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Double pole switches for lighting

Kenneth Odam

I replaced an old fluorescent light fitting with an LED version - it had an emergency backup facility which required a separate unswitched live.

I took a live feed from an existing emergency light to my new fitting.

Everything seemed to work until I turned off the light - the battery charging light went off and the light came on at low power.

It turned out that the original light circuit had a double pole switch.  When it broke the neutral line the emergency light came on.

I bypassed the neutral side of the switch and the lights all work as expected.

I have never come across double pole switches used for lights.  Is there any good reason for this?

There is a double pole cct breaker upstream for maintenance work, so I don't think I'm creating a hazard.

In the unlikely event that the live side of the double pole switch breaks in the on position, the neutral switch would turn out the light but leave it all floating at live potential.  I can therefore think of good reasons not to use a double pole switch.

Thanks

Ken 

Retired MIET

Parents

  • Given the updated rules on switching off for mechanical maintenance (which includes changing a lamp) - i.e. just about full isolation is required - I can see an argument that something more than just an ordinary 6A plateswitch might be needed these days if you want to avoid plunging the whole area into darkness just to change one lamp. That said a lot of 20A DP switches aren't rated for isolation either (BS EN 60669-2-4).

       - Andy.

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  • Given the updated rules on switching off for mechanical maintenance (which includes changing a lamp) - i.e. just about full isolation is required - I can see an argument that something more than just an ordinary 6A plateswitch might be needed these days if you want to avoid plunging the whole area into darkness just to change one lamp. That said a lot of 20A DP switches aren't rated for isolation either (BS EN 60669-2-4).

       - Andy.

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