Weird Nuisance Breaker Trips

[2Cents]

It kind of all started last year when we visited a marina with upgraded electrical system. We found we weren't able to connect to shore power without tripping pedestal...it's not us of course, must be the pedistal...I am sure you all know the answer by now. While out on a two week cruise we lost the generator, and the inverter (old Xantrex RV model, came with boat) started doing weird things like running through the state of charge like a pendulum and was generally acting strange. Oh and alternators didn't seem be charging house batteries. Performed the inverter reset a few times, and that seemed to help, but we made for a nearby marina so we could get an electrician in (hopefully). Guess what? they were upgraded too. No longer could we say the problem must not be us.

So we searched the interwebz and found some likely causes, galvanic isolator (GI), inverter charger, water heaters, ac units. We found when the GI was disconnected, the majority of the issues went away. No nuisance trips, inverter at least didn't appear to be haywire etc. Tested the GI in diode mode, appears to be good.

So must be the Charger/inverter. Replaced that with a new Xantrex XC Pro 3000, wired in per manufacturers instructions. One strange hiccup, will not operate with neg lead connected to the house battery negative. Cleaned up connection bar, all three house negs go there, and tested the 250amp fuse (continuity good) and still nothing. Connect to Engine battery neg connection bar, inverter/charger works fine. Test shore power leads, have too high of a fault current still.

We plug in shore power, with all loads turned off at the breaker panel and two double pole 30amp shore power breakers off, good to go. Close either shore power breaker, still will all loads breakers off, and we trip the GFI.

So a few questions:
- Where to look now?
- Why does inverter not work connected directly to house battery negatives?
- We were thinking isolation transformers to at least not send current back to shore and getting rid of galvanic isolator. Thoughts?

I included a few schematics if that helps. This is really only the start of the weird electrical issues we have. I will post the others in engines and electronics

[Statistical]

We plug in shore power, with all loads turned off at the breaker panel and two double pole 30amp shore power breakers off, good to go. Close either shore power breaker, still will all loads breakers off, and we trip the GFI.

Scenario 1:
If this is genuinely all loads off and you don't have some unswitched always on loads then this isn't a phantom trip short of the GFI/ECLI being defective it means you have AC leakage to ground causing the shorepower GFI (ECLI) to trip to prevent that potentially fatal situation.

Scenario 2:
If you do have unswitched loads (bilge pump? vhf?) I would start with those and temporarily disconnect them one by one and see if the problem goes away. If it does that is the problem source maybe not the device but possibly the wiring. If it doesn't go away with all unswitched loads removes and all switched loads switched off then you are back to scenario one.

Assuming you are in scenario 1 I would check conductivity pust the shorepower ELCI between AC hot and DC ground using a multimeter (and also AC neutral and DC ground). There should be no connectivity at all not even with high resistance. If there is that is the problem. Note this is different than AC ground and DC ground which should show connectivity.

If there is no connectivity and you ruled out scenario 2 above and you still have an isue with all house loads switched off them the ELCI/GFCI is likely bad.

[Statistical]

Noticed on the schematic you have two shorepower inlets. Do you have an issue with both? Only one? If it is both does the issue go away if only one is connected?

[2Cents]

Statistical,

Yes, problem exists on both shore power inlets. Pardon the lack of actual technical terms...LOL I am a mechanical type. VHF is on a breaker, but I will have to look at how to disconnect bilge pumps...there are a few.

As for testing, yes I believe I am trying to figure out scenerio 1. My clamp meter and an electrical club member doing courtesy readings before our home club upgrades to meet new standards have detected too high of a leakage.

[Statistical]

Originally Posted by 2Cents

Statistical,

Yes, problem exists on both shore power inlets. Pardon the lack of actual technical terms...LOL I am a mechanical type. VHF is on a breaker, but I will have to look at how to disconnect bilge pumps...there are a few.

As for testing, yes I believe I am trying to figure out scenerio 1. My clamp meter and an electrical club member doing courtesy readings before our home club upgrades to meet new standards have detected too high of a leakage.

I misread your original post I though it was a ECLI (sometimes called CFCI) on the boat which was tripping. On re-reading it is the GFCI on the pedestal that is tripping correct?

Yeah the clamp meter is probably not going to help you. GFCI will trip on incredibly low current mismatch. So connectivity test is probably going to be easier. The idea is to confirm there is no connectivity between wires that shouldn't have one.

For example there should be no electrical connection between shorepower 1 hot and neutral. There should be no electrical connection between shorepower 1 hot and shorepower hot 2. There should be no electrical connection between either hot and DC ground. There should be a connection between shorepower AC ground and DC ground.

Normally these kinds of trips are caused by equipment but if you are having the issue with the loads off then it is either in the unswitched loads like bilge pumps or in the wiring itself. Until you start doing connectivity checks between wires you aren't going to know.

[2Cents]

Yes it is the pedestals that are tripping. I'm thinking besides battery charger and bilge pumps are only un-switched load, I will check those.

Thanks for the ideas! will look at connectivity checks too.

[Ixium]

Changed out the shore power cable?

[Statistical]

Originally Posted by 2Cents

Yes it is the pedestals that are tripping. I'm thinking besides battery charger and bilge pumps are only un-switched load, I will check those.

Thanks for the ideas! will look at connectivity checks too.

I would disconnect battery charger first and then try. The reason why is it is one system that genuinely has both AC and DC. If it has some kind of fault which is leaking milliamps of AC onto the DC system and thus into ground via the engine block and propshaft that would trip the GFCI. Even with the charger off some internal components could be energized so disconnecting it from AC side removes it as a problem source.

In troubleshooting always worth making the problem simpler first. The breakers isolate all switched loads so removing the unswitched loads would either identify them as the issue or narrow it down to the AC wiring.

[2Cents]

Originally Posted by Ixium

Changed out the shore power cable?

We have two sets, one about 10 years old and a newer set 4 or 5 years old.

We do make sure they are never in the water, and one set stays onboard and is only used when cruising.

[Fishspearit]

Most common cause for this is that you have a grounded neutral somewhere on the boat. It's normal in a house, you ground the neutral at your breaker panel, so sometimes house electricians get on boats and do that. Another common source of the grounded neutral is household appliances. Household refrigerators, ovens, etc. often ground the neutral at the appliance.
You need to track down the grounded neutral that is likely causing the leakage current. Could also be at the shore power connection itself or nearby.

Since it's tripping with all your loads off, I would check the panel and the shore connections and main breakers first.

[Jammer]

Originally Posted by 2Cents

- Why does inverter not work connected directly to house battery negatives?\

According to the schematic, the negative for the engine batteries does not connect to the negative for the house batteries anywhere except at the inverter. Perhaps your original inverter connected them together or did so some of the time. At the inverter, the line marked "-" in the schematic connects only to the negative busbar for the house batteries. The line marked "G" connects to the negative busbars for everything else.


This is an unusual arrangement. Ordinarily the house and engine negatives would be connected together. Most inverters do not connect the battery - to ground, and so perhaps your new one does not leading to some of the confusing problems. Checking voltage with a meter between the +, -, and G terminals at the inverter, with your two different connection scenarios, may help illuminate things.

- Where to look now?


- We were thinking isolation transformers to at least not send current back to shore and getting rid of galvanic isolator. Thoughts?

I included a few schematics if that helps. This is really only the start of the weird electrical issues we have. I will post the others in engines and electronics

So, first of all, removing the galvanic isolator will mask some of the problems (and possibly create an unsafe situation) unless you replace it with a jumper.


Somewhere you have a connection between hot or neutral and ground which is what trips the pedestal. The best way to find it is to disconnect shore power, shut off the inverter, and measure resistance between the neutral and ground bus. It should be very high, over 10K. If it's not, you have to shut off all the individual 120v breakers and then start disconnecting circuits from the 120v neutral bus one at a time until the resistance jumps up. Once it does you've found the bad circuit, and you can narrow it down from there.


You can get an isolation transformer (which may be a good idea in its own right) and that will mask the problem just as disconnecting the galvanic isolator does but it will not fix the problem.

[CharlieJ]

As mentioned above, your boat has an improper N>G bond aboard. You have to be very systematic in your troubleshooting.

The fundamental value is a minimum of 25,000 ohms resistance between N and G.

To begin, disconnect the shore cord from the pedestal, leave it plugged into the boat. Keep the shore power circuit breaker closed.

At the panelboard, check and record resistance between the N and the G bus. If <25kOhm, unplug the shore cord from the inlet and check N>G resistance again; if >25kOhm, the improper bond is in the shore cord. If still <25kOhm, the improper bond is between the shore power inlet and the line side of the so

Use the DMM to measure resistance between N and G busses while lifting the N leads from the N bus one at a time. Leave them lifted as you test. When the resistance jumps to >25kOhm on lifting a N lead, you have found the culprit.

I have found the following when troubleshooting boats to correct this problem:
- N wire landed on safety ground bus
- N>G bond in the shore end of the shore cord; it had been dropped into seawater and not properly repaired
- stuck N>G relay in old inverter
- failed heater element in water heater
- household washer/dryer with as arrived N>G bonding strap installed
- and so on.

Be systematic, build a one line sketch and take notes as you go.

Good luck.

[s/v Jedi]

Best to start by disconnecting everything from the shore power inlet, then rebuild connection by connection while checking after every step.

The attached diagram is the best start for a basic shore power installation.

[NorthCoastJoe]

Have you looked at the back of your shore power connector?

[Cheechako]

Is your generator grounded to the engine? water? or anything else grounded there. I forget what they are but remember from aluminum boat building days of problems due to how to ground generators and still comply with ABYC (at the time)