Feeder pillar query

[mrloy99]

Hi.I've got a couple of queries regarding feeder pillars on a car park I an working at.
There are 3 pillars.All are metal.No 1 is supplied by 70mm 4 core xlpe swa.3 phase and neutral.cpc/bond is the swa.
No 2 is 25mm 4 core. And No 3 is 70mm 4 core. No 2 & 3 pillars also have water supply in a separate compartment.The installation is TN-S..I'm wondering should there be an earth bond run back to supply DB in main building or is the swa sufficient..The main buildings neutral is 150mm (ish) and the main bonds inside the building are 50mm.

 

[Pete999]

Hi.I've got a couple of queries regarding feeder pillars on a car park I an working at.
There are 3 pillars.All are metal.No 1 is supplied by 70mm 4 core xlpe swa.3 phase and neutral.cpc/bond is the swa.
No 2 is 25mm 4 core. And No 3 is 70mm 4 core. No 2 & 3 pillars also have water supply in a separate compartment.The installation is TN-S..I'm wondering should there be an earth bond run back to supply DB in main building or is the swa sufficient..The main buildings neutral is 150mm (ish) and the main bonds inside the building are 50mm.

Who has ownership of these Feeder Pillars? if it's the DNO then that will be their problem not yours, adding anything to them may result in you getting a testiculating. I see where you are coming from though, to be honest I'm not sure of the answer.

 

[buzzlightyear]

delete

 

[mrloy99]

Thanks Pete.Not DNO.
Private.I was wondering do I treat them as if they were a detached building..The 2 metal boxes (feeder pillars) have 6mm bonds to water and 10mm to frame

 

[mrloy99]

did you see the CPC in the SWA in the cable or are they using the concentric wiring has the CPC !

Hi Buz...who mentioned concentric?The CPC IS the SWA

 

[Pete999]

Thanks Pete.Not DNO.
Private.I was wondering do I treat them as if they were a detached building..The 2 metal boxes (feeder pillars) have 6mm bonds to water and 10mm to frame

Not sure of what you are asking "mrloy99, are you doing any work/testing in the FPs?

 

[mrloy99]

Not sure of what you are asking "mrloy99, are you doing any work/testing in the FPs?

I'm testing only.What I am trying to ask is-is the swa of the cable supplying the FPs sufficient to act as main bonding or maybe they aren't main bonds and only supplementary bonding is sufficient?

 

[cliffed]

Tns is different from tncs,so you may be ok,Swa May be sufficient for cpc & main earth bonding.
50mm earth bond may be the bug bear there,would of been great to duplicate at pillar end.
This kinda thing is always a constant pain,the more we get to know,the more this undesirable occurs.

 

[Toneyz]

Is the water feed in plastic and then copper on wooden back board?

 

[Pete999]

I'm testing only.What I am trying to ask is-is the swa of the cable supplying the FPs sufficient to act as main bonding or maybe they aren't main bonds and only supplementary bonding is sufficient?

The Feeder Pillars I have worked on, relied on the sheath, be it SWA or some other armouring (not sure it was a long time ago) as the main earth conductor, you would need to look at SWA data to find out the CSA of the armour and then decide, if it's large enough in CSA to act as a Main Earth and a Bonding conductor, Atatched table is all the info I have, may help.

 

[buzzlightyear]

you should never rely on using the armoured wiring has a CPC.
specially 3 phase .

 

[buzzlightyear]

Use SWA as CPC, a guide to the acceptability of steel wire armour use as CPC. - https://gadsolutions.biz/regulations/swa-as-the-cpc

 

[westward10]

For TN-S the bonding would not need to exceed 25.0, the armour of all cables is inadequate to support 25.0 bonding. What size is the earthing conductor at the source of supply.

 

[mrloy99]

Is the water feed in plastic and then copper on wooden back board?

Yep

 

[mrloy99]

For TN-S the bonding would not need to exceed 25.0, the armour of all cables is inadequate to support 25.0 bonding. What size is the earthing conductor at the source of supply.

240mm