Problem with GFCI breaker popping on my Xantrex inverter

Sdroux
Sdroux 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: 33,431 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
  • Sdroux
    Sdroux Registered Users Posts: 3
    edited July 2019 #3

    This is a stand alone system using a transfer switch between generator power and inverter.
  • Tecnodave
    Tecnodave Registered Users Posts: 437 ✭✭✭✭
    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: 33,431 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
  • Tecnodave
    Tecnodave Registered Users Posts: 437 ✭✭✭✭
    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: 33,431 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
  • Tecnodave
    Tecnodave Registered Users Posts: 437 ✭✭✭✭
    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,
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    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
  • MichaelK
    MichaelK Registered Users Posts: 234 ✭✭✭
    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?
    System 1) 15 Renogy 300w + 4 250W Astronergy panels,  Midnight 200 CC, 8 Trojan L16 bat., Schneider XW6848 NA inverter, AC-Delco 6000w gen.
    System 2) 8 YingLi 250W panels, Midnight 200CC, three 8V Rolls batteries, Schneider Conext 4024 inverter (workshop)
  • MichaelK
    MichaelK Registered Users Posts: 234 ✭✭✭
    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?
    System 1) 15 Renogy 300w + 4 250W Astronergy panels,  Midnight 200 CC, 8 Trojan L16 bat., Schneider XW6848 NA inverter, AC-Delco 6000w gen.
    System 2) 8 YingLi 250W panels, Midnight 200CC, three 8V Rolls batteries, Schneider Conext 4024 inverter (workshop)
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 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
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    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
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    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
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    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
  • Sdroux
    Sdroux 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. 
  • Darniteh
    Darniteh Registered Users Posts: 1
    edited August 2021 #17
    I just wanted to add what I have been working on. I come to this forum every year when I search for answers to this problem that seems to keep happening to me every year as well. We usually swap out the inverter but it's a pity.

    Long story short like yours. I have a house panel that is fed from a Xantrex Prowatt 2000W inverter. Or else I can manually move the breaker in the panel and feed it with the generator.

    Therefor my house panel plugs into the GFCI of the inverter when Im using my batteries. So the inverter GFCI starts tripping randomly. Even with nothing plugged into it (just batteries connected to the back of the inverter) the GFCI trips (with nothing even in it). I called xantrex and they said I need to "reset" it.

    That involves taking everything out of the GFCI receptacle, and taking the positive/ red lead from the batteries off the back of the inverter for half an hour. Than apparently if I hook it back up and it works. yay. And if it doesn't. My inverter is hooped.

    My mysteriously started doing this like the poster too. We took it home to swap out the GFCI and that was a pain in the ass. So many screws to undo, so many different threads on them and sizes, not to mention the two ground leads randomly placed on the unit that I have no clue how the put them on there, but coming from my angle its impossible to put them back in the same spots. Good luck...
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Welcome to the forum Darniteh,

    I think you have this inverter?

    https://www.solar-electric.com/xantrex-806-1220-prowatt-sw-2000-watt-inverter.html

    I am a little confused--Is the GFI receptacle tripping, the A/C inverter shutting down, or both?

    I took a quick look at the manual for the inverter--And I could not figure out if the AC output of the inverter has the Neutral to Ground bonding (green wire from chassis to white wire of inverter output) or not.

    From your description, it sounds like the inverter's neutral is ground bonded (green wire to white wire on the input side of the GFI--Possibly a second chassis ground green wire to the green screw on the GFI outlet--That for the 3rd grounding socket for the outlet).

    If the inverter has a neutral to ground bond inside the inverter, and this is a typical north American home with Neutral bus bar and Ground bus bars tied together--Then having "two ground bonded neutrals" in your inverter to home power system will typically trip the GFI in the inverter. This is because the white neutral wire and green ground wire are sharing current flow. The GFI looks for 'balanced' current flow between Black and Neutral (Hot and Neutral, Black and White, etc.)--If there is some 120 VAC current not flowing "out the Black and in on the White" (such as some current in the green wire), the GFI is supposed to trip.

    The easiest method is to pull the GFI outlet, and remove the green wire to white wire bond (typically g+w on GFI outlet's input terminal)--Tape or remove the unused wire) and replace the GFI with a standard AC Outlet.

    If you need GFI protection--Install (or use the presently installed) GFI outlets near sinks in kitchen, bath, and garage sinks... The GFI+Ground Bonded Neutral is not really correct to power your existing house wiring.

    That is my first set of guesses... GFIs do go bad after some number of years--Could cause false tripping. But it is not common for them to trip with nothing plugged in (or wired to the "output terminals" of the GFI).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    edited August 2021 #19
    GFI's have a common mode (counter wound) winding pair of a couple of turns for hot and neutral wires on a torroid core,  It also has a fine wire many turn isolated winding that is the core field sense winding.

    If the counter wound hot and neutral windings have exactly the same current then the magnetic fields by the counter wound hot and neutral windings cancel out leaving nothing to be picked up by the multi-turn sense winding,   Everything happy.

    Any leakage current past the GFI  on either hot or neutral results in a slight imbalance in the GFI torroid field, producing a pickup in the sense coil that shuts off the GFI breaker.

    Many inverters and some generator have EMI reducing capacitors on hot and neutral to their case.  If the cases are not commonly connected to ground they can create some small amount of leakage current imbalance that is detected by GFI causing it to trip.

    When you switch between gen and inverter the EMI caps may have a short current spike due to voltage shifting due to phasing or absolute voltage matching.

    Other possible cause is the floating push pull H-bridge design of inverters.  They have opto isolator coupler to allow one side of the balanced H-bridge outputs to be neutral bonded but some of the inverter circuitry is still floating. Something like the transformer windings have stray capacitance to their transformer core which may be grounded to case creating some AC leakage current to case.

    The first thing to do is make sure all the various device cases are grounded to a common point.

    GFI maximum ground leakage spec is about 5 mA but there is a lot of variation in their sensitivity.  I have tested some that only require 10 uA of leakage before they trip and that was with a 1500 watt hair dryer.  Pretty remarkable it can detect 10 uA difference in a 12 amp current.