SMA troubles

[jma]

We had a solar system installed that went live(net metering) on 08/11/19. Since then it has not worked properly for more than 2 consecutive days. I stops and shows error 4301 which as far as I have been able to find out, means loose connections somewhere.
The installer has been back 3 times to update the firmware, software, and to reset the inverter, so we have been told. To make matters worse, this is our second home, we don't live there. We were there during the install and we were assured all was well. Not so far. The unit the installer used was an SMA Model SB7.7-1SP-US-40, built 05/2019. It handles 24 Mission Solar panels. The installer now claims that SMA has been having issues with newer units and are working on a fix.
Before I escalate this matter is anyone aware of such issues? Are firmware or software updates a valid course of action? Getting answers from SMA on my own has been impossible, just can't stay on hold forever.
Any help or guidance in this matter will be much appreciated.

Thanks.

[solarix]

Error code 4301 is an arc fault. The bane of solar installers. It means there is a loose connector somewhere in the array. Often times is hard to find the problem connection among the dozens of them up there. And arc fault is almost always an intermittent problem making finding it worse. Could be a slight mismatch between brands of connectors. There are quite a few brands of the "standard" solar wiring connector and they are not all perfectly compatible. Rarely do these arc fault problems cause a real problem or failure - its just that the newer inverters are now very sensitive to it and are required to shut down until investigated. A lot of nuisance trips, but good in the end to catch faulty connections sooner than later. You need to just hang in there and keep riding your installer until they find the needle in the array haystack. Arc fault sensing became a UL requirement a few years ago, and all the inverter brands have trouble with it.
BTW, This is the number one reason for not doing solar roof tiles which have ten times the amount of connectors up on the roof under those tiles in hot, moist conditions.....

[oregon_phil]

I have had the dreaded 4301 arc fault (nuisance, not real). I have a pile of questions for the OP.

Do you have direct INSTALLER access to your inverter?
Are you signed up for Sunny Portal?

With either, you can download your entire list of faults by date/time and can tell me what version of firmware is loaded to your system.

How is you system configured? Strings, panels, rapid shutdown?

Where is your inverter installed?

More questions, but have to go now.

[jma]

Solarix: Thank you for the detailed response, way more informative than anything I had been told by the installer.

I have had the dreaded 4301 arc fault (nuisance, not real). I have a pile of questions for the OP.

Do you have direct INSTALLER access to your inverter?
I do not have access to the inverter, the plan was to have set up access this past weekend but Dorian forced a change of plans. Plan to do it on my next visit at the end of the month, second home, we don't live there.

Are you signed up for Sunny Portal?
I tried, created a profile but that was it.

With either, you can download your entire list of faults by date/time and can tell me what version of firmware is loaded to your system.

How is you system configured? Strings, panels, rapid shutdown?
Not quite sure I can answer this one but I will try: Rapid shutdown, yes. If you mean roof panels, yes, 24 from Mission Solar. I don't know the answer for strings, sorry for my ignorance.

Where is your inverter installed?
Outside, north wall, the least exposed to sun and wind from the coast.
Along with the error the inverter also shows an incorrect date.

Thank you for your questions, I'm learning more and more. Ask away, I'll do my best to answer or get answers from my installer.


More questions, but have to go now.

[oregon_phil]

You have the same set up as I do. SMA rapid shutdown box with secure power outlet. Yes the 4301 error code says you have an "arc fault", but lack so much more potential information. Tell you installer to set up your sunny portal account with your inverter and have them tell you how to access it.

Tell the installer to provide you with a schematic of your system. There's lots of info on the schematic.

In the meantime, ask your installer to access the inverter and download the system logbook (which has all system faults, system restarts, etc)..

For the days that the systems faulted, what does the power output graph look like? Tell your installer to provide this too.

[oregon_phil]

Another thing I thought of is that installers don't always read the fine print in the manuals and assume they followed the schematic.

At the very start of my install, I had 4301 errors due to the way the rapid shutdown panel was wired to the inverter.

Since you have 24 solar panels, I am going to assume you have three strings of 8 panels. This is an assumption, but if I'm wrong then all bets are off.

The SMA inverter has 3 MPPT inputs A,B,C. The rapid shutdown box has four inputs (String inputs 1,2,3,4) but only two outputs A&B.. String inputs 1&2 are combined in the Rapid Shutdown into output A; String 3&4 are combined into Rapid shutdown output B. String 1&2 MUST be identical string lengths and panel type. Same goes for string inputs 3&4, but since you only have three strings, you don't have to worry about this.

Rapid shutdown output A must be uncombined in the inverter into INVERTER INPUTS A & B. This is called a parallel input. The SMA 7.7 will only accept parallel inputs on INVERTER INPUTS A&B. IF THE INPUTS ARE UNCOMBINED INTO INVERTER INPUTS A & C OR B & C YOU WILL GET A 4301 ARC FAULT. String 3 should be wired into inverter input C by itself.

Your installer must verify this on site and not by looking at the schematic. While they have the unit open, have them take a picture of the interior of the unit so you can see how clean they are with the install.

Read the manuals while you are waiting for your installer to do all this for you.

[nwdiver]

Another thing I thought of is that installers don't always read the fine print in the manuals and assume they followed the schematic.

At the very start of my install, I had 4301 errors due to the way the rapid shutdown panel was wired to the inverter.

Since you have 24 solar panels, I am going to assume you have three strings of 8 panels. This is an assumption, but if I'm wrong then all bets are off.

The SMA inverter has 3 MPPT inputs A,B,C. The rapid shutdown box has four inputs (String inputs 1,2,3,4) but only two outputs A&B.. String inputs 1&2 are combined in the Rapid Shutdown into output A; String 3&4 are combined into Rapid shutdown output B. String 1&2 MUST be identical string lengths and panel type. Same goes for string inputs 3&4, but since you only have three strings, you don't have to worry about this.

Rapid shutdown output A must be uncombined in the inverter into INVERTER INPUTS A & B. This is called a parallel input. The SMA 7.7 will only accept parallel inputs on INVERTER INPUTS A&B. IF THE INPUTS ARE UNCOMBINED INTO INVERTER INPUTS A & C OR B & C YOU WILL GET A 4301 ARC FAULT. String 3 should be wired into inverter input C by itself.

Your installer must verify this on site and not by looking at the schematic. While they have the unit open, have them take a picture of the interior of the unit so you can see how clean they are with the install.

Read the manuals while you are waiting for your installer to do all this for you.

If this install is NEC 2017 compliant and was installed after Jan 1 then it won't have a shutdown box. Each panel will have a TS4. The bad string could still be ID'd by operating one string at a time.

[oregon_phil]

I agree with you if NEC 2017 compliant. That 2014 shutdown button below the inverter is what I have (install in 2018).

[jma]

Thank you oregon_phil and nwdiver. I'm going to use your knowledge and ask my installer for specifics. Almost a month now, not very positive results. Now that the threat of Dorian has passed, I'm going to insist they get on this so I get what I paid for.

[nwdiver]

Thank you oregon_phil and nwdiver. I'm going to use your knowledge and ask my installer for specifics. Almost a month now, not very positive results. Now that the threat of Dorian has passed, I'm going to insist they get on this so I get what I paid for.

Have you been reseting the faults or does the inverter stay offline? I had one 4301 fault but I reset it and it hasn't come back in >4 months.

[jma]

Have you been reseting the faults or does the inverter stay offline? I had one 4301 fault but I reset it and it hasn't come back in >4 months.

My neighbor has reset it a few times. Lat reset was yesterday, each time the inverter goes offline shortly after. Last week it worked for two consecutive days, just that one time after a firmware update and reset by the installer. This is very frustrating to say the least.

[oregon_phil]

It's important to rule out potential causes before resetting an arc fault error. The manual says a 4301 arc fault reset must be done by a qualified person. In my case, I'm a retired mechanical engineer and walked through my potential problem matrix with my installer before we both agreed to perform a manual arc fault reset. If it is truly an arc fault, then repeating a manual arc fault reset many many times is the last thing you want to do.

If you read up on inverter arc fault sensing, the inverter is trying to measure arc fault noise on the DC lines vs all the other noise on the lines. I'm sure this is very difficult indeed.

Are all the terminals, ground lugs, electrical connections tightened to spec? This includes the terminations in the rapid shutdown box. SMA likes to use spring loaded electrical connections in many places.
Are there any loose wire strands not properly terminated?
My install required dielectric grease on the internal connections.
Are low voltage DC wires and AC wires separated properly in the inverter?
Is there a wired ethernet or wireless connection?
Are there any open knockouts in the inverter? Are all the wires/cables sealed properly?
Is there any abrasion of the DC wires at the bends of the conduit near the wire pull access points?

All of these questions were asked by SMA technical support after 2 to 3 hour wait.

At the start of my install, I had 4301 faults due to parallel Channels B&C instead of Channels A&B. That got fixed after two days and then I started getting nuisance arc faults about 1/month. That got fixed by verifying all the points listed above (again) and two firmware updates (now at 2.4.92.R) and turned automatic updates to NO since my system is now stable.

Stable enough, but then my display died about two months ago. I'm waiting for warranty replacement.....

[jma]

Thank you again oregon_phil for all your help. They will be back this week, I will have a ton of questions for them and expect answers to them all.

[oregon_phil]

One last thing before you talk to them (until this is fixed, it will bug me).

If your set up is 3 strings of 8 panels, it will be very difficult to determine the exact wiring unless they unhook one string and restart the inverter. I'm thinking they have to go up to the rapid shutdown unit because that's where wiring can get crossed.

Assuming the panels are wired incorrectly, if there is no shade and since all strings are identical, then all panels (therefore all MPPT trackers) will operate identically and might not trigger the arc fault circuit. The problem will occur when shade appears (due to whatever) causing one or more strings to act differently than the others. Good luck.

[jma]

Update:

The system has worked continuously since last Tuesday. I do not know yet what was done to correct the problem, even though I've asked the installer a number of times, very frustrating. I was told by SMA that they asked for instructions about new firmware, so I assume that at least the firmware was updated. The only way I know it's working is by looking at the the data from FPL, always 24 hrs old.

I also asked for the schematics and inverter's log but no luck so far. I'm planning to travel there in the next few weeks and talk to them in person. More to come, I'm sure.