Swa bonding, what method.

[Jason Shawcross]

Hi all

Just need your advice, theirs a discussion going on atm on site between a couple of sparks. We have around 50 apartments being fed by 3core swa from a panel room all glanded into the top of a run of trunking, armour isn't used as cpc. One spark is saying we need to run individual 16mm earth's to each gland
Another is saying 10mm to the first of each set and then looping. I would have thought just bonding the trunking near the board adding some bonding tags in-between the trunking sections and bolting the banjos on would suffice. Tbf the trunking is <o.o1 atm anyway to met. So what's your opinion and regs if possible, don't have book with me.

Thank you.

 

[Ian1981]

People don't gland it to the board enclosure because they are too lazy to find a simple solution to do so, just leave it floating in the cavity no one will know is the remit these days.

There's isn't always a cavity to leave it

 

[Wilko]

IF I understand correctly - the swa armour is not the cpc or the bonding conductor, but must be connected back to met so that it may act as cpc if required. So at least one connection to met and daisy chained with sufficient ccc to satisfy adiabatic is my thought. This may already be achieved by the trunking but your 10mm will surely do it?

 

[westward10]

There's isn't always a cavity to leave it

I know it can be difficult but most things are possible. Entry hole back of board, screw an adaptable box to the rear of it with no lid and use the lid fixing points to fit to the board, gland cable off at adaptable box. Easy peasy on paper and I am already visualizing it in my head

 

[Ian1981]

IF I understand correctly - the swa armour is not the cpc or the bonding conductor, but must be connected back to met so that it may act as cpc if required. So at least one connection to met and daisy chained with sufficient ccc to satisfy adiabatic is my thought. This may already be achieved by the trunking?

If it's not a cpc then it just requires supplementary bonding to earth

 

[Ian1981]

I know it can be difficult but most things are possible. Entry hole back of board, screw an adaptable box to the rear of it with no lid and use the lid fixing points to fit to the board, gland cable off at adaptable box. Easy peasy on paper and I am already visualizing it in my head

Good grief !

 

[Wilko]

If it's not a cpc then it just requires supplementary bonding to earth

Good point
I'm just thinking during the masonry drill attack the armour may be called upon to act as cpc so beef it up ?

 

[Leesparkykent]

The banjos don't even need to be linked together if glanded into a bit of steel trunking that's earthed.

 

[Ian1981]

Good point
I'm just thinking during the masonry drill attack the armour may be called upon to act as cpc so beef it up ?

Depends as the steel armour conductivity isn't the same as copper so tho you might use a fly lead of 10mm the armour may not be even that equivalent

 

[westward10]

The banjos don't even need to be linked together if glanded into a bit of steel trunking that's earthed.

Reg 543.2.7 rather clouds all this.

 

[Ian1981]

I link them anyway, just one of those things I like to do.

 

[Ian1981]

Reg 543.2.7 rather clouds all this.

What is the jist of it without me getting off me couch and actually reading it?

 

[Leesparkykent]

Here..I wouldn't class trunking as an accessory though.

 

[Ian1981]

Here..I wouldn't class trunking as an accessory though.

View attachment 37222

Na that's if you use conduit say as the cpc and you take a fly lead from the metal back box to the socket as the conduit is the cpc.
In this case the trunking is not acting as a cpc it mearly becomes an exposed conductive part because the swa is glanded to it.

 

[Wilko]

Depends as the steel armour conductivity isn't the same as copper so tho you might use a fly lead of 10mm the armour may not be even that equivalent

Agreed.
OP scenario of 16mm is a waste of copper imho

 

[Leesparkykent]

Na that's if you use conduit say as the cpc and you take a fly lead from the metal back box to the socket as the conduit is the cpc.
In this case the trunking is not acting as a cpc it mearly becomes an exposed conductive part because the swa is glanded to it.

exactly my thoughts or using 2core SWA and the armour as the CPC.