Neutral ground bonding relay????

Discussion in 'OnBoard Electronics & Controls' started by cgoodwin, Feb 20, 2015.

  1. groper
    Joined: Jun 2011
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    groper Senior Member

    Why do you need a diagram? A contactor or relay is simply a switch, the only difference here is that your switching both active and neutral , so a double pole switch... A changeover switch is a double throw switch.

    You should have an AC earth bus bar unless your earths are all soldered together in a bundle. You will also have a neutral bus bar in your distribution board. All your actives go through your circuit breakers of course, but your main active coming from the supply will be looped from the main switch to each final sub circuit breaker.

    You will then have a main neutral coming into your neutral bus. You will need another neutral feed to the bus from your inverter, and another from your genset. It is these 3 neutrals which will go through a changeover switch or contactor, directly upstream of the bus. The actives will be switched directly before the main switch.

    You will also need another 2 earth wires from the genset and inverter, these will be bonded to the earth bus, and can stay bonded provided the neutral is switched so that the MEN connection is broken inside the genset and inverter when your on shore power as per sddowney.
     
  2. sdowney717
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    sdowney717 Senior Member

    [​IMG]

    CDK cued me onto this. The relays I used are 35 amp rated.

    For each additional relay you add, you can switch another source.
    for me 3 sources to feed the boat was plenty.
     
  3. cgoodwin
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    cgoodwin Junior Member

    The generator is a Silent Partner 6.5KW no transfer switch made, the inverter is a SW4024 and it only has a SPST transfer switch and no provision for another. I have spoken to at least a dozen switch manufacturers and they all fall short - that is why I am here. There are many transfer switches that will switch between shore and gen or inverter and gen, but none that switch three ways and deal with the neutral ground bond - at least not one that I have found.
     
  4. sdowney717
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    sdowney717 Senior Member

    The drawing is not perfect showing all 4 poles properly, but the concept does work perfectly, it isolates all three sources both neutral and ground from each other.
     
  5. cgoodwin
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    cgoodwin Junior Member

  6. sdowney717
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    sdowney717 Senior Member

    [​IMG]

    Here is a picture of the relays. I improved it a little since then.
    The bridge diode is not good for a GI, you need more to handle power loads. Mine burned out.

    I also added DC volts from a walwart to control the relays, so they dont buzz. 15vdc is perfect.
     
  7. cgoodwin
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    cgoodwin Junior Member

    Thanks sdowney717, let me pencil through it. One issue I am considering is a delay circuit that will allow the gen to stabilize before switching to it, perhaps a 30 second delay.
     
  8. cgoodwin
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    cgoodwin Junior Member

    Nice sdowney717!!!! What was causing the relays to buzz? They should have been stable on 120 60hz
     
  9. sdowney717
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    sdowney717 Senior Member

    Another view showing my disconnect box on right. Both 30 amp shore cords come into the box and 2 GE double pole 30 amp breakers are in there.

    [​IMG]
     
  10. sdowney717
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    sdowney717 Senior Member

    Well, we have free power at the marina, but it is shared to many boats. So a power droop causes the relays to buzz.

    It is a simple fix, a 15vdc wall wart can power the relay. If the VAC drops, then walwart compensates better. DC clicks down the relay with a continuous magnetic field. So it can not buzz, and a power dip,once the relay is locked down it does not take much current to hold it on. Just a simple toggle switch on the neutral side of the walwart circuit is all you need to turn it on and off.

    I modified the outdoor GE box. I bought 2 boxes and used it to put 2 relay holders into one box. Plenty of space in there. GE boxes use copper tinned lugs. I bumped out the cover, and cut a rectangular hole in the inner support plate.
     
  11. sdowney717
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    sdowney717 Senior Member

    I can switch over between a running gen and shore power with a toggle switch, there is enough delay in the relays there is no interconnect between them.

    My Onan GEN, if both relays coils are off, the gen circuit is closed circuit to the boat distribution breaker box panel.
    I did that because the Onan has an auto start feature that detects demand. So the circuit has to close to be on.

    The Inverter powers on the coil closing the relay when it comes on.
    I have a control wire from the gen, so that IF the gen is running, it prevents the inverter relay coil from closing. That guarantees the 4PDT coil relay that switches between gen and inverter, the inverter can never close the circuit, and might blow itself up.

    So if GEN comes on, inverter can not power on coil.

    You can do the same with gen to shore 4PDT relay. In the gen is a 12 vdc circuit that comes on, use another small cube relay that open circuits the shore power toggle switch. That guarantees that the gen as it powers up turns off the shore power toggle relay. The gen's 12 vdc circuit comes on before it spins up the AC output, so there is your delay.

    Other advantage is when you unplug from shore, 4PDT relay coil de energizes so auto switches to GEN power.
    Come back to slip and plug in to shore power, boat auto switches to shore power. It is fully automatic switching.
     
  12. cgoodwin
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    cgoodwin Junior Member

    The diagram does not seem to deal with the neutral ground bonding to the ships bonding strip.
     
  13. groper
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    groper Senior Member

    That's because you don't need to do it! You get your neutral ground bond inside your generator. You don't want the neutral ground bond when on shore power, but as the neutrals are also broken in the transfer, so is the neutral ground bond on the generator!
     
  14. sdowney717
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    sdowney717 Senior Member

    groper is right.
    My Onan Gen is permanently bonded neutral and ground, BUT when the 4PDT relay is energized, both neutral and hot is disconnected, becoming open circuit coming from gen.

    AND when the shore 4PDT relay is closed so that shore power is feeding the boat, it open circuits the feed in from the other 4PDT relay which switches gen and inverter, so it is then also not connected.
     

  15. philSweet
    Joined: May 2008
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    philSweet Senior Member

    Slow morning, so I read the Xantrex Sw series manual (153 pages)
    http://www.xantrex.com/documents/discontinued-products/sw2512mc-sw4024mc2userguide.pdf

    All you do is wire it up. Don't add any relays. Do fuse the battery pos. It has a 60 amp pass though rating on both AC ins, so you are fine there. Do everything AC in #6.

    There is a bit of setup involved. The manual has 50 pages of programming advice. You'll want to get some help with that, I think.

    Don't add any relays. They are all in the box.
     
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