Mains feed help

Postby hughesy1982 » Tue Feb 08, 2011 4:46 pm

Hi guys just need some clarification, im wiring a barn conversion which has a mains feed, meter and a small consumer unit installed in one of the out buildings alongside the barn, I need to bring a feed into the barn for the consumer unit which is around a 50m run.

Ive calculated that the cable requires a 25mm swa which will be run into the barn through a duct which has been installed ready.

The bit which i need help with is how to connect from the meter to the consumer unit in the barn. Obviously i cant connect straight into the consumer unit due to the cable size being too big for the incoming terminals.

Do i use 2 large Jbs either end of the cable to feed both consumer units in the barn and out building?

Rank: Labourer
Progress to next rank:
Posts: 1
Joined: Tue Feb 08, 2011 4:33 pm


Simply Build It

Postby stoneyboy » Tue Feb 08, 2011 10:59 pm

I think you will find the main switch terminals on larger consumer units will take 25mm cable. Suggest you use the samllest metalclad consumer unit which has 25mm terminals so you can fit the swa gland direct into the consumer unit.
Rank: Project Manager
Posts: 2715
Joined: Wed Dec 10, 2008 6:44 pm

Postby ericmark » Sat Feb 12, 2011 4:12 am

There are special adaptors to allow larger cables to go into small holes. However in practice I have found the stiffness of the cable can put too much strain on the RCD and cause it to malfunction. So to fit a metal fuse box or isolator before the consumer unit and then reduce the size of the tails or at least use a more flexible cable is often a better method.

However there are many distribution boards designed to take even 125mm cable and in a barn I would not want to fit a domestic type consumer unit so just a case of selecting the right board.
Rank: Project Manager
Posts: 1429
Joined: Fri Oct 02, 2009 8:49 pm
Location: Mold, North Wales.

Display posts from previous
Sort by
Order by

  • DIY How to Project Guides

  • DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!


  • Related Topics