tns or tncs

[Buzz-light-bulb]

Hello sparks

I am led to believe that doing a pssc and pefc, assuming that the values are same will determine it is a tncs, how accurate is this measurement as I've come across properties today with the dno supply head is in the property next door. Or do I test the resistance.

 

[Guitarist]

Go and look next door...

 

[Buzz-light-bulb]

Can't always get in

 

[Guitarist]

Can't always get in

Sorry, but arrange with the neighbour so that you can.

 

[Richard Burns]

The resistance is not a certain measurement you do need to see it. If there are local PME supplies then this can bring your TNS fault currents to similar levels.

 

[Buzz-light-bulb]

So basically a measurement will not verify

 

[Richard Burns]

A measurement can give you a very good idea, if the two measurements are way out then it is TNS (or a badly connected TNCS!:shame if the measurements are close then it can be either way, a good TNS near other PME or the substation, or a normal TNCS.
Generally if the to earth measurement is higher than to neutral then you are probably TNS.

 

[Guitarist]

The point is, you can't assume anything.

 

[skydog23]

Assumption is the mother of all f&£k ups
Never assume nothing? If your test prove obscure you can always ask the dno
Then record appropriately
I'd hate to record a ze as Tncs or TNS if it wasn't when I had misinterpreted the supply
My apprentice would have a field day of mocking me lol

 

[driverman]

Why is the Head in a neighbouring property? If so ,it's incorrect. Where is the actual meter? Am I missing something?

 

[hillbillie]

Why is the Head in a neighbouring property? If so ,it's incorrect. Where is the actual meter? Am I missing something?

Not common, but I see this sometimes with conversions; service head in the ground floor or basement and tails going up to a meter and D/B in the other flats. The problem then is isolating the supply to the premises.

 

[trebor]

have to agree with guitarist on this, for one measurement will not prove one way or the other, secondly i presume you are doing some sort of inspection therefore the connection to the means of earthing must also be next door and must be checked for security