TNCS - USING NEUTRAL AS EARTH IN BOARD

[assegayer]

Im travelling abroad to a country that has no earthing arrangement and my friend would like me to do a bit of work on his house. My question is Whether or not i could create a link between the Neutral and Earth bar to create a tncs system.

I know it sounds strange but i have just been thinking for the past couple of days how they do it here in the uk. They do the same thing for tncs systems a link between neutral and earth.
Could someone shine some light on the subject as to why it cannot be done and how it can be done here then?

P.s i know a earth rod can be hit into the ground but want to explore all options.

Thanks

 

[Wilko]

Where angels fear to tread ... I'd test it but probably go with RCD and TT at the home end. Making the outside of your coffee machine the same potential as the neutral in an unregulated environment is asking for a zap, IMHO.

 

[assegayer]

But then why is it done in the uk the same problems can happen here????

 

[Wilko]

UK currently not war torn and so we can rely upon the earth provided by the Distribution Network Operator. If DNO does not provide one, then TT and RCD is the go

Just to add a plug - it's only reliable because of the strict application of standards by hard working expert engineers keeping the UK distribution network in top shape. Sounds a bit corny but it is true, again IMHO.

 

[westward10]

But then why is it done in the uk the same problems can happen here????

Yes they can and it does but it is deemed an acceptable risk. But as Wilko says how regulated is the supply there because we have strict guidelines for PME here and that is not foolproof.

 

[assegayer]

UK currently not war torn and so we can rely upon the earth provided by the Distribution Network Operator. If DNO does not provide one, then TT and RCD is the go

No thats not what i mean , forgot war and all that. Why is it that a in one house a tncs system here can be connected to neutral but in another house it cant?

 

[assegayer]

No thats not what i mean , forgot war and all that. Why is it that a in one house a tncs system here can be connected to neutral but in another house it cant?

Isnt all neutals connected to earth at the very begining anyway?

 

[mhar]

Our network is planned and has multiple earth points. There are rules, for instance I think it is every third or fourth pole must be earthed. On tncs we are channeling the fault currents through the network, seems like a good idea to me that we know that the network can take it and not just hope

 

[assegayer]

Our network is planned and has multiple earth points. There are rules, for instance I think it is every third or fourth pole must be earthed. On tncs we are channeling the fault currents through the network, seems like a good idea to me that we know that the network can take it and not just hope

So the neutral is earthed every third or fourth pylon to keep the resistance down?

 

[westward10]

I don't know the intervals and it may vary but the resistance between the neutral and true earth used to have a required maximum resistance of 20 ohm.

 

[The Ghost]

Not all the supply systems are the same. Some are very old and do not suit PME and cannot be upgraded. Systems put in place over a hundred years ago are not suitable for PME now and are being disconnected where possible, and upgraded again where possible. Not all supplies are straight forward three phase supplies due to historical diabolical methods of supply.

 

[buzzlightyear]

many still happilly standing

what tents .

 

[Midwest]

He he he, I had an SSE engineer round to look at a possible dodgy TN-S supply and asked if it could be changed to TN-C-S. Said it could, but 'you'd need to wait 5 weeks, why not do it yourself?', 'Que???'. He then went onto demonstrating connecting EC into neutral of service head .

I didn't, but kept his name in my little black book, for when I need a get out jail card.

 

[mhar]

He he he, I had an SSE engineer round to look at a possible dodgy TN-S supply and asked if it could be changed to TN-C-S. Said it could, but 'you'd need to wait 5 weeks, why not do it yourself?', 'Que???'. He then went onto demonstrating connecting EC into neutral of service head

Hmm. When my youngest was a linesman I asked him if he would remove a knockout on a bakerlite service head as I wanted to upgrade the Earthing conductor to 16mm, Ze was something like .20. His manager gave him permission so he opened it up and was suprised to see a split con cable feeding the head (definitely no n-e link) so the supply was tns although it appeared to be tncs. Out of interest I got the same Ze reading when both n & e leads were on the supply n as when putting the leads on the individual l, n & e conductors. The feed for next door was taken from this service head and someone had done a homemade earth to neutral connection assuming that pme was available. He enquired of the network planner who was insistent that the network would not support tncs and that next door must be tt'd (we were fine as tns). My son wasn't expecting this response, freely admitted that taken in isolation he would probably have thought that next doors supply was ok, and conceded that the only person who would really know the answer to such a query is the network planner responsible for the area.
Only the network planner can tell you whether pme is available. It is so easy to make an earthing enquiry it is stupid to not do it right

 

[Darkwood]

On the same lines as mhar, an assessment of the network conditions and type are crucial to allow for the permittance of a PME/TNCS conversion, the safety of the user, property as well as other users may be at risk if this is done by anyone but the DNO, we have 10's of thousands of miles of old degrading network cables and joints that won't be suitable, although I cannot comment on other countries and their own systems and regulations I can say that under no circumstances should anyone try to do their own conversion even if its just hypothetical, that puts a hypothetical family at risk and its just not worth thinking about let alone undertaking such a task.

 

[Midwest]

Only the network planner can tell you whether pme is available. It is so easy to make an earthing enquiry it is stupid to not do it right

I didn't do it

His argument, was my TN-S supply was probably turned into TN-C-S in the road outside. Whenever, the DNO repair an old cable, it's always turned into PME.