1 wire alternator

Ok spoke with Woody told me install 100 amp breaker keep postive from alternator to the breaker then wire from breaker goes to dash #10 panel and postive side of solenoid does that make sense to everybody

Tony, what amp alt did you buy? also, where/how much? Mine might need replacing soon.

I'm confused though....wouldn't you run the power to the solenoid and then directly to the battery (or isolator/combiner/perko)? whats with wiring to the dash panel?

6 gauge should be enough, but if you plan on adding stereo, etc I'd bump up to a 4 gauge or maybe 2. Yes, you should replace the solenoid wire as well.

It's funny you say that Jeff thats what I was trying to explain to Woody today. sometimes I can't explain well but I understand what I'm trying to due.To make life easier I'm going with only a 60 amp alternator 75 amp breaker I beilieve this set up will allow me to keep everything else the same that #10 wire could handle the amp's coming off the Alt what do you think.

By the way Jeff the #10 wire coming from the breaker goes to a fuse box then all might items are indivudally protected i.e. blower,bilge ,lights and so forth no longer have the circuit breaker style set up to many issues with that wiring if you know what I mean.

   If its a one wire alt that is going in, I would say no to that. 60A for a #10 alt output wire is pushing the luck. I would certaily go with A larger one. What happens is the single wire alt cant adjust for the drop in the cable from its output terminal to the breaker. Of course, the shorter the run, the better it is. The old style with a external regulator senses the voltage at the breaker and the alt compensates for it, maybe putting out 15v at the output stud, but getting 14 at the breaker. This is the reason why you cant hook dual batteries with a isolator(diode bank) with a single wire hookup alt. It wont compensate for the .6 to .7 volt drop through the diodes.
    I would run the #4 wire and go with the 75a breaker seperately like I mentioned before it were mine. My .02 again.
                            Jeff..

Ok Jeff I'm convinced I will leave the orginal set up install 75 ampbreaker to protect wire coming of the new alternator. but were do you want me to install the wire after I come off the 75 amp breaker to the postive side of the solenoid were the #2 wire comes from the battery or just run a longer wire and run to the battery itself.

Factory installed 50 amp with 36 amp alt with #10 wire to dash for the postive feed.

not about loud music only have 4 speakers 2 on tower 2 on the inside. They don't make the alternator that's currently on the boat so I went with 60 amp but probally only a true 56 amp alternator or at least that's what everyone says just want to make sure things are going to be safe. I like to do work once not twice.

It wasn't that Woddy was wrong he mentioned he did not have the wiring schematic. On the rear of the engine was the 50 amp circuit breaker with

on one side red wire #10 which basicaly a short jumper wire that went to postive side of solenoid basically the same spot the postive wire from the battery is attached.

on the other side there are 2 wires attached the orange #10 coming from the alternator and a #10 wire that went into wireharness that looks to be the dash hot feed, Woody thought that wire was the amp meter. I was looking directly at this and knew in fact that it was the dash feed wire not amp meter wire but I understand it's hard to answer questions without having schematic or looking directly at it. Believe me anytime you need an answer he is by far the most informed person out there.

tony. Your breaker does not have to be larger than your alternator. It's nice that you have a 60 amp alternator. The actual amps that flow out of your alternator depend on the amount of electrical devices that "pull" the amps out of the alternator. All of that "amp pull" or "amp draw" as it is called, is also called the electrical load. It's good that the alternator is rated higher than your electrical load.

When amps flow through a conductor heat is given off. The more amps the more heat. Larger wire will handle more heat (and therefore more amps).

The circuit breaker is in the circuit to keep your wire from melting if the amp draw gets too high.

The circuit breaker MUST be rated at an amp rating lower than the amp rating of the wire.

I do not have the specifics of how wire is rated for amps in a boat but wire ratings for various applications are all somewhat close.

We had this discussion on another thread and I kind of hate to bring it up again but I think you need the help.

The National Electrical Code (NEC), which DOES NOT apply to boats but is all I have to go by, and I think Jeff goes by the NEC also, states in one of it's wire rating tables that #6 copper wire is rated at 55 amps. Wires with different types of insulation placed in different locations carry slightly different amp ratings. But using the 55 amp number, which, I admit, is conservative, would dictate that the circuit breaker protecting that wire be rated less than 55 amps - a 50 amp circuit breaker should be OK.

A 100 amp circuit breaker will not trip until the #6 wire is well on it's way to bursting into flames.

My advise, IMHO, (help me out here Jeff), is to either use a 50 amp circuit breaker if you plan to run #6 wire or, if you really want to use a 100 amp breaker run #2 wire, unless it is a very short wire, less than 6 inches, in which case you could probaby get by with #3 or #4 (but I would not run #4 wire a long distance if it were protected by a 100 AMP circuit breaker). EXCEPT, if you know the amp rating of the exact wire you are buying and you know it is rated higher than 100 amps).

Help Jeff!!!   

   Jim, I can say the only music on my boat is the tune of the straight pipes out or the rear!!!
   Tony, forgot to ask if your boat has a amp meter on the dash.

You just have to hate all of this... (I just can't help myself)

Two types of over-current situations:

In a shorted circuit, electric current flows outside of it's intended path and is limitied only by the impedence of the circuit and the ability of the voltage source to supply current. (This is why we have fuses and appearantly, in the case of boats, circuit breakers). Warning warning, here we go again!!!

In an overload, current flows within its intended path but is higher than the design rating of the electrical system.

I may be just learning about boats, which I am, but when it comes to theory (for whatever that's worth) - send me in coach. I've got bits of theory stuck in every pocket and I'm just dying for opportunities to whip it out!!!!

Now all I have to do is go get into my theoretical boat and drink my theoritical beer while I work hard to embarrass myself in front of the theoretical babes in their theoretical thongs!! Sorry Tony. I suggest you sell the damn boat and buy stock in Belden Wire & Cable.

   Yes Jim, as a rule, you have your main batt cable go to your starter (or solenoid), then a wire from that to the breaker. Everything else goes on the other side of the breaker. There shouldnt be anything hooked to the main batt cable unprotected (doesnt mean it hasnt been done). As far as 100a breaker, tony only needs a 75. The 50 would be marginal unless he has a "fixed" accessory load of 20 amps, thus allowing only 40 to go to the batt. Running a #4 wire is fine because the breaker is designed to protect lines from a dead short. A 5 ft. piece of #10 will trip 100a breaker with no trouble. Its a quick in-rush of current for the wire for a short time till the breaker trips, so the wire will never heat up. Just like a starter... can draw 500 or more amps from a #2 batt cable, but crank too long and she burns up. If a alternator diode fails and shorts, it will trip the breaker (or like me and accidently get a wrench across it).
   Tony, easiest way to me would be to install a new 75a breaker near the main batt cable, then run a #4 from the alt to the breaker, then another #4 from the main batt cable on the engine to the other side of the breaker. The key to success is to get the breaker mounted as close to the main batt cable as possible so you have no more than a 1 ft. of wire that is unprotected from the main batt cable to the breaker. Leave the 50a breaker as is.
   Hope this helps and my .02    
                            Jeff...

I think I will go buy A mastercraft now.



Just Kidding you guy's are great

Wow a #4 wire,

man you lost me a while ago.

seems pretty heavy duty running that size wire off of a 100A alt...never seen anything that heavy even on a diesel application(non-18 wheeler).

   A #4 wire is good size, but will give you basially no voltage drop in that short run since its a one wire system. Automovive applications get away with it due to the high-temp insulation they use. On new GM trucks, they use a #4 on their alternators, since they have gone to a one wire system themselves. You would see #10 and #8 on the older trucks without the one wire system where it could compensate for voltage drop for the smaller wire. Not the case here. Also, most alternators are oversized for the application so at idle they will maintain voltage. Will never get full output from a alt at idle, so the smaller wire survives because it usually never sees the full output except at start-up for a bit.

                               Jeff....

Jeff,

As I am sure you know, impedence = the square root of resistance squared + inductive reactance squared. In a DC circuit the inductive reactance = 0. Therefore impedence = resistance. There certainly is impedence in a DC circuit and it equals the resistance. When you are shaving nuts there actually could be some slight inductive reactance and capacitive reactance in a DC circuit, even supplied by the coils in the alternator and the parallel run of conductors in the conductor path, although from a practical point they are usually insignificant.

The word impedence is often used to mean total resistance to current flow including any inductive reactance and capacitve reactance that may exist, even in DC circuits. (Sort of like the input to your DC voltmeter is rated in impedence.)

The rise time of a current wave form is definitly limited by the impedence in a circuit, even in DC circits.

This all goes way beyond practicality in wiring a boat and is therefore pretty much more meaningless dribble. But, if we are going to start dsicussing theory let's get it right.

I love these conversations as they keep me thinking and you keep me on my toes Jeff. Now if you want to discuss how the boat is actually wired? Pffff... beats me.

I thank you Jeff.. I love it keep it coming guy.

Jeff, make no doubt I have limited experinace in the technical aspects of how a boat is wired and I am comfortable with your advise. (you can wire my boat any day...)   

I did look at the wiring in my '68 today. It appears the positive of the battery connects directly to the circuit protector with the battery cable. The alternator cable runs into the wiring loom and goes I know not where. I suspect it runs to the ammeter. It looks like it may be a #10 wire.

There is what looks like a #10 wire that runs from the output of the circuit protector into the wiring loom, probably to my ammeter.

I will stop refering to the device I have been calling a circuit breaker because I have discovered ther is no way to manually disconnet power using that device. It has only a little red button that pops out when a current overload is sensed.

By definition, this will drive jbear to drinking, "a circuit breaker is a device which will open the circuit manually or automatically at a pre-determined current level without damage to itself".

On a final point, I hope, in comparing the AC amp numbers in the NEC wire tables as compared to DC, the AC amp ratings are RMS values which by definition, create the same amount of heat in a circuit as the DC equivilant rating.

I love it Jeff - keep me on my toes!!!!

Have I killed this thread yet? Sorry Tony.

Tony, did you ever get your question answered?

I (and I hope Jeff too) take comfort in that anyone reading this entire thread will probably gain some amount of knowledge. Nighty nite all.