Thoughts on a 24-foot sailboat electrical diagram

Discussion in 'Boat Design' started by souljour2000, Jun 28, 2010.

  1. souljour2000
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    souljour2000 Senior Member

    Hey everyone....I'm trying to get a decent electrical diagram together of how I'd like to re-do the antiquated electrical on my '71 Seafarer 24. This is a bit hard to follow for some I am sure but there are basically two illustrations of the same diagram blended into each other ...two 6V golf cart batteries are charged by a merc Sailpower 9.9 w/generator .....then goes with heavy guage over a 4-foot distance to batt switch on/off.....then staying with heavy guage wire a few more feet to a pos bus bar which will feed the (4) non-breakered cabin dome lights and then off that same pos bus bar is a feed of more fairly heavy guage wire to the breaker switch panel (pos) for stuff that needs rocker switches(nav lights,bilge,etc, then the circuits run out at 14 guage wire mostlyand back to the neg bus bar and then back to neg pole of batt on/off switch and finally back to the batteries .The outline of the boat serves as a map of sorts for the diagram below it if that helps...I'm still in the early stages but was hoping for some early feedback if anyone can decipher my diagram to see if I am on the right track at least..or not...
     

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  2. Deadeye
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    Deadeye Bender of Nails

    Two quick questions:
    You've got a dual-pole battery switch ?

    What's protecting the 'heavy guage' (what AWG ?) lead to the +bus ?

    For starters, I'd suggest poking around the 'resources' page on Bluesea.com. There's a bunch of good info there, including the charts you need (per ABYC) to figure out the wire guage you need for the current and (round-trip) distance for each circuit.

    And.....you'd be surprised at how much wire a little boat can suck up.
     
  3. souljour2000
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    souljour2000 Senior Member

    Deadeye..thanks for your response..I am not sure if it's two-pole..its just has an on and off setting I think...I will only have one battery bank but I may decide to have a second which would be a single 12-volt deepcycle marine battery for emergency bilge/utility which I'd charge via clip- on lead from a solar panel..anyways..I'll have to go check that on/off switch and see what it is and look it up..I have heard that two-pole is the absolute way to go but havent read up on it enuff to remember why...
     
  4. CDK
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    CDK retired engineer

    I'd really like to know the benefit of a switched negative lead.
    It is never done, not in cars, boats, motorcycles or gensets. If a technician wants to check or measure something, he uses the battery negative pole as a reference. Your switch might cause confusion.
     
  5. tom28571
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    tom28571 Senior Member

    To save money, wire and mess, it is OK to group many devices on common positive leads from the main panel. Lights are certainly OK to do this with as well as most all negative circuits. Most devices with their own switches can be fed off common lines. Remote distribution strips are handy to feed the individual positive wires off of. Remote bus strips do the same for the negative lines.

    Charlie Wing's book is THE best guide for boat electrical work.
     
  6. souljour2000
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    souljour2000 Senior Member

    CDK,, I was kinda hoping you might chime in as you seem to be one of the few resident electrical authorities in here it seems....the diagram shows two battery banks when in fact it just poor drawing and redundantly showing two views of the same battery bank...not sure why I kept it like that before posting it to the world..anyways..

    so there are just two 6 volts batts in series which are charged by a simple generator on my Mercury 9.9 sailmaster outboard...the pos will run from pos post of battery #1 to a simple BlueSea on/off switch on the bulkhead under companionway which leads to a pos bus rod and then a heavy guage short run to a fused breaker switch/panel ( from one end of the pos. bus rod)...a negative bus will pick up the return groundwires and complete the circuit with a heavy guage wire back from one end of that "neg bus" back to the neg terminal of batt # 2. Thats my plan so far..,again..apologies for the diagram which appears to show two battery banks with one having it's own negative "gate" or on/off switch..it certainly looks like that...I'll add a new hopefully less-confusing drawing in a sec...
     

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  7. Deadeye
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    Deadeye Bender of Nails

    Just as FYI, a two pole switch in this application would have both positive AND negative terminals. My question came from this:

    The term for a switch for two banks would be double THROW, not pole. A battery switch doesn't normally have a negative pole - the 'COM' (common) pole on a battery switch is NOT negative. Ever !

    I've never seen a battery switch that does that and, like CDK, couldn't quite figure out what it was supposed to accomplish. Coming from a tech's perspective, it makes an extra step to troubleshoot and I can't see a benefit to it.

    Normally with battery switches, you try and keep the switch as close to the battery(s) as possible. I think ABYC says six feet (with caveats) and it's a basic safety issue.

    Looking at your drawing, I'd probably run the water pump, spreader lights and other house circuits off of one bus and the critical circuits like nav lights, bilge pump, horn etc off another. This ensures that all of the important running gear can operate at full voltage while you're using the higher-draw circuits. This is what the 3% vs 10% values on the BlueSea site are for.

    If you note the amps that every piece of equipment draws and the length of the wire runs from the battery to the device and back, you can figure out what guage of wire you need - anything else is a guess. That can be fine so long as it's generously conservative: wire stinks when it burns....

    If you want to run conduits under berths or through lockers, residential pvc water pipe works great and is easy to cut openings in.
     
  8. CDK
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    CDK retired engineer

    With this wiring diagram I fear you trip over all these criss-cross wires and break your neck, but that's probably just your way of drawing things...

    What's missing is a ground wire from the outboard to the negative bus, you probably will install that to obtain charging current.

    I also wonder about the dome lights that bypass the circuit breaker/switch panel. I see no fuses and no means to switch these on or off.

    For the bilge pump wiring that directly from the positive bus with its own fuse and a float switch seems better to me.

    The water pump in or near the tank probably will be wired to a switch in the faucet or a foot switch near the sink.
     
  9. souljour2000
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    souljour2000 Senior Member

    Okay..thanks for the replies and the correction of terminology of double pole vs double throw..these are important distinctions ..I will check that Bluesea on/off switch and see what kind it is,,the wiring in the old girl is obviously still revealing itself to me and I dont even honestly know if that is just a positive lead going to that master on/off or whether both pos and neg leads head to the correct double pole type that is needed...I'll have to get into her guts a bit today...I am not near ready to do the nstall but wanted to get the juices flowing by throwing that schematic up in here ...btw...Dead...good points about having two different pos buses or banks for circuit applications of differing critical importance ,i,e, nav lights/ vhf radio etc vs. fm radio/dc refrigerator.....and about the bilge..I havent got a float switch yet but...I've never had one installed in any of my boats but definitely will get one in this time...the dome lights have switches on the side of dome itself..these are pretty common old dome lights...with metal body...not sure what style or name they are called usually...CDK....thanks for the minder about the outboard ground back to negative bus (can it just go negative pole of batt # 2?
     
  10. CDK
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    CDK retired engineer

    >these are pretty common old dome lights...with metal body..<

    I have a fair idea how they look like. Just make sure they get their 12V through a fuse, so in case of a short circuit only the fuse burns out and not your whole boat.
    They probably have just a 15 W bulb; no need to feed each one individually, just daisy-chain them behind a 6.3 A fuse.

    Wiring the outboard to the battery directly is the normal way to do it.
     
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  11. Fanie
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    Fanie Fanie

    Souljour,

    Not sure if you are just trying to figure the current wiring out, or wanting to fix it, or if you want to rewire the lot.

    Switches are called in terms of how they are switching -

    SPST - Single Pole Single Throw - a simple one contact on off switch
    SPDT - Single Pole Double Throw - a single wiper that switches between one of two outputs (contacts)
    DPST - Double Pole Single Throw - two simple on off contacts in one switch
    DPDT - Double Pole Double Throw - double wipers that switches between one of two outputs (contacts) each.

    A battery's negative pole is only called the negative because it is negative wrt the positive, but it is commonly referred to as ground (or common) once connected. So the battery's negative is connected to the ground (common).

    Usually only the positive from the batteries are switched and fused.

    If you are going to add fuses you can consider polly fuses (also called multi-fuses). Under overcurrent conditions they go open circuit (high impedance) and when the problem is corrected they recover back to a short or low impedance (resistance). If you parallel polly fuses they have to be thermally bonded so they would be equally heated up during an overcurrent. They are available in a few mA to 9A.

    Wires current carrying capabilities are measures in cross sectional area, we use mm, I know some refer to as 'guage'. I prefer to use the cross section or the diameter of the actual conductor, some suppliers give you a thin wire with a thick insulation. Tinned flexable multi stranded wires are always better than solid or few thick stranded copper wire.

    Keep the wiring simple, imo two ways.

    Similar to house wires the Pos and GND follow the same path with fuses or overcurrent and short protection as you go, usually a pos input to a fuse box and from there the positives goes to each power requiring item,

    OR you can use two 'buzz bars' properly seperated ie one on the boat's left, the other in the boat's right and power gets tapped where required, also of course with fuses where you tap.

    The first uses more wires and uses a common route.
    The second is easier to trace if a problem develops.

    If you replace lights, you could consider LED lights. Just do not install the pale white ones, bad for eyes, use the warm white instead, it gives a more yellow colour light similar to sunlight which is more natural. The new generation LED's for lighting is rated for 100 000 hours. Also in red & green for nav lights.

    Compact Fluorescent is also a good light to use, they still beat the LED lights a bit with the amount of light they make, but they are not dimmable like the LED lights and they do not sport the same service life. The old filamented lamps are out.
     
  12. Fanie
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    Fanie Fanie

    It is imo better to use a single 12V battery than series 2 x 6V batteries. During charging from 12V, if the one battery is slightly better than the other, the one will always adjust to a higher voltage and the other will not reach the same level of charge, hence the pair won't last as long. There are ways to 'balance' the charge but it is not something any one can do.
     
  13. Fanie
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    Fanie Fanie

    BTW, the components each have a symbol. By using the symbols it's a lot easier to 'read' a circuit.

    Google for 'Electrical component symbols', you'll get a gazillion references to symbols.

    Here is one with a listing - note some symbols change or vary but they represent the same basic component.

    http://talkingelectronics.com/CctSymbols/Circuit_Symbols.html
     
  14. souljour2000
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    souljour2000 Senior Member

    Thanks for some great info Fanie...I just got back from the boat about an hour ago after messing around...as the boat is currently anchored here by the house where I'm lucky to be a block from my"dinghy beach" of sorts actually a "publicly-accessible stormwater drain right- of -way ..."with a small slice of beachfront .... these are great places to drop a canoe or beach a dinghy if you can spot them..there are alot of these that also are at the end of streets that dead-end into bodies of water and they are public property much of the time though most don't know it...
    Anyways...I digress... I got a few electrical things squared away after crawling down into and under the cockpit lazarette and poking around a bit more...finally ran new nav light wire for my new Attwood LED nav lights..as you mentioned fanie...I bought them for the hUNTER 20 but they should be okay..we'll see..the nav lights on the Seafarer 24 were okay..,but I replaced withh LED anyways...it was just that the wire was corroded so bad as I suspected ...I should have figured it out sooner but me troubleshooting skils are still in infancy..got a polarity tester..a basic voltage tester//amd a cheap multi-meter but have only used tcircuiy tester light thing.

    The exceedingly small cubby hole where they bolted a couple bus bars and the starboard switch panel access ( there are small 4-switch panels on either side as you shoulder through the companionway)is JUST not going to cut it....I'm going to have to build a completely new switch panel from some of the teak I found in dumpsters over the last year..it was an excellent haul of dumpster teak this year..some really nice trimmed and routed stuff..check your cabinet shop dumpsters!
     

  15. Landlubber
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    Landlubber Senior Member

    .....try using tinned wire if possible, a lot less corrosion problems due to salt damp travelling up exposed ends.


    ....Double pole switches are used here in survey vessels regularly, both sides are switched to remove the batteries(electrically)from the boat entirely...especially useful in alloy boats that tend to have more problems than others, mostly user related of course.
     
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