borrowed neutral

[i=p/u]

only on level 2330-5, could anyone shed some light on borrowed neutrals, as i dont know about them? thanks for your input. im guessing its using a neutral from different circuits and to do with old installations..

 

[ezzzekiel]

pretty much as you say, most commonly found on lighting at stairs

normally a live link between the commons of the two way switch downstairs and the neutral is picked up from the upstairs lighting

as it stands it wont cause concern until an rcd is introduced which will detect the imbalance and trip

 

[Sparky Ninja]

 

[j.mawer]

Dilema is that if you pull the fuse on ckt 2 to add a new light it can be shown to be dead.
You disconnect the neuteral on ckt 2 for some reason and someone turns on the light with the shared neutral and that would wack 240V onto the "neutral" in your hand and ...

 

[i=p/u]

would this be using single cores, and in this case you just dont know till your wopped with voltage

 

[j.mawer]

Domestically it would be twin and earth but if you only isolated the one circuit at the consumer unit and disconnected the neutral anywhere then the whole circuit (well the bit that is disconnected from the DB neutral) would be live, you might never know that it had been done. For instance you are fitting lounge ceiling rose and someone turns the upstairs light on then you are working live!

 

[j.mawer]

For reference Regulation
314.1 Every installation shall be divided into circuits, as necessary, to:
vi ) Prevent the indirect energizing of a circuit intended to be isolated

314.4 Where an installation comprises more than one final circuit... for each circuit the wiring shall be electrically separate from that of every other final circuit, so as to prevent the indirect energizing of a final circuit intended to be isolated.