Earthing Issue

[plugwash]

Putting an earth rod in and connecting it to a TNCS or TNS earth can cause problems because there can sometimes be a voltage on a TNCS earth, in other words, TNCS, whilst being protective earth, is sometimes not actually at true earth voltage. Connecting this to a true earth could cause a current to flow. I think thats about right anyway!!!

it could cause a current to flow but as long as the earth rod is connected with suitable size cable this shouldn't be a problem just as it isn't a problem with the main bonds.

 

[Adam_151]

Indeed, plug

The Commentary on the IEE Wiring Regulations includes, much more detailed and practical advice including advice prepared at the request of the DTI on further precautions that can be taken to reduce the risk associated with PME supplies. The UK National Committee considered this matter and recommend an earth electrode is connected to the main PME earthing terminal. This is a very practical solution. The Commentary on BS 7671 amongst its comprehensive advice provides specific guidance as to how the maximum earth electrode resistance can he calculated for particular installations e.g. house, swimming pool, farm etc. This approach provides the reliability and security of a PME supply whilst protecting against the loss of PEN continuity (however unlikely an event this may be).

 

[DDAS]

What is that switch for right in the middle? Where do its wires go?

That is a one way CU supplying sockets in the living room via a radial circuit.

 

[DDAS]

quote]
it could cause a current to flow but as long as the earth rod is connected with suitable size cable this shouldn't be a problem just as it isn't a problem with the main bonds.[/quote]

I assume you mean 16mm earth cable?

 

[DDAS]

will the supply company provide a new service head before a rewire is carried out or at least the CU replaced?

 

[securespark]

I believe it was OK to take the earth from the water mains in the old days, but it was outlawed in the 14th edition (1966) (I think)...

 

[ban-all-sheds]

Indeed, plug

The Commentary on the IEE Wiring Regulations

A good and useful book.