Portacabin/generator earthing

[spud1]

Hi,

I have a metal container / cabin with plastic consumer unit c/w RCD main switch and earth electrode, cabin is being supplied by a diesel generator with a bonded neutral located about 10 metres away in its own shed. Customer has tried wiring this up on their own and called me for help when they couldn’t get a voltage reading between live from the genny and the earth from the electrode . Explained that this was due to the ground earth not being referenced to the genny and that the neutral from the genny should probably also be used to Earth the cabin. But here is my question; Is it acceptable to link the neutral and earth bar within the consumer unit or should both the sub main cpc and neutral be commonly connected at the genny end?
Also in addition should there be electrodes driven in and connected at the cabin and/or genny to reference to ground earth too?

Cheers

 

[Strima]

What's the Kva of the genny?

 

[buzzlightyear]

Check and see if the output of the generator has a voltage to earth. Make sure before you do anything there is 30mA RCD main switch on the consumer unit. If there is no voltage to earth put a link in between neutral and earth at the incomming side of the RCD. This will reference one pole of the generator to earth so you now have a neutral and earth. Do an earth loop test and an RCD test before putting the installation in to service. An earth spike is also recommended.

 

[spud1]

Check and see if the output of the generator has a voltage to earth.

Thanks buzz, haven't been to site yet but what if there IS voltage to earth?

 

[spud1]

An earth spike is also recommended

Spike just at cabin end or genny too?

 

[buzzlightyear]

at the cabin .

 

[spud1]

What's the Kva of the genny?

I think it’s around 12Kva ?

 

[Ian1981]

Generators usually have a neutral-earth link inside making them TN-S.
An earth electrode is needed generally for generators above 10kva to reference the neutral to earth by connecting the generator chassis to the electrode at the generator end.
The upstream installation is then a TN-S earthing system
Guidance can be found in the on site guide and GN8
Might be worth contacting the generator company as well to confirm any earthing arrangement and recommended resistance of the earth electrode.
To measure the electrode an earth electrode tester will be needed as an earth fault loop impedance tester would be useless as the electrode doesn’t form part of the earth fault loop impedance path in this instance

 

[spud1]

An earth electrode is needed generally for generators above 10kva to reference the neutral to earth by connecting the generator chassis to the electrode at the generator end

Would it be advisable to install electrode at the cabin too? Or is genny electrode alone sufficient?

 

[Ian1981]

Would it be advisable to install electrode at the cabin too? Or is genny electrode alone sufficient?

You will have a TN-S earthing arrangement upstream of the generator so not sure what an electrode will achieve at the cabin end.