50 metre swa cable to feed an outbuilding 16mm too much?

jagdeepp · 24 Sep 2009

Hi guys, i'm building an outbuilding which is around 45 mtrs from the house. The lighting will involve a few circuits in 2 rooms. In total, light output will be no more than 1,500watts (1.5kw). for power i'll have an amplifier and subwoofer which'll be around 400-500 watts each, a few av items, mini fridge and a couple of 3kw max radiators. My builder is doing the work and i'm then going to get it signed off by a sparky. He's suggesting a 16mm 3core cable. Thats around £200+VAT. I've spoke to a few gents at TLC who say that 6mm is more than sufficient and that 16mm is totally unnecessary unless i've got massive appliances all wired up at one time, which will never be the case.

Can i please have some views on this. Would 6mm or 10 mm suffice? I was thinking 6...

Also, i read that 2 core should do the job since the armour itself can act as earth. Is this true?

Testing times, credit crunch and all i need to avoid unnecessary costs where possible. Please help!!

londonboy · 24 Sep 2009

You need to get your 'signing off sparky' to tell you what he wants, as its his name on the form.

Ignore the 16yr old in tlc

mikhailfaradayski · 24 Sep 2009

Who would you choose to believe - a qualified sparky who will be taking responsibility for the installation, or some bloke, perhaps untrained who flogs cable and stuff for a living?
I imagine that the cables salesman is focussing solely on current demand and might have no idea about volt drop, disconnection times etc.

Also, 1500W of lighting for an outbuilding? sounds a lot, but if you feel thats necessary, you may want to consider the extra loading of tank heaters, water pumps etc.

Although, you could probably dispense with the 3kW heaters as those high bay sodiums kick out some heat, especially when mounted 3ft off the floor.

Armour can be used as a conductor, subject to a few considerations, but my preference would always be to pay for the extra core if the wallet can handle it. A bit of belt and braces.

Fridge full of wife-beater, sat in your outbuilding, shades on, listening to Osric Tentactles at an ear splitting volume. Happy daze!!

jagdeepp · 24 Sep 2009

i've got 11 gu10s in room one on circuit 1, 6 on circuit 2, ropelight and wall lights. It's all mood lighting and the circuits will be dimmed right down. All wont be on together much of the time.

I'll be going down the energy gu10s route at some point!

I'll definitely stick to the 3 core cable.

I agree about your comments re who to trust. Research still tends to suggest 6-10mm as opposed to 16mm. Anyone? please.. My builder is not a qualified sparky. I've not been able to consult one so far to confirm anything and thought i'd post on here since this site is frequented by a volume of experts. Any advice appreciated..

mikhailfaradayski · 24 Sep 2009

You can easily find a sparky from looking here...

http://www.competentperson.co.uk/search.asp

I strongly suggest you do, as the builder is not really in a position to do the work and then get a spark to sign off. If you want to get it right, talk to someone from this list

flameport · 24 Sep 2009

jagdeepp said:
My builder is doing the work

jagdeepp said:
My builder is not a qualified sparky.

Why have you got someone desiging and installing these circuits when they quite clearly are not competent to do so?

jagdeepp said:
My builder is doing the work and i'm then going to get it signed off by a sparky.

Not going to happen. No one is going to 'sign off' other people's work. With regards to building regulations notification of these works, they won't be allowed to anyway.

Taylortwocities · 24 Sep 2009

If you read many similar posts, you will find that the "find a qualified sparky to sign it off" mantra is often chanted by those who do not know.

Electrcians who are registered to certify that work complies with BS7671 and also to NOTIFY the works to the local authority (you'll need this to get the building signed off) are only permitted to do this for work they have done themselves (known as self-certification).

Any electrician who does otherwise leaves himself open to serious consequences.

Why didn't your builder include electrics in his quote? What did he/you say in your building regs submission?

EDIT: Three-way snap - beautiful!

jagdeepp · 24 Sep 2009

Hiya mate.

Heres the score. My builder has a sparky (Polish) Seems very competent. Qualified in that neck of the woods. I was initially told he was qualified but when i spoke to him he didnt have a certificate in this country. I now need another electrician to inspect, test and certify. I hear what you say but i am where i am. Period.
I'm now looking at a way of resolving this and appreciate the difficulties in getting a sparky to confirm anothers work but again i have no choice.

Please dont turn this thread into a 'slag the builder thread'. Advice re the question i've asked is really needed.

RF Lighting · 24 Sep 2009

1500W lighting
1000W Amp etc.
1000W AV
1500W Fridge
6000W Heating

11000W total.

Cable Type: PVC SWA (2 Core)
Application : Underground
Circuit Type : Lighting Circuit
Ambient Temperature : 30°C
Number of Circuits : 1 Touching
Power : 11000 Watts
Voltage : 230 Volts
Length : 50 metres

Required Cable Size 16 mm
Voltage Drop 6.70 Volts.
Percentage Drop 2.9%
Current Load 47.0 Amps
Max Cable Load* 69.4 Amps

*Max Cable Load referes to the maximum allowable current for the cable used in the configuration given above and will vary considerably under different configurations.

Caution - for Guidance ONLY

As said above, I would install three core for this too.

jagdeepp · 24 Sep 2009

Taylortwocities said:
If you read many similar posts, you will find that the "find a qualified sparky to sign it off" mantra is often chanted by those who do not know.

Electrcians who are registered to certify that work complies with BS7671 and also to NOTIFY the works to the local authority (you'll need this to get the building signed off) are only permitted to do this for work they have done themselves (known as self-certification).

Any electrician who does otherwise leaves himself open to serious consequences.

Why didn't your builder include electrics in his quote? What did he/you say in your building regs submission?

hello mate, he did include electrics in his quote.. he just didnt tell me that the guy wasnt uk qualified. I know.. I'm very angry about this but now just want the build completed. I appreciate i've got a serious hurdle to take on re getting it signed on but theres not much else i can do other than tell the current sparky he's off the job..

Taylortwocities · 24 Sep 2009

He won't need any heating, the lights will keep him warm

jagdeepp · 24 Sep 2009

Taylortwocities said:
He won't need any heating, the lights will keep him warm

Dammit the hostility on this thread....I was hoping i could get some friendly advice but i'm getting thrashed!

Could somebody please advise.

jagdeepp · 24 Sep 2009

jagdeepp said:
Taylortwocities said:

If you read many similar posts, you will find that the "find a qualified sparky to sign it off" mantra is often chanted by those who do not know.

Electrcians who are registered to certify that work complies with BS7671 and also to NOTIFY the works to the local authority (you'll need this to get the building signed off) are only permitted to do this for work they have done themselves (known as self-certification).

Any electrician who does otherwise leaves himself open to serious consequences.

Why didn't your builder include electrics in his quote? What did he/you say in your building regs submission?

Click to expand...

hello mate, he did include electrics in his quote.. he just didnt tell me that the guy wasnt uk qualified. I know.. I'm very angry about this but now just want the build completed. I appreciate i've got a serious hurdle to take on re getting it signed on but theres not much else i can do other than tell the current sparky he's off the job..

THANK YOU so much. thats very very helpful! Electric output is scarey though..lol

ColJack · 24 Sep 2009

jagdeepp said:
Dammit the hostility on this thread....I was hoping i could get some friendly advice but i'm getting thrashed! Could somebody please advise.

RF has already done the calcs for you above and shown that 16mm² is required for the volts drop.. nothing to do with the current capacity..

ban-all-sheds · 24 Sep 2009

jagdeepp said:
i need to avoid unnecessary costs where possible.

Then ditch the idea of using that ludicrously inefficient lighting.

jagdeepp said:
Heres the score. My builder has a sparky (Polish) Seems very competent.

He probably is - I believe that the training and qualifications regime in Poland is much more robust than ours.

But unless he is registered with a UK Competent Person scheme he may not self-certify his work as compliant with the Building Regulations.

I now need another electrician to inspect, test and certify. I hear what you say but i am where i am. Period.

But where you are is somewhere you should not be and cannot remain. No amount of fatalistic shoulder shrugging is going to change the fact that unless you change your plans you are going to end up in a whole mess of trouble with Building Control.

I'm now looking at a way of resolving this and appreciate the difficulties in getting a sparky to confirm anothers work but again i have no choice.

You do have a choice - keep the builder and ditch the electrician, or tell your builder that he must get a registered electrician to do the work.

Please dont turn this thread into a 'slag the builder thread'. Advice re the question i've asked is really needed.

It's not really slagging the builder, although he has stitched you up by lying to you, and you need more advice, of much greater importance, than just the answer to your question.

Which you've been given - as several people have said

My builder is doing the work and i'm then going to get it signed off by a sparky

won't work.

And also as previously asked, what was said on the application for Building Regulations approval about how Part P would be complied with?

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50 metre swa cable to feed an outbuilding 16mm too much?

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