[RE-wrenches] FM80 failures due to arc faults

Wed Jan 26 12:37:31 EST 2022

It’s the gfi breaker that’s tripping right?  

There is another possibility. I’ve seen extremely high loads with weak batteries cause the capacitors in the CC to dump causing the breakers to trip.  

One easy fix is to install more wire between the CC and the battery or a smaller size, within ampacity ratings of course. 

It acts like a choke and the CC can’t dump as fast, it’s worked for me many times in the past. 

Another option would be to install soft start controls on the fans, and /or delay timers so they don’t all turn on at the same time. 

As to the classic not tripping, it’s got a special circuit inside that prevents this dumping of the capacitors. 

Jay

> On Jan 26, 2022, at 10:10 AM, Nick A Lucchese <lucchesesolar at me.com> wrote:
> 
> Thanks Alan, Mac, Jerry and Maverick. Alan, I like your idea of replacing all the FM80’s with Classics. I have had one Classic loaner recently fail there but to be fair I’ve been using it at random sites for years and it has a 2014 manu date so I’m okay with it’s years of service. Maybe I can find a deal on a half dozen of them from the recent DC Solar auctions. All the PV lands on a designated shunt so even though I’d lose some of the granularity in Opticsre I’d still be able to see the sum of current. I think perhaps all of those Classics from DC Solar don’t have internet connectivity either?
> 
> Maverick, yes they are at the end of the 1300’ run. I’ve not gone into his building over there in a long time to check the fans but will do so next time I’m out there. Thanks for the ferrite core suggestion too. Seems like an affordable effort at this point.
> 
> Mac, no Tigo’s on this job since it’s an Ironridge SGA ground mount. Yes I’ve been picturing that long run as a huge antenna as well. It now makes me realize that is something else unique about this site is it’s long wire run itself in addition to the lack of ground. Can’t think of any other off grid sites of mine with such a significant run.
> 
> Jerry, I’ve been through all the connections but always helps to keep looking for the fine details. I will say getting the #4 into the Classic's terminals is a bit frustrating especially with a conductor that’s been in and out a few times, been wishing that part of their controller would get an upgrade for years. I’ve had to trim off the ends and shorten the conductor every time to get a connection with integrity. Going to have to replace the conductor to the 100 amp GFP if this keeps up.
> 
> Thanks for the thoughts. I think the next logical attempt to suppress the spikes will be trying the ferrites as Mac suggested. Hope you all have a great day out there. Off to work, Nick
> 
> 
>> On Jan 26, 2022, at 4:57 AM, Mac Lewis <maclewis1 at gmail.com> wrote:
>> 
>> Hi Nick,
>> 
>> Do you have any rapid shutdown equipment on the arrays?  The only charge controller (Midnite CLassic) that we have ever had that failed with a short on PV Input, had the Tigo Shutdown boxes on them (TS4-AF).  I have always been curious if that failure mode was due to the Tigo signal somehow.
>> 
>> To me, the consistent failure mode of the short on the PV input is an important clue to someone (not me) as to what is happening.  I was always under the impression that the isolation transformers in the inverter did a good job filtering arc faults on the AC side but that 1500' wire run is a huge antenna!
>> 
>> Good Luck out there!
>> 
>> 
>> 
>> On Wed, Jan 26, 2022 at 12:29 AM Nick A Lucchese <lucchesesolar at me.com> wrote:
>>> Hello again Wrenches,
>>> 
>>> While the failed controller topic is fresh I want to ask opinions/advice on arc faults. I know quite well that they can be mysterious so not sure I’ll really get anywhere but here goes. This particular off grid system consists of two Radians, 2 GSLC’s, FNDC, a 25.2 KW array and 6 FM80’s. 4.2 KW STC into each controller which I now know is over their new recommended max wattage after they changed the spec sheets on us a couple years ago without renaming it an FM70. The system has been in for over 5 years now but from the beginning I’ve had a large amount of failures with the FM80’s failing and registering a dead short on the PV input side of the controller. Not exclusive to any one of the six arrays and I’ve definitely gone through to torque and tighten all of the connections. I’ve tried other controllers throughout my troubleshooting and concluded it’s arc faults for a few reasons. Mainly, as long as I have a Midnite Classic installed with the other 5 FM80’s it will absorb the arc fault and just go to it’s temporary state of displaying an arc fault and after I reset it everything starts back up and operates normally. Survives the incident without failure unlike the FM80 and at the same time protects all the other FM80’s. When the site goes back to FM80’s exclusively the failures are inevitably more frequent. I’ve also installed a Magnum PT100 for awhile to see if it would fail too but it survived for over a year before I terminated that particular test.
>>> 
>>> Luckily, one of the times I was there when an FM80 failed so I was able to see that it coincided with some fans (obviously on the AC side) that had kicked on when I observed usage on his Egauge (system has Blue Ion 2.0’s and HI's). I have also been able to determine it’s likely some fans because the long durations without failures also coincide with long periods without the fans although failures are still happening sometimes and he says he’s changed up his fans. The Egauge has been a very useful tool for various reasons but unfortunately I can’t pinpoint when the units fail since they often go unnoticed until I am at the site or notice low PV production on Opticsre. I just happen to get lucky the one time I was there to correlate the exact moment with the fans.
>>> 
>>> One major detail that makes this site different is that after my initial install work he had some other yahoos in to pull the feeders to power his other subpanel some 1300’ feet away. Unfortunately they did so without pulling an equipment ground along with the power conductors so the two sides do not share a common ground. This is the most major deviation from any of the other systems I’m responsible for and this is the only site I have frequent high rates of unwarranted controller failures. I’m uncertain if the failures are due to AC ripples/transients from the extremely long run, lack of common ground or perhaps one particular appliance. My preferred solution in the process of elimination is fixing the lack of common ground by re-pulling all the conductors with an EGC but that would not only be expensive but quite difficult as he just informed me the other day that there are no pull boxes in between the two destinations. I wish I could just walk away from any responsibility since their foolish decision not to pull the EGC originally was not a mistake of mine but I really need to help him resolve this since replacing the FM80’s so often is obviously expensive as well as time consuming. Obviously it would be extremely frustrating and defeating if he were to go to all the effort of pulling the new ground and the failures still occur.
>>> 
>>> I thought about replacing the 6 FM80’s with 4 FM100’s but that would require a profound amount of work by the time I change up the array strings and OCPD’s plus I’d have to re-imagine placement due to the physical differences. To avoid nuisance tripping, I already have the Midnite 100 amp GFP assemblies in place and am adding two more Radians with GSLC’s so feasibly would have the accommodations as far as space for OCPD’s are concerned. We do plan on expanding his arrays soon so at some point I will have to address this known snag of mixing FM80’s and 100’s in the same system as recently discussed on the list. Thinking I might try this mix approach on my own house for awhile but not rushing to deploy at any client sites.
>>> 
>>> Any ideas? Suck it up and have him pull a ground 1300’ at today’s copper prices? I’ve got Midnite SPD’s on all the arrays as well as the AC side but perhaps there’s some other sort of additional surge suppressor or something I can install to suppress arc faults originating on the AC side? WWWMD (what would William Miller do)? Only half joking here, I often find myself asking that when I encounter some sort of unusual solution required to balance something out of the ordinary and William’s procedures have impressed me for decades. No offense to the rest of you pro’s though, his meticulous documentation and notes just appear levels beyond (especially speaking for myself)!
>>> 
>>> Off to work, enjoy your day, Nick
>>> 
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>> 
>> 
>> -- 
>> 
>> 
>> 
>> Mac Lewis
>> 
>> "Yo solo sé que no sé nada." -Sócrates
>> 
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> 
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