110 out of 220?

Discussion in 'OnBoard Electronics & Controls' started by tropicalbuilder, Aug 30, 2012.

  1. tropicalbuilder
    Joined: Jun 2010
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    tropicalbuilder Junior Member

    ok the principle of getting 220 from the two 110 phases is clear ….and actually it is common practice here.
    besides the frequency issue …. is there any other issue to consider when using a 220V two phase instead of 220V one phase?
     
  2. philSweet
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    philSweet Senior Member

    Yes. I tried to point at it in my last post. In order to safe a split phase circuit, you have to break both legs. Circuit protection needs to protect both legs. With single phase, you often only protect the hot side. If you bring spit phase aboard and distribute it through the branch circuits, you may (probably) not have any circuit protection for the half of the wires that are newly hot.

    And sooner or later someone will plug something in that will go up in smoke. You can't assume everything gets sent to the right country in the first place. I just had to put out a fire caused by some renters who plugged in a blender they bought online. At least the breaker tripped.
     
  3. jonr
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    jonr Senior Member

    IMO, a GFI breaker increases safety significantly. In the US, you can buy ones that sense all 3 wires - +120, -120 and neutral.
     
    Last edited: Sep 10, 2012
  4. gonzo
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    gonzo Senior Member

    That is a good point. The breaker has to be a two pole that are tied together. That setup will trip both lines, which are hot, at the same time.
     
  5. Frosty

    Frosty Previous Member

    Just a note --In Thailand they have really good breakers rated from 15 amp up to 60 I think. The are a dual pole for the 2 wire for the 220V live neutral ( no earth in most cases) and cost about 1 dollar 50 cents. They even work with 12 volts but the amperage to operate is different.
     
  6. jonr
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    jonr Senior Member

    To reiterate what philSweet said, if a system was designed for single phase 240V and is then run on split phase, it probably doesn't have breakers on whichever 120V line is being used as neutral. So you have wires running around that are live wrt ground with no overload protection. It works but could create a fire.

    You could replace the panel or use an isolation transformer. At least use a split phase (two pole + neutral) GFCI for the entire boat so that if something shorts to ground, everything will be shut off.
     
  7. tropicalbuilder
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    tropicalbuilder Junior Member

    ok thanks for the help
     
  8. Submarine Tom

    Submarine Tom Previous Member

    Do it right or suffer the consequences.
     
  9. Herman
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    Herman Senior Member

    First check the breakers. Most European breakers (automatich type) break both neutral and live. (not earth).

    Over here 2 systems are commonly used:
    230V and neutral
    -115 and +115

    As for frequency: At 50 Hz the output of the motor (and hence the appliance) is a bit lower. At 60Hz you MIGHT run into problems, but only if the appliance was already running almost in overload at 50Hz, in which case it would not have survived for long anyhow.
    Also check the appliance itself, most have a sticker which mentions the output at 50 and 60 Hz.
     
  10. sdowney717
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    sdowney717 Senior Member

    if you put together 2 120 volts off different phases you get a direct short circuit. That is due to the phases not lining up, they are out of phase, so when the polarity reverses, it is like touching positive to negative on a battery. When one side of the sine wave is positive on one 110 v hot wire leg , the other is negative and vice versa. This power comes from a generator which must be massive and the property is a function of how the gen windings are constructed.

    How the electric company parallels multiple generators to get their outputs in phase with all the others is critical or the grid would short itself out.
    I wonder how they do that. Can they delay or speed up phases to line them up? They could slow down and speed up rotation to line them up like cars on the freeway? If they dont line up phases perfectly there must be some internal shorting loses?

    You can not take 2 ac generators and just join them together or the sparks will fly. Grid tie invertors must have some circuit to do this as in people who send power back onto the grid from a solar system.
     
  11. tropicalbuilder
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    tropicalbuilder Junior Member

    the breakers installed on the bot are schneider electric SD40,
    i just sent an e-mail to their assistance to see if they are right for this type of supply.
     
  12. philSweet
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    philSweet Senior Member

    Old school way. You have your powerplant's generator not connected to the grid. You have a 60W filament light bulb between the grid and your generator. You wait for the bulb to go out signalling phase match, then throw the switchgear. Once synced, they will stay synced. Inverter style generators need circuitry to sync up.
     
  13. jonr
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    jonr Senior Member

    A two pole breaker will look like two side-by-side switches with the two levers connected together. That is what you need to protect both 240V live (aka +120V) and 240V neutral (aka -120V).
     
  14. tropicalbuilder
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    tropicalbuilder Junior Member

    so now if a change the breaker for a two pole one, will this be ok even when i will be connected to a 220V mono phase ?
     

  15. sdowney717
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    sdowney717 Senior Member

    Interesting. So they stay synced up afterwards due to them keeping the same rpm? RPM changes affect frequency.

    What happens if they slowed down even a small amount?
    When the light goes out, what if there is a tiny amount of mismatch between the phases that you would not notice? Power gets wasted?
     
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