So I'm trying to install a smart light switch with a neutral wire. Since the switch is next to a socket, I told myself I could take a neutral wire from there...

Opened the light switch and socket and all wires are red... Tried to determine the neutral wire in the socket without success.

Using a multimeter and testing the wires shows 119v between ground and wire-1 and then ground and wire-2 shows 226v which doesn't make any sense - to me at least -

Using a voltage tester didn't help either, beeping is constant whenever I approach it to ANY wire, except wires connected to the lights...

The house is very old, it started with 110v electricity and used to follow US code, then the country switched to UK standard and switched to 220v .. so I have everything in the ceiling running at 110v and every socket running at 220v

How can I find the neutral in this mess?

  • What make/model of smart switch are you trying to install? Commented Apr 6, 2022 at 4:29
  • Is your new light designed to work on 110/120v or 220v?
    – FreeMan
    Commented Apr 6, 2022 at 15:48
  • The switch is a tuya zigbee switch with neutral. and it's rated for both 110v and 220v
    – brainfault
    Commented Apr 6, 2022 at 16:17

1 Answer 1


Use the unswitched phase

If the switch is 240V ready, then you wire "neutral" to the live phase which is not being switched. If it is not 240V ready, don't use it.

There is no neutral in the Philippines.

It was banned some decades ago when the country switched to UK power (starting on rural electrification where the extra voltage helps. In the US most farmhouses get their own transformer since hauling 120/240V a mile is a lost cause, but that is costly.) However the nation decided to harmonize on this, and so they outlawed the use of neutral in 110/220 areas of the country.

You are to rewire each of your switch circuits to use the two legs of power only and change your lamps to 220V.

The nominal US color code for the two live wires is black and red. Happily, that is the same as the historic UK wire colors for 240V live and neutral. You can re-mark wires using black or red tape.

It sounds like your home was wired in conduit with individual wires, and they just used red for all live wires. If you really want to identify wires, you can hold all other wires while pulling on one, and seeing which wire moves at the other end of the pipe.

If you have any idea of continuing to use 120V, the problem is neutral may be disconnected at the transformer since the power company no longer provides it. On old USA system transformers, the two hot wires will be nominally 110V from ground (though this may drift a bit).

When the old transformer goes, it may be replaced with a Euro/UK style transformer. At that point one phase will be near 0V from ground and the other phase 220V from ground. Obviously that will be very disruptive to people bootlegging 120V neutral off of ground, that is why it is outlawed.

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