Connect Sockets To Shed Supply

[penguinlicker]

Hello,

The shed is supplied with 6mm Swa on a 25amp rcbo. Inside the shed is a 20amp socket circuit and a 5 amp lighting circuit.

Can I add a junction box to the supply cable about mid way and radial off that box to a double socket?

a 32amp radial requires 4mm, and a 20amp radial is 2.5mm. But is there anything saying I can’t add a double socket to a shed supply cable when the cable size and rcbo both seem satisfactory?

thank you for reading and helping if you can

 

[pc1966]

Well you'd hope that if the OP is joining mid-cable he'd have sufficient intelligence to verify that before proceeding!!

Alas, having worked in an academic institute for many years I can confirm without a shadow of doubt that intelligence is not common sense!

 

[penguinlicker]

thanks again for the help.

so if i add sockets to this 6mm shed supply cable would it come under any codes on an eicr?

 

[pc1966]

so if i add sockets to this 6mm shed supply cable would it come under any codes on an eicr?

It would depend a lot on how it is done.

The proper installation of a socket from the cable by means of a junction box or similar is not fundamentally wrong or unsafe, but if the implementation was lacking, or it failed on some key measurement, then it could be an issue.

You would be better putting in a junction box that can satisfactory terminate 2 * 6mm and something like 2.5mm for running to a socket, as already said you will really struggle to get 2*6mm in a typical socket back safely.

Also by putting in a socket there you are ruling out a later instillation of mini-CU in the garage, etc, as you could no longer consider that as a sub-main feed from some other breaker or fused-switch to make that sort of thing work well. So think ahead very carefully here!

 

[radiohead]

I would point out here that I have connected two 6.0mm conductors into decent quality socket outlets many times. I would not see that as an issue if I was doing it..
But prepare the conductors wrongly and yes, it will be a problem.

 

[penguinlicker]

Also by putting in a socket there you are ruling out a later instillation of mini-CU in the garage, etc, as you could no longer consider that as a sub-main feed from some other breaker or fused-switch to make that sort of thing work well. So think ahead very carefully here!

Sorry, I don’t quite understand this bit. You mean if I put a socket on the 6mm distribution supply cable I won’t be able to add new circuits to the shed CU?

thank you for helping me

 

[Pete999]

Can you get 2 x 6mm in the back of the socket outlet?

Can you get 2 x 6mm2 in the terminals even?

Sorry, I don’t quite understand this bit. You mean if I put a socket on the 6mm distribution supply cable I won’t be able to add new circuits to the shed CU?

thank you for helping me

Best get an Electrician to help you with the installation.

 

[pc1966]

It was not obvious from your original post that it is already supplying a CU!

As a sub-main in SWA you have more choices than if it is a final circuit. Specifically you don't need RCD protection on SWA (as the armour protects against cable penetrating damage) and as a sub-main you are allowed up to 5s disconnections times (so you can use a fused-switch to feed it and achieve selectivity with the downstream MCB/RCBO).

Basically having selectivity means that a fault on a final circuit will only trip the local CU's MCB/RCBO, and not take out the whole lot. That is a special risk if the shed is used as a workshop and being plunged in to darkness a safety hazard!

Once you put a socket on the 6mm sub-main it must have both 30mA 'instant' RCD protection and 0.4s fault current disconnection times. At that point you won't be able to achieve any useful selectivity on either earth leak faults or on over-current faults.

Now that may well be how it is currently wired, and if you are OK with that then fine. But if adding circuits to the CU in the future, which I think is notifiable work, you may find most electricians are unhappy at the inability to design/modify for adequate selectivity (as required by the wiring regulations) without having to undo your work.
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Basically you would be well advised to follow telectrix's advice in post #6 and simply run another feed to an outside socket from the internal socket circuit.

If you want proper selectivity it would be notifiable to change the overall CU configuration, but simply running your new socket feed to the existing MCB would make that job much easier in the future. Then any electrician would have the cable there to put it on a separate circuit, RCBO for all if needed, and change the sub-main feed to a fused-switch.

But again that is for future consideration.

 

[penguinlicker]

Hi,

thank you for the advice.

The sheds essentially a storage shed and she just wants a couple of outdoor lights and a couple of outdoor sockets added. She’s not going to be wanting to spend extra money for future workshop possibilities as she’s not looking to ever sell.

Even if I could persuade her to get a registered sparky in to swap the shed CU, she’s not going to swap it for anything other than a basic garage unit.

And looking at the garage units on screwfix and toolstation, most of them just have an rcd protecting 2 mcbs.

So in the event of an earth fault everything’s switching off anyway regardless if the 30ma protection is in the house or in the sheds CU.

And ild rather have it in the house as the cables twin and earth under floorboards in the house and only goes to SWA when it goes outside.

I think I’ll just use some wago connector blocks for 6mm cable and come off the supply cable to an outdoor socket. I can do all the tests to make sure rcd times are met and ZS is ok.

I don’t do Notifiable work as it’s easier to get a registered guy in, so as long as what I have planned isn’t Notifiable then I’m happy to proceed.

thanks again for all the advice

 

[westward10]

From your last post are you an electrician. Your last thread on a similar topic suggests this circuit doesn't have additional rcd protection.

 

[penguinlicker]

From your last post are you an electrician. Your last thread on a similar topic suggests this circuit doesn't have additional rcd protection.

Hi,

im an electrician working in the water industry. The circuit will have rcd protection as soon as it arrives from the suppliers,

 

[pc1966]

And ild rather have it in the house as the cables twin and earth under floorboards in the house and only goes to SWA when it goes outside.

I think I’ll just use some wago connector blocks for 6mm cable and come off the supply cable to an outdoor socket. I can do all the tests to make sure rcd times are met and ZS is ok.

OK, that sounds fine.

 

[7029 dave]

Can you get 2 x 6mm in the back of the socket outlet?

I would not like to wrestle with them.