Radial Circuit in the garden

[diyfiesta]

Hello,

I was planning on installing a ring main in the garden but when I laid my nice new 2.5m SWA in the trenches, I realised I'd come up short somewhat.

So, rather than try and add a join to the existing cable, I was thinking I could just turn the whole thing into a radial circuit and abandon the return cable. Does that sound ok? Is there any regulations around this and Part P when it comes to the garden.

The only other thing I'd planned to do was take a spur off one of the double outdoor switches to provide a lighting circuit in the shed. The total circuit length (from a new mini consumer unit in an outbuilding) would be about 25m (or 50 if it were a ring main).

Cheers for any tips

Toby

 

[RF Lighting]

What on earth makes you think you would ever need a ring circuit outside?

All of this work requires notification to your LABC.

You need to stop right now until you have contacted them.

 

[sparkyspike]

Agreed re RF's post. The job will then be legal and safe, if you follow advice given.

Whilst you are designing this circuit, remember to design the fuse according to the design current and then the size of the cable according to the size of the fuse and the length of the cable.

Normally, for this application, this would be a 16A breaker with RCD protection, with a 2.5mm cable. You need to do your sums, so look up the cable calculator at www.tlc-direct.com.

How is this mini consumer unit wired in, or are you fitting it yourself as part of this job?

 

[diyfiesta]

I contacted the council who said I'd just need to get the Part P which I have an electrician lined up for. He'll test everything and certificate if its all ok.

I'm basically laying the cables, fitting the boxes to the walls etc. The spark will do the final connections. The mini-consumer unit is a garage type with RCD, and two MCBs.

ta

 

[sparkyspike]

Ask your electrician to design the work for you. It will save you a lot of time and you will have more of a chance of doing the job properly.

If you do things this way, you won't have the electrician turning up and having to alter your work, or worse, not being able to complete it. So it will probably save you money too, to have him round before you start.

You know it makes sense Rodney...

 

[securespark]

2.5 can work safely under a 20A breaker, too.

 

[sparkyspike]

Possibly, but watch out for voltage drop. Over ~25m, 20A is pushing it on 2.5mm. Work out the exact length and then use the voltage drop calculator to see whether it is within limits.

You may need 4mm cable. This is why it is so important to establish your load first, before selecting your cable.

 

[electronicsuk]

Not liking the sound of 'ring circuit' and then 'spur off of the double outdoor switches'. What loads are you expecting on the circuit? From what you've said I get the impression that you want to mix lighting and socket outlets on the same circuit. However, unless you feed the lighting from a suitable FCU, you would have to downrate the protective device for the entire circuit to a current less than or equal to the rating of the switches. Manufacturer's instructions may also stipulate a particular fuse rating to protect their light fittings.

If you are indeed mixing lights and sockets on the same circuit as I suspect, then you may be better off laying an additional circuit to allow you to split the load across two protective devices and alleviate the need for FCUs. It would work out cheaper when you consider the price of decent quality outdoor accessories.

 

[sjwkmje]

If you are indeed mixing lights and sockets on the same circuit as I suspect, then you may be better off laying an additional circuit to allow you to split the load across two protective devices and alleviate the need for FCUs. It would work out cheaper when you consider the price of decent quality outdoor accessories.

You should see how he did the connections, I do not like the look of this at all, not going to even bother listing all the faults as its all obvious from the photo:

View media item 12022
Adam

 

[sparkyspike]

Apart form the exposed single-insulated cores, I'd like to know how the armour is connected to earth and how the cable will be protected from the weather!

 

[Taylortwocities]

Adam, Do we assume that you've been to see diyfiesta's little project.

It gets worse. See his other thread at //www.diynot.com/forums/viewtopic.php?p=1244912#1244912

 

[ban-all-sheds]

diyfiesta, you are so incompetent it beggars belief.

Even if your assumption on how you get the work certified for Building Regulations compliance were correct (it isn't), the chances of anybody certifying this abomination would be precisely zero.

Please give it up now, and get a registered electrician to do the whole job.

 

[sjwkmje]

Adam, Do we assume that you've been to see diyfiesta's little project.

It gets worse. See his other thread at //www.diynot.com/forums/viewtopic.php?p=1244912#1244912

Yup I followed it and I decided not to give any comments, its a bodge from the start, no way would you get me to sign that off or even come close to it. I was going to show photos of the correct way to do it but I have been away this weekend and I could not find the photos when I came back home today.

 

[Taylortwocities]

Adam, dont worry about that = a link to the correct way to do it is on the other thread,...