Flickering lights on new EX-6500 system

[KRP]

I recently replaced my old 12V system (16 yo lead-acid batteries died). Kept my 5kw array of Uni-Solar flexible panels (they are a thin film panel that glues onto standing seam metal roofs. No mounts, no penetrations.) Installed 2 EX-6500 inverters in split phase and 6 EG4 48V 100Ah batteries. I followed al l the guidance, so there are breakers between the batteries and the inverters, PV combiner boxes creating 3 strings, DC Cutoffs between the PV Combiner boxes and the inverter MPPTs. The attached wiring diagram shows it all as best I can do. There is also a transfer switch to connect the generator as a source when the grid goes down.
AC IN power to the inverters is direct from one of the house's two main service panels. AC OUT serves a sub panel with critical loads.
All in connected and in service, functioning properly EXCEPT, I have flickering in certain lights in the house. The flickering varies with what loads are on, whether PV is connected or not, night versus day. But no condition eliminates the flicker. I'm guessing it is a grounding issue. These inverters are the latest (Feb '23) so I assume they do NOT have the ground/neutral bond screw installed. And they have the latest firmware, according to Signature Solar.
My grounding setup is all grounds joined at a local terminal block, then grounded back to the sub panel. There is no ground neutral bond in the subpanel, only in the main service panel. Since the wiring diagram was drawn, I have separated the DC and AC grounds, with DC ground direct to a house plumbing ground fixture. I also tried running separate ground wires from each inverter back to the sub-panel, but no change in the flickering. The flicker also appears in some circuits that are not powered (fluorescent lights).
I have been trying to get a response from Sig Solar for over a month. I can't get a return call and email responses are at least a week apart.

So does anyone here have any idea of how to resolve this issue, or at least something to diagnose it? Thank you.

 

[houseofancients]

did you do a forum search?

 

[dcg9381]

So taking a look, you have your AC input which is shown as neutral and Hot (x 2) going into both inverters.
What I don't see in your diagram is a grid source to ground. When I've run in this configuration (charge off the grid), the grounds on my inverters tie to the ground in the source panel.

You have PV grounding, but I see no ground tie back to the panel.

It flickers with all sources, PV, grid, and battery, correct?




I just ordered a new set of inverters EG-4 6500s. I spoke to SS support. They assured me they were going out with ground screws installed. I pointed out my 2/2023 order and indicated that I had a SS video indicating that there were not shipping grounded. What I got back was "I'll get back with you" and that was about 10 days ago. You need to confirm the N/G bond on the inverter... I suspect they are not bonded also.

 

[KRP]

did you do a forum search?

yes. here and elsewhere. Most of what I find is general grounding discussion or the specific problem SS had recently with firmware starving a rectifier in the inverter. But mine has the firmware that is supposed to have fixed that.

 

[KRP]

So taking a look, you have your AC input which is shown as neutral and Hot (x 2) going into both inverters.
What I don't see in your diagram is a grid source to ground. When I've run in this configuration (charge off the grid), the grounds on my inverters tie to the ground in the source panel.

You have PV grounding, but I see no ground tie back to the panel.

It flickers with all sources, PV, grid, and battery, correct?




I just ordered a new set of inverters EG-4 6500s. I spoke to SS support. They assured me they were going out with ground screws installed. I pointed out my 2/2023 order and indicated that I had a SS video indicating that there were not shipping grounded. What I got back was "I'll get back with you" and that was about 10 days ago. You need to confirm the N/G bond on the inverter... I suspect they are not bonded also.

Good catch on my drawing. I did not show the ground from the Grounding Block back to the sub panel. It is installed but I failed to show it.
I can confirm that it flickers on PV and Battery. It has only been on Grid power once since commissioning, after a string of 3 rainy days. I don't remember if it flickered then or not, it was middle of the night and not much was on. I suppose I could cut out the batteries at night to test that.

 

[KRP]

I also want to clarify that the ground from the PV is from the lighting protectors in the PV Combiner box.

 

[SoVT]

Maybe this helps…

 

[Markus_EG4]

I recently replaced my old 12V system (16 yo lead-acid batteries died). Kept my 5kw array of Uni-Solar flexible panels (they are a thin film panel that glues onto standing seam metal roofs. No mounts, no penetrations.) Installed 2 EX-6500 inverters in split phase and 6 EG4 48V 100Ah batteries. I followed al l the guidance, so there are breakers between the batteries and the inverters, PV combiner boxes creating 3 strings, DC Cutoffs between the PV Combiner boxes and the inverter MPPTs. The attached wiring diagram shows it all as best I can do. There is also a transfer switch to connect the generator as a source when the grid goes down.
AC IN power to the inverters is direct from one of the house's two main service panels. AC OUT serves a sub panel with critical loads.
All in connected and in service, functioning properly EXCEPT, I have flickering in certain lights in the house. The flickering varies with what loads are on, whether PV is connected or not, night versus day. But no condition eliminates the flicker. I'm guessing it is a grounding issue. These inverters are the latest (Feb '23) so I assume they do NOT have the ground/neutral bond screw installed. And they have the latest firmware, according to Signature Solar.
My grounding setup is all grounds joined at a local terminal block, then grounded back to the sub panel. There is no ground neutral bond in the subpanel, only in the main service panel. Since the wiring diagram was drawn, I have separated the DC and AC grounds, with DC ground direct to a house plumbing ground fixture. I also tried running separate ground wires from each inverter back to the sub-panel, but no change in the flickering. The flicker also appears in some circuits that are not powered (fluorescent lights).
I have been trying to get a response from Sig Solar for over a month. I can't get a return call and email responses are at least a week apart.

So does anyone here have any idea of how to resolve this issue, or at least something to diagnose it? Thank you.

Are your PV grounds tied together with your inverter grounds?

 

[KRP]

Maybe this helps…

Interesting. I hadn't seen that video before. I think I'm more confused now. I've been in lots of solar powered facilities and not seen this light flickering. My old system never did that in 20 years of use.
My current issue (pardon the pun) includes flickering in incandescent bulbs, not just LED. And there are fluorescent bulbs that flicker when turned off at the switch. That's got to be a ground issue, I think.

 

[KRP]

Are your PV grounds tied together with your inverter grounds?

I had it that way originally, which was a mistake, and it is shown that way in the wiring diagram, but I have since separated the DC and AC grounds. AC goes to the sub panel, DC now goes direct to a cold water pipe.

 

[Markus_EG4]

Interesting. I hadn't seen that video before. I think I'm more confused now. I've been in lots of solar powered facilities and not seen this light flickering. My old system never did that in 20 years of use.
My current issue (pardon the pun) includes flickering in incandescent bulbs, not just LED. And there are fluorescent bulbs that flicker when turned off at the switch. That's got to be a ground issue, I think.

With these high frequency inverters I notice it more especially if you have a mixture of bulbs like led and incandescent

 

[KRP]

With these high frequency inverters I notice it more especially if you have a mixture of bulbs like led and incandescent

Appreciate the response, Markus, but there has to be something else going on here. Lights that are switched off flickering?

I got a message from a Tier 1 tech at SS that said "What we'll need to do is remove the grounding busbar from the system entirely per our R&D team. This should resolve the flickering lights issue we're experiencing. The PV needs to be designated its own earth ground at the array."
I wrote back (6 days ago) to ask for some clarification, but got no response. If he means remove the Grounding Terminal block between the inverters, I tried that and it made no difference. I'd like to get some clarification about how he thinks it SHOULD be grounded.
Also, I don't know what he means by grounding the PV "at the array". These panels have no metal to ground, just plastic laminate, with + and - leads. Those go in to a PV Combiner box, with a fuse for each string, a 2 pole breaker, and a surge protector. The surge protectors meet at a separate terminal block which is grounded to a cold water pipe. Not sure how else to do that, but would love to get some more detail to his response.

 

[Zapper77]

.

Flickering won't go away until you find the item(s) that is(are) creating the flicker. In my case Deep Freeze compressor and Hvac blower are two items that cause most of my Led light flicker (strobe). UPS is another common colprit (or maybe it's that Mac Mini that's attached to the UPS.)

 

[Markus_EG4]

Appreciate the response, Markus, but there has to be something else going on here. Lights that are switched off flickering?

I got a message from a Tier 1 tech at SS that said "What we'll need to do is remove the grounding busbar from the system entirely per our R&D team. This should resolve the flickering lights issue we're experiencing. The PV needs to be designated its own earth ground at the array."
I wrote back (6 days ago) to ask for some clarification, but got no response. If he means remove the Grounding Terminal block between the inverters, I tried that and it made no difference. I'd like to get some clarification about how he thinks it SHOULD be grounded.
Also, I don't know what he means by grounding the PV "at the array". These panels have no metal to ground, just plastic laminate, with + and - leads. Those go in to a PV Combiner box, with a fuse for each string, a 2 pole breaker, and a surge protector. The surge protectors meet at a separate terminal block which is grounded to a cold water pipe. Not sure how else to do that, but would love to get some more detail to his response.

What he means is to have a separate ground rod for your PV. The lights that are flickering when they are turned off? Are the fluorescent
Lights by chance?

Also capacitors going out on freezers or fridges can cause issues like this. We have had customers unplug a fridge or freezer and everything work fine after that. They have also found the bad component (capacitor) and fixed the problem.

Does this problem only exist on 1 phase or both?

 

[dcg9381]

Good catch on my drawing. I did not show the ground from the Grounding Block back to the sub panel. It is installed but I failed to show it.
I can confirm that it flickers on PV and Battery. It has only been on Grid power once since commissioning, after a string of 3 rainy days. I don't remember if it flickered then or not, it was middle of the night and not much was on. I suppose I could cut out the batteries at night to test that.

I also want to clarify that the ground from the PV is from the lighting protectors in the PV Combiner box.

So I'm educated guessing:

You're grounded when passing grid power. You have a solid ground there. My inverters worked fine when passing grid power also.

I had ground issues when on battery. I assume I would have on PV also. Have you seen SS's video on proper grounding? I don't want to speak to your configuration, but EG-4 6500 EX inverters 2/2023 and after (in my experience) are not N/G bonded. Prior inverters of that model were.

You need to check the configuration (everything off) to see if you have a N/G bond on the output.

I don't see any way you have a N/G bond unless it's on the output panel when on PV or battery.

 

[Quattrohead]

You need to check the AC output with a meter or scope, or even on the monitoring website and see what the voltage is actually doing. It should be rock steady 120v

 

[KRP]

What he means is to have a separate ground rod for your PV. The lights that are flickering when they are turned off? Are the fluorescent
Lights by chance?

Also capacitors going out on freezers or fridges can cause issues like this. We have had customers unplug a fridge or freezer and everything work fine after that. They have also found the bad component (capacitor) and fixed the problem.

Does this problem only exist on 1 phase or both?

Markus, I do not have a separate grounding rod for PV. The PV Combiner Box grounds go to a water pipe that goes underground. Should be equivalent, right?
The lights that flicker when switch is off ARE fluorescent (4 foot tube ceiling lights).
Also, I have a couple of Motion Sensor switches (laundry room, closets). Those do not work anymore. They stay on all the time and never switch off. And the monitors on our computers (also on the sub panel) have started to blink off, then back on.
The problem fixtures ARE on both legs.
I can try unplugging the fridge, freezer, etc. Do I need to unplug from the wall or is opening the breaker to that circuit sufficient?

 

[KRP]

You need to check the AC output with a meter or scope, or even on the monitoring website and see what the voltage is actually doing. It should be rock steady 120v

I've checked the AC Inputs and Outputs with a multimeter and it all looks pretty normal (I think) Running 122v steady AC IN and 119 AC OUT. AC IN shows about 0.3v N to G. AC OUT is about 2.2V N to G. I don't currently have access to a scope but could borrow one. How would I test with that and what would I look for?

 

[dcg9381]

Markus, I do not have a separate grounding rod for PV. The PV Combiner Box grounds go to a water pipe that goes underground. Should be equivalent, right?
The lights that flicker when switch is off ARE fluorescent (4 foot tube ceiling lights).

This is a code issue. Electrically, back in the old days, houses were grounded through copper plumbing. I do not believe that this is allowed anymore.

Report back on "everything off" N/G bond test (continuity) on your inverters.

Scopes are cheap these days. You're likely looking for a quick fluctuation in voltage or frequency - it's a clue on the flicker.

 

[FilterGuy]

I do not believe that this is allowed anymore.

It is required to ground metal plumbing, but it is no longer considered sufficient for establishing earth ground.