AC/DC Wiring: GFCI Tripping Unexpectedly (LV2424)

nicorellius

Troubleshooter
Joined
Jul 13, 2021
Messages
47
Location
Portland, Oregon
I was just reading this post:


My problem feels similar but it's not quite the same. I'm likely doing something wrong so I want to get a sanity check before proceeding.

My solar system is working fine, so this is mainly about the charger/inverter (which is has AC input for backup power from a GFCI outlet) and running power to a shed. I don't have a diagram handy but I'll create one if needed. Here's the scenario:

I've got the LV2424 connected to batteries and AC input. The AC input is coming from a GFCI in my house, on a circuit in the main breaker box. This all works fine, as a few times during cloudy days (when I don't get enough sun and my batteries run down), the AC kicks in to deliver power to loads and charges the batteries.

I've got the AC output connected to a 15 A surge protector (close the the LV2424), which delivers solar/battery power to various endpoints. This has been working great for a couple months or more with no issues.

I dug a trench and ran wire in conduit to deliver power to a shed about 50 feet away from the LV2424. Because I want to deliver power to both the existing surge protector and the shed, I installed a three pronged plug to one end (A) of the 12-2 UF-B that is close to the LV2424 (inside the house). The other end (B) is connected to a 20 A circuit at the shed (with a breaker in a box). I've got a single circuit in the shed, with one GFCI outlet, a light switch, and a simple overhead light. The shed wiring is (seemingly) correct.

When I plug end A into the surge protector, the GCFI delivering AC input to the LV2424 trips. But also, if I go out to the shed and flip that breaker, everything in there works fine. I've tested with multimeters and an outlet tester all with good results. Inside the house, if I press the Reset button on the GFCI it doesn't reset. It stays tripped, so I know I've got a problem.

What are the likely causes for this? Should I be doing what I'm doing in this scenario?

Any assistance is greatly appreciated.
 

OffGridInTheCity

Solar Addict
Joined
May 23, 2021
Messages
437
Location
Southern Oregon
I'm following this with interest. I believe I've encountered a similar issue. I have an MPP Solar 3048LV in a trailer -> camper. When I power it from a house (grid) plug - it trips the GCFI on that house circuit.

The MPP Solar input is 120v with ground - and the ground is wired to MPP Solar as one would expect. The output of the MPP Solar is wired to a standard RV distribution box with a ground busbar separated from neutral busbar (as it should be). The 120v ground is not connected to the trailer frame or anything like that.

The trailer is on tires but the stabilizers 'kind of' make a path from the frame to the ground. The inside of the trailer is all 120v plugs - with TV, microwave, LED lights, 120vac -> 12vdc stepdown, and things like that - nothing you would think would cause GCFI to trip.
 

Cheap 4-life

Solar Enthusiast
Joined
Jan 20, 2021
Messages
312
I'm following this with interest. I believe I've encountered a similar issue. I have an MPP Solar 3048LV in a trailer -> camper. When I power it from a house (grid) plug - it trips the GCFI on that house circuit.

The MPP Solar input is 120v with ground - and the ground is wired to MPP Solar as one would expect. The output of the MPP Solar is wired to a standard RV distribution box with a ground busbar separated from neutral busbar (as it should be). The 120v ground is not connected to the trailer frame or anything like that.

The trailer is on tires but the stabilizers 'kind of' make a path from the frame to the ground. The inside of the trailer is all 120v plugs - with TV, microwave, LED lights, 120vac -> 12vdc stepdown, and things like that - nothing you would think would cause GCFI to
There most likely is a discrepancy of current on the hot vs neutral. That’s what causes a gfci to trip. I’d assume with the inverter completely removed that the gfci from the house wouldn’t trip. This tells me that there is a discrepancy of current on the hot vs neutral inside the inverter that comes from the house. After the inverter powers a load I’d assume the discrepancy would balance out on its hot/neutral output therefore no longer tripping the gfci. You can’t test that because the gfci trips before the hot/neutral current can balance. I don’t have a fix for the problem, just thinking out loud
 

enough

New Member
Joined
Dec 25, 2020
Messages
24
In your 20A breaker box, is the neutral kept isolated from the ground? If not, the ground conductor returning to your inverter will split the current with your neutral, this in turn will lead to a difference in the load and neutral seen at your GFCI. I'm not 100% on this as am not sure why it would be tripping when the battery charger is 'off' but this is something to check
 

nicorellius

Troubleshooter
Joined
Jul 13, 2021
Messages
47
Location
Portland, Oregon
In your 20A breaker box, is the neutral kept isolated from the ground? If not, the ground conductor returning to your inverter will split the current with your neutral, this in turn will lead to a difference in the load and neutral seen at your GFCI. I'm not 100% on this as am not sure why it would be tripping when the battery charger is 'off' but this is something to check
Good thought. Yes, it should be. I will double check, to be absolutely certain. Unless I made an error, all wires should be isolated correctly. And the LV2424 charger is not necessarily off; it could be charging (or not) during the GFCI trip. I'm pretty sure it was charging each time I tried this (eg, solar was delivering enough power for loads and charge).
 
Last edited:

nicorellius

Troubleshooter
Joined
Jul 13, 2021
Messages
47
Location
Portland, Oregon
I just did some research online and looked into my 70 A Homeline load center a bit further. Apparently the unit doesn't include a ground bar. I missed this in the docs, so that's on me. However, the instructions I received in the package are garbage. I apparently misunderstood the diagrams, though to be fair they are very confusing and misleading.

Sure enough, @enough, you were right. I had my ground and neutral wires connected. I didn't purchase a separate ground bar so I simply attached the two grounds I had to the box (which is what the ground bar would attach to anyway). This worked and now I've got power to the load center and my inside GFCI is not tripping.

Thanks a lot for the tip. It really helped.

@OffGridInTheCity What do you think? Obviously my issue was a rookie mistake. But from what I've gathered, you have been doing this a while. What's going on with your system?
 

Cheap 4-life

Solar Enthusiast
Joined
Jan 20, 2021
Messages
312
I just did some research online and looked into my 70 A Homeline load center a bit further. Apparently the unit doesn't include a ground bar. I missed this in the docs, so that's on me. However, the instructions I received in the package are garbage. I apparently misunderstood the diagrams, though to be fair they are very confusing and misleading.

Sure enough, @enough, you were right. I had my ground and neutral wires connected. I didn't purchase a separate ground bar so I simply attached the two grounds I had to the box (which is what the ground bar would attach to anyway). This worked and now I've got power to the load center and my inside GFCI is not tripping.

Thanks a lot for the tip. It really helped.

@OffGridInTheCity What do you think? Obviously my issue was a rookie mistake. But from what I've gathered, you have been doing this a while. What's going on with your system?
Good you got that straightened out. Having ground bonded to neutral at more than one location is bad bad..
 

OffGridInTheCity

Solar Addict
Joined
May 23, 2021
Messages
437
Location
Southern Oregon
I just did some research online and looked into my 70 A Homeline load center a bit further. Apparently the unit doesn't include a ground bar. I missed this in the docs, so that's on me. However, the instructions I received in the package are garbage. I apparently misunderstood the diagrams, though to be fair they are very confusing and misleading.

Sure enough, @enough, you were right. I had my ground and neutral wires connected. I didn't purchase a separate ground bar so I simply attached the two grounds I had to the box (which is what the ground bar would attach to anyway). This worked and now I've got power to the load center and my inside GFCI is not tripping.

Thanks a lot for the tip. It really helped.
Excellent - love to read that a problem is understood/solved.

@OffGridInTheCity What do you think? Obviously my issue was a rookie mistake. But from what I've gathered, you have been doing this a while. What's going on with your system?
OK - I took some pictures and realized something..... bear with me....
1) Here's the incoming and outgoing 120v at the MPP Solar - very straight-forward ground, line, neutral.
1631645044906.png
2) Here's my 120v distribution center - notice neutral and ground have their own buss-bars. (Yes I know I'm improperly overloading bus-bar slots with multiple wires per hole)
1631645065167.png

3) I have a Rotary Switch so I can bypass the MPP Solar (leave it off) in storage and take grid directly to the Distribution panel - here's the wiring diagram. Note - I wired all the grounds together in the Rotary switch.
1631645180560.png


Today I did some experiments
1) With the Rotary set to position #2 - e.g. PIP running on PV + battery and no external grid. Plugged the PIP 120v into the GCFI and It worked! I swear this tripped in the past - but now I'm not so sure.
**Scratching my Head - maybe I had water/ground/short as the wire is outdoors and its dry today**

2) Left the PIP 120v plugged into the GCFI with the PIP running and turned the Rotary to position #0 - e.g. bypass. *GCFI Tripped*

3) Reset the GCFI and it worked. Turned the Rotary to position #2 - same thing, reset GCFI trip and it worked.

CONCLUSION:
*With the grounds all tied together (e.g. PIP 120v in, 120v out, Grid, Distribution panel) the switch over (to Position #0) to bypass the PIP tripped the GCFI. Something about switching the active PIP in/out of the circuit trips the GCFI.
* This is not as worrying to me in terms of safety since it works once the Rotary is switched and I reset the GCFI.

God Bless us DIY 'Electricians' (NOT!)
 
Last edited:

Cheap 4-life

Solar Enthusiast
Joined
Jan 20, 2021
Messages
312
Excellent - love to read that a problem is understood/solved.


OK - I took some pictures and realized something..... bear with me....
1) Here's the incoming and outgoing 120v at the MPP Solar - very straight-forward ground, line, neutral.
View attachment 64625
2) Here's my 120v distribution center - notice neutral and ground have their own buss-bars. (Yes I know I'm improperly overloading bus-bar slots with multiple wires per hole)
View attachment 64626

3) I have a Rotary Switch so I can bypass the MPP Solar (leave it off) in storage and take grid directly to the Distribution panel - here's the wiring diagram. Note - I wired all the grounds together in the Rotary switch.
View attachment 64627


Today I did some experiments
1) With the Rotary set to position #2 - e.g. PIP running on PV + battery and no external grid. Plugged the PIP 120v into the GCFI and It worked! I swear this tripped in the past - but now I'm not so sure.
**Scratching my Head - maybe I had water/ground/short as the wire is outdoors and its dry today**

2) Left the PIP 120v plugged into the GCFI with the PIP running and turned the Rotary to position #0 - e.g. bypass. *GCFI Tripped*

3) Reset the GCFI and it worked. Turned the Rotary to position #2 - same thing, reset GCFI trip and it worked.

CONCLUSION:
*With the grounds all tied together (e.g. PIP 120v in, 120v out, Grid, Distribution panel) the switch over (to Position #0) to bypass the PIP tripped the GCFI. Something about switching the active PIP in/out of the circuit trips the GCFI.
* This is not as worrying to me in terms of safety since it works once the Rotary is switched and I reset the GCFI.

God Bless us DIY 'Electricians' (NOT!)
Since the house gfci doesn’t trip after its reset, I think it has to do with the neutral being switched by the rotary switch. If the neutrals were all wired nutted together there wouldn’t be a chance for discrepancy of current on the neutral vs hot. The rotary switch makes hot and neutral contact at basically the same time but it’s still making contact and while trying to do so the gfci trips.

I use that same rotary switch. But I’m not using any gfci. I use the rotary to switch the power supply to a critical loads panel. The grid and the offgrid inverter are the two power sources being switched by the rotary. I’m actually switching ground neutral and hot from both power sources. The offgrid inverters case is wired to the main panels ground. The inverters output ground is also wired inside the inverter to the inverters case before it goes to the rotary switch. I guess I could have simply wire Nutted all the grounds together in the rotary box. The ground for the inverter would come from the main panel, instead of the case being grounded to the main panel. Still trying to figure out pros/cons of grounding the inverters case when the case is wired to the inverters output ground anyways.
 

Attachments

  • 02D02946-CEDE-455C-94DA-1D1473DA10C3.jpeg
    02D02946-CEDE-455C-94DA-1D1473DA10C3.jpeg
    617.2 KB · Views: 3
  • 4652E884-2250-4D75-9884-A91398ED3CF8.jpeg
    4652E884-2250-4D75-9884-A91398ED3CF8.jpeg
    602.2 KB · Views: 3
  • DD0AC155-7DEA-4440-A2AF-979E3A4035D6.jpeg
    DD0AC155-7DEA-4440-A2AF-979E3A4035D6.jpeg
    663.3 KB · Views: 3
  • 0C07FD72-1D3C-43B4-AD09-32E3A4DF295A.jpeg
    0C07FD72-1D3C-43B4-AD09-32E3A4DF295A.jpeg
    1 MB · Views: 3
Last edited:
Top