Fuses

Discussion in 'Electrical Systems' started by WesS, Feb 18, 2010.

  1. jonr
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    jonr Senior Member

    Neither of which is related to the fire risk. A long wire causing x watts of energy loss (ie, voltage drop or heat) has no problem dissipating the heat. That same voltage drop across a short wire will melt it.
     
  2. The copper guy
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    The copper guy Junior Member

    I like what CDK seed and agree hole heartedly.

    You got a lot of helpful info and i agree with heaver wire, Bigger is better (The current only travels on the out side of the wire) and who knows what you may want to run on the same wire later? (don't forget to run well marked spar"s)
    Just one more point not mentioned yet, Don't run any ring mains this will inter fear with compass and electronics.
    Good luck with the project its all a learning curve m8.
     
  3. WesS
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    WesS Junior Member

    Next question- wire size to switch panel from battery? Also- thanks for all the help!
     
  4. Fanie
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    Fanie Fanie

    Sum of the total current that will be tistributed.
     
  5. kim s
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    kim s Junior Member

    Hmmmmmmm not sure about that one.
    If that was the case, then why dont wire manufactures just have a ring of wires with a cheap core :?: like a rope

    The electrons wthin the metal dont know wether they are in the middle or on the outside.

    Wess, PLEASE go and get a one of the many books available like the "electrics afloat" by alastair Garrod. or the Yachtsman 12 bible.

    A breaker can be made alot more accurate than any fuse. When a bit of wire is stuck inside a tube "filled" with a vacuum:rolleyes: Then there is no way of really testing to see how accuratly it will blow.
    The differents between slow blow and fast blow is that there is normally a tensioning arraingment ie a spring. If you look at a fuse as it blows it heats up and deforms and eventually breaks, but this might take several seconds damaging any delicate bits. with a quick blow, the spring pulls the wire apart quicker so there is less chance of damage.
    With circuit breakers, these can be tested and checked for accuracy and can be rated and can blow within milliseconds and to a very close tollerence to the max current
    The reason that they say they say on a motor have a slow blow fuse, is that an induction motor( or any inductive load) will draw approx 1.8 x working current for a very short time, so you dont want the fuse going every time you switch it on. (windscreen wipers, bilge pumps etc)
    As to the size of wire from the batts, add up all the wattages that every bit of kit will draw, double it, (allows for inductive load and takes care of volt drop) divide by voltage then find a bit of wire that will take that current.

    Kim
     
  6. Fanie
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    Fanie Fanie

    Only with high friequency or high voltage. No bearing on your situation.

    This is not true either !

    The right type of fuse is far more accurate and faster than any electro mechanical circuit breaker. In the case of a ie a short in the wiring the fuse will just go open circuit, while the circuit breaker has some mechanical parts that has to be set im motion before it goes open circuit. This can cause the current peak to far exceed the circuit breaker rating !

    The difference between fast and slow blow fuses is the type of material used for the fuse wire, and the diameter of it determine the current.

    The springed setup is used in some places to increase the gap where the fuse burned off so the arc that can develop is extinguished quicker. In some cases they put sand in the fuse to do basically the same and some fuse wires operates in a gas. None of this has again any bearing on your requirement.

    In the case of a boat and similar to automotive you need slow blow fuses and breakers is also ok. You will be protecting the wiring and the battery, the equipment is supposed to come with it's own protection.

    In some cases a single high current fuse ie 60A is installed right at the battery to protect the battery as close to it's terminals as possible and yes, it's a slow blow.
     
  7. WesS
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    WesS Junior Member

    Man- You all love this electrical stuff. I sure appreciate all the info and discussion. I'm just a simple redneck from Tennessee wanting to build a hunting boat.

    Its crazy... all I'm building is a 12' duck hunting rig and need some light to see early in the morning, a bilge to pull the rain water out, and a depth finder to check for the motor. Thought all of it would be simple to do, guess not. I just want it to work and not set my wood boat on fire.
     
  8. TollyWally
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    TollyWally Senior Member

    LOL,
    All you need are a few switches and fuses. Use fatter wire and heat shrink tubing, wire zip ties and common sense. I didn't realize what we were trying to wire before and was assuming we were talking about bigger boats in bigger waters. It will be easy. If you can wire the trailer the boat might ride on you can wire the boat. Splurge and put in a big disconnect switch real close to the battery, all will be well. Show us some pics of the boat you want to build.
     
  9. WesS
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    WesS Junior Member


  10. TollyWally
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    TollyWally Senior Member

    Wes,
    Edith is going to be a splendid boat. You are moving along at a pretty good clip. LOL you did the right thing redoing that plywood. It would have bugged you forever. Now it will give you a wry grin as you shake your head a little bit.

    More on topic I see you even provided yourself with a conduit wireway. Way too many of the big boys don't even do that. You are going to have no real problems wiring this boat. Many people can help you, many here are more qualified than I. That being said if you have any questions either ask here or via PM. Carry on.
     
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