southern electric tt to tncs

[urchy107]

Hi all, I was at a job with a tt system and a ze of 299 ohms, so made a call to see if it was possible to swap to tncs. Normally I call western power they tell me if they think its possible,send someone out, if it is possible they put the connector in, put a sticker on and send me a bill. now with this I had to call southern electric due to the area, I spent about twenty minutes on the phone and initially it was like I was asking for something unknown. the guy said that my reading required an emergency call out after I had explained many times the reading was from the spike and I can try to improve it, but im just trying to find out if its possible to swap it. I left the conversation feeling confused and have just been contacted by the customer saying that they have been round and taken a reading of 0.29 and that,s all they have said, not even left a contact number.
I have always thought that if the swap is available then its advisable but didnt seem to be the case with them?
and im still unaware whether I can now connect it as a tncs or not as they have taken a ze reading of 0.29 which is obviously a good reading.
Thanks for any advise anyone can give me on this.
Cheers Matt

 

[robd]

Maybe they've just plugged in near the board and got a lower reading courtesy of the bonding to the water pipe?

 

[jase]

maybe your reading was correct off the earth rod, but they do indeed have TNC-S available and have a reading of .29, you need confirmation of what they have done and how they got the reading, round here they are converting a lot of TT to overhead pme

 

[Engineer54]

The old Regional electric boards had an ongoing program of converting overhead supplies to PME, in fact it was the initial reason for bringing PME. That all seemed to stop when they were privatised, ....costing them too much money and had to keep the shareholders pleased ...lol!!

 

[urchy107]

I think there must be tncs to get that reading, the incoming water is plastic and theres only an oil tank which isnt earthed, but will be when I get back there. im just gonna do my best with the rod if its not obvious when I get there. otherwise il be on the phone all day speaking to someone in accounts again. cheers for the comments

 

[wildgoose]

Scottish Power will visit a domestic property to take a reading. If it's within their spec (<0.35ohms?), they can immediately link-in their TNCS connector, providing the existing power head is already equipt with an earth block.

Last one I requested 4wks ago, was done FOC. Their very helpful Electrician rang me on my mobile to discuss and advise that using the SP TNCS earth block was now possible.

Good service & very impressed with SP efficiency in this instance - looking forwards to continued similar responses!!!

 

[Engineer54]

Scottish Power will visit a domestic property to take a reading. If it's within their spec (<0.35ohms?), they can immediately link-in their TNCS connector, providing the existing power head is already equipt with an earth block.

Last one I requested 4wks ago, was done FOC. Their very helpful Electrician rang me on my mobile to discuss and advise that using the SP TNCS earth block was now possible.

Good service & very impressed with SP efficiency in this instance - looking forwards to continued similar responses!!!

It's not just a question of the neutral being less than 0.35 ohms, it depends if the neutral has been PME'd or not. You can't just take an earth off the neutral, willy nilly because it has an acceptable low reading i'm afraid!!! There are many a TN-S earth that has a much lower Ze than some PME earths, if you catch my drift....