Wiring aluminum boat

Discussion in 'OnBoard Electronics & Controls' started by fishNduck, May 27, 2007.

  1. michael pierzga
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    michael pierzga Senior Member

    Bert, electric systems are isolated, floating , to prevent corrosion. This isolation of the electric system prevents corrosion of boats in Spain and all over the world. Your hull must not be one leg, one pole, of the electric system.
     
  2. BertKu
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    BertKu Senior Member

    Well, maybe for 230/380 V AC system, because you have so many phase capacitors which are connected to the casing and earth. However for a 12 to 24 Volt DC system, I have my doubts and it is against any electrical logic to do so.
    But I will find out and see why #34 paragraph, is the only regulations which has it right and make sure that the negative is connected to the seawater.

    Why should an aluminium boat be different? Except if you have an isolated plate from the hull, mounted with insulators to the hull, which is connected to the ground/negative batteries etc. But it does not make sense, as the seawater will automatically make short circuit between the insulated plate and hull.

    Are you telling me that an aluminium boat has NO lightning protection?
    I better don't order a boat from Spain. If you are using the alu mast as lightning conductor. A resistor to the hull, for preventing static build up I accept, but not totally electrical floating. Let see what other people think about this.
    Bert
    Bert
     
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  3. michael pierzga
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    michael pierzga Senior Member

    of course an alloy boat is lightning protected and the chassis of all electrified equipment on an alloy boat is bonded to the hull. The electric system is not connected to the hull.

    Marine equipment is isolated...two pole. Neither pole is in contact with the equipments chassis.

    The bonding strap from equipment chassis to the hull is used to dissipate an internal short circuit in the equipment and prevent the operator from being electrocuted or fire hazard.
     
  4. CDK
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    CDK retired engineer

    Bert, Michael Pierzga doesn't know what he is talking about, but unfortunately that didn't keep him from writing 1141 annoying posts. He wouldn't recognize a phase capacitor if he tripped over one because his bible is the 12V handbook for simpletons and it doesn't mention that.
     
  5. BertKu
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    BertKu Senior Member

    Your people are dangerous there in Spain. What do you think would happen if a lightning strike strikes your boat and the electrical system is floating. What energy do you think would be induced into the wiring system while floating. 50.000 Ampere, approx 40 -50 burts within one or two second, and you think that your 1000 Volt insulation will cope with that??
    Bert
     
  6. BertKu
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    BertKu Senior Member

    Before I have a misunderstanding . Do we talk about 220/380VAC or 12/24 DC , or both? Are you telling me that a laptop is floating? or also "bonded" to the hull? Does absolute not make sense what you are proposing. But let me shop around and see how boatbuilders truly are connecting their electrical systems.
    Bert
     
  7. Mat-C
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    Mat-C Senior Member

    Thanks CDK. One thing I'm still not completely clear on though.... The battery (both + & - of course) are connected to the engine via both starter and alternator. Does this provide the engine ground, or is there a separate additional wire on the -ve side that is connected to somewhere else on the engine? I'm assuming that if it's the latter, then the manufacturers would provide for such a connection...
     
  8. Ike
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    Ike Senior Member

    Mat-C, from a previous post
     
  9. BertKu
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    BertKu Senior Member

    I am inclined to agree with you. First at all the original question #1 was for a 16 feet aluminium boat, not a massive 300 yard long container ship. I have checked a number of electrical switchboards special made for small yachts. All of them have single throw switches. None state "Not to be used with aluminium boats".
    The regulations I have read, are all stating, negative to be connected to seawater/hull. Michael must have his wires mixed up and be confused with 220/380V AC.
    Bert
     
  10. FMS
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    FMS Senior Member

    My fuel fills all have had a ground wire to them in the boat.
    But none of the gas docks I have ever filled up at had a separate wire with ground clamp to attach before fueling.
     
  11. BertKu
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    BertKu Senior Member

    CDK, let us turn it around. We assume that Michael is correct and we create a scenario. Here is a man and woman, on the Atlantic , have an aluminium boat with a switchboard made by a Spanish shipyard, double throw switches and the electrical system is floating. The woman is wearing a nice nylon top and is working on her laptop to figure out where they are. The laptop is connected to the grid, but floating. Static is building up on the electrical wiring. The man has decided to fill up the petrol/gas engine and first made sure that the jerry tank is discharged to the aluminium deck. Now he opens the fuel container and start pouring the gasoline/petrol into the engine fuel tank. Now, according to Michael, the Spanish builders have the electrical system floating, thus also the engine is not grounded to the hull. You cannot have the electrical system floating on an engine, no manufacturer in the world makes such an engine. Boooom.!!!
    Sadly we will read later a newspaper report of a missing yacht, presumable sunk.
    Now the second yacht also have the same system, but is grounded with a 100/ 1000 Ohm resistor to the hull. The static from the Nylon top , the woman is wearing, is no longer building static up on the electrical system. They are happily arriving back at the harbour reading about this sadly event of the other sailors.
    Moral of the story, You may as well use single throw switches and have the negative connected to the hull, just make sure that the hull has proper Zinc protection as per your thread explaining the use of Zinc on a yacht.
    Bert
     
  12. BertKu
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    BertKu Senior Member

    IKE, I have read your post on corrosion due to stray currents. Would you be willing to take a risk and have your electrical system floating? You yourself personally?
    Can we define stray currents?
    My view is: rather have corrosion tackled with Zinc, then to have the risk of static and also problems due to electrical surges in the air (close by lightning strikes).
    Bert
     
  13. FMS
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    FMS Senior Member

    Connected to the seawater/hull where Bert?

    The way I read this both Ike and Michael are advocating great care to transfer all negatives to a single bonding post to not allow the hull to become the negative conduit along its length for fear of greater corrosion.

    Are you and CDK advocating multiple ground connections to a metal hull along its length as ok?
     
  14. BertKu
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    BertKu Senior Member

    No, single point.

    In my view certainly not floating, as you have to make your mind up between static or corrosion. What are stray currents, which creates corrosion. Stray currents occur, when a return wire is badly making contact at a connection point, under rated or is having multiple connection points with different metals. The current start finding an alternative route, normally through the metal hull..
    Corrosion is not created because you have a well thought out single throw switchboard with a central earth connection to the hull. Corrosion is created when you create a voltage potential between two metals with the salt moisture as dielectric. If your boat is 100 meters long, your parallel cables running close to the metal hull will induce stray currents in the hull, if the currents are high and the cable run close to the hull wall. But even then I would not advocate floating electrical system, but at least with a resistor to the metal hull, to avoid static.
    But we are talking about a 16 feet hull. Sure, any good electrician can ensure correct thickness of cables, good connections and ONE good central negative, normally the engine block. In my case I don’t have an engine, as it is an electric boat with DC currents of up to 500 Ampere, I will take the negative battery buss-bar as negative, grounded to the metal seawater point.
    The trick lies in having a good electrician who knows what to do, don’t have two different metals bonding, don’t under calculate the thickness of the wires, don’t create static build up, use the same type of metals for the connections points. Etc.
    Bert
     

  15. CDK
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    CDK retired engineer

    Although shafts, pipes etc. generally form an electrical path it is good engineering practice not to rely on them but to install a dedicated ground strap or cable.
    A strap or cable, firmly attached with a bolt and spring washer and protected from moisture is more reliable than mechanical parts that may contain gaskets, greased bearings or painted surfaces.
     
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