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Switched neutral

Harry Macdonald
Looking at the BS7671 AMD2 out for consultation, I noticed clause 463.1.2. This shows an arrangement whereby the control device for a lighting circuit is switched by a switch on the neutral side of the device.

Clearly this works but why would anyone want to do this?
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    Why? Surely it's safer only to have a single source of supply, than provide a separately switched line, given your argument?


    Especially true in TN systems where isolation of the Neutral is not necessary. Also, better to ensure the circuit can be isolated from a single point of isolation, because there's nothing in BS 7671 to mandate that the coil is supplied (through the light switch) from the same points of isolation as the switched line through the contactor ... which is why we end up with fan isolators with the extra pole for switched line.
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    Why? Surely it's safer only to have a single source of supply, than provide a separately switched line, given your argument?


    Especially true in TN systems where isolation of the Neutral is not necessary. Also, better to ensure the circuit can be isolated from a single point of isolation, because there's nothing in BS 7671 to mandate that the coil is supplied (through the light switch) from the same points of isolation as the switched line through the contactor ... which is why we end up with fan isolators with the extra pole for switched line.
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