Supply to loft.

[Jimbo1978]

Hi Folks.

I am looking to run power into my loft for 2/3 double sockets and a light. I have a spare 16a and 32a breaker on the box and room to feed a cable down to it. I take it I would be best using the 16a as I only intend to have a light, tv, playstation, alarm clock plus a couple of spare sockets just incase. I am ok with running cable and siting boxes and switches but always make sure before I start work. Anything I should be doing or not doing?

Cheers

Jimbo

 

[Aragorn84]

Given that you have a 32A breaker available, it would probably be best to run a pair of 2.5mm cables and create a ring main in the attic?

 

[Taylortwocities]

Why on earth does he need a ring final? he only needs 16A. Radials are a prefectly good way of providing power (our European neighbours do it all the time).

a single length of 2.5mm T&E cable and a 20A breaker is what's needed.

Oh yes there is more, including:
continuity testing
insulation testing
installation and testing of RCD if there is not one on the consumer unit
certification of the new circuit

 

[ban-all-sheds]

Anything I should be doing or not doing?

You should be getting Building Regulations approval before you start.

 

[londonboy]

Remember you need to fuse the 16/32 down to 3/5amps using a fcu for the lighting.

 

[toasty]

Remember you need to fuse the 16/32 down to 3/5amps using a fcu for the lighting.

...or use a switch capable of handling the full current. (might be simpler)

 

[londonboy]

Ok then.. And cable.

 

[Taylortwocities]

You should be getting Building Regulations approval before you start.

Is that true for Lanarkshire?

 

[thatguy250]

Practically, it will work fine. But with the new regulations, probably not so much lol. I think to comply with the new part P electrical codes, you would technically need to use 4mm cable for a radial circuit which has more than 2 double sockets on it just in case you decided to plug more than two 3kw electric space heaters in up there lol. You also technically have to inform building control that you are unscrewing your consumer unit, as it's dangerous for us unqualified peoplings to add a new circuit into a consumer unit. I've done it though. Use your judgement. I have a 2.5mm radial that goes through my airing cupboard to the loft, running 2 plugs and a power shower pump, and it's more than adequate. There will be 1.5mm lighting cables in the loft already for the light you want to add.
Have fun.

 

[AshleyWilliams]

I agree use the 32 breaker and run a ring. When wiring lights use a switch fuse spur and fuse it down. Remember to consider loft insulation on your cable calcs and make sure you clip cables to the sides of beams.

A

 

[Taylortwocities]

But with the new regulations, probably not so much lol. I think to comply with the new part P electrical codes, you would technically need to use 4mm cable for a radial circuit which has more than 2 double sockets on it just in case you decided to plug more than two 3kw electric space heaters in up there lol. Have fun.

Please get your facts correct. There are no 'new Part P electrical codes'.

The BS7671 Wiring Regulations were re-issued in 2008 that have some changes. Do not get confused between Building Regulations and Wiring Regulations.

In BS7671 there is no such regulation re

need to use 4mm cable for a radial circuit which has more than 2 double sockets on it

The standard radial arrangements are 2.5mm cable protected by a 20A cpd or 4mm cable protected by a 32A cpd. It is up to the designer to determine the load on the circuit.
The (BS7671 - 2008) regulations state that a separate circuit is required for devices (like heaters) that are more than 2KW - but that is as a way of reducing the load on ring final circuits.

From the OP's requirements a 20A radial will be more than adequate. If he is turning the loft area into a habitable space then its a different design criterea.

 

[Aragorn84]

He's talking about running an alarm clock and TV, which surely implies a "habitable space" like a bedroom...

Yes it could be run from a 20A radial, but surely when hes got the walls/floor/whatever opened up, he may as well just install a ring, so that in 1,2,5 or 10 years time when someone decides a heater would make a nice addition to their loft conversion, theres enough capacity there already.

The cost difference will be marginal at best, and certainly cheaper than having another electrician out in a few years to change the circuit...

 

[chapeau]

Please get your facts correct. .........

There was no reason at all to jump on thatguy250 in that manner. He appears to know what he is talking about and gives practical advice to a fellow DIYer (what this site appears to be about) which will allow future upgrades. Putting a 2.5mm radial would not.

 

[ban-all-sheds]

You should be getting Building Regulations approval before you start.

Is that true for Lanarkshire?

No, but it's true for Lancashire, and I could have sworn that's what I read....

 

[Taylortwocities]

Maybe he moved since he posted, perhaps following Holmslaws example