SWA into plastic cu

[longers30]

Hi guys just finishing off a rewire where I have a 6mm 3 core SWA Sub main running to an outbuilding. I'm connecting into a 10 way plastic cu in the house which is going to be positioned just under the ceiling in the hallway with the cable dropping down from above into it. Just wondered on the best way to connect the SWA I've heard people mention earthing nuts but never come across them. It is a T-N-CS earthing arrangement and is going on a 40a MCB, non RCD, protected running to a metal clad board in the outbuilding with the 3rd core used as the cpc and armour connected on the supply end. Any advice would be appreciated

 

[Simon-0116]

box

100 x 100 plastic or galv box, gland off into that then into board

 

[trev]

Gland the swa into the CU, where you fit the banjo drill through and drop a bolt into the hole. After you fit washers and a nut or 2 crimp a lug onto an appropriately sized fly lead and take that to the earth bar with the third core.
Btw, if you're fitting a CU up against a ceiling you need a rethink.

 

[trev]

Re: box

100 x 100 plastic or galv box, gland off into that then into board

Why complicate things?

 

[davesparks]

You will need to earth the armour properly at the other end too as the gland in to the metal board there will give a partial connection even if you don't intend it to.
At the supply end I would probably gland it into a galv through box and then bush that to the CU. That gives you good mechanical fixing of the SWA to prevent it bending your CU out of shape and a handy earth terminal to bond the armour.

If you search for pirannah earthing nuts you will see what you have been missing out on there.

 

[Hawk81]

Or gland into the board and use 1 of these

 

[Octopus]

Or gland into the board and use 1 of these

Could be tricky doing anything like this if the board is that close to the ceiling with the cable coming down!

 

[longers30]

Yeah the cu has to go up against the ceiling really it's pretty tight for space and it's where all the cut-out and meter are so the owner wants it all boxed in when it's done.

 

[longers30]

Yeah this is the problem with the position of the board. I may have to consider placing a box as suggested to the side of the cu, gland into that and take the cores through the side. Any thoughts on this?

 

[Hawkmoon]

If you are installing a 6mm swa (I take it there is nothing extraneous in the 'outbuilding' ?) then it shouldn't stress the CU if you cleat appropriately - I would go with Trev's idea since it's in a hall and appearance may be an issue.

 

[Engineer54]

As Hawkmoon has indicated if the supply is PME/TNC-S and this outbuilding has any extraneous metalwork/pipes etc, then a 6mm 3 core isn't going to crack it. It's then going to be either a 10mm 3 core, or running in a separate 10mm earthing conductor alongside the 6mm SWA...

 

[HandySparks]

Yeah this is the problem with the position of the board. I may have to consider placing a box as suggested to the side of the cu, gland into that and take the cores through the side. Any thoughts on this?

Yes, I go with this option. Either a galv adaptable box or a right angle galv conduit box. Either would give a solid connection and look neat.

 

[longers30]

There are no extraneous metal parts in the outbuilding just some lighting and power.

 

[longers30]

So am I right in saying that with these earthing nuts you gland the cable as normal and the earthing but just goes over the thread and is held with the grub screws? Then a fly lead from this to the MET?

 

[Richard Burns]

So am I right in saying that with these earthing nuts you gland the cable as normal and the earthing but just goes over the thread and is held with the grub screws? Then a fly lead from this to the MET?

Yes you just replace the banjo and retaining nut with the piranha nut.
The grub screw prevents the nut from loosening and the screw holds a ring terminal for the earth fly lead.

 

[Patto]

They look like a fantastic design never seen them before

 

[gazj82]

They are good, but they do take up some considerable room, and are not always suitable for smaller enclosures.

 

[shanky887614]

Could gland into a coupler with an earth connection on and bring the cpc through with other cables etc.

 

[davesparks]

What do you mean my a coupler with earth connection on ?

 

[shanky887614]

What do you mean my a coupler with earth connection on ?

Can some of you old codgers explain XD

In the past when conduit was used as the cpc, they used couplers with a cpc connection on the outside so a piece of cable could be used to connect the cpc

found a pic

 

[davesparks]

Pic didn't work, I can't say I've ever seen such a thing though, top hats are the only type of coupler I know of with better earth connections.

And what do you mean by in the past? Conduit is still used as the cpc.

 

[shanky887614]

Pic didn't work, I can't say I've ever seen such a thing though, top hats are the only type of coupler I know of with better earth connections.

And what do you mean by in the past? Conduit is still used as the cpc.

Really?

You do much comerical/industrial?

a lot of designers spec cpc's in conduit now a day's.

Search in google for 20mm earth coupler and it be one of the first pics

 

[Robotstar5]

Well you learn something every day, I've worked with tubing for nearly 40 years and never seen one of those couplers before, must have led a sheltered life

 

[shanky887614]

Well you learn something every day, I've worked with tubing for nearly 40 years and never seen one of those couplers before, must have led a sheltered life

Same as ive never seen an electrician who dyed his hair pink

 

[trev]

I've never seen a fat electrician but I have seen a spark's GF who had/has pink hair

 

[shanky887614]

I've never seen a fat electrician but I have seen a spark's GF who had/has pink hair

What about that fat electrician in the paper that would struggle through a loft hatch?

 

[7029 dave]

I've never seen a fat electrician but I have seen a spark's GF who had/has pink hair

We are about. The best are fat.lol

 

[shanky887614]

We are about. The best are fat.lol

You will be double my weight then

 

[7029 dave]

You will be double my weight then

No three times:devilish:.

 

[shanky887614]

No three times:devilish:.

Im 10 stone so possible

 

[7029 dave]

Im 10 stone so possible

Ha Ha not quite, have not seen that weight since I was 20, 30 years ago.!!

 

[davesparks]

Really?

You do much comerical/industrial?

a lot of designers spec cpc's in conduit now a day's.

Search in google for 20mm earth coupler and it be one of the first pics

I do a bit of conduit work and always use use the conduit as CPC when the calculations allow (which has been always so far)
I am aware that designers do like to waste miles of copper like that yes, I guess it just proves they like to go for the easy life rather than designing properly. Guidance note 8 is pretty clear on the subject when it says that adding a cpc in steel conduit is a futile exercise.

I can honestly say i've never seen a coupler like that before, and it looks a bit ridiculous to me.

 

[trev]

Guidance note 8 is pretty clear on the subject when it says that adding a cpc in steel conduit is a futile exercise

I had an argument at work last week with the senior spark on the job.
2 steel boxes joined with a bush and couplers, I didn't link the 2 with a bit of copper. He said I was wrong, he also said that the NIC man wants it done his way. I told him the NIC man was a dick who didn't know what he was doing (also implying the same about him)
We juiced up the circuit and took Zs readings, there was no difference.
Me 1, him and the NIC man 0

 

[7029 dave]

All the conduit work I have done in the past have always provided cpc in the spec.

 

[gazj82]

I had an argument at work last week with the senior spark on the job.
2 steel boxes joined with a bush and couplers, I didn't link the 2 with a bit of copper. He said I was wrong, he also said that the NIC man wants it done his way. I told him the NIC man was a dick who didn't know what he was doing (also implying the same about him)
We juiced up the circuit and took Zs readings, there was no difference.
Me 1, him and the NIC man 0

This is why I hate the NIC,

Not in the NIC, follow BS7671

In the NIC, follow BS7671 + some idiotic rules they think up!

 

[trev]

All the conduit work I have done in the past have always provided cpc in the spec.

Why's that mate? I realise that there's a belt and braces argument but if the conduit is mechanically and electrically sound and disconnection times are going to be met it seems like a waste of cable

 

[Hawkmoon]

Why's that mate? I realise that there's a belt and braces argument but if the conduit is mechanically and electrically sound and disconnection times are going to be met it seems like a waste of cable

Agreed, in fact I'd add, it doesn't just seem like a waste of cable, it is a waste of cable!

 

[shanky887614]

Why's that mate? I realise that there's a belt and braces argument but if the conduit is mechanically and electrically sound and disconnection times are going to be met it seems like a waste of cable

True but around birmingham a lot of the sparks dont bother to tighten things up.

Everything is finger loose as one of them like to say

You can undo it with 1 finger

 

[davesparks]

Then they aren't proper sparks.

 

[Robotstar5]

True but around birmingham a lot of the sparks dont bother to tighten things up.

Everything is finger loose as one of them like to say

You can undo it with 1 finger

I must be in the minority then