Electricity in shed

Inoyton

Hello there,

Apologies if it was raised before, but I couldn't find the answer.

I have built a solid shed on a concrete foundation and would like to use a part of it as a very small workshop: minilathe, drillpress, ocassional welding with a small welder, etc. This is purely for hobby, nothing else. So far it has no electricity. Ideally I'd have a separate line, but it would be extremely complicated and it's very tempting to hook up to an external socket on the wall of the house. Would it be ok to do so?

The problem is - it's a part of dining room socket line with 20A breaker (and RCD covering it).

I was thinking about building a small consumer unit with 20A RCD + few MCBs for lights, sockets and welder socket separately, but now not really sure that putting another RCD is a good idea.

2011

It would not be possible to supply a distribution board from a socket.

Depending on the size of the loads it may be possible to provide a supply to a board in the shed from the main distribution board in the house.

Edit: Corrected confusing spelling error!

Inoyton

https://www.boards.ie/discussion/comment/121581560#Comment_121581560

Thank you for your answer! Why wouldn't it be? Isn't it the same as adding few more sockets after that one? Is it prohibited legally or there is physics I don't understand well?

GreeBo

The problem is that your shed, with multiple sockets would draw more current through that single cable and the cable feeding the external socket than the cables are rated for.

samcr440!

Hi OP. There is no way you could supply a distribution like that. The plug and socket are only rated to 13 amps. Might be OK to run a few lights and stuff bit still would not be advised. Definitely couldn't run mentioned welders etc.

SCOL

get yourself a diesel generator for the welder

monseiur

Look at it this way - Replace, in your mind's eye, your external socket with a standard garden half inch hose. Would you consider it realistic to connect a 2'' hose to this garden hose and branch off 4, 5 or more say 1'' pipes off this 2'' hose and expect loads of water pressure in all branches simultaneously, together and at the same time😉

GreeBo

https://www.boards.ie/discussion/comment/121588880#Comment_121588880

In terms of safety I would look at it as, if you have a climbing rope rated for 1 person, would you connect 5 ropes to that same rope and expect it to support 5 people?

Inoyton

Many thanks for your replies, folks, I really appreciate help.

Few clarifications:

1) I of course didn't want to use socket for that, I wanted to hook up to it;

2) I planned to use 2.5mm armoured cable and put it underground;

3) This line has only 3 sockets in it and external socket is the last one;

4) Line has 20A MCB, and I planned to cap at 16A in the shed; (16A sockets, 16A for welders socket, 6A for lights)

5) Cable that is used to wire sockets (in the house) is 2.5mm

Does it change the picture or I am grasping at straws?

Donald Trump

I'm not an electrician, but I'd suggest trying to run the gas off the electricity and the electricity off the gas. We did it here and saved 200 pounds per year.

GreeBo

https://www.boards.ie/discussion/comment/121594139#Comment_121594139

"Using" and "Hooking up" to the socket are the same thing, the problem is not the socket, its the wiring behind the socket.

Frankly the cable between the socket and the shed is largely irrelevant to the problem, its the cable from the socket back to your CU.

You need a mini CU in the shed and it needs to be done by a certified electrician. You can save yourself a lot by doing the trenching and access into the shed yourself, but I would talk to an electrician first so that you are both in agreement on where it should run and where/how it should exit the house and enter the shed.

Inoyton

https://www.boards.ie/discussion/comment/121595299#Comment_121595299

What if the cable between CU and socket is sufficient?

GreeBo

https://www.boards.ie/discussion/comment/121596460#Comment_121596460

Is it a radial or a ring main?

GreeBo

The other aspect is the length of the run.

Your 2.5 armoured cable is going to dram more from the CU because of the length of the run, this will increase the load on the "internal" 2.5 to your socket.

So you wont get 20A in the shed or the internal sockets when you have stuff running in the shed, especially a welder.

Also, how were you planning to connect the SWA cable to the exterior socket?

Inoyton

https://www.boards.ie/discussion/comment/121596481#Comment_121596481

It's radial

Inoyton

https://www.boards.ie/discussion/comment/121596520#Comment_121596520

I planned to use socket's terminals OR terminal strip.

GreeBo

https://www.boards.ie/discussion/comment/121597265#Comment_121597265

So I'm pretty sure thats too many sockets for a 2.5 radial anyway

https://www.boards.ie/discussion/comment/121597305#Comment_121597305

I meant more how would you physically get the cable into the external socket box? Does it have glands?

Inoyton

https://www.boards.ie/discussion/comment/121597397#Comment_121597397

It's the 3rd socket in that line. It doesn't have a gland at the moment, it has a pre-pressed hole and I planned to use female conduit adaptor.

https://hager.com/uk/products/h/wxpss81-ip66-single-13a-dp-switched-socket

2011

The only way to do this properly is to bring a dedicated supply from the main distribution board to supply a sub distribution board in the shed. I would expect the minimum specification of the cable required to do this properly would be a 3 x 6 mm sq. SWA based on the information provided. This cable should not be protected by an RCD as the welder may trip it plunging the shed in to darkness which could be dangerous. RCD's for final circuits within the shed should be installed within the shed sub distribution board so that they can be reset locally. Further analysis would be required to size the cable properly.

Based on the questions asked it is clear that this work is beyond the capabilities of the OP. Time to get a professional in.

@Inoyton I suggest that you call a REC.