Shore Power Circuit Breaker Tripping Often

[noblewarrior]

As previously suggested get (borrow/buy) voltage tester, Then check the voltage with the power off, switch on an appliance and check again if you have an ammeter see what the current draw is. if the voltage is dropping you probably have a bad connection upstream of the test point.
Also check the type of load that is on when it's tripping, these breakers can be oversensitive to big induction loads such as chargers, motors.

[Ding Duck]

Hi Ray, sounds as though you have some gremilins. I hope i'm not insulting anyone here, but thought I would give some insight on how these work. If you know how it's suppose to work is sometimes the easiest way to fix the problem.
With respect to the Overcurrent part of the Circuit Breaker, it comprises 2 devices inside the unit. The first is like a solenoid coil, which acts on the magnetic field created by a short circuit. This drives a small plunger to force the contacts apart and 'trip' the breaker. This is series with the load and is calibrated to operate at multiple of the rated current of the breaker. Different types of breakers are available and generally is dependant on the type of load to be protected.
The other device is a bi-metallic strip which is used to do the overload protection. In your case this is dampened by the hydraulic part. Essentially, heat is proportional to current, so more current, the more heat and the breaker trips quicker. You will not neccessarily notice the heat as the current path through the breaker is wrapped around the bi metals. As the Bi metals heat up, the distort and operate nthe tripping mechanism of the breaker.
Attached is a time current curve, so you can see each part. The reason there are 2 lines is due to manufacturing tolerances. Time is the vertical axis and multiple of current on the horizontal axis.
The breaker can only protect what is downstream of it, so if you have your C/O switch to Off and the breaker downstream of this, it should not tripping on overcurrent faults. The only way to test for overcurrent is with a Ammeter or Clamp tester. If are considering purchasing one, suggest a AC/DC clamp, as it can measure DC current as well. It can be used as a Voltmeter and Continuity depending on the model.

The Ground Fault part of the breaker is simply a small Torroid whch both Active and Neutral pass through. Whats goes in must come out, so the nett result of current the torroid sees in zero (if everything is in order) Should there be a fault, then the out of balance is going to Earth. This may be through your body if you happen to be in the current path.

Every device 'leaks' some current, but this may be 5mA here or 10mA there. This generally nothing to worry about, but you can have what they call a summation problem, when you add all the leakages up, it exceeds the trip threshold and the breaker says you have a fault. Heater elements are notorious for this until the heat up a bit.

Other issues with Earth Leakage breakers is they can trip on Neutral faults, where the Neutral resistance is high. This helps to protect you if the Neutral is lost or high resistance as instead of being at zero Volts, it can now be at a value up to line voltage. The breaker will trip and at the end of the day, it's doing it's job, protecting you and the installation.

With all the lead wriggling going on, I'd be looking at this first, checking for good connections and polarity through the plugs and sockets.
As your on the end of a 100' lead, I'd also check for what turns on when the breaker trips. Maybe a slight phase shift if a Inductive load kicks in, or charging capacitors on the Inverter. As the yard has been through a Hurricane, if you can note the trip time and see if anyone else has turned on a piece of equipment. If they have a bad neutral, it is possible for their fault to be detected by your breaker
Good luck with this one

[Sardean]

There is some great fault finding info here. Im not saying i know what the problem is, just relaying problems ive come accross.
I have found Fresh water in electrical connections that caused circuit breakers to trip after a random amount of time.

[smac999]

so you now have an ELCI that feeds the shore switch?

and both are triple pole? and the switch is directly after the elci?

and the elci trips when the switch is off? then it's probably a bad elci ....

if your switch is not triple pole but only switches 2 hots, it could be a neutral to ground bond on the boat.

do you have an inverter charger on that boat? those can cause havoc due to them having a N-G bond as the boat is getting plugged. if they are not wired properly with a separate neutral bus. but normally that trips ELCI's as soon as the boat is plugged in.

[svlamorocha]

Originally Posted by masonc

Electrician here.If the power you are using is 240v three wire (120-N-120) which is standard US residential power, and you have a heavy 120v load, you may have a neutral problem. When the neutral connection is high resistance, the heavy load will push the neutral potential awsy from ground potential. This could result on high voltages on the other leg and high current on the first leg. That can trip your breaker.

Breakers trip because of current, not voltage. It is true that with motors when voltage is low current goes up.....

[svlamorocha]

Originally Posted by DeepFrz

What cables were wiggled?

Sounds like a bad ELCI or you have a serious short in your boat wiring prior to the shore power switch.

+1
If a) the ELCI is installed upstream of the GENSET-SHORE-OFF switch; b) you have a modern two-pole GENSET-SHORE-OFF switch (ie it cuts both hot and neutral; two breakers joined together; one for hot and one for neutral) and c) the ELCI trips on (50A) current (as opposed to say 30mA ground fault) with the GENSET-SHORE then first hypothesis is a serious hot-to-neutral short between ELCI and the GENSET-SHORE-OFF switch.

If b) is not true let us know. The root cause may then by be a really bad neutral-to-ground fault DOWNSTREAM of the GENSET-SHORE-OFF switch compounded with a neutral that is far from ground (broken neutral at the power source ashore UPSTREAM, such as when the Marinco shorepower connectors are defective). In order for this hypothesis to be true the fault has to be so bad so bad (say 10 times the 50A rated current; see curve) that it will trip magnetically on current before the 30 or so milisecs delay of the ground fault device.

Cheers