Earthing arrangements query....Most common systems in UK:TN S;TN C S;Regardless of the system in all domestic?

The difference isZe or Zs values.The regs don’t allow use TNCS sys.in detached garage.Supply should be converted into TT.WHY?


IF U use drill in garage-fed from internal socket(RCD protected)through ext.lead - than this is OK. So why I have to create TT system in garage?


What if I have TNCS and want external socket, if is RCD protected–that comply? - Or I am not allowed to have it-Unless its part of TT system?


Imagine TNS system with damaged earth connection.U request upgrade of the earthing arrangements and They connect new earthing conductor into N is it? In all those systems the N is connected to E anyway


What if I will have high Ze value in TNS and connect my Main Earthing conductor to N at the service head–the Ze value should be lower?I think - in almost all cases when new supply is connected in London they provide PME supply regardless that your next door neighbor may have TNS system which is connected into the same underground supply conductor…..


What do you think?

Earthing arrangements query....Most common systems in UK:TN S;TN C S;Regardless of the system in all domestic?
Your garage is outside the "normal equipotential zone" therefor if you are supplying power to is as a separate fixed circuit then to guarantee an effective earth you should supply a means of earthing normally an earth rod(TT)You do not have access to the suppliers neutral terminal to connect your own earth to .If you have a socket that is protected by an rcd then it can be used outside no problem the rcd doesn't even have to be on that socket only it could be the main breaker
Reply:Ze is EFLI measured at the incomer,


Zs is EFLI measured at the accessory.





It's the supply company who do not permit you to export their earth. Nothing to do with wiring regulations. http://www2.theiet.org/Publish/WireRegs/...





Using an extension lead to supply a tool outdoors is not an installation by the very nature of it's temporary duration. Therefore also exempt from BS7671.





BS 7671 permits external sockets where RCD protected. On the house wall is still considered to be 'within the equipotential zone'





And while it's also up to the supplier to determine what earthing system you are give; the advantage of TNCS over TNS is that an earth doesn't have to be 'sweated' onto the lead sheath thus removing its (sweating) associated health and safety risks.





And you are breaking the law if you touch anything (Cut-out) owned by the supplier . It is THEIR property, not yours.
Reply:TT every time, that way you know there is a path to earth. It's not my profession so I am just expressing an opinion, but I always grew up working on the principle the shortest route to earth must be through a direct connection and not anything that goes via me or has any likelihood of doing so.


Top question though because I have never quite understood why PME is the preferred option nor why you would even want to rely on a armour sheath TNS to carry your earth back to the transformer via the neutral, which is live as soon as a phase is connected to it. It all gets to be a complex balancing exercise which is easily resolved by connecting the consumer end directly to earth as well.


I always guessed it was a cost cutting exercise to avoid additional cable runs for earth and saved the hassle of driving rods into gas mains etc. in towns


My system is generator and solar but I still have copper rods firmly driven in at all the connecting points.


I look forward to other answers.