Earthing help!

[D Brennan]

I have just started some work on 2 large stables, roughly the size of a football pitch each, The supply is 3 phase and no earth supplied, from the main cut out the cable run which supplies both stables is around 250 meters away. The electrician that started the job sadly passed away and i have no idea what he has done regarding earthing, im told that there is some sort of earth matt near the main cutout & ifaik he has just used the armours to provide an earth to the main DB which then also supplies the next stable which is around 30 meters away.

Would you just rod each building so they have there own seperate earth?

Also the building structure is all steel, i can only see he has bonded this in one place (16mm), should bondings be on every gurder?

Whilst there i noticed that the lighting was supplied using a 7core 1.5 swa and 3 cores on seperate breakers rated at 16amp which all meet a a large termination box for each of the three rows of lighting, the swa was red hot, i advised the customer this should be changed but as per normal "it works".

Also what size of main earth should i be running to each db from the rods?

cheers all

 

[binky]

Whilst there i noticed that the lighting was supplied using a 7core 1.5 swa and 3 cores on seperate breakers rated at 16amp which all meet a a large termination box for each of the three rows of lighting, the swa was red hot, i advised the customer this should be changed but as per normal "it works".

Off the top of my head 1.5mm will carry 16A max (haven't got book to hand to check), but would then have to be derated because of bunching cables, so probably overloaded, and judging by the heat, it is overloaded.

 

[Andy™]

i dont see a problem with using 1 earth rod/mat for everything. you could always stick a few extra rods in if necessary.

1.5 SWA should take 19A ref method E on 3 phase, but 7 core may be slightly less. could the problem be an overloaded neutral if shared? what are the loads on the lighting?

 

[D Brennan]

i dont see a problem with using 1 earth rod/mat for everything. you could always stick a few extra rods in if necessary. 1.5 SWA should take 19A ref method E on 3 phase, but 7 core may be slightly less. could the problem be an overloaded neutral if shared? what are the loads on the lighting?

I n each building there is also water and gas to bond, all all earthing ok then supplied from one earth matt 250 meters away from the first building db??

 

[Andy™]

I n each building there is also water and gas to bond, all all earthing ok then supplied from one earth matt 250 meters away from the first building db??

may be easier to TT each building

 

[Evans Electric]

I think rods for each building is the best idea . Bonding to one girder should be enough as they are all bolted together. What size is the incoming supply ? I presume a 3pole RCD would have to be fitted or RCDs for each circuit.

 

[D Brennan]

may be easier to TT each building

thats what i was thinking, am still unsure as what to do though as as it is at present there actually is an earth to each db in each building fed from the earth matt next to the incomer 250 meters away using the armours on the swa....

 

[D Brennan]

I think rods for each building is the best idea . Bonding to one girder should be enough as they are all bolted together. What size is the incoming supply ? I presume a 3pole RCD would have to be fitted or RCDs for each circuit.

25mm swa feeding the first building and then 25 mm swa from db1 on 3p breaker to second building

 

[D Brennan]

I think rods for each building is the best idea . Bonding to one girder should be enough as they are all bolted together. What size is the incoming supply ? I presume a 3pole RCD would have to be fitted or RCDs for each circuit.

rcbos for each circuit

 

[Andy™]

25mm swa feeding the first building and then 25 mm swa from db1 on 3p breaker to second building

25mm SWA for 250mtr? whats the load?

 

[D Brennan]

25mm SWA for 250mtr? whats the load?

thats whats already been run in before i got the job ha ha, lighting, treadmills for horses, showers, heating, allsorts

 

[Andy™]

thats whats already been run in before i got the job ha ha, lighting, treadmills for horses, showers, heating, allsorts

do they shop here

 

[D Brennan]

do they shop here

they may do ha ha

 

[Evans Electric]

I suppose then if the Ze is OK back to this earth mat then its OK . I suspect Andy is about to adress the VD .!!

 

[D Brennan]

I suppose then if the Ze is OK back to this earth mat then its OK . I suspect Andy is about to adress the VD .!!

my first thoughts when i seen the run

 

[D Brennan]

anyhow, what you thinks the best thing to do leave earth connected to the matt or rod each building?

 

[Zeespark]

Build D, the best earthing conductor around if the building is metallic construction.

AndyGuiness Drink

 

[D Brennan]

bit off topic but whats up with my flag?

 

[Zeespark]

You just need to re-register it mate. It was a matt finish, now they fly about so to speak.

AndyGuiness Drink

 

[D Brennan]

>>>>>>>>>>>>>>>>>>>>