Another question on electricity - boat wiring:

Discussion in 'Boat Modification Journal' started by kat in the hat, Feb 29, 2008.

  1. kat in the hat

    kat in the hat New Member

    Messages:
    4,875
    State:
    Missouri
    On my car stereo, I ran 8 gauge hot and ground wires to my amps, along with a 1.5 micro farad capacitor to keep my battery charged when it's under a heavy load. My amplifiers add up to 650 watts, and I have a pretty serious EQ. I'm drawing about 35 amps when I got it cranked. In that application heavier wire delivers more current from what I understand, and cuts down on heat.

    My question is, in a boat, is there any advantage to running hot and ground wires of that size from the battery to the fuse box? I haven't added up the total amps of all the components, but we're gonna be running a 200 watt stereo, trolling motor, 2 bilge pumps, the usual safety lights, and will have 3 DC outlets for various applications like spot lights. Not everything will be running simultaneously, but I wanna be on the safe side. Can't remember the size of the wire we bought, but I think it's 14 gauge.

    Also alot of the wiring will be isolated from one another, but should the hot and ground wires be isolated from on another, or is it no big deal? I'm definitely keeping the stereo wires isolated from the rest so there's no interference from other components that might cause it to hum.

    Any help would be greatly appreciated. In the past, 14 gauge wire was used on all the wiring. Just wanted to know if I need to step it up to something more substantial.
     
  2. Big Dav

    Big Dav New Member

    Messages:
    1,016
    State:
    Southwest
    Matt,
    DC power will not carry over distance like AC will in small wire. It will encounter lots of resistance from the size of the wire and build up heat and blow fuses on a regular basis. DC needs wire size to move over any distance at all. The longer the distance the larger the wire needs to be. That has to be accounted for as well as the load you will be placing on the wire.
    You need a decent size main lead tot he fuse box, especially with a lot of accessories. You trolling motor should be on a totally separate set of wires from the rest of your accessories or wiring. With its out form of protection, be it a fuse or circuit breaker.
    I would recommend 10 GA or even 8 GA wire to the fuse box and keep the wire size the same for both + & - wires. I would also suggest a main circuit breaker within 18 inches of the batter on any power lead you are going to have. This does not take the place of separate fusing for each accessory. It just prevents battery damage is the wire is ever shorted.
    Using marine grade wire would also be a good idea. It is made for this purpose.:big_smile:

    You should be fine running the wires together. A common rule of thumb and a professional practice in the 12v audio industry is always keep and power wires away from you signal wires. If they do need to cross paths, cross them at 90 degree angles and never parallel to each other. RCA's, and speaker wire down one side of the car and power wires down the other.

    I tried to explain it with out a lot of unnecessary details but if you need more I can try and help on that also.:big_smile:

    I hope this was some help.
    David
     

  3. PHLIPS4BIGKATS

    PHLIPS4BIGKATS New Member

    Messages:
    2,679
    State:
    Alma Kansas
    I used to install car audio and with 14ga you restrict current flow. But for a small application of 50 to 75 watt amp it will be fine. Like you sead it will get warm. As for isolating your power and ground you can run those side by side and be ok. With a 200 watt system you will probably draw about 20 to 25 amps at full volume. So you can 10ga it handle up to 500 watt systems and not hardly make it get warm at all. I would wire in a seperate circute breaker just for your amp just to be safe in case of an overload and it will trip it not pop any fuses.

    Hope this helps.

    Chris
     
  4. kat in the hat

    kat in the hat New Member

    Messages:
    4,875
    State:
    Missouri
    Yeah, I hear y'all. I know Mark posted a chart before.

    I can't see putting the fuse box, and switches for everything right next to the battery, and I can't see going with wire bigger than 8 gauge. It's maybe 6' from the batteries to the console. In my car, the 8 gauge power wire runs from my battery to my trunk, and that's about 15 feet, and the wire doesn't heat up under a load. It's been opperating perfectly for 5 years now. I've gotta check how much amps all the components draw, but I think my car stereo draws more.

    I do want to do things right. I don't think that the fuse box will accept wire larger than 8 gauge. I could be wrong, and I don't have it here to look at, but I don't think it does.

    I used a calculator. Entered 12' round trip distance, and estimated a 40 amp load, but I don't think it will be that high. Anything un-kosher about this?

    The following calculator calculates the voltage drop, and voltage at the end of the wire for American Wire Gauge from 4/0 AWG to 30 AWG, aluminum or copper wire. (Note: It just calculates the voltage drop, consult the above table for rules-of-thumb, or your local or national electrical code or your electrician to decide what is legal!) Note that the voltage drop does not depend on the input voltage, just on the resistance of the wire and the load in amps.

    Select Copper or Aluminum Copper Aluminum
    Copper
    Select American Wire Gauge (AWG) Size
    8 AWG
    Select Voltage
    12 VDC or 1-phase AC
    Enter 1-way circuit
    length in feet (the calculation is for the round trip distance)
    12
    Enter Load
    in amps
    40
    Voltage drop
    0.62
    Voltage at load end of circuit
    11.38
    Per Cent voltage drop
    5.17
    Wire cross section in circular mils
    16510
     
  5. Big Dav

    Big Dav New Member

    Messages:
    1,016
    State:
    Southwest
    Matt,
    With keeping things as simple as they need to be. :big_smile: Use 10 ga or even the larger 8 ga wire. Fuse it at the back and use fused (or breakers) distribution at the point where you chose to locate it (usually under a console) then to your switches. The smaller the number in wire (to a point, until you get to 0 ga then 1/0, 2/0, 3/0, etc and the size gets larger with the first number. Not relevant here.) the larger the wire. 8 ga is larger wire than 10 ga. 8 ga should carry any load that you would have in a boat unless you are traveling extreme long distance or are in 24 or 36 volt systems.
    Again the quality of wire also make a difference in the harsh marine environment. When possible I use marine wire.

    Thanks
    David
     
  6. kat in the hat

    kat in the hat New Member

    Messages:
    4,875
    State:
    Missouri
    Thanks Dave. That's exactly the plan. I misunderstood something you said. ( I would also suggest a main circuit breaker within 18 inches of the batter on any power lead you are going to have.) I thought you meant to put the fuse box itself 18" from the battery, but you meant what you said, and put a circuit breaker in the line before it gets to the main panel. My bad. Now, the plan can proceed lol.:smile2: Thanks for your advice Dave.
     
  7. wolfman

    wolfman Well-Known Member

    Messages:
    9,179
    State:
    Triadelphia, WV
    Name:
    Walter Flack
    8 or 10 gauge should be sufficient enough for your application. You might want to run a 3rd marine deep cycle battery though. Also use marine wire rather than standard copper. The copper will deteriate faster than marine wire.

    You definately want to keep your electrical wires seperate from your fish finder cables due to interference. Your stereo electrical wires should go to one of the deep cycle batteries while the ignition/starting electrical wires goes to your marine starting battery. this will prevent any noise or "hum" even if they're run together. Good luck
     
  8. Big Dav

    Big Dav New Member

    Messages:
    1,016
    State:
    Southwest
    Matt, you are welcome, and I am sorry for the misunderstanding. I have a lengthy background in the automotive 12-volt industry and a good amount in wiring boats. I just do not want to introduce unnecessary technical information and terminology that will serve to confuse more than it will help. I have done my best to use terms and wording that is accurate and understandable to those who may not know anything about DC voltage, and wiring. I am in no way saying you or anyone else in particular does not. Generally speaking it is easier to explain something it terms all can for the most part understand. I hope that I succeeded in my goal.:big_smile:

    This is how I would do it and suggest. I am not saying my way is best but it works. Look through my boat mod journal if you want to see how my work looks and ends up. I showed some pictures of just a little of my wiring in that thread.

    Everything starts on paper. Get a game plain of what you are going for. Get your supplies ready. I usually go about 30% over on wire just in case. Shipping will eat a project up if you have to re order several times. Order extra the first time and save it for later if there is any left over. (Usually there won't be as much as you figured would be left)
    Go for quality in you electrical parts like switches, breakers, fuse holders (both in line and fuse blocks), wire (I have expressed my thought on using marine wire, use it), connectors (terminals), heat shrink (adhesive lined), solder and necessary tools. Good tools are a very wise investment for electrical work. A quality soldering iron, crimper's and a quality set of wire strippers are all very important to have. That is if you are going to be doing this type of repair and maintenance to you boat or boats.

    If you ever have a fact based doubt on the wire size, increase one size in wire gauge. In addition, never cut the wire to size until you are making the connection and never pull that connection tight and then cut. Leave yourself a little "wiggle" room with the wire. It is easier to tuck some away than it is to stretch the wire if it is short.

    Find you location for your switches, breakers and or fuseing. Make your runs with the necessary wire. I use a small 3M adhesive tape numbering/marking tape to index the wires. Masking tape marked with a pin will also get the same results. Label both wires in a set, one label can easily pull off or torn off and that leaves you testing or guessing. Be sure to write down on your notes what wire color / number goes where, could save hours of guesswork and testing later. If possible do not use all the same color wire for your hot leads to you accessories.

    Example:
    In my latest project, the 12-volt outlets were red and black 14-ga wire. The courtesy lights were 16 ga wire, yellow, and black in color. The outlets for the blacklights were 14 ga white and black wires. All connections crimped where necessary (terminals), then soldered, covered with liquid tape, and the adhesive lined heat shrink. Sounds like overkill but it will most likely never fail.

    Make your runs with the appropriate size and color wires (according to you labels and notes) to the accessories you are adding. Leave extra length in the wire, a few inches is usually plenty. These smaller gauge wires (usually 16 or 14 ga) should be run from the fuse or breakers panel, to the appropriate switch and then to the accessory.

    Be sure you use quality sealed switches rated at the correct amperage for that accessory. Quality switches can be and are very expensive but they will last (when correctly sized and installed) a long time.

    You will need to run a main positive (hot wire) and main negative (ground) lead from the battery to the fuse / breaker distribution box. Place a main (high amp) breaker or fuse within 18 inches of the battery on the positive wire. This is not to protect the accessories; it is for protection in case the wire was to short out on something in the boat. I run no smaller gauge than 10 ga and usually run larger 8 ga wire for the main leads (+ & -, both always the same size). This may sound like over kill on wire size but I would rather have too much than not enough. If radio's (FM & VHF), accessory lights, fish finder / Gps units, spot lights, 12 volt accessory outlets, gages, running lights, navigation lights, blacklights, bilge bumps, live well pumps, and any thing else you can add will be ran into the fuse box, the drain can add up in a hurry. Connect this main positive wire to the fuse or breaker distribution. It is also easier to run the main ground wire to a grounding lug or barrier strip and connect all the grounds to that location. Do not try to connect twenty grounds to the negative terminal of the battery. :crazy: Most high quality marine fuse / distribution panels are available with provisions for grounds built in. I have used Blue Sea Systems fuse blocks on my last couple of projects and I can say they are quality made products, just a little pricey so shop around for a better deal. They are available with ground and positive connections in one unit. I can provide item numbers if interested.

    Any time you run high amp draw accessories link trolling motors, power anchor retrieval systems, large stereo amplifiers, etc. You will need to run separate wires. Never tie them into the fuse distribution system for the rest of the boat. The fuse block is not for that purpose and is not rated for that purpose. In addition, you do not want all you accessories (lights) to go out if your trolling motor or anchor winch trips the breaker. For this type of accessory, you only need one breaker (fuse if you must but I suggest manual reset breakers) within 18 inches of the battery for that accessory. Run you ground and hot wires directly to the trolling motor or other accessory with as few connections as possible. Connection in wire can act like a resistor (figure of speech) and reduce the wires capability to carry the necessary power for your accessory. Resulting in continues tripped breakers / blown fuses and premature failure of your accessories. Restricted power flow creates heat; heat will kill your electric motors. Bad Ju-Ju!

    A quality battery and a quality charging method are necessary for you to get the full benefit of your work and accessories. The best batteries in the world are only as good as the charge that you supply them. Half-charged batteries will not last as long as fully charged (common sense) and incorrectly charged batteries fail prematurely. You need a charger designed for your batteries, not a 30 min or 1 hour hot charge from the 39.95 charger from Wal Mart (again, figure of speech). Fast chargers like that build up heat and will reduce the life of the battery. Most quality marine chargers will take between four and eight hours to correctly charge a battery. They will also change modes in order to top off the battery and again to maintain the battery once it reaches max charge.

    I hope that I covered it all with this post but I am sure that I have missed some things and some things are not as others would do or have done them. This is just how I would do new wiring and suggest to others as a good method to not have wiring (electrical) problems because of re worked wiring in your boat.

    So please take this for what it is worth, as my opinion and my methods for wiring. This post and methods are nothing more than my opinion and results that have worked for me on way to many projects over the years.

    I hope this will be of help to you and possibly others.
    David
     
  9. Big Dav

    Big Dav New Member

    Messages:
    1,016
    State:
    Southwest
    I also like to have three batteries in a 12 volt system for my boats, all separated from one another. If you wish to use all the batteries for the same purpose, you can use battery switches to select the batteries job. if that makes any sense at all. :smile2::roll_eyes:
    One for nothing other than to start the motor, a second for any accessories, and a third for the larger accessories like the trolling motor and electric anchor's.
    An automatic bilge is also a great accessory to add. just be sure it has its own non switched fused connection directly to the battery. You don't want your radio fuse blowing and killing power to your bilge or when you kill the main switches you kill power to the automatic bilge pump.:eek:oooh:

    Thanks
    David
     
  10. dledinger

    dledinger New Member

    Messages:
    34
    State:
    NC

    Nonsense. AC or DC doesn't matter...it's the voltage.


    kat in the hat,

    Calculate the load. No one can give you an answer without knowing that.
     
  11. BKS72

    BKS72 New Member

    Messages:
    3,361
    State:
    East of KC
    I think you meant amps - your starter and headlights on your car are both 12v. Try and use the same size wire to crank your starter as you do to run your headlights and see what happens:smile2:

    Matt was calculating his loads, that's why he posted the amp draw (load) for his stereo and other components. :wink:
     
  12. dledinger

    dledinger New Member

    Messages:
    34
    State:
    NC
    No, I don't.

    I think you mean "amperage", or "current"....but I definitely mean voltage.

    You're right in a way...in that both voltage potential and current are both needed to calculate voltage drop.....but that has nothing to do with what I posted.

    He posted what I assume is an estimated total, and the power output of his stereo system. Output means virtually nothing without knowing effeciency, or class of the amplifier.
     
  13. Big Dav

    Big Dav New Member

    Messages:
    1,016
    State:
    Southwest
    Like I said in my original post I don't see the need to get technical and introduce terms that everyone won't understand. I was trying to keep it simple and on point.
    DC (12, 24, 36 volts or more) is much more sensitive to voltage drop over distance than AC. Think about your reply "voltage" and you will agree that I was right in the statement that you so politely called "nonsense". When dealing with DC a drop of 1 volt or even .5 volt is much more crucial that the same drop over the same distance in AC where you have 120 +volts.
    What matters in most cases in boat wiring is have a large enough wire size to carry the needed amps and cover the distance necessary. You will have resistance over distance in any copper wire, regardless of size. This is multiplied over distance and increases the load placed on a wire. The wire is rated to carry certain amps and to figure that you must include the distance / resistance. If the load and distance are greater than the run of wire is rated for you will see one of two things, constant fuse blowing or if no fuse is in place you will see the insulating coating melt off the wire and a possible (more than likely) fire.. Where DC motors are concerned you will see a third issue, built up heat and failure of that motor before its time. Heat is the enemy..
    Like I said when in doubt on wire size move up to the next size / GA wire.
    The drop over distance is more substantial in DC because like you said we are dealing with much lower voltage and a drop or resistance of 1 or even .5 volt is my more substantial when dealing with 12-14 volts VS 120 volt plus current.

    Branden is also correct about amps or draw. It looks like we are all three saying pretty much he same thing in different ways.
    Like I said in my original post. With DC when in doubt on the load go up to the next size wire just to be safe and keep it simple.
     
  14. kat in the hat

    kat in the hat New Member

    Messages:
    4,875
    State:
    Missouri
    No amplifiers will be used. Just a 200 watt head unit, a couple of bilge pumps, some running lights, and a couple of power outlets for a spotlight. Nothing complex at all. We have decided to devote one battery to the trolling motor, one to power the accessories, and one for cranking. Still haven't calculated actual amperage yet because I don't have the components here to examine. I would like to use 8 guage wire, but I don't think that the rocker panel will accept wire that large. Might have to do some more shopping around in that department.
     
  15. dledinger

    dledinger New Member

    Messages:
    34
    State:
    NC
    If you took it as rude...I'm sorry. It was short, but I'm not trying to be rude.

    You are still wrong though.....

    It has absolutely nothing to do with the fact that it is a DC circuit. The difference in the analagy is that one is 120 Volts, and the other is 12. AC or DC does not matter.

    When dealing voltage drops its not about .5 volt...or about 1 volt...it's all about percentages. 1 volt is a much greater percentage in a 12 volt circuit than it is in a 120 volt circuit. If you compare percentages....neither is "more sensitive" than the other.

    Sorry if I insist on being excessively technical...I get paid a decent buck to work on electrical circuits in multi-million dollar generators. Boats, houses and cars are pretty simple.
     
  16. kat in the hat

    kat in the hat New Member

    Messages:
    4,875
    State:
    Missouri
    It seems to me that the main power cable diameter would need to be larger than the sum of the individual leads that it powers, or there would be resistance, and heat involved. I know it's more complicated than that, but I don't think it would be right to power a rocker panel with a 14 guage wire that is being used to distribute power to 5 accessories with the same size wire.

    dledinger, I guess that without being real specific about what components are gonna be used, it would be difficult to know what my needs are. I value everybody's opinions. What it boils down to for me is, how big does my main power lead to the fuse box that distributes power to the accessories really need to be? I used 8 agw in my car, but I'm running 3 amplifiers (650 watts total) and an active crossover/EQ off of it. I don't think that the accessories in the boat would have same needs as my car stereo, but I don't want to skimp either. I've got one shot to get it right.:wink:
     
  17. Big Dav

    Big Dav New Member

    Messages:
    1,016
    State:
    Southwest
    You and I are saying the same thing in a different way. 1 volt or .5 volt is DC or 12 volt is a much higher percentage than the same drop in AC which is commonly called 110. Therefore it does make more of a difference in DC over Ac because you are dealing with lower voltage. You will never see a DC system in any of our cat boats over 36 volt and most are no greater than 24 volt. There fore the resistance in the wire is going to be more relative in DC (12-16 volt) than AC (120 volt +). Making DC more sensitive to what takes place over distance in wire. Same statement in a different way of wording it. All the technical jargon in the world is useless in you and one or two more are the only ones on here that understand what your saying. I have a pretty extensive background in 12 volt and/or DC electronics myself.
    Spin it like you wish, this should not be about who is "wrong" like you seem eager to try and point out to members. It is about getting Kat the right size wire to do the job. Were not building car audio systems or generators.
    I do appreciate your desire to express you technical knowledge in your field of expertise. Glad you also get paid well for it. I also got paid pretty well during the 15 years I spent in the automotive 12 volt industry, before I broke my back and had to take a "slight cut in pay":eek:oooh:.

    Kat,
    I am running four LED black lights, 8 courtesy lights, two GPS fish finders, VHF radio, four 12 volt outlets (powering things from spot lights to crappie lights), Golight spot light, horn, gages (8 total), five areator pumps (750 gph each), a bubble pump, two bilge pumps (1000 gph each), six live well lights, and might even through in a CD player. All this is going to be on a 8ga run approx 18 ft long. One thing to keep in mind is that all the items will most likely never be on at the same time.
    What are you calling rocker panel that won't accept the 8 ga wire? There are also safe and effective ways around that.:big_smile:

    Thanks
    David
     
  18. dledinger

    dledinger New Member

    Messages:
    34
    State:
    NC
    Again....has nothing to do with one be AC and one being DC.

    I pointed out that you were wrong because this guy is looking for advice. You posted false information...and this guy needs to know that if he's going to be taking your advice and spending money based on it.

    I don't know what you mean by "automotive 12 volt industry", but you would do well to brush up on theory before you try to help anyone out.

    Boats, generators, cars, houses....doesn't matter. Electricty is electricity.
     
  19. Whistler

    Whistler Well-Known Member

    Messages:
    3,084
    State:
    TN
    Pretty rough statement there. I think we could keep this friendly and simple. If you don't agree with something, then ignore it. But DO NOT go so far as insulting someone for trying to help another member out. Right or wrong. If you don't agree, make a post stating why, and leave it at that. Thanks!
     
  20. dledinger

    dledinger New Member

    Messages:
    34
    State:
    NC
    I don't mean to insult anyone....words from a "stranger" probably seem stonger than if you knew me. Also....they keyboard tends to lack much "emotion"....

    You are right.....good on him for trying to help.