Earthing Via the SWA on sub mains???

[Cazmac1]

Hi Guys, I have a question for you and no doubt I will have more as the week progresses:dizzy2:. I started a new job and I'm doing a 5 year periodic on a residential care home I have previous experience on domestic installations but this is by far the biggest thing I've taken on.
My question is this, the intake room has a three phase supply which feeds DB1, this in turn feeds 7 other 3 phase distribution boards via SWA sub mains cables. The problem I have is that none of the sub mains have a cpc conductor and are earth via the SWA itself, some of the brd's have 10mm earths connecting the earth bar to the sub main banjo and some are only connected via the gland and case itself. On all but two of the brds I have good EFLI readings and the other two are high 0.27?
Is this type of arrangement acceptable or do they need to have new earth installed back to the main dist brd.

 

[DurhamSparky]

the Gland needs to have a fly lead back to the Earth Bar on all joints if this arrangement is used to supply a Earth

other than that 0.27 as a ZdB thats fine...!!

what earth is in the property TN-S or PME

 

[telectrix]

as he says ^^^

 

[DurhamSparky]

another post for the Tel count ^^^^^ lol

 

[Cazmac1]

the Gland needs to have a fly lead back to the Earth Bar on all joints if this arrangement is used to supply a Earth

other than that 0.27 as a ZdB thats fine...!!

what earth is in the property TN-S or PME

PME

So all what code would I put on the SWA with no connection to the earth bar within the dist brd. C1???

 

[DurhamSparky]

the fact that the SWA lock nut is glanded to a steel box does not make it immediately dangerous as you have obtained a relevantly good ZdB reading of 0.27. rules out code 1

but on the flip side its against the regs past and present so it cant be code 3

personally i would give it Code 2 (still a fail) as it could potentially be a problem in future if some one snapped the gland out the Db or some thing...!

 

[Cazmac1]

Thanks.

 

[johnboy6083]

If the equipment is made from a conducting material, and that equipment is realiably and effectivley connected to earth, then a fly lead is not required. The gland must be in good contact with the equipment though. The same principles apply to MICC, SWA, steel trunking and conduit.

 

[Engineer54]

If the equipment is made from a conducting material, and that equipment is realiably and effectivley connected to earth, then a fly lead is not required. The gland must be in good contact with the equipment though. The same principles apply to MICC, SWA, steel trunking and conduit.

Agree, .... A good method would be using a biting type nut as the locknut, such as a ''Piranha nut''!!... lol!!

 

[somersetsparks]

Agree with johnboy and engineer54, there is no 'absolute requirement' for a banjo and flylead. In many cases a serrated washer is better. As long as the paint is scratched off beneath the gland and it is done up properly, and I got good readings, I would not code it. I would definately check that the armouring is of a suitable size to be used as a cpc though.

 

[johnboy6083]

Note: if using a serrated washer, then usually long neck glands are required.

 

[Engineer54]

Agree with johnboy and engineer54, there is no 'absolute requirement' for a banjo and flylead. In many cases a serrated washer is better. As long as the paint is scratched off beneath the gland and it is done up properly, and I got good readings, I would not code it. I would definately check that the armouring is of a suitable size to be used as a cpc though.

Very slim chance that the SWA armuoring wouldn't comply, if the conductor core sizes are under 95mm, even for 2 core!! If very long runs, then i would maybe start doing a few calculations, just to satisfy myself...