T&E to outbuilding?

[jamesmcbride]

I need to supply power to a barn that we have just had built - when it was built the builder installed a service duct between the house and the barn. The cable run will need to be about 50 metres, can you used twin and earth for outside runs in conduit / ducting?

The barn itself has already been wired and the CU has been installed. I reckon that i will need 16mm2 cable to supply it - a 32A ring and lighting.

Connecting up at the house end shouldn't be too much of a problem - I have had the supply upgraded from 60A to 100A - this is happening on Tuesday and the meter is going to be moved from inside the house to a box on the outside - my plan is to put a 100A main switch in this box and then have a 60A fused switch for the house and a 40A one for the barn

Any thoughts / advice would be great

 

[Lectrician]

16mm Sounds good to me - You cannot use T+E.

You could use some 16mm split concentic. This is how I would go if it is ducted.

40amp is a good size, but no need to down rate the house to 60amp because of this!

You could fed the barn via the main consumer unit - I don't like submains from domestic CU's usually, but with that light loading (doubtful of ever having 40amps flowing for sustained periods), it is fine.

 

[jamesmcbride]

Hi, thanks for the reply,

The house currently only has a 60A supply at the moment anyway - it is an onld house and tbh the electrics need some attention at some point anyway - the consumer units in the house appear to be protected by an rcd that is rated at 60A so i thought it best to split it out before going anywhere near that. In the longterm the plan is to replace the various consumer units with a decent split load one.

i am guessing split concentic is what is currently supplying the house - does it look like SWA but nothing like as thick?

Thanks again

 

[securespark]

What's your house CU like? If it has a main switch <100A, you cannot add a 40A sub-main to it. Or indeed any other circuit above 30/32A...

 

[jamesmcbride]

there is a 60A RCD that everything goes through before it gets split off into several consumer units -
theres one that covers most of the house - lights, sockets, shower etc

there is another one that has the cooker and kitchen sockets on it - i added the kitchen ring because perivoiusly it was just a spur off:

another one that supplies power to the garage and an extention that was buillt in the 60's

from what i can see none of the sockets (except the kitchen) are wired in rings because they are all running off 15A fuses with just one put of 2.5mm t&e going into it.

 

[Paul Barker]

i am guessing split concentic is what is currently supplying the house - does it look like SWA but nothing like as thick?

Thanks again

It is concentric as it's name suggests, so instead of two pvc coated live conductors (phase and neutral) running through the middle surrounded by armour which is used as the protective conductor as in SWA, the inner layer is the pvc coated phase conductor, then the bare copper earth conductor surrounds the pvc coated phase, then a layer of pvc coated neutral conductors surrounds the earth, then there are a couple of strengthening protecting and insulating strings and layers terminating in pvc.

It is smaller in diameter than Armour about 2/3'rds but probably manufacturers vary as they do with t and e, what I have used is around 1/2" thick.

 

[Lectrician]

It is actually "Split Concentric" as the name suggests As in the earth and neutral are 'split' apart.

Concentric has a CNE conductor surrounding the live, with no insulation other than the sheath. CNE - Combind Neutral & Earth.

Click Here For Some Photos.

 

[jamesmcbride]

it looks like it is actually straight concentric that supplies the house

do you know where i would be able to get split concentric - I have done some searching on t'internet and can't seem to find any suppliers?

 

[Lectrician]

Any wholesaler will stock it, or be able to get it.

 

[jamesmcbride]

is it cheaper / more expensive than SWA? if its more expensive, what are its advantages over SWA?

thanks again

 

[RF Lighting]

The last load of 16.0mm² split con I bought was 30p a meter cheaper than SWA.

It's also smaller and lighter than SWA, which makes it more practical for drawing through duct work, and doesn't require special glands to terminate the ends.

It does lack some of the impact resistance of SWA IMO, but for this sort of installation it will be fine.

Our wholesaler doesn't carry it as stock, but they can get it for the next working day.