Bathroom Downlights & 2 Core Cable

[sobeitjedi]

Hi.

I am installing some 12V low voltage spotlights/downlights in the bathroom.

I need to buy some 2 core cable to connect the lights, but what amp should the cable be - 3, 6, 10? etc etc

I'm sure 3amp will do, but I just want to check.

 

[ban-all-sheds]

Hi.

I am installing some 12V low voltage

//www.diynot.com/wiki/electrics:voltage-bands

spotlights/downlights

You do realise that you'll be installing lighting which has been deliberately designed to be no good for lighting up rooms?

in the bathroom.

This work is notifiable

And relevant to that, if there's a loft above the bathroom, you will also have to show compliance with Parts C and L, as well as Part P - are you aware of the requirements and do you have a plan for compliance?

And/or if the bathroom ceiling is a fire compartment barrier because this is a flat or there's a loft conversion etc, there will be Parts B and E to consider.

http://www.legislation.gov.uk/uksi/2010/2214/schedule/1/made

http://www.planningportal.gov.uk/buildingregulations/approveddocuments/

I need to buy some 2 core cable to connect the lights, but what amp should the cable be - 3, 6, 10? etc etc

Do you mean the lights, or the transformers? If you mean the latter then you need twin & earth cable, not 2-core.

What wattage are the lights? It's a simple enough calculation...

http://www.the12volt.com/ohm/ohmslaw.asp

I'm sure 3amp will do, but I just want to check.

So no more than 36W then?

Voltage drop can be an issue with ELV lighting, and you should try to keep all of the ELV cables the same length or the lights will be different brightnesses.

http://www.tlc-direct.co.uk/Technical/Lighting/VoltageDrop.html


Also cables are sold by size - their current carrying capacity depends on how they are installed.

http://www.tlc-direct.co.uk/Book/4.3.2.htm



But overall, given what you've written here, and what you said in your other recent electrical post I would strongly advice either getting an electrician or spending some time learning about electrics before actually doing it.

• http://www.google.co.uk/search?q=electrical+circuits+101
  
  
• http://kevinboone.net/electricity.html
  
  
• http://web.archive.org/web/20080213151445/http://www.kevinboone.com/domesticinstallations.html
  
  
• //www.diynot.com/wiki/electrics:books
  
  
• //www.diynot.com/wiki/electrics
  
  

 

[sobeitjedi]

Thanks for the long and complex reply, but I just want a straight answer. It's 7 12v lights I'm connecting which are mains powered.

 

[ban-all-sheds]

Thanks for the long and complex reply, but I just want a straight answer.

That's what you got.

Surely you don't think that you should be doing this work in contravention of the law of the land, the Wiring Regulations and the laws of physics?

It's 7 12v lights I'm connecting which are mains powered.

So when you asked about the cable, were you talking about the one on the LV or the ELV side?

If you do mean the former then you were wrong about the number of cores needed and you were wrong about the current carrying capacity required because of this:

//www.diynot.com/wiki/electrics:mcbtocable


You have to do this properly, or not at all.

If you cannot or will not learn how to do it properly then get an electrician.

 

[sobeitjedi]

Thanks, but I'll just buy the 3Amp then. Quicker and easier. Thanks very much indeed for your help.

 

[ban-all-sheds]

Mods - will you please bar this complete idiot and delete all of his posts.

 

[riveralt]

Thanks, but I'll just buy the 3Amp then. Quicker and easier. Thanks very much indeed for your help.

Given your desire to carry out work on this property that you do not understand and do not care that you do not understand, I would strongly suggest that you buy one of these:

http://www.screwfix.com/p/first-alert-long-life-ionisation-smoke-alarm/67523
I would also suggest this:
http://www.fireprotectionshop.co.uk/results.cfm?secondary=5&gclid=CKXxqZ_3260CFUQMfAodNUjbkw

 

[Taylortwocities]

Thanks for the long and complex reply, but I just want a straight answer. It's 7 12v lights I'm connecting which are mains powered.

Yes, but you have missed out basic but very important bit of information.

What power are these lights (watts)

also

how many transformers? one per light or one transformer for all seven lights

There will be more questions following your answers.


Oh yes, just thought of something: is this lighting circuit RCD protected?

And something else: have you applied to the local authority regarding your electrical work in a bathroom?

 

[ban-all-sheds]

 

[stillp]

And a couple more questions:
Are these lights Class II?
What do you mean by "3Amp cable"?

 

[ban-all-sheds]

Are these lights Class II?

He neither knows, nor understands, nor cares.

What do you mean by "3Amp cable"?

Ditto.

 

[dhutch]

Cable size is measured in mm^2 not amps as the current carrying capacity is also effeced by how the cable is installed and the lenght of run.

7x 50w bulbs is 350watt which at 12volt is 29amps, nearly 10 times the current you are planning to provide cable for.

Not only is the work prepose to do illegal its down right dangours and stupid.


Daniel

 

[EFLImpudence]

The most baffling thing is -

Why did he ask?

 

[ban-all-sheds]

Because he wanted someone to tell him to use 2-core 3A cable.

 

[dhutch]

Because he wanted someone to tell him to use 2-core 3A cable.

Daniel