Adding plugs to loft

[mikeh391]

Right, the plan is to add some sockets to my loft, for a bit of a conversion. I've already got lighting up there from the main lighting ring.

Instead of trying to tap into an existing mains ring, I was considering creating a radial circuit from this distribution board:

View media item 38854
View media item 38853
On the above picture, the 5th MCB from the left (which is 6A) goes into the box on the left of the board, and then goes out to the other side of the wall (see picture below) and then feeds a single PIR outside light.

View media item 38855
What I am looking to do is switch this connection to the 6A MCB to the unused 16A MCB (3rd from the left), fit an external junction box where the cable comes out of the wall and run 2.5mm cable directly up and into the loft. I've estimated the cable run will be about 18m. I was also going to then spur the existing external light off the junction box, which is located approx 4m right of where the cable comes out the wall.

As you may have guessed, I am no electrician, but can exercise a degree of common sense and follow clear instructions. I hope I've provided enough information.

Could anyone see any flaws in my plan or have any recommendations?

All help gratefully received.

 

[ban-all-sheds]

What size cable is the existing? Will it be OK on a 16A breaker?

Does the light require fusing at 6A?

How will you test the new socket circuit for continuity and fault-loop impedance?

Twin & earth is not suitable for running outside.

Loft conversions require Building Regulations approval, so what do you plan to say will be the way that you'll comply with P1?

 

[PrenticeBoyofDerry]

Twin and Earth cable is not suitable for external environment, if your creating a new circuit it notifiable work.
//www.diynot.com/wiki/electrics:part_p#
Do you have any sockets near to the location of the loft, either extending the circuit or adding to the circuit an existing socket circuit upstairs, in to the loft will not need to be notified.

 

[ban-all-sheds]

either extending the circuit or adding to the circuit an existing socket circuit upstairs, in to the loft will not need to be notified.

No, but the loft conversion will have to be, which means that the electrical work (which always has to comply with P1) will fall within the scope of the plans submission and approval process, therefore as part of the application for approval mikeh will have to say how he plans to comply with P1.

 

[mikeh391]

Perhaps my term loft conversion is a bit misleading. Basically, I'm planning to board the loft and run some computer equipment (e.g home server, etc) up there. It's not going to be a usual room, so not requiring planning permission (surely?).

If I can't use 2.5mm straight up the wall, what cable do I need? I'm planning on the cable providing 6 plugs.

 

[mikeh391]

I've just had another thought - isn't the cable you can see running on the outside wall to the PIR light 2.5mm cable? Are you saying this isn't correct, and really needs changing?

 

[ban-all-sheds]

Perhaps my term loft conversion is a bit misleading. Basically, I'm planning to board the loft and run some computer equipment (e.g home server, etc) up there. It's not going to be a usual room, so not requiring planning permission (surely?).

Well - actually I said Building Regulations approval, which is not the same as Planning Permission, and for an actual loft conversion you might not have needed PP (depends on the rules where you live) but you would have needed the BR approval.

But as this isn't a genuine loft conversion, i.e. no creation of habitable space, no structural work, then you don't need that either.

Two things to bear in mind, though:

1) Check that your roof will support the weight of boarding, people moving about etc. Modern trussed roofs are strong enough to support the plasterboard ceilings in the rooms below, and not much else - I kid you not.

2) Assuming your loft floor is insulated, it's going to get very cold up there in winter and very hot in the summer - probably outside the suitable operating temperatures for the equipment.

If I can't use 2.5mm straight up the wall, what cable do I need? I'm planning on the cable providing 6 plugs.

I's not the size that's the problem it's the type - twin and earth is not suitable for use outside.

If you must run it outside use armoured cable, or put it in conduit (and it's hard to pull T&E through conduit). Route the cable internally.

All the other points I raised still apply - if you put the existing light cable onto a 16A breaker you must confirm that it's OK for that, and you must check to see if the makers of the light allow that or if they want it on a lower rating. And you should test the new sockets for continuity and fault loop resistance.


Some reading for you:

• 
  
  
  
• //www.diynot.com/wiki/electrics:mcbtocable
  
  
• http://www.tlc-direct.co.uk/Book/4.3.1.htm (all subsections)
  
  
• http://www.tlc-direct.co.uk/Book/4.3.11.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/5.3.1.htm
  
  
• //www.diynot.com/wiki/electrics:mcb2
  
  
• http://www.tlc-direct.co.uk/Book/8.1.1.htm
  
  
• //www.diynot.com/wiki/electrics:swa-gland

 

[PrenticeBoyofDerry]

I've just had another thought - isn't the cable you can see running on the outside wall to the PIR light 2.5mm cable?

Not sure if it's 2.5mm, more likely to be 1.5mm or 1.00mm but it is t&e

Are you saying this isn't correct, and really needs changing?

It's not correct because it's t&e not because it's could be 2.5mm.
Does it need changing Well it should never have been installed the way it has, as t&e perishes in frost, heat and direct sunlight.
You could put it in conduit!

 

[ban-all-sheds]

I've just had another thought - isn't the cable you can see running on the outside wall to the PIR light 2.5mm cable? Are you saying this isn't correct, and really needs changing?

As I said - it's not the size which is the problem it's the type. I'd replace it with HiTuf or Tough Rubber Sheathed cable (which being round cables would be much easier to gland into the light anyway)

And instead of the choc-block in that box next to the CU put a double-pole switch, then if the light gets water in it and causes the RCD to trip you can isolate it completely.