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I have 4 cables from a power supply which are 3 phase WYE 208 volt. so if I measure between neutral and hot I get 120V.

The problem is that I need to hook up a compressor for 110V single phase (just normal wall socket) to this particular combination.

Question 1: Is this just a bad idea to begin with since the phases are 120deg apart instead of 180? If it is is there some gadget I can buy to convert correctly?

Part 2: My attempt: so I tried to hook it up and I soldered the neural to the ground of a cut 3 prong extension cord, the I soldered a hot wire to the small and large hole of the plug. This was a bad choice because after I ran the compressor I triggered the circuit breaker. Then i realized that i was feeding it 240V instead of 110V.

Question 2: Do you think I should try to leave the ground on the prong open and instead solder the neutral to the small hole and one of the hot wire (does it matter which) to the big hole. This way I would supply the compressor with 110V?

As far as I understand, it doesn't matter now that the phase is 120 between the hot wires, because I am using neutral to hot, right?

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    You know the words but obviously don't understand the basic concepts of electrical wiring. This is an extremely dangerous combination. Call a professional before you kill yourself or someone else. If you've done any electrical work anywhere else, get a professional to inspect it.
    – longneck
    Commented Jun 29, 2013 at 2:30
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    I agree with @longneck. You shouldn't be soldering anything to do with your houses electrical system. You shouldn't be connecting neutral to ground. Yes it matters which "hole". One is neutral one is hot. If you mess this up you will electrify devices plugged into it and ultimately electrocute yourself or others.
    – Steven
    Commented Jun 29, 2013 at 3:49
  • @longneck,@Steven Thank you, i know i dont know what im doing, but im trying to make this work. (1) why is soldering house electrical system bad? (2) what will happen if i connect neutral to ground? or the ground of the device to the neutral? (3) whats a good place to get started to understand the "basic concepts of electrical wiring?"
    – Zlatko-Minev
    Commented Jun 29, 2013 at 7:06
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    If you connect neutral to ground anywhere other than at the main panel, you create a situation where a neutral fault goes undetected but electrifies the exterior of all your grounded appliances. If you create a better path to ground that the house wiring, you'll be electrocuted when you touch the device.
    – BMitch
    Commented Jun 29, 2013 at 11:14
  • @BMitch sorry, what do you mean when you say "neutral fault"
    – Zlatko-Minev
    Commented Jun 30, 2013 at 23:56

2 Answers 2

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In a 208Y/120 4 wire Wye system, you'll get 120 volts between either ungrounded (hot) conductor and the grounded (neutral) conductor. So if you're trying to connect a 120V appliance, all you need is one ungrounded (hot) conductor, one grounded (neutral) conductor, and one equipment grounding conductor.

The ungrounded (hot) conductor will connect to the brass colored screw terminal on devices (the small hole/blade), while the grounded (neutral) conductor will connect to the silver colored terminal (the larger hole/blade). The neutral conductor should never be connected to the equipment grounding conductor, or equipment grounding terminal on devices.

Notes:
Since it sounds like you're a bit over your head, you should probably contact a local licensed Electrician to finish the project and for any future electrical projects.

While you can solder connections in house wiring, it's not a common practice anymore. You'll also want to insure that you are using solder that is rated and labeled for the use, and that your solder joints are strong and insulated.

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  • Thank you Tester101! Just to make sure I understood, all I have to do is hookup the neutral wire to the larger hole/blade, one hot wire to the the small hole/blade, and I can leave the compressor ungrounded (I will check the solder, they are well isolated). I should clarify that I have the 4 wires of the 208V sticking out of a panel (isolated safely) and I am soldering them to the wires of a power cord set NEMA 6-50R into which I will plug the compressor. Maybe you can clarify what you mean when you say GROUNDED neutral, sorry I know this sounds very basic.
    – Zlatko-Minev
    Commented Jun 29, 2013 at 19:13
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    @AimForClarity You shouldn't be using the end of a NEMA 6-50R cord (or really any cord) like that. For one it is for 240 volts not 110/120. It should also be an actual outlet mounted in an electrical box.
    – Brad Gilbert
    Commented Jun 29, 2013 at 20:24
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    @AimForClarity No, you shouldn't do anything else yourself. You should contact a local licensed Electrician, or a friend who knows what they are doing to finish the project for you. An electrical system is made up of 3 types of conductors, ungrounded, grounded, and grounding. ungrounded conductors are your "hot" conductors, grounded conductors are "neutral" conductors, and grounding conductors are equipment grounding conductors or "earth" conductors.
    – Tester101
    Commented Jun 30, 2013 at 0:28
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    @AimForClarity en.wikipedia.org/wiki/NEMA_connector If you are only drawing 6A why aren't you just using a 5-15 receptacle that is wired properly, with a 12 or 10 gage extension cord? The connector tells you the voltage, and current capability. I would hard-wire a compressor before trying to use the wrong connector, or hard-wiring an extension cord. You could possibly make a NEMA 5-15 extension cord out of the one you were trying to use. (Make sure that you don't swap any of the conductors.)
    – Brad Gilbert
    Commented Jul 2, 2013 at 4:51
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    I've called a professional. Thank you for the help!
    – Zlatko-Minev
    Commented Jul 4, 2013 at 16:33
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all connections must be made with listed pressure connectors (wire nuts) are the standard , code specificly states that connections cannot be made by solder alone. other than that the others that weighed in on the grounding issue are correct, you dont want an alternate ground path that could energise the rest of your house including making "ground loops that can dammage switching powersupplys used in computers and most new TV's and electronic devices

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