When Is A Panel Bad?

[geostrick]

I have a thirty-panel array on south facing roof with no obstructions and just completed two years of operations. The panels have to date met the proposed annual output at the time of purchase. The panels and inverters have a 25-year warranty, parts only. In monitoring performance, I am noticing a disparity in individual panel performance. Some panels are not performing like the rest. Three of the panels only report 1/2 to 3/4 of the output of the balance which may have a range of +/- 5%. At what point do I complain to the installing company that the panels are "not performing" and should be replaced per warranty? I am struggling finding literature to address this issue. There is an install cost to replacement panels that must offset the cost of power lost, but I have 23 years remaining on the warranty. Any thoughts? Help? Experience? Thanks

[J.P.M.]

Start with a careful read of the contract you signed. See what it says about what you bought and how it's intended to perform.
Then, double check your equipment information and understand how your system works.

Depending on what U.S. state or what country you live in, part of what you paid for is a warranty of the equipment and probably at least some of the labor to fix problems that arise is covered either through the installer or the equipment manufactured or by statute.

After your further self education, call the installer and inform them of your suspicion that your equipment seems to be malfunctioning and why you have that oipnion.

Most every reputable installer wants to have the equipment they installed running as intended.
They are also the best source of information, diagnosis and correction of system problems. Use them as a resource for further information.

Give them a call and an opportunity to straighten things out.

As to advice or troubleshooting from this end, you will need to provide more information about your system before anyone here can take a guess about what's going on and without being on site it'll still be a crap shoot compared to inspection by someone who's there to look and poke around.
But, as a SWAG only, sounds like you have micro inverters or optimizers, and a couple may have failed. Either that or a wiring problem of some sort.

Call the installer and give them an opportunity to straighten things out.

Welcome to the neighborhood.

[bcroe]

Assuming no shading issues. In my opinion the failure is more likely a
micro inverter or optimizer problem, than a panel. If so it may well get
worse soon. good luck, Bruce Roe

[SamirD]

I posted a similar question earlier today because from what I've read on enphase community is that a percentage drop like 1/2 or 1/4 indicates a bad diode on a panel which will usually have multiple diodes, hence the fractional drop like that.

[geostrick]

Thanks, guys. The information has been very helpful. I did go back to the warranty on the panels and found that they are warranted for 94.5% of the initial power levels in the specs based on the time in service. Interestingly, you have to take 94.5% of the average of the array. For a one-month period, I found that 5 of the 30 panels do not produce up to 94.5% of the average for that month. This is enough information for me to contact the installer and get him involved. Of course, I don't know if the problem is in the panels, or in the inverters (Enphase individual inverters per panel), but I will lean on them to figure that out and repair one or the other. I observe that the panels in question are always deficient, I just used one month to capture the individual data to document the degree they are under-performing. Now, I have real work to do, because enforcing the warranty is a completely different animal. Thanks, again.

[SamirD]

Best wishes in your warranty journey. I will be watching your process as I know I have a panel that's not performing as well and Peterson Dean is long gone.

[davidcheok]

[QUOTE=geostrick;n441007 For a one-month period, I found that 5 of the 30 panels do not produce up to 94.5% of the average for that month.[/QUOTE]

And how did you come to that conclusion? Keep in mind that a panel's output depends on multiple variables which are often not consistent day to day ranging from solar irradiation at a time of day, ambient and panel temperatures and even cloud cover.
If you install a pyranometer and a weather station that records data and then find that the panels maximum output keeps decreasing with consistent environmental factors, then you have something to based the claim on. On top of that, panels do not all perform identically due to inconsistencies in the manufacturing process or ingredients or even inverter quirks.
I would minimise the urge to nitpick and stress yourself over little things like these. As long as overall, you are getting enough energy as a whole, just enjoy it. I would worry when a panel consistently produces less than 50% on a bright sunny cold day and look at whether the diodes have activated maybe due to broken connections or even the inverter itself. But 10% only, i wouldnt sweat it. Life is too short.

[Rade]

...when it gets bad tattoos and takes up smoking?

Joking aside; we're still new to our solar installation - about 5 months in. I watch our system through the online app, and am now fairly versed in the about how much power we should expect when the sun is at a given point in the sky. If I see the production numbers drop and remain down (our network bounces a lot), I will look at the PVLinks through the inverter screen for any issues. We had one array that developed a hairline crack on one panel, and during a torrential rainstorm, put that array into ground-fault mode. Luckily our installation is still covered under full warranty, and it took them around two weeks to get the replacement panel in, installed and the PVLink reconfigured.