2 hots no ground...explain this.

Discussion in 'General Electronics Chat' started by revekozu, Mar 20, 2005.

  1. revekozu

    Thread Starter New Member

    Mar 20, 2005
    3
    0
    While doing some renovations on a house with a friend I realized I had bought a 240 volt baseboard heater for a small room. I said I'd go exchange it rather than have to re-wire. Old house with only hot and neutral wire.

    He then said it was possible to run 240 with just 2 hot wires. This didn't make sense to my "complete the circuit" way of thinking about electricity and I didn't believe him. (By the way I never considered installing it this way)

    To prove his point he hooked up 2 hot wires to the heater (no ground no neutral)and it did work. He claimed he has seen a lot of old stoves hooked that way. I'm guessing it works because of the alternating current. But I'm stil scratching my head...
     
  2. Firestorm

    Senior Member

    Jan 24, 2005
    353
    0
    in a 240 volt power supply the 3 wires are hot, hot, and ground.
    i l ----both are hot....in a 120, only the left is hot and the right is as you
    . --- ground said neutral

    basically it will work...if you need more detail, just say so....hope this helps...thx l8er

    -fire
     
  3. revekozu

    Thread Starter New Member

    Mar 20, 2005
    3
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    That spells out who it should be wired, which I already knew. then again I don't follow if "i l ----both are hot" means anything or if that's a typo. You guys have probably worked out textual ways to communicate this stuff.

    I want to know why it works with only 2 hot wires and no ground, was not grounded in the test in any way and with no neutral. No it won't be installed that way. This is not a how to install question. More of a how do the electrons flow here question.

    and also....why is there air? :)
     
  4. Erin G.

    Senior Member

    Mar 3, 2005
    167
    1
    The power coming into your house does so on three wires, 2 hots and one neutral. If you were to take the cover off of your panel board and measure between the two hots, you would find 220VAC. If you then measure between each hot and the neutral, you would see 110VAC. Your 220Volt heater does not require a neutral, nor does any 220VAC load. Only 110 VAC loads use the neutral. Grounding is a matter of safety, and not necesarrily a part of the circuit. A lot of old houses have no grounds at all, like my house, that was built in 1900.
     
  5. revekozu

    Thread Starter New Member

    Mar 20, 2005
    3
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    OK, it's getting a little clearer for me now!

    Would I be correct in guessing that the 2 hots that come into the house are out of phase and this is why the current can flow between the 2 hots?
     
  6. Firestorm

    Senior Member

    Jan 24, 2005
    353
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    yes, im fairly sure about that. basically your house has 3 wires that look like this(another diagram so bare with me lol)
    _________________
    ------------------------
    _________________

    then bottom and top wires are the hots and the middle is the ground. In 110, all that happens is the bottom turns into a neutral (normally 0v).
    thx l8er
    -BTW- the i l were the 2 slots in a plug outlet and the period underneath was the ground.

    -fire
     
  7. Erin G.

    Senior Member

    Mar 3, 2005
    167
    1
    The two hots are 120 degrees out of phase with each other. Unless the neutral is loaded, you would have 0 volts, and therefore, 0 amps on the neutral under normal conditions. A loaded neutral is usually caused by bad wiring or harmonics. Treat all wires as if they are hot.

    Hooking up your baseboard heater to the two hots (220VAC) without the ground is not going to hurt anything. It was designed to work that way. If there is a ground wire on the heater, then you should try to find a good ground to fasten it to. If not, then trade it in for 110VAC model. The NEC defines the neutral as a "grounded conductor". With this in mind, if you have no ground wires available for this heater, then at least by using 110VAC model heater, you can change out the receptacle feeding the heater for a GFCI recep and still have some ground fault protection.

    Good luck and be safe!
     
  8. n9xv

    Senior Member

    Jan 18, 2005
    329
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    One small correction guys. The two hots are 180-degrees out of phase with each other. The voltage between the the two "out of phase" hots will be 240-volts (120-volts per side). The two hots are opposite ends of the secondary winding of the transformer.
     
  9. Ahmetochek

    New Member

    Mar 28, 2005
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    sorry
     
  10. n9xv

    Senior Member

    Jan 18, 2005
    329
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    SSSARRRIGHT :D
     
  11. ifrythings

    New Member

    Apr 3, 2005
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    ok look at my picture, your use to the 0 and 120v wires coming off of the transformer right?

    so if you were to get rid of the 0(zero) wire you now have twice the winding which is also 2x the voltage ( 120+120=240) basicly if you get rid of the 0(zero) wire the -120 becomes the new ground (or return path) and the +120 get dubbled to 240
     
  12. Erin G.

    Senior Member

    Mar 3, 2005
    167
    1
    ifrythings, please don't try this at home.

    In the examples we've been talking about in this thread, we're discussing AC (alternating current) power, so there is not a negative or positive 120 volts present. It's just 120volts, AC, period.

    Your drawing is accurate in that the center tap (which you call "0") is where we derive the neutral for the 120 volts. From that point, we measure 120volts on either side of the transformer winding.

    From the outside points of the winding (your + and - 120volts) there is already 220volts present, with or without the center tapped neutral.

    If you take the cover off of the service panel in your house you will see this. There are two, big black wires that connect at the top of the panel. They feed the left and right circuit breakers. There is a third wire (usually marked with white tape) that connects to a neutral bar. All of the white wires in your service panel will connect to this bar. When you measure from the neutral bar (the center tap (your 0) of the transformer) to either of the black wires feeding the circuit breakers, you'll find 120 VAC. When you measure from one black wire to the other (from your - and + 120), you'll find 220 VAC, with or without the neutral connected.

    By-the-by, the only way the circuit will work as you described is in a small, regulated DC power supply, such a 12 / 24 VDC.
     
  13. ifrythings

    New Member

    Apr 3, 2005
    4
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    I know I was just tring to make a simple example for the guy, anyways you also see a circuit like that in a class B amplifier, thats were I got the idea from.
     
  14. rukrazy?

    Member

    Mar 5, 2005
    21
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    partial quote

    In the examples we've been talking about in this thread, we're discussing AC (alternating current) power, so there is not a negative or positive 120 volts present. It's just 120volts, AC, period.

    This is not so. In a transformer that has 220 volts on the secondary, one leg shows a positive going voltage starting at zero volts and increases to +110 volts before dropping back to zero volts as the other leg is negative going voltage starting at zero volts and increases to -110 volts negative before dropping back to zero volts . They are in phase with each other. Unless you are using deta or wye wiring for 3 phase.

    [​IMG]
     
  15. Erin G.

    Senior Member

    Mar 3, 2005
    167
    1
    This is EXACTLY so.

    You're are also correct, but you're putting too fine of a point on it. Alternating current does go positive and negative (60 times per second in the US). But you will not be able to see a positive or negative potential with a volt meter on either side of the transformer (primary or secondary). You will only see 220 volts AC, or any other voltage that a x-former is rated at.

    In other words, if you use an AC volt meter on the 220AC volt secondary, you will see "220" on a digital meter, or the sweep will land on or near 220 on an analog meter. The volt meters will NOT go positive and negative with the alternations of the AC current. If your were to try to see the peak-to-peak swings, you would have to use a frequency meter, which would merely read "60", to show 60 hertz, or 60 alternations between positive and negative, per second.

    In the example ifrythings was giving, he was trying (as best as I could understand) to derive a "negative" voltage path for a ground wire off one of the hots from a residential transformer secondary.

    "the -120 becomes the new ground (or return path) and the +120 get dubbled to 240"

    On a residential service, this will cause a ground on the secondary of the service transformer. As I said earlier, the 220 (240 in ifrythings post) is there, whether or not the neutral is used. The neutral is safely referenced from the center of the secondary winding to ground, via a bonding conductor, and THAT is where the 120VAC is derived from.

    rukrazy, you sound as though you're very knowledgeable about electrical theory. Please remember that in this particular thread I was trying to give a practical answer to revekozu's questions regarding a 220volt baseboard heater.
     
  16. recca02

    Senior Member

    Apr 2, 2007
    1,211
    0
    just wanted to know:
    i came to know abt the distribution method adopted in USA when i joined this forum (i remember mr thingmaker posted a link in some thread)
    the mains for a phase contain two hot (live) live wires 180 degree out of phase
    and a neutral and possibly a earthing right?
    so is it just a method adopted in USA or is it the same in other places as well.
    why was it required? (perhaps since old system was made of 110v and equipments were designed for 110 accordingly)
    in my country we just have a live terminal(400/sqrt(3)) a neutral and earthing.
    also how are these two 180 degree hot wires obtained ,i mean wont this make it a six phase system ? i believe we all use a three phase transformer.


    edit: didnt realsie there was second page (maybe some of the answers are in it already) for other answers plz reply.
     
  17. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Hi, Recca! (You don't have to call me "Mr." - we're informal around here.:D)

    The split phase system used in the US relies on a transformer mounted on the utility company's pole.

    Tony Kuphaldt explains far more eloquently than I could:
    http://www.allaboutcircuits.com/vol_2/chpt_10/1.html
     
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