Multiple TT outbuildings

[sam400]

Just after people opinions on this.

I ve just finished installing a kiosk which supplies 3 buildings,
The DNO was not clear on the earthing system they would be providing, in case I ended up with PME I earthed the submain armouring only at the kiosk
(2 core SWA) and isolated it at the load end with a stuffing gland into metal clad board. Earthing was provided for locally at each outbuilding with a rod - readings all good.

When the DNO turned up they fitted a cut out with earth bar on the side PME style but said I couldn’t use it because of high network ELI. No problem I fitted a 100mA types S after meter to provide earth fault protection on my submains.

Everything’s up and running but now wish I’d use standard SWA glands to tie all the earthing together and put all the rods in parallel.

I am pretty sure it’s compliant as is but am tempted to fit the glands all tho it won’t be fun.

Whats the general concensus?

Cheers

 

[davesparks]

My opinion is that having all of the earthing joined together will lower the overall Ra and give a level of redundancy. This assumes the CPC between each point is suitably sized for this to be viable.

 

[sam400]

Thanks Davesparks,

Can you expand on the CPC sizing?

Are you saying that to have built in redundancy the CPC has to be sized to act as another buildings earthing conductor?

Or that the CPCs impedance has to be low enough to contribute positively to that buildings earthing?

Cheers

 

[Wilko]

Hi - agree with Dave, it's an improvement to join the outbuilding rods. This may only practical if the outbuildings are fed from the first TT building, which it sounds like what's been done (?).

 

[sam400]

It’s fed from a kiosk 3 x submains, 3 x buildings.
To connect it all together I have just got to swap the compression glands for SWA glands

 

[suffolkspark]

If your readings are already good and your on a price leave it....
If your on hourly rate and want to make it the best it can be change the glands

 

[bigspark17]

What swa have you ran to each outbuilding? What size DNO supply isit?

 

[sam400]

100A 3 phase supply. 2c x 50mm and 2c x 35mm submain.

I prob will change it as it will bug me. Although it’s compliant it could be better
I just wanted to see what others thought.

Thanks

 

[bigspark17]

Sounds ok. Whats your main cu set up? Type S rcd then bs88 fuses on submains & main switch rcd 30mA inbuildings? Have you bonded in building to steel frame?

 

[Nigel]

Personally I would never use a stuffing gland on an SWA. I would have made them off into plastic boxes.

But in your scenario I would not change anytjing so long as Ze is acceptable.