SMA Tripower Core1 Arc Faults

ggunn said:
Simply that problems with RS devices in general can be a result of inverter - RSD incompatibility.
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That, and I have some experience with crosstalk issues in multi-inverter PV systems with SMA inverters and RSDs.
 
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ggunn said:
A couple of things...

One is that what you speak of is not the only possible effect of crosstalk. In one system we installed with two SMA inverters, when we started one inverter it came up and worked fine, but when we turned on the second inverter, about half of the strings on the first inverter went into shutdown. We had run some of the DC conductors for both inverters in the same cable tray and the keep alive signals from the inverters were not in sync, so some cancellation occurred and some of the RS boxes lost the signal.
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First time I have heard of this complaint. Everyone I have heard from talking about crosstalk it's that they can't get just one inverter's array to shutdown while the other are up.

ggunn said:
The other is that (as in what you said) one inspector failed an inspection of ours because when he turned off the breaker to one of the ten SMA inverters, not all of its strings went into shutdown because of crosstalk from the others. I pointed out to him that the code only requires a singe RS initiator (in this case the PV disco on the whole system), but he was having none of it. In order for us to satisfy him we had to not only separate the DC conductors to the array to each inverter from the others, but we also had to air gap the racking for each inverter's modules and ground them separately. It was a laborious and expensive PITA.
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You have a way of finding inspectors who just don't seem to care what the NEC says if it does not agree with their personal beliefs. It's quite a knack. :)
 
pv_n00b said:
You have a way of finding inspectors who just don't seem to care what the NEC says if it does not agree with their personal beliefs. It's quite a knack. :)
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Mostly it has been just a few of them whom I have repeatedly encountered.
 
pv_n00b said:
First time I have heard of this complaint. Everyone I have heard from talking about crosstalk it's that they can't get just one inverter's array to shutdown while the other are up.
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It surprised me as well.
 
Coincidentally, just today I found out one of my inverters in my home system, a SB 7.0 with no RSD, was not working. The event was series arc string A, and also an 8206 electric arc detected. SMA helped me reset it and it seems to be fine now. I inspected the wiring but did not see any issues . I'll have to keep up closer eye on it and see if it happens again.
 
electrofelon said:
Coincidentally, just today I found out one of my inverters in my home system, a SB 7.0 with no RSD, was not working. The event was series arc string A, and also an 8206 electric arc detected. SMA helped me reset it and it seems to be fine now. I inspected the wiring but did not see any issues . I'll have to keep up closer eye on it and see if it happens again.
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I had two customers the past 2 weeks ith Solaredge inverters in lockout due to arc fault. One was cleared by restarting / resetting the inverter and problem has not recurred, the other is reporting the same error after restarting, and I'm going to the site Friday to check the PV.
 
ggunn said:
A couple of things...

One is that what you speak of is not the only possible effect of crosstalk. In one system we installed with two SMA inverters, when we started one inverter it came up and worked fine, but when we turned on the second inverter, about half of the strings on the first inverter went into shutdown. We had run some of the DC conductors for both inverters in the same cable tray and the keep alive signals from the inverters were not in sync, so some cancellation occurred and some of the RS boxes lost the signal.

The other is that (as in what you said) one inspector failed an inspection of ours because when he turned off the breaker to one of the ten SMA inverters, not all of its strings went into shutdown because of crosstalk from the others. I pointed out to him that the code only requires a singe RS initiator (in this case the PV disco on the whole system), but he was having none of it. In order for us to satisfy him we had to not only separate the DC conductors to the array to each inverter from the others, but we also had to air gap the racking for each inverter's modules and ground them separately. It was a laborious and expensive PITA.
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Bless your heart. I always debate code with inspectors in a curious and professional manner. I get along with 99.9% of inspectors out there because I do know my code well, and when I am missing something, I am able to admit fault and adjust. I'll even change things that I think are silly if it makes the inspector happy and is not too costly. I look at it as a show of respect to the inspector, plus, of course, there is that whole 90.4 thingy ;).

But doing all that crap because the inspector thinks he is an engineer now and knows better than the manufacturer, no sir. Interpretations by the AHJ that have such significant impacts have to be established in writing ahead of time and not pulled out of a hat as a "gotcha". So, unless you can show me a local ordinance that was written before I applied for this permit, then I'm fighting tooth and nail and probably putting strychnine in the quacamole before I let an inspector bleed all that time and money out of me just to make him feel better about unqualified persons servicing the array and hurting themselves.

Rant over... Kind of.

Furthermore, crosstalk issues that create thermal events have been addressed by manufacturers by either getting away from PLC and going with a separate data cable, or by syncing all of the PLC signals so the contactor in the RSDs doesn't start opening and shutting out of confusion. Infact, I went searching late last year for any new guidance from SMA and/or JMS about cross-talk mitgation and couldn't find anything. The closest thing I found was a small mention in the APsmart manual that said to keep conductors from different transmitters apart by 'X' amount of feet unless the inverter manufacturer has internally addressed the issue (which they have by ensuring the signals are all synced up).

I swear, sometimes I wonder if all this PITA RSD and 3741 crap was just cooked up by "big micro". lol
 
We have also seen a recent increase in nuisance arc fault errors. My tech told me that SMA has blamed the shade-fix on some sites. We always keep ferrite cores in our service vans in case they encounter a site with welders or other large equipment that could mimic an arc-fault. Even though that is on the AC side, it was pointed out that sometimes the sensor can see that on the DC side and trip. Ferrite cores were the solution for attenuating the arc "signal" in order to avoid the nuisance trip.

We aren't sure what is happening right now, but I am very suspicious of the firmware. And unfortunately, it is probably a firmware that they have to have tested by UL before pushing out a fix, like with the ARTX and BFD boards we kept having to swap out back in 2020/21 while waiting for the new firmware to be listed. In the meantime, we will continue to bleed out on service calls until someone can figure out what is happening. I recently told my tech, that after he has done a comprehensive inspection of any ground-mounted PV system and verified all connections, to go ahead and disable the operation inhibition until further notice, since the NEC has an exception for arc fault requirements on ground mounts.

I guess I'll also be waiting for a long time to get this final payment from a developer as well because a 6-month-old site just had a crap ton of seemingly random arc faults start showing up as well. ugh

I like SMA for many reasons. They are typically bulletproof; the issues are rare, but when there is one, they fix it, and it's gone. But sometimes it can take a while for Germany to get those fixes figured out.
 
solarken said:
Are there any UL3741 certified systems for sloped roof, metal roof, non-ballasted applications?
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I was on Sunmodo's website recently and saw that they now have a 3741 listing for one of their rooftop racks. It looks like manufacturers are bringing back the shutdown boxes similar to what the 2014 cycle (or original iteration) of 690.12 had produced, but without the "Birdhouse" switch, lol. Who remembers that one? I think it was midnite solar that went all in on the birdhouse theme.
 
McMac said:
I was on Sunmodo's website recently and saw that they now have a 3741 listing for one of their rooftop racks. It looks like manufacturers are bringing back the shutdown boxes similar to what the 2014 cycle (or original iteration) of 690.12 had produced, but without the "Birdhouse" switch, lol. Who remembers that one? I think it was midnite solar that went all in on the birdhouse theme.
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The problem all manufacturers have with 3741 listing of residential racks is that since the inverter will not be installed within the array boundary there needs to be a SID at the array boundary to satisfy 690.12(B)(1). So far there are not many canned options. It requires a remotely controllable disconnect which then needs a remote RSD initiation device.
 
McMac said:
Bless your heart. I always debate code with inspectors in a curious and professional manner. I get along with 99.9% of inspectors out there because I do know my code well, and when I am missing something, I am able to admit fault and adjust. I'll even change things that I think are silly if it makes the inspector happy and is not too costly. I look at it as a show of respect to the inspector, plus, of course, there is that whole 90.4 thingy ;).

But doing all that crap because the inspector thinks he is an engineer now and knows better than the manufacturer, no sir. Interpretations by the AHJ that have such significant impacts have to be established in writing ahead of time and not pulled out of a hat as a "gotcha". So, unless you can show me a local ordinance that was written before I applied for this permit, then I'm fighting tooth and nail and probably putting strychnine in the quacamole before I let an inspector bleed all that time and money out of me just to make him feel better about unqualified persons servicing the array and hurting themselves.

Rant over... Kind of.
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The inspector in the case considered himself to be the AHJ (he said so to me in so many words), and he had no technical oversight in his chain of command. His boss was a really nice guy but he neither knew the code nor electrical theory. The inspector made up code on the spot and was the last word in enforcement; there was no one above him to whom we could appeal to challenge his antics. It was a systemic problem in the municipally owned POCO; we had no recourse short of filing a lawsuit and possibly waiting months or years for it to be resolved. We (our management) caved.

Addendum: As a result of many complaints from solar companies, the inspector was eventually relieved of his duties as Chief PV Inspector and reassigned to the meter shop. We all breathed a sigh of relief, but then he came out to set the PV meter on a supply side interconnected system where he refused to set the meter because he didn't like that the POI was in a gutter. Here we go again... Was it a coincidence that the installer of the system was one of the complainers that got him reassigned? I think not.
 
pv_n00b said:
The problem all manufacturers have with 3741 listing of residential racks is that since the inverter will not be installed within the array boundary there needs to be a SID at the array boundary to satisfy 690.12(B)(1). So far there are not many canned options. It requires a remotely controllable disconnect which then needs a remote RSD initiation device.
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I mean, depending on the AHJ, I'm not afraid of a little redneck engineering if they'll let me. I haven't looked yet, but if I could find such a thing, all I'd need is N.O. DC contactor with 120V AC coil voltage, powered from the AC combiner or the PV disco (using my tap rules in 240.21), and Bob's your uncle.
 
Hey, I learned a little troubleshooting tip from my tech today on this issue. We had to go back out and work with a developer on thier box store project we just installed. The developer also mentioned that it wasn't until the new SBSE and STPX that they started noticing all these arc fault issues come up so my inner slueth is telling me this is totally a firmware issue.


Anyway, sorry, the good stuff now. So my tech picked this up from Tier3 tech support when he was out at a GM recently, before they just turned off the interupter. He said;

"if you're seeing arc faults on a Core1 and you're not sure if they're real, you can have the inverter perform a curve trace. And if the fault is real, the curve trace will force an arc and fault out the inverter."

And he did clarify that the STPX models can't run the curve trace, so it's just for the Core1s.

Hope this helps while we wait for a fix
 
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