Unused shower cable, how to reuse for sockets?

[privatewid]

Hi,
We've recently had a rewire done and the original plan was to run a 9.5kW shower but it's now running off the combi-boiler instead so I have a 10mm2 cable that goes into the consumer below with a 40A MCB.

Now decided we want a couple of double sockets up in the loft so was wondering what's the best and safest to go about it?

Thought about these options...
1. Attach 10mm2 directly into a 13amp double socket - imagine that's quite difficult and would restrict running other double sockets off it?
2. Replace cable with 6mm2 and MCB with 32A, same as the house sockets run off.
3. Buy an new mini consumer unit like the ones often used in garages and attach 10mm2 cable to that then run several sockets off it.

There's currently no lighting on the loft either so we would like something permanent so I'm guessing that's only possible with option 3?

Anyone give any advice on what they would do?

Cheers

 

[sparkwright]

Option 3 would make good sense, as it would make terminating the cable easier, and a neat way to 'fuse down' the loft light to 6amp.

Some here would say it's overkill, 2 way garage boards are quite cheap.

I think anyone working on the 10mm2 circuit in the future would appreciate this garage board more than finding a double socket with a 10mm2 cable + another cable stuffed into it.

Another option would be to use a 60amp junction box and then reduce the cable to 6mm, and fit a switched fused spur to the loft light.

You'd probably have a better chance buying a garage board than buying a 60amp jb on a Sunday...

 

[privatewid]

Thanks Sparkright,
If I go for option 3 would it matter if the circuit would then have two RCDs on it?

 

[sparkwright]

It wouldn't, although can make testing a little difficult. You never know which RCD will trip. I wouldn't be too concerned about it personally, though a regular main switch could be fitted to the garage board.

 

[privatewid]

There's a few options at Screwfix for 2 way consumer units, I need a 6A MCB for lighting and will be installing two double sockets in the loft for a computer NAS device and 8 port gigabit switch so what size MCB do I need for the sockets and what size for RCD, 40A or 63A?

 

[EFLImpudence]

I need a 6A MCB for lighting

You don't really; that's just what is done in Britain.

and will be installing two double sockets in the loft for a computer NAS device and 8 port gigabit switch so what size MCB do I need for the sockets

That depends on the cable you use and the installation method.
2.5mm² will likely be used so 16A or 20A for a radial circuit.

and what size for RCD, 40A or 63A?

40A, 63A or 80A is just the maximum current an RCD can handle so it doesn't matter.
30mA is the important bit.

 

[AndyPRK]

A 40A RCD is likely to be cheaper and perfect for what you require

 

[privatewid]

So of the two listed here... https://www.screwfix.com/c/electric...230028&amprating=40_a&consumerunittype=garage

One comes with a 16A MCB and the other a 32A MCB, which one should I get considering my usage?

 

[AndyPRK]

The 32a one will need you to connect the sockets as a ring if using 2.5mm cable.

 

[privatewid]

What if I used 6mm2 cable?

 

[AndyPRK]

A radial would be perfect on 6mm 32a

A bit hard work connecting sockets up but if you have 6mm cable go for that.

 

[AndyPRK]

Chint are poor quality.

 

[winston1]

Never heard of anyone putting a mini CU in the loft. Surely the way to do this is:
Change the RCD in the main CU to 32 amp.
Fit a JB in the loft and run a small ring from there in 2.5 mm t&e (lollypop circuit).
In fact I probably wouldn't bother with a fcu for lights and instead run them from the upstairs lighting circuit. This way if the lollypop is tripped you still have the lights available.

 

[scousespark]

Your house sockets would not likely be 6mm2. A ring has a 32A MCB and 2.5mm2 cable. A radial has a 20A MCB with 2.5 mm2 cable or a 32A MCB with 4 mm2 cable. You don’t need a CU for 2 sockets and a light in a loft. If you are set on a dedicated circuit, replace the MCB and install a radial and install a radial from your existing CU. To feed the light, fit an FCU with a 3A fuse. You could feed the sockets from your upstairs socket circuit and optionally feed your light from your landing light. I have no idea why Winston would recommend installing a lollipop circuit. FYI, this work is notifiable to you LABC.

 

[privatewid]

Unfortunately wiring a socket coming off the upstairs sockets isn't an option now as the be all been bonded and plastered.

I didnt mention this originally but the 10mm2 former shower cable is goes straight up the wall and into the loft, would it not be an option to replace this cable with 2.5mm2 and the MCB to 32A at the consumer unit then add a couple of sockets and come off the upstairs lighting as you mentioned? I think it should be possible to take the 2.5mm2 cable to the end of the 10mm2 once disconnected at the CU and feed it up by pulling the 10mm2 up in the loft? It's in white trunking.