Replace red and black 10mm cable to loft conversion?

[SJRSJR]

Hello

I’m doing some renovation and I have a loft conversion which has its own small CU for its light and sockets. It’s fed by a 10mm cable from the main CU on its own RCBO.

However it’s black and red and I wondered whether it’s considered old.

I obviously won’t be attaching it, but I could run it up there for the electrician to finish off. Should it be brown and blue cable by now?

Thanks

 

[pete01]

Probably perfectly fine....but I've recently been rewiring my own house and changing red and black for brown and blue for no reason other than I want to, so up to you really.

 

[mattylad]

The electricity does not care what colour it's insulation is

 

[flameport]

it’s black and red and I wondered whether it’s considered old.

Black/red cable went away about 20 years ago, and was used for more than a century before that, so the colour of it reveals nothing about it's age other than it's at least 20 years old.

 

[Jurassicspark]

I’m doing some renovation and I have a loft conversion which has its own small CU for its light and sockets. It’s fed by a 10mm cable from the main CU on its own RCBO.

Ay, not the best method as it may not achieve discrimination.

Is the main consumer unit full?

However it’s black and red and I wondered whether it’s considered old.

If it tests fine then it’s okay.

Is it PVC?

I obviously won’t be attaching it, but I could run it up there for the electrician to finish off. Should it be brown and blue cable by now?

Only if you want to spend more money.

 

[SJRSJR]

Thanks all. I just looked at Building Regs and it looks like the conversion was done in 1991.

I’ve got no problem with it, but I wondered if it’d give a better impression down the line if the house was ever sold.

 

[SJRSJR]

Is the main consumer unit full?

No, there’s plenty of space in the CU. Getting more cable through the back might be a challenge though.

Is it PVC?

Looks like it. Shiny red and black.

Ay, not the best method as it may not achieve discrimination

Had to Google that and still don’t understand!

 

[Taylortwocities]

I wondered if it’d give a better impression down the line if the house was ever sold.

It won’t matter a jot. If you want to spend some money, the consumer unit may need an update. If it’s dated from 1991.

 

[Jurassicspark]

Had to Google that and still don’t understand!

As the supply, both the lights and sockets, are fed from the single RCBO from the main consumer unit, no one can be for certain which RCBO/RCD/MCB will trip first, whether at the main consumer unit, or the one for the loft conversion.

For example, if the socket circuit developed a fault, the RCBO, one at the main consumer unit, may trip first, affecting lights for the loft too, leaving the room in darkness.

It’s not much of a biggie.

Enter the keyword “selectivity in electrical circuits UK” on Google.

 

[SJRSJR]

Thanks Jurassicspark.

So does that mean it would be better to have the loft lighting and sockets as two separate circuits from the main CU and forget about the loft CU?

 

[Jurassicspark]

So does that mean it would be better to have the loft lighting and sockets as two separate circuits from the main CU and forget about the loft CU?

It’s not a requirement.

But tell me this, how many time have you experienced the scenario which I’ve mentioned above?

 

[SJRSJR]

But tell me this, how many time have you experienced the scenario which I’ve mentioned above?

Yes, what’s the point in all circuits tripping when just one could.

So it’d be more useful to run a lighting cable and a socket cable to the loft?

This may be where I feel out of my depth and leave well alone. Do the cables run to the loft CU or does that become redundant? If so would you have to run two 2.5mm cables for the ring? Thanks

 

[flameport]

So it’d be more useful to run a lighting cable and a socket cable to the loft?

It would have been, and if doing the conversion today the more usual choice would be to have a circuit for the lighting, another for the socket outlets and perhaps more for other things if they were required.
That could be circuits just for the loft, or extending those which already cover other rooms.

For reasons no one will ever know, someone decided that installing a single large cable was the best option. Perhaps it was at the time, which would have been when RCDs were only needed on a few circuits.

would you have to run two 2.5mm cables for the ring?

If it was a ring, then 2 cables are required.
Other types of circuit are available.

What's there may not be the absolute ideal, but there is nothing particularly wrong with it, so unless you want to spend a pile of money and time changing it, probably best to leave it just as it is.

 

[AndyPRK]

A radial will be fine for a loft. 2.5mm cable, 20A circuit protection.

But if what you currently have works for you, leave it alone.

 

[SJRSJR]

Thanks, it does work so I’ll leave it be. Everything else in the CU is blue and brown so it’s not too ancient.