Earth rod Cable Query

[Darkness]

I have an outbuilding which is about 100m away and I am about to run a tempory cable running to this building as I am currently carrying out other building work and cannot lay a permanent cable until all work is finished.

Anyway the building I will have power to has a 40A Garage CU fitted already.

I have an earth rod here doing nothing so I was going to install it. What size of cable should I use to connect to the earth rod?

I have some 6mm but I doubt that will be suitable even for a 3m max run from rod to CU.

Because of the distance, and on a TT setup I could put this Rod to good use.

Cheers.

 

[Spark123]

Sorry,
imo installing a TT earth rod is not a recommended project for DIY as it must be tested to confirm it is in good contact with earth.

 

[Darkness]

I'll be installing it myself and family friend will be testing it when he next passes by.

Would ask him for cable size but he's on holiday until next week.

 

[andy]

I'll be installing it myself and family friend will be testing it when he next passes by.

Would ask him for cable size but he's on holiday until next week.

TT needs 6mm² at least for the main earth. altho i would install 10mm²

 

[Darkness]

Cheers for that Andy.

 

[Spark123]

Please note that the TT install must not be used until it has been adequately tested. You should also take into account the earth fault loop impedance which will most likely mean RCD protection for the whole CU on the TT install. Socket outlets must be on 30mA RCD.

Copper earthing conductor sizes for TT supplies with efli not less than 1 ohm:

Burried:
Unprotected 25mm²
Protected against corrosion (by sheath) 16mm²
Protected against corrosion and mechanical damage 2.5mm²

Not burried:
Unprotected 4mm²
Protected against corrosion (by sheath) 4mm²
Protected against corrosion and mechanical damage 2.5mm²

 

[Darkness]

The CU has the 40A incomer, RCD protected so everything is RCD protected.

Nothing will be used util the rod is tested.

 

[Spark123]

Sorry if I sound a bit OTT with this, it is just if a TT system is not correctly commissioned it can be very dangerous.