Swa Banjo?

[Rpa07]

Adding onto @Richard Burns reply as I can’t quote at the moment -
. . . besides oxidation over time leading to an even poorer earthing connection. Banjo and fly or piranha - it’s the only fun we get in this game!

 

[magnoliafan89]

I use these when terminating into a plastic box. Great way to maintain earth continuity

 

[Octopus]

Interesting thread .................. especially for those who insist on using 2 core SWA and use the CPC to the outer protection .....................

I prefer to use 3 core ..........

 

[Anthony S]

Very basic stuff and some people wonder why the industry is in such a mess.

 

[Ian1981]

Interesting thread .................. especially for those who insist on using 2 core SWA and use the CPC to the outer protection .....................

I prefer to use 3 core ..........

When using swa for the ‘tails’ I use 2 core 25mm swa and a 16mm earthing conductor in parallel

 

[MDJ]

Hello everyone, having a debate with colleague, concerning SWA connected into metal CU. Can anyone advise the exact reason for the banjo, brass washer with cpc tag, is it compulsory rather than it just looks nice.
Any thoughts sound reasons would be nice also is it a requirement under the regs?

 

[Spoon]

When using swa for the ‘tails’ I use 2 core 25mm swa and a 16mm earthing conductor in parallel

So what's the price comparison between the above and 3 core SWA?
I haven't got the charts on me at the mo but isn't the armour on 25mm sufficient for the earth?

 

[Ian1981]

The armour would not be 16mm equivalent copper as I’m talking about the main earthing conductor
Also if I used 3 core then a 25mm earth conductor is way overkill

 

[Spoon]

The armour would not be 16mm equivalent copper as I’m talking about the main earthing conductor

That's what I was going on about. I will have to look that up as I thought it would be.

 

[Ian1981]

The armour can be used as a cpc but it won’t be 16mm CSA copper equivalent which is what the DNO require on a new supply

 

[Ian1981]

As a rule of thumb 85mm steel is only 10mm at copper equivalent using the formula in gn8 anyway.

 

[Leclanche]

Just returning to the banjo's how many folk use brass bolts nuts & washers to secure the fly lead to the banjo?
I've lost count of the number of zinc plated roofing/trunking bolts I've seen on jobs with swa installed probably doesn't make a lot differance but it's looks right & is right.

 

[Ian1981]

Just returning to the banjo's how many folk use brass bolts nuts & washers to secure the fly lead to the banjo?
I've lost count of the number of zinc plated roofing/trunking bolts I've seen on jobs with swa installed probably doesn't make a lot differance but it's looks right & is right.

I always use M6 25mm brass nuts, washer and bolts as it’s always the way I was tought and is my preference.
Piranha nuts are a great alternative, tho when using larger glands say 32 mm and up,I’ve not seen them made for this size

 

[westward10]

Like Ian I always use brass.

 

[Pete999]

The armour would not be 16mm equivalent copper as I’m talking about the main earthing conductor
Also if I used 3 core then a 25mm earth conductor is way overkill

The csa of the steele armour on a 25mm2 2core SWA equates to 60mm2 which in terms of CU eqates to 26.6mm2

 

[Pete999]

I always use M6 25mm brass nuts, washer and bolts as it’s always the way I was tought and is my preference.
Piranha nuts are a great alternative, tho when using larger glands say 32 mm and up,I’ve not seen them made for this size

Piranha nuts 20mm to 32mm

 

[westward10]

The csa of the steele armour on a 25mm2 2core SWA equates to 60mm2 which in terms of CU eqates to 26.6mm2

Not in terms of conductivity it doesn't.

 

[Pete999]

Not in terms of conductivity it doesn't.

What do you mean?

 

[Strima]

Brass for me as well, reduces the risk of bi-metal corrosion and you can undo them in ten years time.

 

[Richard Burns]

What do you mean?

There are two comparisons for steel and copper.

One is where the conductor is to be used as a cpc and will have to withstand a very high current for a short period of time, in an earth fault.

The other is where the conductor is a bonding conductor and may in certain circumstances have to carry a significant current for a sustained period.

Steel is ~8.5 times worse at conducting electricity than copper but steel is better than copper at maintaining its integrity under thermal stress of high current.

So the where the steel is used solely as a cpc the combination of the two factors means steel comes out at about 2.25 times worse than copper for use as a cpc.

However where the conductor may have to carry long term current only the comparative resistances are considered and steel is then about 8.5 times worse than copper.

This means that for a cpc calculation the 60mm² steel armour in PVC /ST/PVC SWA is comparable to a 26mm² copper conductor in a cable.

For a bonding conductor calculation the 60mm² steel armour in PVC /ST/PVC SWA is equivalent to a 7mm² copper conductor in a cable.