Circuit Breaker Tripping Randomly

[Tellie]

Be careful going up in size of either fuses or breakers. Doing this takes as bit more electrical experience than I humbly suggest you have at this point. Boat manufacturers are notorious in sizing wiring and breakers to just meet the needs of what is installed at the factory. As a boat ages more electrical equipment is added and changed out causing different loads not originally anticipated. This can increase the load on the circuit and trip a breaker as it should. Going up in size with breakers or fuses and not understanding wiring itself sized for the breaker and circuit can be dangerous. Improper sizing of fuses and breakers have burnt more than one boat to the waterline. A 12Volt system can carry a lot of amps fast on a dead short or an oversized fuse or breaker and turn a wire cherry red in an instant.

https://www.youtube.com/watch?v=PqyUtQv1WoQ

[Dmeistar]

Originally Posted by Tellie

Be careful going up in size of either fuses or breakers. Doing this takes as bit more electrical experience than I humbly suggest you have at this point. Boat manufacturers are notorious in sizing wiring and breakers to just meet the needs of what is installed at the factory. As a boat ages more electrical equipment is added and changed out causing different loads not originally anticipated. This can increase the load on the circuit and trip a breaker as it should. Going up in size with breakers or fuses and not understanding wiring itself sized for the breaker and circuit can be dangerous. Improper sizing of fuses and breakers have burnt more than one boat to the waterline. A 12Volt system can carry a lot of amps fast on a dead short or an oversized fuse or breaker and turn a wire cherry red in an instant.

Thats very good advice, thank you. Please excuse me while I find a clean pair of underwear

[Tellie]

This also was a good seminar on boat electrical. The first five minutes introduction applies here as to doing things the RIGHT way..

https://www.youtube.com/watch?v=fHZtYFH-0Pc

[skipmac]

All good advise but I'll add my two cents. If couldn't track it down a short by with a meter or testing circuits I would do a visual inspection.



When doing this bear in mind that the overwhelming majority of the time a short or bad connection happens at one of the ends of the wire so I would start there.



Next most likely is anywhere it can chafe on something like passing through or around a bulkhead or engine or any other hard point. Of course a lot of these locations are difficult or impossible to see and of course that's were the short will be.

[ebs001]

Intermittent faults are always tough. There are certain things that you can eliminate as the potential source of the fault and others you can be pretty sure are not the source. The connected devices are not the problem because you eliminated each one and still had the problem. The observation by your GF of the amps spiking leads me to believe it's not the breaker but an over current problem That leads me to believe it's in the branch circuit wiring. First thing to do is isolate the loads. That can be stated by putting the AIS circuit on another breaker. It would make life simpler if you could put the other loads on separate breakers but that may not be possible. Once you have separated the loads you can determine which circuit is the problem. If the busbar cct trips remove the circuits one at a time until the breaker no longer trips. Once you have identified the fault circuit try it on its own to verify that it is the fault circuit.

Having identified the fault circuit it's most likely the wire itself causing the fault and not the connections. A bad connection will result in loss of power not a short circuit. The easiest thing to do is replace the wire.

The hardest thing is to get the breaker to trip on demand so it's going to take some time. Good luck.

[garison]

what is the cb rated at what is the current draw of every item on it , are you just overloading it , as we often just add stuff to circuits without doing the sums

[waterman46]

Originally Posted by Wotname

Eyeballs are the best way to find an intermittent short but you can make things easier.

You have several circuits feed by this one circuit breaker. You can add a temporary in line fuse (rated say at 50% or less of the circuit breaker) at all the busbar distribution points mentioned in your opening post.

Wait until a fuse blows instead of the circuit breaker and you have isolated the section of faulty wiring considerably.

This is the best. Just will add that unfortunately it may be more likely that one of the load devices has an internal short, rather than just the wiring. In either case, separate fuses on each circuit will help isolate the problem.

[Dmeistar]

Thanks again for all the words of wisdom! I am pretty sure I found the culprit. I decided to start by replacing the positive wire leading from the panel to the cockpit. Not as easy as replacing the breaker but it seemed like the most likely culprit. I crimped a ring terminal onto my new wire and tied it to the old wire, then started pulling it through. The terminals kept getting snagged as I pulled the new wire through. I became worried as I approached a blind run that went under the floor—if it got jammed in there I would have a tough time fishing it out. Sure enough it got caught. I gave it a tug and the terminal pulled off the wire! Crapola! After several attempts to push the new wire through, I actually managed to get it out the other side, and continued on.

While in the engine compartment I found a small puncture in the old wire—it looked like a small nail or screw had gone through it, and I was feeling hopeful that I had found the source of the short.. Finally I got the new wire up through the binnacle and out the top! My 20 feet of wire didn’t have 6 inches to spare.

With the new wire safely in place I went over the old wire. The portion of the old wire that was inside the binnacle had a huge area of insulation stripped away! There was also a butt splice in there that wasn’t heat shrunk and just horribly corroded. Parts of this wire looked to be in near perfect shape, but where it weathered hard it was just horrible.

Thanks again to everyone for the help!

[Cheechako]

Not sure what style of breaker you have, but many of the boat-use breakers are infamous for being defective and tripping. I have had a few that did that. Often, they seem to have a spring that keeps the breaker right on the edge of tripping just from spring pressure alone. On a small boat I had the little panel was down low, if my jeans bottom brushed the panel a breaker would trip!

[waterman46]

That is wierd about the damaged insulation. Wonder what type of insulation was used. Inside the binnacle out of sun, insulation on marine or even automotive wire should last longer than the age of your boat in my experience.

Are your engine controls located on the binnacle? If so, make sure all wires cannot contact any moving parts of those controls.

[CarlF]

While that wire obviously needs replacing, I'd also replace the breaker. It's so cheap and easy to do. While the random nature of the trip could be the bare wire or the splice moving around, that seems a stretch. Just increased resistance from corrosion wouldn't cause random trips.

It's far more likely that the breaker is running very close to the edge. It could easily be slightly out of spec and trip at 10% under its rating. And when the current is just slightly over that actual trip point, it can take a while to trip making it look random.

A new breaker is less than $20. Or swap a breaker with the same rating from another circuit.

[wingless]

The factory used split loom for all the concealed wiring running through inaccessible pathways and for all the exposed wiring, such as in the engine room.

The factory didn't encase all the wiring in split loom inside the main wiring panel compartment and split loom was also not used in the snap cover wiring raceways.

That wiring style was retained for all the additions and modifications that I performed on the boat. It is virtually impossible to discern OEM wiring from my wiring.

The advantage is chafe protection, plus ease of pulling new / old wires.

The usage of cushioned Adel clamps along the length was retained. All my wires are labeled at both ends. New wiring diagram pages were created for all the updates, or existing pages were marked up to show the changes.