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power/3 phase

he needs to use two hots and a nuetral for 220/v single phase one hot and a nuetral would give him 120v only,
sounds like he needs an electrition
chris smith
paradise porter maine


  • bill/tonybill/tony Posts: 1Member
    3 phase power to 1 phase system

    Little help plz,a friend of mine had a 220 volt 1-phase system installed,and he has only 3-phase coming in to box.(ques.on a 3 phase 220 or the wires 120 degrees out of phase? and if he used 1 of the wires,and a netural for the 220 single phase unit, would that be a problem,anyway thats what they have done,and now the lites dim when unit comes on????ref.this is a 400 amp 3 phase box,and the unit is a 3 ton a/c gas pack tks tony/bill
  • Murph'Murph' Posts: 209Member
    should be a wild leg....

    at 270 volts, needs a meter to be sure. probaly marked with orange lable if its true three phase!! if not probaly does not matter!!

  • EarthfireEarthfire Posts: 543Member
    3 phase info

    Some 440 volt 3 ph systems have a 277V to neutral high leg usually designated by orange marking, other two legs(one at a time) will give 240V to ground or neutral. Any two hot legs, as in hot to hot will give 440V to 480V single Phase. (Any reading in that range acceptable.)3 hots will give 440 V 3 phase.
    240V 3 phase is 3 hot from 240V system, 2 hot legs give 240V single phase. Any one leg gives 120V+/- to ground or neutral.Most 3 phase equipment can be used on 440V or 240V systems, you just have to change the wiring at the power input junction READ THE INSTALLATION MANUAL.USE a good meter to check your voltage and wiring ( use the 600V scale) or if unfamiliar with electricity get an qualified electrician !!!!!440v is not 120v, It Can and Will bite hard and fast. SAFETY FIRST
  • DaleDale Posts: 1,317Member
    Find out from the utility

    It would be nice to know if this is a Y or delta service and at what voltage. Most of the 3 phase here for smaller loads is 208 Y. This way you can take the 120 single phase lighting loads without unbalancing the circuit. If the voltage is 440 I wouldn't touch it. If the service is delta with a center tapped N you do indeed test for the 190 volt wild leg connection if you are looking for 120. Some services are just straight 240 delta ungrounded from the pole. Find out what you've got first.
  • Steve EbelsSteve Ebels Posts: 904Member
    All of the above are true

    If you don't know how to test to see what you have I would highly advise hiring someone to find out before you burn up your A/C unit.

    That being said, Take your VOM and check from each of the three legs to ground to determine what is there. For instance a standard 3 phase in these parts will be 120, 208,120 to ground and 240 between any two hot legs. You can get 240 anywhere and 120 on all but the wild leg.

    Again, If you are not trained in this stuff leave it alone and hire someone who is. It ain't worth your life.
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