Personal information.

[JohnW2]

Yes, I realise that.

I thought you would - but then you wrote TN-S

No, but if all you had was a 100Ω earth which is not effective for ADS then CPCs aren't much use, are they?

Quite - so that's why we have RCDs in TT installations (and CPCs ).

Kind Regards, John

 

[EFLImpudence]

I thought you would - but then you wrote TN-S

Ah. sorry. I missed the 'C' in your response.
Is that the case, then? Are your pipes and CPCs connected to the supply neutral?
I thought the installation was TT but the 'good' earth came from a neighbour.
Having written that, I see what you mean. Does that count as TN-C-S in your property?

Quite - so that's why we have RCDs in TT installations (and CPCs ).

Yes, I'm getting muddled thinking of my own situation.[/quote]

 

[JohnW2]

Ah. sorry. I missed the 'C' in your response. Is that the case, then? Are your pipes and CPCs connected to the supply neutral?

Very probably (albeit not within my house/installation) - via the water pipe and the neighbour's TN-C-S.

I thought the installation was TT but the 'good' earth came from a neighbour.

Indeed it is - see above. My earth electrode alone is usually about 75Ω. However, with main bonding connected, the Ze is something around 0.3Ω.

Having written that, I see what you mean. Does that count as TN-C-S in your property?

Quite. As things are, it would seem that it effectively is. I'm pretty sure that, with the present situation and bonding connected, all of my final circuits have low enough Zes for MCB-based ADS. However, I clearly can't rely on that, because one dark night Anglian Water could sneek into my village and insert some plastic pipe! I therefore have every final circuit protected by an RCD (or, in a few cases RCBO), as one normally would with a straightforward TT installation. I have even retained the up-front 100mA time-delayed RCDs. Although they are not needed for any of the final circuits (since they have their own RCDs/RCBOs), they are theoretically necessary to protect my distribution circuits - so I thought I might as well keep them (useful as isolators, if nothing more ).

Yes, I'm getting muddled thinking of my own situation.

Fair enough

Kind Regards, John