Power to the garden shed

[stepheng17]

In the house we just moved in to we currently have a standard socket on a mains ring in the utility room in which there is a plug plugged in which goes to a junction box and gets converted to a shielded cable & then out the wall and down to the bottom of the garden.
At the bottom of the garden is a broken ip66 double socket which I need to replace.

I'd also like to add a couple of additional outdoor sockets which I'm in the garden so I have been looking on what is needed.
I don't see any RCD so I think I need one, I also need a FSU so that I can extend the spur.


So would I be safe to do this: replace the old black juction box with a new RCDFSU box inside the house, then outside to a T junction box up to a replacement double socket and also extending along to another T juction box where I'll terminate inside and also connect a 2nd double socket.
Or should I replace (if it's possible) the wall socket with a RCD socket and plug back in the existing plug & juction box, just adding my new sockets & T junctions as described

If we swap the shed for a better quality one, maybe there could be tv, games console, possibly a heater on the end of the spur (not in the immediate future but I do see it happening sometime in the next 5 years)

Currently it's just lawn mower, strimmer

new thing:

thanks
stephen

 

[oldbutnotdead]

First off, have a look in the consumer unit, see if there are any RCDs in there (post a pic if you're not sure what you are looking for).
Next job (if you are feeling brave) open that black JB and see whether the swa is 2 core or 3 core, also check how well the armour has been earthed (my assumption is not very well, you can't get a lot of torque on the terminals in those junction boxes).

 

[stepheng17]

Hi
The consumer unit is pretty old, but the extension box (this is on the End Room fuse) is a bit more modern.
Good news is that the cable is shielded.

 

[ericmark]

The wiring regulations are not retrospective, so one can leave things as they are, but once you modify then it should comply with current regulations.

So you need RCD protection. Theroy is the RCD should have the BS EN number listed in the regulations, this means can't use RCD FCU or scoket, to my mind this is rather pedantic.

However once the rules are broken then one can't use the rules to say what can be done. You can do a risk assessment but to do that you need to understand the risk.

I have cut corners, but I can understand the risk, the problem is to change the consumer unit needs notifying. So the first job is not really DIY.

 

[Taylortwocities]

Trying to decipher some things here.

Which of the MCBs in your consumer unit turns off the external circuit? I don’t see anything labelled as “end room”
If it is one of the socket circuits on thd left hand side then those are protected by the RCD in the consumer unit.

That junction box needs sorting. First of all, the armoured cable is not terminated properly. The armour should be terminated in a proper SWA gland and the armour earthed. It isn’t at present.

Also, the white wire that comes into that round junction box appears to be way too small. Can’t tell how big it is but I would want it to be 1.5mm, assuming you have a 13amp fuse in the plug.

Quite honestly, feeding the circuit from the plug is quite adequate. Assuming you are happy with thd maximum current being 13amp. You don’t need any further FCUs. You circuit is already RCD protected.

Can you advise the size of the armoured cable? The size may be embossed on the cable. It may say something like 1.5 x 3. Please advise this, also the cable length.

 

[oldbutnotdead]

OK. There is an RCD in that consumer unit. Push the TEST button, see if it works. Then see if it is powering the socket that your external lash-up is plugged into- if yes then hurrah, continue. If no then stop.
'Shielded' is not useful for a power cable-the word you are looking for is Armoured -but it is 3 core SWA so that's a bonus.
Your first job is to reterminate the SWA at the house end so that the armour is earthed. Easiest way will be an adaptable box- gland the SWA in, gland a bit of flex out. That swa looks like 2.5 but it might not be, see if it is marked anywhere
You then get to decide whether to connect that flex to an FCU or leave it on the 13A plug. There's no harm leaving it on the 13A plug, depending on the size of the swa and the length of the run you might need a smaller fuse.
The other end of the SWA also needs terminating properly (that outside socket in the pic would take a proper gland so that's potentially fine). If you're going to put additional sockets on the line the swa must be properly terminated at all of them.

 

[chivers67]

How many cables feed into that external socket is it just the one? With all those other "cables" near it, it looks rather odd or are some of those watering pipes?

If you do upgare your shed into some kind of garden room I'd think about running a more substantial SWA.

 

[ericmark]

I had not realised the cable in the junction box was steel wire armoured. As others have said, the armour needs to be earthed.

It could be earthed either side, or both, garden electrics earthing is complex, in the main we earth the socket, but then don't use the earth, so lawn mower or strimmer is class II so it really does not matter how you earth the socket.

With a wooden shed, as long as the power only used inside the shed, again no real problem with the earth.

Where the problem arises is when a class I item is used in the garden, be it an inferred heater, a flood light, hot tub, or EV charging point.

The problem is in the UK the supply authority is allowed to combine earth and neutral, the supply is then called PME or TN-C-S and this is OK unless the combined earth and neutral is lost, called loss of PEN.

This is rare, around 300 cases a year, of which around 10% result in a shock, however we still need to consider the risk, and with class II also called double insulated garden equipment there is no risk, only with class I.

With EV charging points we often have a disconnection unit which disconnects not only line and neutral but also earth, and it measures the voltage to know when to disconnect, volts need to be within the 207 to 253 volt range.

Other methods is to turn the supply to TT, that means it uses an earth rod, but then one has to consider distance between the two types of earth, easy in a caravan site where TN-C-S is banned, it is a large field with no services, but in the garden not so easy. Gas pipes, and water pipes may run so there is not enough gradent between the earths.

So the electrician needs to design the system so as not to introduce danger, and where class I items are used this is not easy, with class II as said no real problem.

Even as an electrician I find deciding on how to export power to the garden is complex, to try and explain how to do this DIY I find hard, but in Wales where I live the garden is a special location so DIY is not allowed.

So I will let the English explain how it can be done safely.

 

[stepheng17]

Thanks for the advice.
I've replaced the old junction box with an earthed adaptable box & glanded & earthed the SWA.
In the garden the old socket has been replaced with a WP22RCD double RCD socket, glanded & earthed the SWA.

thanks

 

[Taylortwocities]

Thanks for the advice.
I've replaced the old junction box with an earthed adaptable box & glanded & earthed the SWA.
In the garden the old socket has been replaced with a WP22RCD double RCD socket, glanded & earthed the SWA.

thanks

Did you need an RCD socket? Thought the circuit was already RCD protected.