Multiple types of domestic power sockets around the world (including the ones in my country) do not distinguish between live and neutral even when ground is present.

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I am shopping for an AC-DC PSU and almost every product from reputable brands, clearly labels the live and neutral terminals:

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Will swapping live and neutral cause any harm? More in general, are there cases where swapping live and neutral can be somehow detrimental or dangerous for the functioning of a particular device?

  • 3
    \$\begingroup\$ Won't affect function but can make things dangerous. \$\endgroup\$
    – DKNguyen
    Dec 14, 2021 at 15:33
  • \$\begingroup\$ @DKNguyen can you explain in what way and if there is any precaution that can be taken? \$\endgroup\$
    – DarioP
    Dec 14, 2021 at 15:47
  • \$\begingroup\$ I was told that there is some device (something related to furnaces for house heating, can't remember) which will not work if mains live is swapped with neutral. Not dangerous but nasty. Anyway those devices don't use mains plugs. \$\endgroup\$ Dec 14, 2021 at 16:39
  • 1
    \$\begingroup\$ Humans don't, REALLY don't ... \$\endgroup\$
    – user16222
    Dec 14, 2021 at 16:50

1 Answer 1


It depends. Always ask the manufacturer. I should guess there are power supplies that are made to expect to be correctly connected inside a fixed equipment with electrical connections made by electricians.

In general swapping the inputs makes no real difference, but in practice if there is only one fuse then it will be on one of the wires. There might be other things that make them unsymmetrical.

If, however there is an earth connection on the supply, it must be earthed properly, it must be connected to an earthed mains plug and it must be connected to earthed mains wall socket. If there ever is a short circuit, and the blown fuse happens to be on mains neutral, the earth connection will keep things safe even if live is still active inside the power supply.

  • \$\begingroup\$ If the device is plugged into a GFCI protected circuit, the placement of the fuse does not matter as the same current is imposed on live and neutral, right? There is still the point of other asymmetries, but hopefully no one will put on the market a product that will be dangerous if L/N are swapped, worst thing it should not turn on. \$\endgroup\$
    – DarioP
    Dec 15, 2021 at 18:02

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