non-grounding solar panels

so in relation to MPP solar inverters one thing on my inverter and the replacement I am looking at is they state"Be sure to use Non-Grounding solar panels, because they will cause current leakage".. ok..

so after a quick google search I could not find any info on this ie.. "how to know if your solar panels are non-grounding"??

I hope someone here can shed some light on this.. I have Trina TSM-250PC05A panels.

Non-grounding solar panels means you don't connect the Negative terminal to the frame to ground it. At least, this is what I think that means.

The only thing that would be grounded is the frame and the structure (if made of metal). Maybe even the frame wouldn't be connected and you'd use rubber washers to keep them separated from the structure frame

well I did think that originally. but when they suggested it was a type of panel it confused me. so your talking about grounding/earthing the panels such as lightening protection etc.? or is there types of panels which actually are wired up like that and grounded to frame?

most panels I look at are alloy framed ones, if they do not have a wire connecting from the black box to the outter frame, would one be safe to assume that it is then "Non-grounding" ?
Cheers,

I think a lot of panels that are considered grounded have a grounding wire inside the black box on the back of the panel. You might be able to disconnect this wire and separate the frame from the cells.
Again, I'm not entirely sure and I'm hoping someone with more solar panel knowledge chimes in, as I'm also interested in this clarification.

Did some digging, and it might have to do with this:

https://iaeimagazine.org/magazine/features/ungrounded-electrical-systems-ungrounded-photovoltaic-pv-systems-what-is-the-world-coming-to/ said:

In utility-interactive PV systems, the inverter can be greatly simplified to a conceptual switching device and a filter with other added control components. Of course, how the utility-interactive inverter actually works is far more complex. The switch reverses the polarity of the dc output from the PV array 120 times per second to generate a 60 Hz waveform that is shaped into a sine wave by the filter. In Europe, they use 100 switches per second to get 50 Hz. Because the European PV arrays and the electrical system are ungrounded, the PV utility-interactive inverter can be relatively simple compared to what is required in the United States. In the U. S., with a grounded circuit conductor from the PV array and a grounded circuit conductor in the ac inverter output circuit, it is not possible to use a direct switching device because the switch would be shorted as it tried to reverse the polarity of the dc circuit into an ac signal. A transformer is required in inverters used in the U. S. to isolate the grounded dc circuits from the grounded ac circuits. The transformer is usually a heavy, costly, and bulky device that decreases efficiency, increases the size, and increases the shipping costs of the inverter.

U. S. inverter manufacturers and inverter manufacturers in the rest of the world can now sell transformerless inverters in the U. S. Those inverters must be used with an ungrounded PV array, and theNECallows such ungrounded PV arrays (see 690.35).

Click to expand...

I am guessing maybe others haven't come across the issue because most of the solar charger controllers (regardless of what equipment it's installed in) is either already isolated or they use a large transformer. So the short circuiting effect doesn't happen.
Interesting

Korishan said:

https://iaeimagazine.org/magazine/features/ungrounded-electrical-systems-ungrounded-photovoltaic-pv-systems-what-is-the-world-coming-to/ said:

In utility-interactive PV systems, the inverter can be greatly simplified to a conceptual switching device and a filter with other added control components. Of course, how the utility-interactive inverter actually works is far more complex. The switch reverses the polarity of the dc output from the PV array 120 times per second to generate a 60 Hz waveform that is shaped into a sine wave by the filter. In Europe, they use 100 switches per second to get 50 Hz. Because the European PV arrays and the electrical system are ungrounded, the PV utility-interactive inverter can be relatively simple compared to what is required in the United States. In the U. S., with a grounded circuit conductor from the PV array and a grounded circuit conductor in the ac inverter output circuit, it is not possible to use a direct switching device because the switch would be shorted as it tried to reverse the polarity of the dc circuit into an ac signal. A transformer is required in inverters used in the U. S. to isolate the grounded dc circuits from the grounded ac circuits. The transformer is usually a heavy, costly, and bulky device that decreases efficiency, increases the size, and increases the shipping costs of the inverter.

U. S. inverter manufacturers and inverter manufacturers in the rest of the world can now sell transformerless inverters in the U. S. Those inverters must be used with an ungrounded PV array, and theNECallows such ungrounded PV arrays (see 690.35).

Click to expand...

Click to expand...

Interesting... Maybe something like this is what killed my Reliable 3000w inverter when I hooked the house (US AC) ground to the inverter ground. The fine print of the inverter manual says 'don't do it' - but I didn't read the fine print till it was too late.

Almost No panel is grounded via the negative lead. Wouldnt work since you would not be able to Connect Them in series......


That is an old statement and doesnt really apply today. The framme of the panel is not connected to the electronics part

The wording "Be sure to use Non-Grounding solar panels, because they will cause current leakage" suggests that that inverter is sensitive to ground leakage issues between panel's silicon cell strings & the panel's frame (should be grounded for safety, no question there).
Panels may have gotten better recently but a few years back a common fault was this leakage to the frame. In lower voltage systems it would be less of an issue but in higher voltage eg 400-800VDC or so strings (before they were limited to max 600V I think) it was worse.
The OP's Trina panels (one of the best brands) should not have leakage issues & as manufactured, the cells will not be connected to the frame in the junction box - the strings of cells inside will be isolated. Like daromer mentions, they couldn't be used in the mass market systems (solar > inverter > grid) if they were.

If that inverter has issues with safety ground on the panel's frame, another brand/model might be a better choice...

This is the statement from MPP Solar's HV2-5048

PV panel selection for HV2 models
Because the HV2 is designed based on high PV input which should require uses to wire panels in series as much as possible, without exceeding the max PV input limit. When selecting panels, be sure to use “non-grounding” panels as otherwise this could cause a leakage current problem on the HV2 inverters which are non-isolated design.

Click to expand...

I have two strings of 8 normal 250 watt panels properly earthed with bite in clips and separate green yellow grounding wire on the mounting rails down to the combiner box where I have a breaker and a lightening arresting clamp which is also earthed on each string before combining . Input voltage on each string is less than 300V DC.

The inverter ,the combiner box ,the panels and the RCD on my 240v outlets are all earthed to the ground rod . My Inverter runs as normal so far and I have seen no issues yet.

My Grid is not connected to this inverter but Australian Grid is 240 volts single phase . That entails the neutral wire being earthed/grounded in the meter box . So fingers crossed you are correct Redpacket. Its only been properly earthed for about 2 weeks. The two grounding rods , mine and the grids are about 20 feet physically apart in the ground.


EDIT 22/4/21
I have since confirmed in Australia that my MPP solar Inverter needs the neutral to be joined to the earth in the inverter . If that is not done having your laptop connected to the grid supply and connecting the usb cable attached to the inverter may blow your software monitoring cable and I noticed this because when plugging the usb cable to the laptop a spark jumpped across which turned out to be about 100 volts.