Earthing neutral

I don't see the need to isolate the PE between the transformers and gear- I would earth them at both sources and the gear without hesitation.

That wire (between the sources) is logically the system Neutral (even though it's not distributed to the loads in this case) - which for a TN-S system can only be earthed at one point (otherwise it becomes a TN-C-S system and you have a whole pile of other potential problems to deal with).


It probably helps to read it along side the preceding diagram (9A in appendix 9 of BS 7671) where the N is distributed to the loads - to which the same notes apply.


Also it's not the case that the regulations are saying that this conductor must be treated as a PEN. The text is simply describing it as being similar to a PEN (and as it's an earthed neutral conductor, it is does have some similarities). Also note that this text is only a note to a diagram in an informative appendix to the regulations - it's important to understand the it is does not form part of the regulations proper and should not be taken as such - appendices that are part of the regulations are marked "Normative" instead of "Informative".


   - Andy.

I don't see the need to isolate the PE between the transformers and gear- I would earth them at both sources and the gear without hesitation.

That wire (between the sources) is logically the system Neutral (even though it's not distributed to the loads in this case) - which for a TN-S system can only be earthed at one point (otherwise it becomes a TN-C-S system and you have a whole pile of other potential problems to deal with).


It probably helps to read it along side the preceding diagram (9A in appendix 9 of BS 7671) where the N is distributed to the loads - to which the same notes apply.


Also it's not the case that the regulations are saying that this conductor must be treated as a PEN. The text is simply describing it as being similar to a PEN (and as it's an earthed neutral conductor, it is does have some similarities). Also note that this text is only a note to a diagram in an informative appendix to the regulations - it's important to understand the it is does not form part of the regulations proper and should not be taken as such - appendices that are part of the regulations are marked "Normative" instead of "Informative".


   - Andy.