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.

 

[Pete999]

Deleted

 

[Pete999]

The SWA armour not being used as a cpc needs to be earthed at the supply end and isolated from earth at the load end, I think

 

[Bobster]

The SWA armour not being used as a cpc needs to be earthed at the supply end and isolated from earth at the load end, I think

Why???

 

[Pete999]

Why???

I did say I think, so why not?

 

[Bobster]

I did say I think, so why not?

The only real reason you would keep the armour floating at one end is on a TT/IT install where you are keeping separate earth potentials apart.

Another reason is then the armour can't handle the expected fault current on it's own. This isn't likely to happen on an install like this.

 

[telectrix]

yhink OP's argument is to use the trunking as cpc.

 

[Bobster]

Still no reason not to earth the armour at both ends.

 

[LeeH]

Needs to be at 1 end at least. No requirement for both but why wouldn't you.

 

[topquark]

If it's a PME supply then 16mm min for the earth and 10mm min for any bonding needed (can require up to 16mm for bonding if Ze > 0.35 by agreement with DNO, up to Ze of 0.50 if memory serves correct).

 

[HandySparks]

What size is the 3 core SWA?

 

[Ian1981]

The armour being glanded into the steel trunking requires supplementary bonding only if not being used as a cpc in which this situation is not being used as the cpc.
Gland into trunking and link all earth rings together with a supplementary bonding conductor (like 4mm) and take one common supplementary bonding conductor to an earth like the MET or to the panel DB

 

[Ian1981]

If the db in the flat is wall mounted and the swa is buried in the wall(masonry or no void) then if your entering the back of the db , it's not always possible it gland the db end.
So gland the supply end.

 

[LankyWill]

I'd banjo the armoureds and just run an earth from the met to the trunking. Then link them together with a bit of 4 mm.

 

[westward10]

If the db in the flat is wall mounted and the swa is buried in the wall(masonry or no void) then if your entering the back of the db , it's not always possible it gland the db end.
So gland the supply end.

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.