SWA to shed - agree with my proposal?

[sparky05084]

Hey all

Been quite some time since I've been on here so first off a big hello and hope everyone's well. Personally, I've gotten a dose of Man Flu but I just have to get on with it I suppose.

I'm after some advice really and any opinion's would be greatly appreciated. I am going to be starting a job this weekend that entails a partial rewire to the property and the installation of a new consumer unit. The con unit comprises RCBO's and I am considering putting the shed (will be fitted at a later date) on it's own individual circuit.

The shed itself will house a light, a socket and an alarm. You might ask why an alarm? well, that's what he wants so I'll fit one.

There is no facility on the rear kitchen wall to come off a socket and add an FCU, hence my proposal to run it from the new con unit in the house. I wonder if this is overkill because of the fact the shed will have such a minor current demand.

The shed will be located approx 2M from the rear wall so I thought I would run a 2.5 T&E to an adaptable weather proof box and then from there run a 2.5 SWA 3 core to a small dist board in the shed. Put it on 20A RCBO so it's RCD protected.

Not sure if this is the most practical or best design method. Am I missing something? What would you do?

Thanks guys

 

[uksparks]

Or just a bit of 2.5mm 3 core swa terminated into metal clad socket in the shed then from there either more sockets or you could put a sfcu as the light switch and then a fcu for the alarm. If you do this you could technically come off a socket in the house via a 13a spur. Just a thought...

 

[7029 dave]

Yes I would go for beefing up that supply to with swa 4mm, you never know.

 

[keane161616]

Can I ask what the house earthing system is?

 

[Geordie Spark]

Are you hinting that this type of question has been asked before...

Yes it has .... once or twice - along with bathroom lights & extractor fans, RCDs tripping after a re-wire, and "Why does my landing light not work since I changed the light fitting in the hall?" .. etc. etc ..... not to mention "Does this gas pipe need bonding?"

 

[davesparks]

What I don't get is why in these threads so many people are so desperate to put unnecessary joints into submains?
Run the bleeding SWA back to the CU and don't install a brand new cable with joints in it!

 

[Spoon]

With this type of question there are so many ways it can be done. From really cheap (tapping into existing house circuit, use 2.5mm SWA to shed....) to spending a bit more and having something that you can expand on in the future.
Personally I would go with 4mm SWA back to house CU. Small 4 way CU in shed. ( room for future stuff, like garden lights and instantaneous inflatable dolls that scare off burglars.... ) One RCD on shed CU (as mine has only tripped once in about 12 years) and MCB in house CU. If I had a bit extra to spend then go with RCBO's in garage CU.

 

[Welchyboy1]

Just put an upfront rcd in shed to cover any future add ons, what's the point in shelling out extra for rcbos?

Spend the extra on a larger size swa cable

 

[Knobhead]

Yes it has .... once or twice - along with bathroom lights & extractor fans, RCDs tripping after a re-wire, and "Why does my landing light not work since I changed the light fitting in the hall?" .. etc. etc ..... not to mention "Does this gas pipe need bonding?"

The list goes on ad nauseam.

 

[spadge47]

I personally would run a 4/6mm2 fed from 32A supply to a little CU in the shed (CU with 30mA RCD as main switch, and option to put 6A and 20A radial in . I would make the CU a TT system (earth rod) just so you dont have any nuisance tripping from the house, just in case they put outside lights. (the amount of times i get a phone call saying the RCD in their house wont stay on because water has got into one of their outside lights.

hope it helps

 

[keane161616]

Cant understand why people are saying that you can tap a cable straight out the back of a socket especially if its a pme installation in the house. I do agree that taking the swa back to the mains rather than joining it is a good idea but one join in an adaptable box Is not the end of the world. Also you have to consider how the cable from the mains to the shed is being installed, if it is surfaced trunked then it doesnt necessarily have to go through an rcd but if it is buried in the wall in twin and earth then it must be covered by a 30ma rcd or rcbo. If the installation is pme I would recommend a minimum of a 4mm 2 core swa to the shed then I would cut the armouring off in the shed and install a earth stake on the shed. If the cable therefore from the house to the shed is covered by and rcd or rcbo then just install a main sw plus mcbs in a small shed consumer unit.

 

[Geordie Spark]

Or just a bit of 2.5mm 3 core swa terminated into metal clad socket in the shed then from there either more sockets or you could put a sfcu as the light switch and then a fcu for the alarm. If you do this you could technically come off a socket in the house via a 13a spur. Just a thought...

You could even put one of them wind turbine thingies on the roof and save the bother of running a length of cable from the hoose.

 

[Jay Sparks]

Cant understand why people are saying that you can tap a cable straight out the back of a socket especially if its a pme installation in the house. I do agree that taking the swa back to the mains rather than joining it is a good idea but one join in an adaptable box Is not the end of the world. Also you have to consider how the cable from the mains to the shed is being installed, if it is surfaced trunked then it doesnt necessarily have to go through an rcd but if it is buried in the wall in twin and earth then it must be covered by a 30ma rcd or rcbo. If the installation is pme I would recommend a minimum of a 4mm 2 core swa to the shed then I would cut the armouring off in the shed and install a earth stake on the shed. If the cable therefore from the house to the shed is covered by and rcd or rcbo then just install a main sw plus mcbs in a small shed consumer unit.

If there are no pipes or equipotential parts entering the shed then there is no need for the earth rod at all, whether its TNS or TNCS!!! And I think the op has already suggested running the submain in SWA, maybe with T&E in trunking inside the house, so no need to RCD/RCBO at the house end. This would be a right pain in the back side, every time it tripped, you would need to go into the house and reset it, instead of just into the shed.

There are allot of variables to consider with this install and the OP hasn't given enough info!

 

[Octopus]

This thread reminds of the time I once ventured on to a big shed (excuse the pun) forum.... a joke

 

[Jay Sparks]

This thread reminds of the time I once ventured on to a big shed (excuse the pun) forum.... a joke

Was it orange Murdoch??????

 

[Knobhead]