swa cable to shed

[sxturbo]

i know this has been asked a million times, but i have done a some research, and things get a bit conflicting and confusing at times.

so anyhoo


before i moved into my house the previous owner had removed an old cast concrete garage, to this garage was 2.5mm swa cable.

i want to now relocate this swa cable into my shed, so i can run 2 double sockets in the shed and 2 double sockets on the decking out side.

(the existing swa cable is wired in to the main consumer unit with its own rcd at one end, and currently bare the other)

8 low power led lights on the decking and 1 light in the shed.

i want to run the swa cable into a small consumer unit and then run 2 different circuits, 1 for lighting and 1 for power sockets.

the total run of cable is about 25 meters.

the most these sockets will run is a 900w sds power drill and that would be occasionly, i mainly want the sockets so i can plug in laptops and charge up power tool batteries.

i have been on tlc-direct.co.uk and there calculator says the minimum cable thickness of 2.5mm can take 4kw of power, i dont ever intend on using this much power in the shed.

my intention is to install all the cables etc and then get an electrician round to wire the consumer box and check everything.

hopefully i have written all the needed information, and any help would be appreciated.

 

[PrenticeBoyofDerry]

Off tops of ones head, I would say standard 20A or even 16A socket radial, 6A lighting circuit, SWA buried underground, 25m run=at least 4.0mm2 SWA cable.

 

[sxturbo]

Thank you for the reply.

The cable will be clipped to concrete wall. Does this make a difference?

 

[JohnW2]

Voltage drop is likely to be the limiting factor, rather than current carrying capacity.

If you were sure that the required power was never going to exceed what you have mentioned, you could probably get away with a 6A or 10A circuit (fed from a 6A or 10A MCB), which would be OK in terms of voltage drop with 2.5mm² SWA.

However, I think that approach would probably be pretty short-sighted - the day will probably come when you realise why you need more power! It would therefore be better (as suggested by PBoD) to contemplate at least a 16A or 20A circuit, and that would (again as suggested by PBoD) require at least 4mm² SWA if you wanted to strictly comply with the regulations regarding maximum permitted voltage drop (3%, aka 6.9V) for the lighting circuit.

KInd REgards, John

 

[sxturbo]

thanks to all.


my question has been answered. i shall fit a larger cable.

 

[PrenticeBoyofDerry]

The cable will be clipped to concrete wall. Does this make a difference?

In this instance no!

i shall fit a larger cable.

Be aware of requirements of new circuits.
//www.diynot.com/wiki/Electrics:Part-P

 

[JohnW2]

i shall fit a larger cable.

Be aware of requirements of new circuits.
//www.diynot.com/wiki/Electrics:Part-P[/QUOTE]
Do you think that replacing the cable of an existing circuit (even if with a larger CSA one, constitutes installing a new circuit? Even pre-April 2013, that would probably have been non-notifiable if the cable were 'damaged'?

Kind Regards, John

 

[sxturbo]

I won't personally fit the new cable. I shall do all the labour intensive bits and run the cables.

A qualified electrician will then be called round to wire it all in and do the necessary certification.

 

[PrenticeBoyofDerry]

I think that we have an instance where a circuit was used to supply a garage, this cable nor circuit was never intended for powering the shed and it is taking a different route and being removed and another cable being installed and being used for a completely different location. It is a bloody new circuit fullstop! As will be the circuits from the DB in the shed.

 

[JohnW2]

I think that we have an instance where a circuit was used to supply a garage, this cable nor circuit was never intended for powering the shed and it is taking a different route and being removed and another cable being installed and being used for a completely different location. It is a bloody new circuit fullstop! As will be the circuits from the DB in the shed.

I'm not sure I necessarily agree, particularly if the 'garage SWA' did not go all the way to the CU. If it went, say, to a box where it changed to T+E, one could (without notification) modify that existing circuit by disconnecting the SWA at the box (and, if one wished, connect some accessory instead). One could then 'extend' that existing circuit, with new SWA, to wherever one wanted, again without notification, couldn't one?

I agree, however, that the argument would get weaker if the 'garage SWA' is terminated directly into the CU.

Kind Regards, John.

 

[winston1]

i want to run the swa cable into a small consumer unit and then run 2 different circuits, 1 for lighting and 1 for power sockets.

You don't need a CU in the shed. Run direct to the sockets and run the lights off a fused connection unit.

 

[PrenticeBoyofDerry]

I'm not sure I necessarily agree, particularly if the 'garage SWA' did not go all the way to the CU.

In the opening post the OP seems to indicate that this cable was directly connected to the consumer unit at a RCD.
And that is what my post replies are based on, not a fictional scenario

 

[JohnW2]

In the opening post the OP seems to indicate that this cable was directly connected to the consumer unit at a RCD.

Indeed, that's what the OP wrote - but, taken literally, it doesn't really make sense - one would not connect SWA directly to the RCD of a CU. I therefore interpreted this as meaning that there was an RCD for the circuit external to the CU (connected to CU by T+E), and quite probably at least some T+E on the downstream side of the RCD (I don't think that terminating SWA directly into a standalone RCD would usually be possible).

And that is what my post replies are based on, not a fictional scenario

If one changes 'fictional' to 'speculative' then, in view of the above, I don't really think I'm being any more speculative than you are!

If there is currently any T+E between the SWA and the OPD in the CU, then I still think that, in the manner I suggested, the word of the current rules/words would probably allow the circuit to be extended with anything, to anywhere (other than a special location ), without notification. I'm not commenting on whether I regard that as sensible, merely indicating what the law would apparently allow.

Kind Regards, John

 

[sxturbo]

i dont know how the cable is terminated into the cu,

i just know that there is a circuit breaker named "outbuildings" in the cu, and have tested it for power when i switch it on.

all i know is that the swa cable goes into the back of the cu as there are no extra boxes around the cu, or on the outside wall, so i assume the swa cable is terminated in the cu somehow.

 

[sxturbo]

You don't need a CU in the shed. Run direct to the sockets and run the lights off a fused connection unit.[/quote]

what would be the "best" and nicest solution?