a new outdoor socket)
- 3-core 4mm2 SWA from junction box to garage at rear of garden. SWA is earthed at house end.
- Junction box on outside of garage 4mm2 takes carriers into garage consumer unit.
- Sockets and lighting from garage consumer unit as normal.
Part of the reason I'm looking at doing it myself is to minimise exposure to the outside world in the current climate.
Does anyone have any thoughts? Thanks
As above, if the socket is for charging an electric car or a caravan hook up, other rules apply.
I'm not trying to put you off, but as so often with apparetlyuy simple questions, 'more info needed' I'm afraid.
I'm also assuming you can make off the SWA glands properly - as a note try the John Ward tutorials on-line if a bit rusty, and you posses a meter and the ability to check earth continuity polarity etc.
I have just undertaken a consumer unit renewal. The house was previously owned by a builder. The new owners are having lots of work done including a new kitchen. The builder had run an S.W.A. cable from the back of a downstairs' room socket through the wall to a pond pump position. The cable did not have the armour earthed, well it was not even connected. The outdoor socket was an ordinary indoor type on a pattress mounted on a low wooden stake. No R.C.D. protection at all. The circuit was protected by a B.S. 3036 30 Amp fuse. The socket was protected from the elements by a removable wooded "hat" that wobbled a bit on the socket stake. Needless to say I disconnected the cable.
Sounds like one of the better jobs that builders tend to do Zoom 😉
- Earthing of house is TN-S.
- Breaker for the garage is 32A.
- RCD is 63A/30mA.
- The SWA is only earthed at the house end. The garage earth is through a 4mm2 carrier within the SWA, back to the earth of the house.
- The SWA does not run all the way back to the CU of the house. It only goes as far as the junction box that I want to replace with a socket.
With TN-S you do not need to worry, just export the house earth as-is.
Of course some of TNS properties are now on a mix of TNS-TNC-s on the same substation, and you may not know, but that only changes when new properties are added or significant repairs to the network on an estate of existing houses the risk of sudden change are quite low.