Jointing an incoming SWA

[willowwaters]

Hello,

Wondered if anyone could help. Im jointing a SWA incoming feed under the floor in a bungalow.

Is it ok to use 6mm T+E in a joint box and take it 2 metres up the wall to the new position in the incoming supply of the dis board?

Would appreciate your comments.

Thanks

Craig

 

[Graeme Harrold]

Where does the SWA come from?

 

[willowwaters]

Hi Graeme,

I live on a fishing holiday complex and the SWA comes from the main supply board situated about 100m away.
If this helps?

 

[Davey101]

I'm sure there will be lots of questions, heres a couple to start-

1 What size is the incoming SWA? You must use the same size, or more correctly, the same rating of cable (SWA can carry more current than a T+E). 6mm would sound a little small, especially on a 100 meter run.
2 What are the conditions like? If it is damp, you'll have to think about that, also if animals will be likely to get at the T+E.
3 The joint really needs to be easily accesible.
4 Are you an electrician? SWA glands and jointing cables isn't that complicated, but considering that it is the main supply to where you live, it really needs doing correctly.

Make that 4

In principle at least, I know of no reason why you shouldn't join an swa to T+E. I'd perhaps be thinking of using SWA rather than T+E, and a weatherproof resin joint kit if it were me though.

 

[willowwaters]

Its under the floor so wont really be accesible after the floor is put on. So I could use a resin joint as ive used them before.

The reason I wanted to use a smaller cable is because its going up a breeze block wall and is going to be plastered so a SWA would be too thick unless i grind out a channel in the wall.

But if this is not neccessary I would rather put a smaller cable in as its easier to work with.

I did City and guilds electrical about 12 years ago so I know about electrics but not up to new editions.

 

[Davey101]

I cant qoute a reg number for you, but its not acceptable to change cable sizes (unless done properly with a fuse of some sort).
Couple of reasons-
1 The smaller cable will (obviously) not be able to carry the same current as the larger one. Without knowing what size fuse is protecting the circuit,and how much current your bungalow is using, you cant decide what size cable to use.
2 Even if you do know what size fuse is installed (or change it to one suitable for the new cable), there is the danger that someone will one day replace that fuse with a larger one, which may be suitable for the cable at the supply end, but not the cable that you have used at your end. This is open to debate, as you shouldnt really upsize the fuse without inspecting the equipment supplied by it.

Also, it really wouldn't be a good idea to bury your incomer in a wall, especially if it was T+E. The new regs also wouldnt aloow for this.

In short, the answer is no I'm afraid.


On a similar note, has anyone worked on street lights which are wired in decreasing cable sizes, i.e. from mains in 10mm, dropping down to 4mm halfway?
Any thoughts on this anyone?

 

[willowwaters]

Ok,

What would you do then? The fuse board use to be at low level and I need to move it up to high level. Without showing the incoming cable.

Cheers

Craig

 

[pennywise]

Chase it up the wall scotch joint in the floor.

 

[willowwaters]

So its ok to bury an incoming SWA in the wall?

Whats a scotch joint????

 

[Deleted member 9648]

Ok,

What would you do then? The fuse board use to be at low level and I need to move it up to high level. Without showing the incoming cable.

Cheers

Craig

This sounds like an impossible one to answer from the information you can provide on here,I agree with Davey a 100m run going to 6.0mm T/E feeding a bungalow sounds way too small.Really think you need to get a qualified person to have a look at it for you.

 

[pennywise]

It's a resin straight joint just a different name for it. You can bury SWA in walls as it gives the required mechanical protection.

 

[Deleted member 9648]

[ QUOTE] On a similar note, has anyone worked on street lights which are wired in decreasing cable sizes, i.e. from mains in 10mm, dropping down to 4mm halfway?
Any thoughts on this anyone?[/QUOTE]

Funnily enough was fault finding on some today...went from 10.0 at supply end to 2.5 on the last post,all to keep within the volt drop allowed...as far as I can see as long as the protective device at the origin is of a rating < the lowest rated cable no problem.

 

[willowwaters]

Cheers for the responses

 

[ian.settle1]

So its ok to bury an incoming SWA in the wall?

Whats a scotch joint????

Are you sure you are an electrician asking questions like this?

 

[Davey101]

To be fair mate, I've never heard it called a scotch joint (I'm probably the only spark on here who hasn't). Probably only done about 15-20 in my life, but dont remember anyone calling them that.