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I'm looking to add a switch to an existing 240v circuit to switch power between two appliances. Do I need a 2 pole switch and just have the neutral attached to both appliances or do I need a 3 pole switch and switch neutral.

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    You should never switch a neutral, nor a ground. No point and dangerous. But from what it appears like you are attempting to do is sounding like a hack job. Probably dangerous and not code legal. Please edit your question to include more details as to what you are really trying to accomplish so that we can give you better answers. Dec 14, 2021 at 3:31
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    @George Anderson "You should never switch a neutral" - are you really sure?
    – xeeka
    Dec 14, 2021 at 3:38
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    F.e. GFCIs for (sub-) panels must - at least in Europe - also switch off the neutral. The neutral contact opening has even a tiny delay in order to avoid dangerous voltages in case of asymmetry. Also many extension plugs do switch off both poles (hot and neutral) - if they have a switch.
    – xeeka
    Dec 14, 2021 at 3:52
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    @George Anderson Maybe you mean "You should never switch neutral ALONE", i.e. without switching the corresponding hot leg(s)? That recommendation could be very useful.
    – xeeka
    Dec 14, 2021 at 3:56
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    I agree that this sounds very much like an XY Problem. If you'll tell us more about the situation, we may be able to help you come up with a better solution than inventing something yourself. Including things like where in the world you are (code matters), what appliances you're trying to switch, and a picture of the outlet(s) in question and the breaker panel/customer unit will be very helpful.
    – FreeMan
    Dec 14, 2021 at 13:34

1 Answer 1

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It is always better to switch all 3 poles in that case.

In case of defects or a lose neutral connection in the incoming supply line, the neutral could have a dangerous voltage, fed by the 240V appliance switched on, f.e. in case of asymmetrical loads.

Even GGCIs would not necessarily trip in that case, since the sum of both hot legs plus neutral currents might be still 0.

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