Earth and Neutral wrong way round

[Rob_the_rich]

Went to fit a bathroom fan at a job and tested Zs at the light fittings before work, got 26 ohms! checked Zs at other light fittings, also high. Then checked Zs at a socket outlet, got 29 ohms. So then did Ze and got 35 ohms! The supply was TNCS. Phoned the electricity suppliers who said they could come around on the 18th but gave me EDF number who arranged to come around the next day (yesterday).

After digging two holes in the street they managed to find the supply came from next door's property and apparently the earth and neutral were fitted the wrong way round.

would this explain these readings?

Is this a common mistake?

Any thoughts please

 

[NozSpark]

Rob,

On a TNCS earth and neutral are the same conductor at the head,,, it's only at that point that it splits

 

[Rob_the_rich]

I know, it doesn't make sense does it. but thats what they told the client. could the PEN conductor be connected to earth?

 

[Manator]

I know, it doesn't make sense does it. but thats what they told the client. could the PEN conductor be connected to earth?

Because it is a direct link it would not effect the arrangement. To all intent and purpose, the PEN is shared. I doubt any direct link could be reversed.

 

[Rob_the_rich]

They must have been telling her porkies then. Could the PEN have been broken which produced the high readings? in which case it doesn't look good for the main bonding

 

[Manator]

Is the supply underground or above? I suspect a broken or loose connection probably from an overhead.

 

[Rob_the_rich]

supply is probably underground, as it is in London, and they dug up the street to try and find it. It was the client who noticed that the supply cable came from the house next door where the fault probably originated. So if the PEN was dodgy or broken the property relies on the main bonding as an earth. To get such high readings, the main bonding must be dodgy too, is this right?

 

[PC Electrics]

But......was the problem (high Ze) fixed??

 

[Rob_the_rich]

The client says they are now safe but I haven't been back since the first visit

 

[steptoe]

TNCS

Says it all!

Its a rubbish system, always has been, and until they implement it properly it always will be. IMHO.

Rip it out and TT it.

 

[Rob_the_rich]

Thanks for your replies. went there again today, Ze was 0.16. Fitted excellent Quietair fan and we couldn't tell when it switched on! Upgraded main bonding to gas and water to 10mm and left existing 6mm in situ.