Moving existing wire

[IT Minion]

Hi All,

I've got an existing 7mm twin and earth cable that goes from a main distribution box to a smaller one.

Right now it runs through the cavity of my wall up to the loft. This isn't good and isn't safe if I get the cavity filled.

I've found another route for it (punch through the wall, run externally and punch back through) but I dont know if it's either legal or safe for me to do it. Obviously if either is a no then I'll get a sparky out for it.

Also, assuming it's legal for me to do it, can I cut the wire part way to make re-running it easier and connect with a wago box? Bonus points if it'd be good to replace some or all of it with 10mm just for fun.

 

[davelx]

7mm? That is not a valid cable size. What dimension of the cable is 7mm?

PS - we like (and need) photos!

 

[IT Minion]

7mm? That is not a valid cable size. What dimension of the cable is 7mm?

PS - we like (and need) photos!

Probably 6mm then, but what's a cross sectional mm between friends over a 20m run?

If you like I'll crawl up into the loft and get a shot of the cable, but presumably the distribution boxes would be more meaningful?

 

[davelx]

Do you mean 6mm²? ie the cross sectional area of the copper conductor?

We have to check as people routinely measure the width of the cable in its sheath and think that is the cable size.

Any photos you can reasonably provide will be helpful

 

[IT Minion]

Do you mean 6mm²? ie the cross sectional area of the copper conductor?

We have to check as people routinely measure the width of the cable in its sheath and think that is the cable size.

Any photos you can reasonably provide will be helpful

Yes, cross sectional. Helpfully printed on the side of the cable.

But since I got the size wrong once already ,I'll get that photo

 

[sparxxxx]

I've found another route for it (punch through the wall, run externally and punch back through) but I dont know if it's either legal or safe for me to do it.

Thats ok, but T&E cable is not uv proof, so it will need protection capping or conduit.

 

[sparkwright]

Hi All,

I've got an existing 7mm twin and earth cable that goes from a main distribution box to a smaller one.

Right now it runs through the cavity of my wall up to the loft. This isn't good and isn't safe if I get the cavity filled.

I've found another route for it (punch through the wall, run externally and punch back through) but I dont know if it's either legal or safe for me to do it. Obviously if either is a no then I'll get a sparky out for it.

Also, assuming it's legal for me to do it, can I cut the wire part way to make re-running it easier and connect with a wago box? Bonus points if it'd be good to replace some or all of it with 10mm just for fun.

Why don't you just leave it
or
Pull a larger cable through the cavity in place of the old one?

 

[IT Minion]

Why don't you just leave it
or
Pull a larger cable through the cavity in place of the old one?

I thought 1) cables shouldn't be run through cavities as they aren't accessible and 2) if the cavity were filled, as is planned, the cable would have to be derated.

 

[sparkwright]

The accessibility of a cable in a cavity doesn't come into it.

Replacing the cable for one a size or two higher may sort out the risk of thermal effects.

I don't think anyone has specially re-wired or upgraded electrics because they were having cavity wall insulation fitted.

Polystyrene cavity wall insulation can cause harmful effects to the cable sheath over time, but there are other types of cavity wall insulation.

 

[IT Minion]

Replacing the cable for one a size or two higher may sort out the risk of thermal effects.

May is such a fluffy word. If I were a qualified electrician I'm sure I'd know enough to know if it was or wasn't ok on the thermal concerns, but since I'm not itd mean Id have to get a sparky in to do the calculations.

A qualified electricians I've spoken to in the past have told me it's a no-no to run cables in cavities.

Back to the original question, is it ok for me to go into the distribution box, remove the wire and replace or reroute and reattach? I'm happy with sockets but I've never done anything at the distribution box level.

edit: Just to be clear, I do appreciate the info being provided and don't want to appear ungrateful. But electrics are a topic I'm cautious about, I've just enough education on power electronics to know how dangerous they can be.

 

[EFLImpudence]

Back to the original question, is it ok for me to go into the distribution box, remove the wire and replace or reroute and reattach? I'm happy with sockets but I've never done anything at the distribution box level.

If you have to ask - then, no.

 

[IT Minion]

If you have to ask - then, no.

So it is legal, thanks.

 

[Taylortwocities]

So it is legal, thanks.

Legal? The Wiring Regulations are not statutory.
The only legal statutory instrument is P1
You can view it here:
https://www.diynot.com/wiki/Electricsart_p:Statutory-Instrument
Basically it says that you should make reasonable provision that electrical work doesn’t harm anybody.

So, you have to decide if your planned work complies with the wording of the SI.