Earth Cable To Sub Distribution Board.

[gerard]

Hi All,

I recently installed a new dist. board with 95mm sq 4 core swa cable. I used 35mm sq earthing cable even though I should have used roughly half the size of the live conductor. I used this because I had it, and was hoping it will be ok. I now fear that the cross section of the cpc. Is it possible to install an earthing point close to the new board to prevent me from installing a new earth cable?

Confused?!?

 

[telectrix]

can you calculate for the armour and add that to the 35mm, see if it satisfies the adiabatic?

 

[gerard]

I could only terminate the swa on one end with a compression swa gland, access to the other side made it impossible so I just used a brass bushing. So, although it's a good idea, I can't use the armour. Any thoughts on another earthing point?

 

[Darkwood]

The armour needs earthing correctly but if you run a seperate earth that meets the csa needs of the sub mains then you only need to earth the swa at the supply end, but it still must be earthed regardless of the additional earth cable.

 

[Knobhead]

Hi All,

I recently installed a new dist. board with 95mm sq 4 core swa cable. I used 35mm sq earthing cable even though I should have used roughly half the size of the live conductor. I used this because I had it, and was hoping it will be ok. I now fear that the cross section of the cpc. Is it possible to install an earthing point close to the new board to prevent me from installing a new earth cable?

Confused?!?

I could only terminate the swa on one end with a compression swa gland, access to the other side made it impossible so I just used a brass bushing. So, although it's a good idea, I can't use the armour. Any thoughts on another earthing point?

I’m sorry Gerard. But all the above would be totally unacceptable to me!

 

[Engineer54]

Hi All,

I recently installed a new dist. board with 95mm sq 4 core swa cable. I used 35mm sq earthing cable even though I should have used roughly half the size of the live conductor. I used this because I had it, and was hoping it will be ok. I now fear that the cross section of the cpc. Is it possible to install an earthing point close to the new board to prevent me from installing a new earth cable?

Confused?!?

Had you terminated this 4 core 95mm SWA correctly, you would not have needed any separate CPC. The armouring would have been more than sufficient for your needs....

 

[Bobster]

What's a compression SWA gland? Just a normal stuffing gland?

 

[Engineer54]

What's a compression SWA gland? Just a normal stuffing gland?

I'm hoping he means an external SWA gland, with the bushed stuffing section at the rear!! ...Fingers crossed like!! lol!!

 

[Bobster]

I do hope it's a cw gland.

By brass bushing I'm hoping its not just got the swa shoved through the hole in the panel.



edit:

I've seen it before so it wouldn't supprise me.

 

[Darkwood]

You can get liquid tight swa gland which is like a stuffing gland on the back of the swa gland to seal upto the sheath cw are not waterproof as many assume with their outdoor use.
Ive a feeling though this isnt the gland hes refering to.

 

[drew35]

The way it reads to me is that one end of the SWA is just sitting inside a brass bush.

 

[Bobster]

You can get liquid tight swa gland which is like a stuffing gland on the back of the swa gland to seal upto the sheath cw are not waterproof as many assume with their outdoor use.
Ive a feeling though this isnt the gland hes refering to.

Yes it's stated for outdoor use with cw glands, never seen a problem with properly fitted ones, even with a jet wash used to clean the plant down. The mistake most people make is over tightening the compression seal.

I have seen the ip65 swa glands, but I don't use them very often.

 

[Engineer54]

I prefer to use internally glued heat shrink than the standard shrouds in externally exposed locations, that are subject to adverse conditions...

 

[gerard]

The swa is passed into the panel at one through a 50mm brass bush. I considered this OK under the circumstances as:
1. I would never have been able to fit a cw gland
2. the cable has no chance of moving as it is under ground, well supported, will never move and completely protected from people and elements.
My only concern is the size of the CPC, it is 35mm sq and the rule of thumb is half the size of live conductor. I do think the cpc is sufficient but I would be happier if it was say 50mm sq. So, my original question was - can an earth rod be installed near a new db to compensate for the undersized cpc?

 

[johnboy6083]

In my opinion, there's not many places a gland can't be used. Even if you have to use the cone types with a jubilee clip like the ones found on some street lighting cut-outs. Not my favourite by a long shot, but would be better than not bothering at all.

As for the CPC, why can't the adiabatic be used? A 1 min calc, and you will be left in no doubt.