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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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    Also anyone who uses the light switch as a means of isolation before working on the contactor will find out the hard way why it is a bad idea.


    BS 7671 is probably even more out of step with common sense that you'd imagine - table 537.4 decrees that an ordinary lightswitch (probably to BS EN 60669-1) isn't suitable for isolation, no matter which conductor it's in. Since recent changes to 537.3.2 it's not even suitable for switching off for mechanical maintenance (as the requirement is now that it must provide full isolation for that function) - so you can't even use the light switch to switch off to replace or even clean the lamp!


       - Andy.


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    Also anyone who uses the light switch as a means of isolation before working on the contactor will find out the hard way why it is a bad idea.


    BS 7671 is probably even more out of step with common sense that you'd imagine - table 537.4 decrees that an ordinary lightswitch (probably to BS EN 60669-1) isn't suitable for isolation, no matter which conductor it's in. Since recent changes to 537.3.2 it's not even suitable for switching off for mechanical maintenance (as the requirement is now that it must provide full isolation for that function) - so you can't even use the light switch to switch off to replace or even clean the lamp!


       - Andy.


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