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

 

[La Poste]

Why do we use 230 Volts as our starting voltage when in reality it is 240 Volts or maybe 235 volts?

It seems these volt drop calculations are making us buy bigger cables than we need to.

 

[EastAnglian]

Why do we use 230 Volts as our starting voltage when in reality it is 240 Volts or maybe 235 volts?

/QUOTE]

From Wikipedia:

"Following voltage harmonization, electricity supplies within the European Union are now nominally 230 V ± 6% at 50 Hz.[SUP][1][/SUP] For a transition period (1995–2008), countries that had previously used 220 V changed to a narrower asymmetric tolerance range of 230 V +6% −10% and those (like the UK) that had previously used 240 V changed to 230 V +10% −6%.[SUP][2][/SUP]No change in voltage is required by either system as both 220 V and 240 V fall within the lower 230 V tolerance bands (230 V ±6%). In practice, this allows countries to continue to supply the same voltage (220 or 240 V), at least until existing supply transformers are replaced. Equipment used in these countries is designed to accept any voltage within the specified range."

 

[La Poste]

So maybe we use 230 Volts as our starting figure just in case the supply companies change the voltage to 230 Volts in the future.

 

[mikehopkins]

Itll work and then when u move a sparky will put it right if it don't kill someone in the meantime,. This is the problem with electrical work, it's works so folks think its fine, a car with no brakes , an aeroplane with no landing gear , need I go on.!

 

[Guitarist]

You sure Part P allows someone else to sign off another's work?

 

[Guitarist]

Itll work and then when u move a sparky will put it right if it don't kill someone in the meantime,. This is the problem with electrical work, it's works so folks think its fine, a car with no brakes , an aeroplane with no landing gear , need I go on.!

I had this discussion the other day regarding adequate earthing. I asked em why they bothered with a seatbelt....

 

[EastAnglian]

You sure Part P allows someone else to sign off another's work?

No, it doesn't!

 

[GLENNSPARK]

as the weatherproof joint box will be under the decking upon completion.....has the O/P considered access for this weatherbox.....and the joints within?...

 

[RISElectrical]

No, it doesn't!

However LABC are allowed to come and see the job and then get someone in to sign of the works?

You don't need to be a member of a scam to do notifiable works

 

[RISElectrical]

1.5mm on a 16A type B MCB would be fine IMO will also need RCD too don't forget.

From your first post, making a few assumptions I got the vd to be 4.6v on the 1.5 cable over 15 meters

 

[GLENNSPARK]

However LABC are allowed to come and see the job and then get someone in to sign of the works?

You don't need to be a member of a scam to do notifiable works

but its whether you can convince a customer to see to that....the extra expense....the hassle...

 

[RISElectrical]

I was referring in the case to the OP as its his own decking so I understood so if he did inform LABC then the cost incurred would probably be < paying an electrician to do the works which is why I thought he would be doing it himself, if that makes sense.

Agree that the most cost effective way to the customer is to be a scam member, if they even know what part p is!

 

[GLENNSPARK]

I was referring in the case to the OP as its his own decking so I understood so if he did inform LABC then the cost incurred would probably be < paying an electrician to do the works which is why I thought he would be doing it himself, if that makes sense.

Agree that the most cost effective way to the customer is to be a scam member, if they even know what part p is!

well its a classic example of where someone may want to install the cable themselves...then see if they can get an electrician to notify it...hense my question about accessability to that IP box....

 

[sedgy34]

How have you come to that conclusion ?
And you're incorrect anyway.
Anyone can carry out electrical work in their own home so long as they notify the local council , pay the appropriate fees , and have the work inspected and tested by a competent person.
Simples.

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.

 

[rustynails]

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?

1.5mm on a 16A type B MCB would be fine IMO will also need RCD too don't forget.

Type B 16A 30mA RCBO 61009-1

From your first post, making a few assumptions I got the vd to be 4.6v on the 1.5 cable over 15 meters

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.