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What earthing arrangement is this?
Former Community Member
The supply is from a private transformer in a four core cable 3ph + n. The cable armour is earthed and connected to the MET. However there is also a green and yellow cable connected to the neutral terminal at the main isolator going back to a the transformer casing. The transformer is only 5 or 6 metres away. I think this must have been intended to make it a tncs supply but seems to me to just create parallel neutral conductors. Or is it tn-s-c-s? I have only been able to go off visual inspection because I could not disconnect the supply..
The 'systematic' T[TN]etc naming came to the UK via CENELEC/IEC from other countries (French origin?). PNB/PME are names of UK origin and almost purely UK use. So they're not exclusive: a system can be both PNB and TN-S, PME and TN-C-S, non-PME but TN-C-S (in some countries, anyway), etc.
I'd go for TN-S (if it fits the description others have already given for having a single N-E conection), as it seems the EIC forms are aligned to the IEC-style naming. Isn't it possible to append '(PNB)' to that (if handwriting), if you're really wanting to make sure you've declared every detail?
The 'systematic' T[TN]etc naming came to the UK via CENELEC/IEC from other countries (French origin?). PNB/PME are names of UK origin and almost purely UK use. So they're not exclusive: a system can be both PNB and TN-S, PME and TN-C-S, non-PME but TN-C-S (in some countries, anyway), etc.
I'd go for TN-S (if it fits the description others have already given for having a single N-E conection), as it seems the EIC forms are aligned to the IEC-style naming. Isn't it possible to append '(PNB)' to that (if handwriting), if you're really wanting to make sure you've declared every detail?
