Rewiring my boat

Discussion in 'OnBoard Electronics & Controls' started by dreamer, Jul 16, 2012.

  1. dreamer
    Joined: Nov 2004
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    Likes: 12, Points: 0, Legacy Rep: 188
    Location: Minnesota, USA

    dreamer Soñadora

    I have spent almost 2 years refurbishing our 1979 Baba 30. I am in the final stages and that includes fixing the rat's nest of wiring 'improvements' by the previous owner.

    One of the problems is that the distribution panel only has so much room behind it. The P.O. crammed all the wiring (factory and 'additional') back behind this panel. But once that was filled, they decided to add various busses and connection blocks in hidden spots throughout the boat. It took a fair amount of time to figure out what was going on, but I think I've got it sorted.

    I decided to create a model to help me figure out how I could re-route the wiring. We have AC/DC on board and I want to be sure that my grounds and galvanic protection are wired properly.

    I have gone through ABYC and have tried to create the model based on my understanding of the recommendations. Of course, this understanding could be wrong and if it is I'm hoping someone could help improve my understanding.



    Take a look at the attached images. Hopefully they are self explanatory.
     

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  2. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    No, the images are not self explanatory.
    What I see is a very good looking control panel on the right and some add-ons with basic wiring on the left picture. A 33 years old boat usually has a lot more wiring, part of it not used anymore but still there because nobody dared remove it.

    If you really want to make a clean start, draw a complete wiring diagram with cable colors and locations. Then decide what to leave in place and what to replace.
    It is good practice to keep AC and DC wiring away from each other and maintain a strict color scheme throughout the boat for safety reasons and to make any fault finding easier.
     
  3. dreamer
    Joined: Nov 2004
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    Location: Minnesota, USA

    dreamer Soñadora

    After removing all of the previous owner's 'improved' wiring (and I do mean ALL of it), I was left with the basic factory installed wiring which consists of interior lighting, navigation lighting, shore power inlet and several AC outlets. I have traced it all and have already decided what to keep and what not to keep.

    The model represents pretty much a clean slate. I do not show any of the DC wiring yet other than the neg DC bus as I am trying to nail down the AC ground (green wire). AC and DC will be kept in separate runs between the panel and the distribution. I realize I am stretching things a bit by having AC and DC on the same panel, but on my 30'er finding room to split these up is a challenge. I took my cues from BlueSea as they have no problem offering AC/DC in a single panel.

    The only real question I have right now is whether or not I have the grounding set up right. In the model (I will post a schematic) I have the batteries' neg terminals going to a busbar which then goes to engine grounding lug as well as DC ground bus. ABYC specifies that battery neg should go to the engine's grounding lug or "its grounding bus".

    [​IMG]

    does the engine grounding bus (I have it labeled 'Main Grounding Bus') need to be able to take the full starting load? Most of the information I've read says it doesn't need to, but I'm still not clear as to why not.

    As for the green wire, my understanding of how it needs to be installed is that in the event of a short in the AC circuitry, there is a direct path to ground through the grounding lug which should then trip the breaker. Without being properly grounded, a short would 'energize' the boat without tripping the breaker (since the breaker doesn't 'see' anything wrong) and could cause someone in the water to get electrocuted or paralyzed and drown.
     
  4. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    The way you've drawn it, the negative bus carries full starting current. Nothing against that as long as the wire size is adequate. What is adequate and what is not is debatable. It depends on both the starter size and cable length.
    I would prefer a direct connection between battery and engine ground lug because only the starter will draw 200-400 Amps, keeping it separate from the rest means that the ground bus could be chosen somewhat smaller. But if it is already there, leave it.

    The green wire from the AC system is the ONLY one connected to DC ground. It is called "protective ground" because it normally plays no role where current carrying is concerned. Only if a piece of equipment develops a ground fault or a junction box gets wet, part of the AC current is dumped into ground causing the safety device (GFI) to trip.

    The flip side of the medal is that shore power ground may not have the same potential, causing current to flow from metal parts to the water, causing rapid galvanic corrosion. The solution is to use a galvanic isolator (ABYC) or simply remove the green wire from the shore power socket (my preferred method).
    If the green wire is not tied to ground at all, the safety device will only trip if there is another path to ground like someone touching the kitchen sink and the fridge simultaneously....
     
  5. dreamer
    Joined: Nov 2004
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    Location: Minnesota, USA

    dreamer Soñadora

    Thanks for the info CDK

    well, I think I'll keep the green wire in the shore power socket. We've had our boat in a marina for the past 10 years (well, I guess that would only really be 5 since in MN the sailing season is 6 mos if you're lucky). All that time it has been connected to shore power and we have not had any galvanic corrosion. In fact, the zincs still look as good as the day we put them on 10 years ago.

    The grounding bus and galvanic isolator were all previously installed, so I'll just go with those.
     
  6. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    .....In fact, the zincs still look as good as the day we put them on 10 years ago......

    That's not good! Check the conductivity between the zincs and the prop/shaft/rudder. After 10 years there should be clear signs of wear, even if the boat sails on lakes only.
     
  7. missinginaction
    Joined: Aug 2007
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    Location: New York

    missinginaction Senior Member

    A couple of things.

    1. Consider reading Boat Owners Mechanical and Electrical Manual by Nigel Calder. Charlie Wing also writes a good text on electrical wiring. Calders book was indispensable to me as I set up my new electrical system.

    2. If you've not bought wire yet, consider yellow colored wire for your DC grounds. This keeps you from confusing traditional black DC grounding wire with AC hot.

    http://www.amazon.com/Boatowners-Me...=boat owners mechanical and electrical manual

    I knew practically nothing about electrical wiring a couple of years ago. With Calders book and some advise from guys like CDK I'm now capable of this.....
     

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  8. dreamer
    Joined: Nov 2004
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    Location: Minnesota, USA

    dreamer Soñadora

    ok, that was an exaggeration. Of course there's some deterioration, but they aren't practically gone like they were when I bought the boat.
     

  9. sdowney717
    Joined: Nov 2010
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    Location: Newport News VA

    sdowney717 Senior Member

    Since it is a fresh water boat be extra certain not to have any ground faults as they are more deadly if people are in the water. People conduct current better than fresh water. Salt water is not as much of a problem for electric shock drowning.

    They make ELCI main breakers which click off at a higher fault level than GFCI. GFCI should stil be on all outlets.
    I think the shore docks should all be ELCI on the shore not just leaving this up to the boat owner.
    Even at 30 MA to trip ELCI breaker, you could be killed at 6MA and ELCI still allowing power into the water but better than no protection.

    Also ELCI only on the boat does nothing if your shore power cord has a fault (like from getting pinched between boat and dock) and it is sending power into the water.

    So should be on the dock, not on the boat.

    http://www.edsboattips.com/maintenance-a-diy/21-introducing-the-elci
    http://www.tradeonlytoday.com/home/520723-four-dead-after-electrocutions-on-lakes
     
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