Tripping the Breaker at the dock Pole

Discussion in 'General Maintenance/Repair Questions' started by dtfeld, May 19, 2022.

  1. dtfeld

    dtfeld Water Contrails GOLD Sponsor

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    12" Axiom and 9" Axiom+ MFD
    Cat 3126 V-Drives
    I’ve been away from the boat for a couple weeks and returned to find the shore power off. It had tripped at the main dock breaker. I reset that breaker and came back to power everything up, and my main AC unit attempts to start then trips the breaker on the boats MDP. After a couple attempts, seems like the AC compressor is locked up. Gets worse.

    I take the boat for a short cruise, and once back in the slip, I reconnect shore power but now it immediately trips the main dock breaker. As soon as I attempt to add any load ( battery charger, front AC unit) it immediately trips the main dock breaker. I swapped to a different pedestal, same results.

    I was able to get the power on with the boats MDP Shore Power breaker on and all individual circuit breakers off, so it seems to be down stream of that. I’ve tried isolating an offending circuit by removing one circuit (actually remove the wire from individual breakers on the boats MDP, but can’t isolate it to a single circuit).

    I thought maybe the Main AC unit had failed in a way that shorted to ground, and removed the power to it at the MDP, that does not solve it either.

    I now have the generator fired up to charge the batteries, but an going to have to leave the boat completely unpowered. For a couple days including no battery charger.

    Ideas? Call an electrician? This one has me stumped.
     
  2. ttmott

    ttmott PhD in OCD TECHNICAL Contributor GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    Hi Dave
    It sounds like there may be an issue with your xfer switch. Maybe a wire came loose and shorting.
    Standard breaker trip or GFCI trip?
    Also there are a lot of history on corrosion where the shore power cord connects to the boat's systems (that interface receptacle)
     
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  3. unsalted

    unsalted Active Member

    135
    Jan 21, 2022
    Grand Haven, MI
    2001 Sundancer 310
    Twin MX 6.2L MPI w/Bravo III Drives
    And all of you AC loads function fine on generator? If so, I start to suspect your MDP and/or the transfer switch between shore and genny or maybe your galvanic isolation transformer?
     
    dtfeld likes this.
  4. dtfeld

    dtfeld Water Contrails GOLD Sponsor

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    12" Axiom and 9" Axiom+ MFD
    Cat 3126 V-Drives
    GFCI on the dock pedestal trips. It’s new in the last 3-5 years and I believe it has been updated to the newest code. But has been working flawlessly for 4 years.
    Line 1 is much more sensitive/problematic. I attended to jump Line 2 to the battery charger just to get that working, but that tripped the breaker at the pole as well.

    Been at this several hours now.
     
  5. spikedaddy99

    spikedaddy99 Well-Known Member

    Jun 11, 2008
    Prentice, Wi
    2005 500 DB
    QSM-11
    Does all work normally on the generator?
     
    dtfeld likes this.
  6. dtfeld

    dtfeld Water Contrails GOLD Sponsor

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    12" Axiom and 9" Axiom+ MFD
    Cat 3126 V-Drives
    In the process of troubleshooting, looks like my AC pump relay is connected directly to the generator/shore power…not on its own breaker!!???
     
  7. dtfeld

    dtfeld Water Contrails GOLD Sponsor

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    12" Axiom and 9" Axiom+ MFD
    Cat 3126 V-Drives
    All works normal on the generator, with the exception of the main Salon AC. It attempts to start but trips is dedicated breaker on the boats MDP. Possibly a bad start capacitor. I need a 30+6 370v. All I can find is a 30+5 370. I assume this would work.

    beyond that, maybe bad compressor(or really the whole AC unit!)
     
  8. dtfeld

    dtfeld Water Contrails GOLD Sponsor

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    12" Axiom and 9" Axiom+ MFD
    Cat 3126 V-Drives
    I’m suspecting the galvanic isolator as well. It about the only thing left. Might get on in order.

    anyway to troubleshoot a galvanic isolator?
     
  9. ttmott

    ttmott PhD in OCD TECHNICAL Contributor GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    Can't be. That device only connects the boat's ground to the shore power ground.
     
    dtfeld likes this.
  10. dtfeld

    dtfeld Water Contrails GOLD Sponsor

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    12" Axiom and 9" Axiom+ MFD
    Cat 3126 V-Drives
    Enlighten me...I obviously thought it was doing something different then
     
  11. dtfeld

    dtfeld Water Contrails GOLD Sponsor

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    12" Axiom and 9" Axiom+ MFD
    Cat 3126 V-Drives
    Bad ground somewhere?
     
  12. northshore

    northshore Well-Known Member

    Jan 17, 2011
    Cleveland, OH
    1989 340 Sundancer
    Raymarine E90W Radar/Chartplotter
    Twin 454 Mercruiser 340's
    Don't discount the possibility of a 'weak' breaker on your dock.
    We chased an incredibly similar problem down on a friends boat a few years ago.
    Quick to test, just tie in to a neighbors electrical and see if the problem continues.
     
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  13. ttmott

    ttmott PhD in OCD TECHNICAL Contributor GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    All that device does is block galvanic current from traveling from the boat to the marina's ground system but does allow large shunt current in the event of a short or fault. The hot and common wires do not connect to the galvanic isolator.
     
  14. dtfeld

    dtfeld Water Contrails GOLD Sponsor

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    12" Axiom and 9" Axiom+ MFD
    Cat 3126 V-Drives
    First thing i did was swap to a new box. Same results...tripped dock breaker. I also tried a differnt set of dock lines, no change there either. I swapped line 1 to line 2 and it seems to be a bigger issue with Line #1, but in the end, if I try to add any load, the dock breaker trips.

    I can get the small AC units fan running, but as soon and the pump and compressor try to start, the dock breaker pops. Same with the battery charger, it will power up, but as soon as it starts to pull a load to charge, it pops the breaker.
     
  15. dtfeld

    dtfeld Water Contrails GOLD Sponsor

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    12" Axiom and 9" Axiom+ MFD
    Cat 3126 V-Drives
    At this point, I'm think its something in my boat. The shore power plugs and the wiring behind that needs to be pulled and looked at.

    MDP looks solid. I went back and checked all the screws were tight, no loose or broken wires that were obvious.

    This must have just happened yesterday just as I was getting to the boat, as there was still frozen frost in my Norcold.
     
  16. hughespat57

    hughespat57 Well-Known Member

    960
    Sep 25, 2016
    Rock Hill, SC
    300 Sundancer 1994, trailered tri-axle LoadRite roller
    Mercruiser 5.7 260HP Alpha One Gen II, twin
    Sounds like a good time for a refresher on how GFCI/ELCI devices are wired and how they trip.

    While called a "ground fault circuit interrupter" that term can be a bit misleading because the devices interrupt the the hot leads. And actually don't even require the ground lead (surprised?). This is because they monitor the flow of current on the hot and neutral wires. Any imbalance in the current flow and the devices assumes the "missing" must be returning via a ground path, which it never should, thus a "ground fault".

    This is also why the galvanic isolator plays no role, it's not in the sensing loop.

    So a typical panel GFCI such as in the pedestal is wired this way:
    Note that the white neutral does not go directly to the load but also passes thru the GFCI.
    This is so all load wires hot & neutral pass thru the sensing loop.

    upload_2022-5-19_15-42-50.png

    Inside the ELIC is this:
    This diagram is a boat side ELCI but the sensing principle is identical
    [​IMG]

    Any imbalance in the hot/neutral is assumed must be going to "ground" and trips.
    It could in fact be going back thru the water or the green shore conductor.

    Ground and Neutral are tied together, but ONLY at the "source" this is the marinas main entry panel from the utility.
    Another concept to understand, if electricity has two parallel paths, both the Neutral and Ground, the current will divide and use both paths. If equal in resistance each path would carry 50% of the current this is how the imbalance leakage can be sensed. But only 0.030A / 30 MilliAmp and the GFCI will trip.

    So your case,
    Not the cords, not the sockets, (would have tripped even if the boat main breaker was off)
    Main breaker on, individual circuits off. Did not trip (not in the panel itself before the individual circuits.

    Now gets interesting, correct anything I say here if not absolutely matching.

    You can turn on all the individual breakers and it does NOT trip.
    But if you start "drawing a load" it does. ?

    "I can get the small AC units fan running, but as soon and the pump and compressor try to start, the dock breaker pops. Same with the battery charger, it will power up, but as soon as it starts to pull a load to charge, it pops the breaker."
    All runs on fine generator.

    So here is the one exception for the the grounding.
    The Neutral and Ground are connected together ONLY at the "source" on shore power at the marina.
    On generator power the genny IS the source and they are bonded together there.
    This is why Generator Circuit breaker or transfer switches MUST interrupt the Hot and the Neutral leads when switched to shore mode.
    EDIT: genny or inverters, Any inverter onboard?

    All this is why ground faults are difficult to find. So what does it mean to test next?

    Disconnect all the shore power cords and set on the dock. generator off, NO AC power on the boat!!
    breakers off, transfer switch off or shore.
    Multi-meter on the low resistance scale (use a scale with diode arrow symbol this setting provide a bit more test voltage)
    1. Check between Neutral buss and Ground buss resistance should be and open circuit (infinite)
    2. Check again with meter on highest resistance scale mega-ohms, should still be infinite however it MUST be MORE then 3,000 ohms it will be in the trip range.
    If it fails this test (and it should) disconnect one neutral at a time until it goes open
     
    Last edited: May 19, 2022
  17. fwebster

    fwebster Well-Known Member TECHNICAL Contributor PLATINUM Sponsor

    Oct 6, 2006
    Middle Tennessee ; Panama City Beach, FL
    1996 450DA
    3116 Caterpillars
    There was a common problem with some Merritt Island and Palm Coast boats in the 1995-2005 time period. The clue for me is that your boat functions properly on generator power and your problem only surfaces on shore power.

    Sea Ray was training some new boat builders (my theory!) and quiet a few have turned up with bad connections on the shore power connections right behind the receptacle. The wires going to the receptacle were stripped but the insulation was not removed far enough back up the wire so when the wire was inserted into the sleeve and crimped, the crimp sleeve closed on the insulation and did not make complete contact with the wire inside the insulation. That creates a high resistance connection that overheats and causes the nearest upstream breaker to trip, plus burning several inches of the wire going from the receptacle to the main panel.

    Look at the end of your shore power cord nearest the boat to see if it has overheated and turned the plug end black. This happened to me on the first trip we took on our 450DA and nearly caused a fire on the boat.

    Hope this is it…..it is an easy one to see/find when you kind of know where to look. For me, the hardest part of replacing the receptacke was removing the burned one from the boat.


    Frank
     
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  18. mrsrobinson

    mrsrobinson Well-Known Member SILVER Sponsor

    Mar 9, 2006
    Virginia, USA
    2001 Sea Ray 380DA
    3126 purring CATs
    Mostly over my head, but I think I learned something, thanks for sharing.
     
  19. dtfeld

    dtfeld Water Contrails GOLD Sponsor

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    12" Axiom and 9" Axiom+ MFD
    Cat 3126 V-Drives
    @hughespat57

    Yes, I have an inverter. It is wired as a source as well with the neutral also switched by the ATS. It seems to be in working order.

    Yes the review was definitely in order...my brain at 2am was thinking of the second picture with 30mA floating throught it.

    My main cabin AC is the one thing that has changed and it's on System #1, so I can't help think it's related.

    However, I will follow your procedure and report back.
     
  20. dtfeld

    dtfeld Water Contrails GOLD Sponsor

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    12" Axiom and 9" Axiom+ MFD
    Cat 3126 V-Drives
    @fwebster

    Good to know and that item will be pn the list to look at as well.
     

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