Shed Power

[padstar]

I am about to build a "shed" at the end of the garden.

From the shed i plan to power the following;

2 internal lights
3 double sockets
1 roller shutter
1 ring floodlight camera
a few external lights

I currently have an external power radial feeding 2 double sockets in the back garden ran in 2.5 T&E with a B32 RCBO. I also have space in the box for additional circuits if required.

Can the shed be added to the external power circuit or is it best to bring a sperate feed into a smaller board within the shed and then feed from that?

If the 2nd (i assume it is) then what size armoured cable would be best suited?

The shed would be approximately 35-40m from the main board.

 

[JohnW2]

From the shed i plan to power the following;
2 internal lights
3 double sockets
1 roller shutter
1 ring floodlight camera
a few external lights

Someone is bound to ask ... what loads do you envisage having in the shed, now or possibly in the future? The nature of sockets is such that "3 double sockets" could, in theory, equate to zero load or 78 A (about 18 kW) of load, or anything in-between!

 

[padstar]

Sorry i should have said that. Very little. The sockets will be to plug in the odd tool or charger etc. Nothing pulling big loads planned for it

 

[blup]

Just feed the 2.5mm into an FCU at the she’d and split the light and power circuits, rcd/rcbo at the main board

 

[ericmark]

2.5 T&E is not rated at 32 amps. So that overload needs changing, but my shed is on a 16 amp RCBO type A double pole switching, and the only time it gets any real load is when my son comes and plugs his EV into the outside socket. So 16 amp for me is ample.

It was considered we would have a few BBQs and used the socket for cooking stuff, warming plates, and induction hob, but it never happened.

 

[Murdochcat]

Just to echo what was just stated are you 100% sure the the existing sockets are on a dedicated radial from a 32A breaker with 2 x sockets

 

[padstar]

Definitely a 32A breaker I may be wrong on the radial i will check as it may be a ring. I assume that would then be the correct protection for the cable.

 

[padstar]

Assuming that is the case can i just pull off the circuit and run a 2.5 T&E down to the shed and into a small box.

 

[JohnW2]

Definitely a 32A breaker I may be wrong on the radial i will check as it may be a ring. I assume that would then be the correct protection for the cable.

As has been said, a 2.5mm² radial would not be adequately protected by a 32A breaker - it would need to be at least 4mm². A 2.5mm² ring would probably be OK with the 32A breaker, but you would know if it is a ring since there would then be two 2.5mm² cables.

 

[JohnW2]

Assuming that is the case can i just pull off the circuit and run a 2.5 T&E down to the shed and into a small box.

See my recent message. A 2.5mm² radial would not be adequately protected by a 32A breaker. You would either have to use a fatter cable or reduce the breaker to 20A (maybe 25A if one were available for your CU) ... or use a 2.5mm² ring.

 

[ebee]

As has been said, a 2.5mm² radial would not be adequately protected by a 32A breaker - it would need to be at least 4mm². A 2.5mm² ring would probably be OK with the 32A breaker, but you would know if it is a ring since there would then be two 2.5mm² cables.

And measure continuity to be sure they are not just two radials connected as one circuit - seeing if all sockets are fed from two cables not one might give you your first indication of that and measuring could confirm it

 

[JohnW2]

And measure continuity to be sure they are not just two radials connected as one circuit - seeing if all sockets are fed from two cables not one might give you your first indication of that and measuring could confirm it

True, but 'the other way around' (which quite probably is the OP's situation), a 'cable count' would be decisive - if there is only one cable for the circuit at the CU, it cannot possibly be a ring circuit (and the OP believes his is a radial).

[ I suppose some clever clogs might suggest that with a single cable at the CU it could still be a 'lollipop' circuit. That's true, but even if that were the situation, a 2.5mm² 'handle' of the lollipop would not be adequately protected by a 32A breaker! ]

 

[padstar]

If going with a dedicated supply straight from the house consumer unit would this require 4mm or 6mm SWA to be run. I have service ducts laid already for a granny annex in a nearby location so will probably go down this route as it should be a simple albeit expensive cable pull which I can do myself then get an electrician to terminate and check over.

 

[ebee]

You might even consider 1 x 2.5 cable suitably changing in the mcb or fuse if this will accommodate your maximum demand via careful planning of accessories and volt drop considerations etc etc but I do agree that running a larger cable would likely give you more headroom for what you might need at present and what you might be thinking you might add in future,

Always allowing for small additions in any circuit can one day be beneficial and we would usually take at least some account of this either most circuits unless prohibitive economically.