TT or TNCS

[La Poste]

Greetings.
I am working at a friend of the families house helping to make the place safe and will be shortly arriving at the decision of what earthing system to use.
The house allready has an earth rod although the readings on it are rubbish.
The main bonding is giving an earth fault loop impedance of 18 ohms, much better than the rod I might add.
The suppliers have said TNCS is available but after reading much on the subject of earthing I'm a little undecided.
I have read about losing a neutral on the siupply side that is pretty much catastrophic if you have TNCS.
Also the neightbours electrical standards are pretty low from what I have heard and with TNCS I might be importing a whole lot of aggro from next door.
The thing that puts me off the earth rod is the high earth fault loop impedance. If the gentleman in question had a faulty RCD then if he had an earth fault no MCB's would trip, the earth fault current wouldn't be high enough with an earth fault loop resistance of 18 Ohms.
In doing my research I have realised some people have very strong views on this subject so I am asking which earth method would you prefer?
Thanks.

 

[SirKit Breaker]

I had a PME connection done on a job recently for £154 all in. Rods are adequate, but in my opinion PME is much better, especially as we are in 2010 not 1910.

Just an opinion and a preference.

Cheers..............Howard

 

[La Poste]

with a TT syatem, you rely on the |RCDs to trip in case of a fault current to earth. The Mcbs cover L/N overcurrent/short circuit

Exactly, you have no second leyer of protection in case of an earth fault at all, only RCD's.
TNCS would give you this second layer of protection, RCD's and MCB's in the event of an earth fault.

 

[telectrix]

agreed, you just got to weigh up the cost of TNCS, as sirkit says about 150-200quid. having said that, it's more reliable than TT.