Outdoor electric circuit

[rustynails]

Hi,

I'd like to install electric to an outside deck I have, supplying three brick lights and a weatherproof socket. It's about 13m to the point where a weather proof junction box is required under the deck, then another 1.5/2m to each fitting. The total wattage of all the fittings is 3240, given that a 13amp outdoor socket is 3120 watts and the lights are E27 lampholder max 40 watts each. I used an SWA calculator and It came back saying that I can use 2.5mm 3 Core SWA? Which means I'll need to install a 13m length of 2.5mm 3 Core SWA, buried 600mm deep, from an outside junction box on the external house wall to a bigger outisde junction box underneath the deck where I can spur off to the 3 lights and the socket, in a radial. Can I use 1.5mm to the lights from the deck junction box? Obviously I need to run 2.5mm to the socket. Does this all sound like good practice?

THanks

 

[Guest55]

I come to that conclusion because the law states competent persons!!!
the OP is maxing out a cable he hadn't put in yet and some of you are giving him the answer to his Calcs, Im assuming here he has priced the cable up and is trying to verify 1.5 mm is ok to use rather than spend an extra £3 to get appropriate cable to do the job.
How can the OP be competent when someone has mentioned your calculater says 2.5mm and he's just thrown some Calcs back and referred back to 1.5mm.
Just to clarify law states competent persons!! Not anyone as you said so YOU are incorrect,also if he does do the work is he upgrading any equipotential bonding in his house first that may need doing the OP isn't in my opinion competent to do all this for it to pass labc.

Ring up your local planning office and pretend to be a diy'er wanting to put up decking lights.
They will confirm what i said in my earlier post.

 

[RISElectrical]

When i said using 1.5 would be ok, i also assumed SWA/XLPE and also that this would be from the DB outwards, not ran in T&E from the DB then changing. If you did run from the DB in 1.5mm SWA/XLPE then this would be fine for carrying the current and for volt drop on a 16A OCPD. To be honest I didn't bother with calcs etc tho as it was a quick "bang it in the computer and computer says yes" exercise. Your doing the job so you need to be 100% sure it checks out first.

As for the needing to be competent, i agree that you do however the argument over needing to be scheme registered is a no brainer and you DO NOT need to be. Nothing anywhere in any legislation says that you need to be to enable you to install anything electrical.

The fact that these "scams" only require a reg qualification to join speaks volumes. Anyone can revise an exam and pass and I am sure with some intense theory practice along with a little coaching it will be equally easy to pass a "scam" assessment considering they want 1 job and that can be in your own home. How do they know you have even done the job they are assessing? Talk the Talk, bang out a few tests that are heavily documented in the OSG and online and pay £500 and boom, your suddenly deemed competent to do the exact same thing that the OP is proposing to do and being told "you cant do it because your not part P". Rubbish.

Part P rant over, its a farce and we all know it is, we just have to live with it.

For example the OP gets a quote from a sparky for labour only, assuming materials are supplied by the OP and the quote is £300. The OP phones LABC, explains the job and position he is in and they charge him £150 for the certifying. That means the OP could do the job at a weekend instead of watching top gear re-runs and saves a tidy £150 in the process. Maybe he isn't competent and in the long run it costs more to put it right, however saying that I have seen DIY'ers that although no formal quals have a lot of experience and are capable of a better install than some of the scam registered sparks that are in circulation.

 

[Guest55]

^^^Agreed , i've seen decent electrical work done by diyers that have never been near a "domestic installers" course.
And i've seen garbage done by electricians with fancy stickers on the side of their van.
Go figure ?

 

[Richard Burns]

1.5mm T&E, if it is run in insulation anywhere, is getting close to the current carrying capacity of the cable if it is protected by a 16A RCBO and could be overloaded if it is surrounded by insulation.
Please remember that the diagram is only intended to describe the voltage drop technique and not to be a design guide for your installation. As I have not seen the installation I cannot provide advice on the way it is installed only information on the cables and currents based on your information.

 

[sedgy34]

Basically I'm tight as a ducks arse then!

This is just theory. I can read that the regs say use 2.5mm, but calcs are saying that 1.5mm is usable. With copper prices being what they are these days, esp swa prices it's a thought provoking discussion, right?


Type B 16A 30mA RCBO 61009-1



How's that then?

Although, looking at one of my posts I made the length of run too long. Just to re-iterate to everyone whos remotely interested. I'm working out a design as per the diagram posted by Mr Burns:

http://www.electriciansforums.net/a...ircuit-volt-drop-patio-socket-light-split.jpg

Tho this was a helpful diagram created by Mr Burns, cheers for that. It doesnt include the 3m drop from the consumer unit to an outside junction box on the external house wall. That's where the diagram begins. 13m run to 4 smaller runs of less than 2m each see diagram. All wiring in diagram is multicore swa pvc and internal wiring would be standard two core and earth.

no intention to offend anyone if your doing the works yourself use the 2.5 swa as stated and fuse down for the lighting the run is neglegable and most sparks dont go into cable calcs for something like this 2.5mm comes to mind automatically.