Problem with GFCI breaker popping on my Xantrex inverter

SdrouxSdroux Registered Users Posts: 3
I have a Xantrex SW2000 12V inverter that the GFCI breaker keeps on popping every time I switch from generator to inverter via my transfer switch (TS-30 power switch).  While looking at my main panel, I discovered that my neutral to ground bonding wire was previously disconnected by someone else.  Attaching the ground wire back to the neutral bus instantly causes the GFCI breaker to pop.  I am at loss to explain why this is happening?  Checking the ground wire to neutral bus with a volt meter, I am not seeing any voltage.  This problem started up about a year ago, with the GFCI popping whenever I switched from the generator to the inverter.  The system had previously been working flawlessly for 5 years.

Comments

  • BB.BB. Super Moderators, Administrators Posts: 30,633 admin
    It is difficult to be sure--But lifting the ground/neural bond was probalby a fix years ago to popping your GFI.

    The way a GFI works is to measure all of the current through your two AC main wires (hot and return). If the difference in current is zero amps (actually less than ~0.010 amps), then everything is "OK". If the difference is over ~0.010 amps, then the GFI trips--Under the assumption that some of the AC current is going through your body to a ground/another electrical connection (reduce the chances of electrocution, especially around water/wet areas).

    With AC power systems, you want to either "float" the Hot and Return leads (typically done with small AC gensets or AC inverters) or ground the "white wire/neutral" in one location--Typically the source of the power (larger AC gensts/AC inverters), or the main AC panel for the house with utility power for safety.

    You do not want to "multi-point" your Neutral (white) AC connection to several Green Wire safety grounds... At the very least, you have your return current flowing through both the Neutral/white wire, and your green wire safety ground. You never want normal return current flowing through your green wire safety ground.

    With GFI breakers (and GFI outlets), if you have a Neutral/Ground bond at the main panel, and another Neutral/Green wire bond somewhere else (downstream of the GFI protection), you have a parallel current paths in Neutral and Green wire grounds. The GFI "sees" that there is a "current leak" that is taking a second path back to the power source (main panel, AC inverter, etc.)--Tripping the GFI to prevent an (apparent) electrocution in progress.

    With RVs (and boats, etc.) the whole green wire/neutral bonding gets to be a complex issue. And to be "done right" there is usually a transfer switch that turn on/off the Neutral/Ground bond in the RV depending on the power source (utility power is neutral/ground bonded, so you cannot bond in the RV--When running from genset/AC inverter, need to provide a Neutral/Ground bond inside the RV).

    So--Details matter here... Larger gensets and AC inverters typically have a neutral/ground bond internal to the device... And if if the genset and/or inverter have GFI outlets (typical these days), this "double neutral/ground bonding is guaranteed to pop a GFI (especially with heavier loads).

    There are different solutions possible that are "safe"--But need to know about the basic setup (RV, home backup power, etc.) and your needs (using power near water/outside, specialized loads like fluorescent lights or automatic spark ignition heaters, etc.).

    The quick and dirty solution (and usually safe and legal) is to typically protect each branch circuit with GFI breakers/outlets (one per circuit--Using a panel GFI breaker + downstream GFI outlet is redundant and could cause false trips).

    The "right way" is to use a transfer switch to "lift" the neutral/ground when running with shore power, and connect neutral/ground bond (inside the RV) when running from genset/AC inverter (typically, the Neutral/Ground bonds are both disconnected inside the genset and AC inverter with a separate neutral/ground bond behind the AC transfer switch).

    This stuff is complex--And the above is a quick explination of how and why things are done... Again, the details matter and need to be thought out rather that just "lift the ground bond and walk away" (although it is possible that is the solution for your setup--just do not know from my keyboard).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SdrouxSdroux Registered Users Posts: 3
    edited July 2019 #3

    This is a stand alone system using a transfer switch between generator power and inverter.
  • TecnodaveTecnodave Registered Users Posts: 418 ✭✭✭✭
    sdroux,

    You cannot have a neutral to ground connection after a GFCI, it will cause the GFCI to "see" a leakage to ground. The real fix is to do the neutral to ground for the generator, at the generator, not after the transfer switch. That way you have two different neutral to ground bonds, but only one at a time. You will be protected both ways, internally in the inverter when it is in use, and at the generator when it is in use. Not covered in the NEC this way but you would not have two neutral to ground bonds connected at the same time, which could cause circulating currents.

    david
    2 Classic 150, 2 Kid, 5 arrays 7.5 kw total  2ea.  2S6P Sharp NE-170/NE-165, 1ea. 12P Sanyo HIT 200,  2ea. 4/6P Sanyo HIT 200, MagnaSine MS4024AE, Exeltech XP-1100,  2 Banks L-16 battery, Rolls-Surette S-530 and Interstate Traction, Shunts with whizbangJr and Bogart Tri-Metric, iCharger i208B  dc-dc buck/boost converter with BMS for small form lithium 8S 16650 or LiFePO4,
  • BB.BB. Super Moderators, Administrators Posts: 30,633 admin
    1) is the Xantrex inverter a PSW/TSW (pure/true sine wave) AC inverter?

    PSW/TSW inverters are generally OK to ground reference one AC output fo be the "neutral". MSW (Modified sine/square wave) AC inverters generally cannot have a ground bonded AC neutral (and ground bonded battery bank negative terminal) as this will short out the MSW inverter.

    2) Is the transfer switch just switching the AC hot/L1 or both the L1 and neutral (assuming 120 VAC only genset and inverter)?

    If the neutral is carried from the genset to the AC inverter to your GFI to your load(s) and is not switched--Not a problem.

    If the neutral is bonded at the genset -> GFI -> transfer switch -> AC inverter -> Loads (or -> GFI -> loads), the ground bonding in the AC inverter will trip the GFI on the genset.

    If both L1 and Neutral are switched between genset and AC inverter--Generally ground bonding the neutral in both locations is fine because only one ground bond at a time is active.

    3) Where are your GFI breaker / outlets? Is there one on the genset, and another on the AC inverter? Or just one GFI after genset+transfer switch+AC inverter? Which/were is the GFI tripping?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • TecnodaveTecnodave Registered Users Posts: 418 ✭✭✭✭
    edited July 2019 #6
    BB,

    IN reading the post, it's the built in GFCI in the inverter...there is only the one GFCI 
    2 Classic 150, 2 Kid, 5 arrays 7.5 kw total  2ea.  2S6P Sharp NE-170/NE-165, 1ea. 12P Sanyo HIT 200,  2ea. 4/6P Sanyo HIT 200, MagnaSine MS4024AE, Exeltech XP-1100,  2 Banks L-16 battery, Rolls-Surette S-530 and Interstate Traction, Shunts with whizbangJr and Bogart Tri-Metric, iCharger i208B  dc-dc buck/boost converter with BMS for small form lithium 8S 16650 or LiFePO4,
  • BB.BB. Super Moderators, Administrators Posts: 30,633 admin
    David,

    If you are correct (and you probably are), there is only one GFI and it is in the AC inverter and that is the one failing... Then either the GFI is detecting unbalanced AC output current on L1 and Neutral (transfer switch has gotten wet inside, a "real" fault in the load circuit...). Or the GFI outlet has gone bad.

    I have had GFI outlets go bad and they just need to be replaced. With one, the plastic reset button shattered and spit the guts (spring, plunger, broken plastic) out the faceplate (garage outlet... cool temperatures, no sun on face, no vibration, etc.). 5-10 years of GFI service--I would not be surprised the GFI outlet failed.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • TecnodaveTecnodave Registered Users Posts: 418 ✭✭✭✭
    BB, 
    If the transfer switch switches only the hot lead and there is an external bond ground to neutral then that bond will trip the GFCI. The transfer switch should switch both the hot and neutral and the generator neutral to ground has to be before the transfer switch, not in a distribution panel after the transfer switch.

    Stroud,
    Do you have a distribution panel after the transfer switch, or where is your ground to neutral bond, and is the transfer switch switching hot and neutral?

    david
    2 Classic 150, 2 Kid, 5 arrays 7.5 kw total  2ea.  2S6P Sharp NE-170/NE-165, 1ea. 12P Sanyo HIT 200,  2ea. 4/6P Sanyo HIT 200, MagnaSine MS4024AE, Exeltech XP-1100,  2 Banks L-16 battery, Rolls-Surette S-530 and Interstate Traction, Shunts with whizbangJr and Bogart Tri-Metric, iCharger i208B  dc-dc buck/boost converter with BMS for small form lithium 8S 16650 or LiFePO4,
  • EstragonEstragon Registered Users Posts: 4,478 ✭✭✭✭✭
    If the transfer switch is this one (and is wired properly), it looks like it switches both L1 and neutral:
    https://www.amazon.ca/Go-Power-TS-30-Automatic-Transfer/dp/B00153EYTO

    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • MichaelKMichaelK Registered Users Posts: 129 ✭✭✭
    I was over at Denny's place on Sunday, and tried to help him troubleshoot his system.  We swapped out my old 12V Xantrex inverter (sine wave), and reproduced the same GCFI breaker popping on my inverter as did his, so I would conclude it is not a bad GCFI socket on the inverter itself as BB suggests.  I didn't see the outside cover of the transfer switch, because Denny already had it removed, but I think the one Estragon is referencing is the same. 

    I'm not 100 percent sure, but I believe it was wired such that both the hot and neutral wires are connected to the transfer switch.  To answer TechnoDave's questions, the transfer switch is upstream of the power distribution panel, that's where the disconnected ground to neutral bond wire is located, and yes, it appears that both the hot and neutral from the generator are wired into the transfer switch.  

    Denny said that the system was working fine for about 5 years, then in this last year, the random popping started to occur, usually when the generator was just being shut off.  When I was over at his place last Sunday, he first found the disconnected neutral to ground bond, which someone else must have disconnected in the last year.  He said that he did have some new electrical work done, and new lighting added to the cabin, so it might have been disconnected by the person helping him wire it.  I won't be up there till the end of July, so Denny himself will have to answer any additional wiring questions.

    Hope that was helpful?
    15 Renogy 300w panels,  Midnight 200 CC, 8 Trojan L16 batteries, Schneider XW6848 NA inverter, AC-Delco 6000w gen.
  • MichaelKMichaelK Registered Users Posts: 129 ✭✭✭
    BTW, Denny says that he's having administrative problems responding to the questions, so perhaps there's some kind of block on his new account.  Could an administrator shed some light on that?
    15 Renogy 300w panels,  Midnight 200 CC, 8 Trojan L16 batteries, Schneider XW6848 NA inverter, AC-Delco 6000w gen.
  • BB.BB. Super Moderators, Administrators Posts: 30,633 admin
    I looked at @Sdroux 's account and even tried posting under his account--And I did not have any problems.

    If Denny needs a password reset or something... Let me know.

    I have not seen anything from him in the spam queue...

    If he had electrical work done on the 120 VAC side, it is possible that a new lighting fixture has tied or mixed up neutral and ground connections ?

    Or if he has something like a computer, transmitter, or other device with heavy 120 VAC input filtering--It is possible to have >5 milliamps of "leakage current" through the ground lead.

    If there is water in a box somewhere (or even main panel) where Hot to Ground path...

    If the transfer switch is switching both Hot and neutral, then Neutral to Ground bonding in each device (genset and AC inverter) should not affect each other (each should be isolated by the switch).

    Assuming the GFI is tripping as designed--Then the only problems should be from a Hot to Ground or Neutral to ground current leak in the 120 AC line after the GFI outlet...

    -Bill "I am lost" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • EstragonEstragon Registered Users Posts: 4,478 ✭✭✭✭✭
    Just a thought... if the problem often happens just as the generator is being shut off, there may be a clue there.  My generator tends to shake quite a bit while shutting down, which makes me wonder; if genny wiring is chafed and/or loose somewhere, the shaking could be creating a momentary fault path?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • EstragonEstragon Registered Users Posts: 4,478 ✭✭✭✭✭
    In a similar vein, the triggering relays (assuming mechanical) in the transfer switch might cause some vibration within the switch, maybe enough for a marginally good wire or connection to fault?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • EstragonEstragon Registered Users Posts: 4,478 ✭✭✭✭✭
    I have a gfci for a submersible lake pump.  It's a 240v, powered off an x-240 autoformer.  I've found that if the pump switch is closed when the autoformer is powered up, it often triggers a gfci fault.  If the autoformer is powered first, it never faults.  Although not directly applicable to your problem, it does make me wonder if the inverter going suddenly from a search or sleeping state to supplying loads could be part of the problem.  Is there any correlation between loads and the fault events?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • SdrouxSdroux Registered Users Posts: 3
    Hi this is Denny. A little more background on my GFCI problem. The wire off the ground has been off for years and things always worked fine. Several months after the generator started tripping the GFCI,plugging a vacuum cleaner into any household receptacle and turning it on will trip the GFCI. If I plug the vac. into the GFCI on the inverter it starts and runs fine.
    The generator disconnects by a breaker. 
Sign In or Register to comment.