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  • Help in Korea

    I am living in Seoul, Korea supporting the US Forces in Korea. I just moved to an apartment which originally all 220v 60hz (the circular outlets with the 2 round prongs and a metal ground clip). The apartment was modified with a 5k, 220v to 110v transformer running to all the wall outlets except 1 which remains 220v for
    the air conditioner. The outlets all have a 2 prong to 2 prong 110 adapters plugged into them (no ground). I fried 3 surge suppressors the day I moved in, nothing was connected to them. When I use just a power strip or say plug the TV directly to the wall everything works fine. The maintenance man from the apartment said that my surge suppressors were either defective or made in China, and that was the problem. I then got a multimeter and measured the voltage coming across hot to neutral and it measured 110v, hot to ground measured 110v, neutral to ground measured 220v. I believe that neutral to ground should be 0. Since on the one 220v outlet hot to neutral
    was 220v, hot to ground was 220v, and neutral to ground was 0. My question is, is this situation dangerous/unsafe or is it kosher.

    Thank you,

  • #2
    From what you have said, it seems to me that anything that does not have a ground should be safe to plug in. Otherwise, I am not so sure. I pulled the folowing from

    "In North America, the standard 110 volt household supply is
    single phase, 110 volts hot with a (grounded) neutral return
    wire, 60 cycle. It's named 110 volt, but it usually runs at
    about 118 volts.

    A household will also get 220 volt dual phase, two hot lines
    at 110 volts to ground, out of phase, with no return line, for
    stoves and water heaters. Inside the house, both of these are
    taken for the 110 volt circuits. It's relatively rare for a
    house to be heated with electricity, but when it is it uses
    that dual phase 220 volt supply, with service wires with a
    higher current rating."

    I would call the maintenance man back. What do you think?

    Good luck in Korea and welcome to the forum!


    • #3
      Welcome to Korea. I also am an American living here and I have repaired what you have in your apartment many times.

      What happens is when they wire in your transformer (they call it a down-trans), they connect the hot (220V) and the neutral to one side of the transformer and then they connect the hot and neutral of the circuit breaker to the other side of the transformer. What you actually get from the transformer is what you see... 220 V on one line and 110 V (but out of phase) on the other line. The resultant voltage is 110 V (220 V - 110 V), BUT, that is not what you want or need. Korean electricians just think that is fine for us, but it is very incorrect and highly incompatible with things like surge protectors and other devices that use the wiring in your home for other uses (like radio and TV antennas or phone line via electrical wire devices). The surge protector actually crosses over both lines and things go real bad (I had a friend that burned up all of his electonics when he connected his electrical outlet based stereo antenna).

      Now I have told you the problem, and on to the solution.

      You need to remove the wire on the output of the transformer that is measuring 220 V to ground (use the frame of the circuit breaker box or the neutral coming into the transformer to check each line voltage). You will ultimately have the 110 V out of the transformer connected to the breaker and the other side of the breaker should conncet to the same neutral that you are feeding to the input of the transformer. This will give you 110 V on one side and the neutral on the other side for a healthy 110 volt outlet... just one more thing... verify that you have the hot and neutral on the correct wires in the outlet. Some electronics and surge protectors are very finicky about the flavor of the electricity. I have a simple little plug in device that I use, but you can also look it up and verify it with your multimeter by plugging into each side of the outlet and checking voltage between the respective outlet side and any ground that you can reach.

      Speaking of ground... that is another beast all together. Most Korean apartments have no ground or a ground that is floating. I find that my ground is slightly hot (by a matter of a couple of volts).


      • #4
        BTW ... any more question and I will be glad to help. I am currently researching hooking up a 220 V (2 phases of 110V) American clothes dryer to the Korean 220 V single phase. I know it can be done (perhaps with the use of a couple of transformers creating 2 phases of 110 V), but I don't have it worked out yet.