What SWA cable?

[thatsitivehadenough]

Hello,

Can someone advise me what size SWA I should purchase for the following? (3 x 4mm ect!)

less than a 30 Meter run from the house to a garage sub board. The garage will have 4 double sockets and 2 strip lights. Sockets will be used for power tools, pillar drill, grinder ect! May have a fridge down there one day!

I ask because I can purchase my cable very cheap and I'm getting it in ready.

Thanks.

 

[ban-all-sheds]

• //www.diynot.com/forums/viewtopic.php?p=81696#81696
  
  
• http://www.tlc-direct.co.uk/Book/4.3.1.htm
  
  
• http://web.archive.org/web/20080213151445/http://www.kevinboone.com/cableselection_web.pdf
  
  
• http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html
  
  
• http://www.tlc-direct.co.uk/Book/8.1.1.htm
  
  
• //www.diynot.com/wiki/electrics:part-p
  

Or you could do the sensible thing and ask the electrician who'll be doing the work what cable to get, as he will be the one who will have to sign a declaration saying that he chose it. At the same time you could check the pricing, because if you can't get the cable cheaper than he can it'll probably end up costing you more in total than it will if you let him supply it.

 

[thatsitivehadenough]

OK

 

[ccam108]

I get 6mm so don't know where you are getting 2.5mm from. clicky

Less voltage drop is allowed for lighting remember.

Colin C

 

[thatsitivehadenough]

OK

 

[ccam108]

That's my mistake. I put 2 core SWA instead of 3 core.

It's always better to get bigger than you need anyway, just in case you decide to buy that welder you've always wanted...

Colin C

 

[thatsitivehadenough]

OK

 

[ccam108]

Thanks for your help, I will get the 6mm. I would like to have a welder one day. Would there be any extra earthing requirements to take into account as it will be 30 meters from the earth at the main board.

I am not going to answer this as it falls outside the scope of what I know for certain. Hopefully someone will come along soon with a definite answer though.

Colin C

 

[flameport]

Would there be any extra earthing requirements to take into account as it will be 30 meters from the earth at the main board.

Yes, but the distance from the house is not the main issue regarding earthing - the type of supply your property has and what is actually in the garage will be.

There is also the question of what protective device this cable will be connected to.

 

[ban-all-sheds]

In short, there's more to it than just picking a cable size. That you did 3-phase calculations shows that you don't really have a proper grasp of it all and the questions you're asking about earthing go way beyond just sizing a cable. As you're using an electrician you don't have to do all that design work.

Find an electrician - tell them that you work for a company that makes armoured cable so you can get it dirt cheap/free, and so when they quote they should do so on the basis that you will supply the cable, and take it from there.

 

[thatsitivehadenough]

OK

 

[ban-all-sheds]

So why did you think they would provide the option of 2 or 3 cores?

Why would the sizes change between single-phase down a 2-core compared to 3-core?

 

[thatsitivehadenough]

OK

 

[ban-all-sheds]

I'm not taking the p*** out of you for anything.

You wanted to embark on circuit design, so I was asking you what you thought would be the reason for there being a difference between the sizing for a 3-core cable vs 2-core.

 

[thatsitivehadenough]

OK