Another thread about power to a shed

[va-it]

Hello, this is my first post on the forum. I have read several threads about bringing power to a shed in the garden, but besides one where a gentleman wanted to charge a toy car overnight, they don't have many similarities with my case.

Ultimately I will involve a competent electrician for the job, but before I go around asking for quotes, I would like to better understand my options. I don't want to be taken for a ride...

So, here is the situation. I have an outside socket, and I would like to take electricity from there to power a shed I am building (3m x 2.4m). The shed is going to be roughly 5m from the house. By the way, the house is a new build.
In the shed, I would like to have at least 1, but ideally 2, double sockets and a small LED batten (~15w). I don't intend to run much from these sockets, besides the occasional drill, jigsaw etc.

I believe the socket from which I am going to take power is on a radial circuit with a 32amp MCB (picture 1).

So, here is my plan: 3 core, 2.5mm SWA cable from the outside socket, then underground, ending in a weatherproof box on the outside of the shed. From there, I think I have two options.
Option 1: Split the circuit into a line for the lights (behind a fused switch (6A?) acting as the switch for the light) and then another for the two sockets (picture 2)
Option 2: Feed into a consumer unit, with a 6A MCB for the light (operated by a normal switch), and a 32A MCB for the sockets (picture 3).

I prefer option 2, despite costing me more, because that way I can isolate the sockets and the light from inside the shed, but if it doesn't make sense please let me know.

Inside the shed, I would run 20mm PVC conduits to keep everything tidy.

Does all this make sense? I would be very grateful if anyone would give me their opinion on this setup.

As I said, I will ultimately get in touch with a registered electrician, but I would like to do as much as I can to save money and, more importantly, to do a tidy job that is up to my standards. My experiences with tradespeople, so far, have all been very poor and I know that nobody is going to put as much care into it as I would.

Thank you again, and I look forward to receiving some opinions.

 

[EFLImpudence]

Outside power is not a DIY job so ask your electrician - but believing what you say - picture 2 is theoretically fine.

You will need 4mm² cable from the house because of the 32A.

Why would you not have the 'weatherproof box' inside the shed?

 

[Taylortwocities]

Looking at your CU. I do not think that the socket is on a 32A radial.
Probably it is a spur from a 32amp RING.

If the latter is the case, then what you can and cannot do depends on if the outside socket is directly spurred or if there is a fused switch between the supplying circuit and the outside socket.

 

[va-it]

Outside power is not a DIY job so ask your electrician - but believing what you say - picture 2 is theoretically fine.

You will need 4mm² cable from the house because of the 32A.

Why would you not have the 'weatherproof box' inside the shed?

Thanks @EFLImpudence. I thought it would look tidier than feeding the SWA cable through a small hole in the wall of the shed.

 

[va-it]

Looking at your CU. I do not think that the socket is on a 32A radial.
Probably it is a spur from a 32amp RING.

If the latter is the case, then what you can and cannot do depends on if the outside socket is directly spurred or if there is a fused switch between the supplying circuit and the outside socket.

Thank you @Taylortwocities. The only fused switch in the house is one close to the gas boiler, labelled BOILER.

 

[Taylortwocities]

Then, as there is no 32amp MCB dedicated to the outside socket, then we can assume that it is a spur from a ring final.
You cannot spur from the socket if it already is a spur, unless a 13A Fuse is provided between the source socket and the existing outside socket.
Once that is done you could do as you plan. 2.5mm will be gone as thd max total current wound be 13amp.

Plan 2 is pointless, in that case.

 

[EFLImpudence]

Plan 2 is pointless, in that case.

Typo ???

 

[Taylortwocities]

Typo ???

No point in having Plan 2, as the one in picture 3.
No point having a whole consumer unit with a 6A and a 32A MCB in it if the supply is limited to 13amp.

 

[va-it]

Thank you, I understand.

Just for completeness, say the socket was in fact part of the ring, then plan 2 (with a 4mm cable) would be the best option?

Thanks again to both.

 

[EFLImpudence]

No point in having Plan 2, as the one in picture 3.
No point having a whole consumer unit with a 6A and a 32A MCB in it if the supply is limited to 13amp.

Ah sorry, I was referring to the picture numbers.

Picture 2 good - with FCU.

 

[Notch7]

are you exporting the earth?
wood shed or metal shed?

 

[va-it]

are you exporting the earth?
wood shed or metal shed?

Hi @Notch7, yes, I would be taking the earth from the socket and using that. The shed will be made of wood and it will sit on a concrete base.
All the advice I have found so far regarding earthing suggests that it's fine to do it this way.

For example:

I hope I am not misunderstanding.

 

[EFLImpudence]

That's fine as long as there are no metal parts emerging from the ground in the shed.

Its just an extension lead really.

 

[Harry Bloomfield]

I've not read the entire OP, but I would...

Run 1.5mm 3c armoured, from a box, on the outside wall, cable cores left long enough to go to a double-pole fused spur unit on the inside. Protect cables through the wall with some tube. Spur unit, connects to socket on ring, or radial. The 13amp supply would be more than adequate for tools and light. One core of 3c is used as earth, 1.5mm is adequate for 13amps, though 2.5mm would future-proof a little.

The double-pole, allows outdoor circuit to be isolated, as a cause of RCD/RCBO trips.

In the hut, just take the armoured straight in, to the nearest socket, use metalclad, and from that, to the second socket with T&E to the second socket, then to a fused spur for the light switch.

 

[Murdochcat]

Thank you, I understand.

Just for completeness, say the socket was in fact part of the ring, then plan 2 (with a 4mm cable) would be the best option?

Thanks again to both.

4mm no

Replace outside socket, assuming it’s a spur with a ip rated SFCU, the connect outside socket and shed to load side of SFCU,