Working on Maggie's Farm.

[Phoenix]

I think there was a concern with the fuel tanks in the ground being a better earth than anything off the supply network, so any fault currents were expected to go down via thhe fuel tanks instead of the mains.

It wasn't fault currents that was the issue, if you think about it you'd still have that issue with TT, even more so, the buried metalwork being a better earth than the electrode

More so, it was the currents that flow when there isn't a fault... the tanks and the ground being a parralel path to the supply neutral conductor and currents flowing in normal operation., obviously not as good a path, but still good enough that some of the neutral current would return this way, most installations this isn't an issue, but must don't have anywhere near as many voltile hydrocarbons to worry about! Of course the dropped neutral chesnut is a worry as well!

 

[Evans Electric]

Thanks guys , :Salute I think I see the light now after initial confusion . I was conjuring up a problem that wasn't there and assuming I had to change to either TN-S or TT .

You get some assistance on here !! I think I might stay .

 

[Sidewinder]

Deke,

Just remember a few other things.

1. What you are trying to protect against, i.e. step voltages, live extraneous parts etc.

2. Vermin attack.

Also the agricultural section does not apply to the house.

As long as your bit is TN-S, I would drop rods everywhere you can.

Use SWA where ever you can, RCBO's if possible.

Bond all metalwork if there is a hint of it being extraneous, or exposed.

Personally I would make all earthing and bonding conductors = to the incoming tails S if possible.

Along with the cpc of any sub mains if separate, if SWA I would run 3/5 core & run the armour in parallel, reduces the chance of vermin attack and the RCD requirement.

Also remember BW glands are only IP44 "officially".

Any reduced current sub mains, you may need to consider the earthing conductor sizing due to the supply characteristics.

Consider adding additional rods to steel framed buildings.

Question for anyone who went to Elexx.

Did you notice anything that could be considered "unusual" about the earthing arrangements for the building?

Clue: It is a little relevant to this thread!