How to Checkout Installed PV System?

[voyager]

About 6 years ago we had a PV system installed, 16 Solarworld 280w panels, with 16 Enphase M250 inverters, - a 4.5Kw system.

About 2 years ago we had a new roof put on.
They had to remove and replace the solar array to make the roof installation.

There was a problem with the re-installation of the PV system.
One panel ended up off line.

I called them back to fix the problem.
During the fix it became apparent that the "electrician" was not the brightest bulb on the string.
While standing on the ground, I had to point out to him what he was doing wrong.

To lower our electrical usage even more, we have had a solar hot water system added recently.
So far it's working great,
It has brought our electrical usage way down.

Again for the last few months, a single PV panel is off line.
It hasn't been a problem because of being on a Net Metering program in an unusually clear, sunny, drought period.
We have been over producing, building a credit, for the last several months.
I'm beginning to feel a need to get the problem fixed and increase our credit rate before the drought ends and our production slows down.

I assume it will entail checking the individual panel and inverter outputs.
Hopefully, all it will need is for connections to be cleaned up and reset.
Some panels may need to be removed to access the inverters.
So, how do I check out the functioning of the panels and inverters to locate the inoperative portion, an inverter and/or panel?

[Mike90250]

That's why I like string inverters, sitting at eye level.

If real clever, you might be able to use a FLR IR camera to photograph the panels several times a day. The one not producing, will be hotter, than the others (Its not converting 20% of the solar energy to electricity, it's all heat)

[voyager]

Thanks for your response Mike, but ...

Since the PV system was installed, I had lost all my browser access to info on the installation.
I have just worked out how to get that info back.
It is again in my browser Favorites.

I now have access to the onboard Envoy System information, giving me the serial number of the offline panel, and the Enphase website with its diagram of the dead panel's location, plus the day it went offline.
They have much more info between them than I need for this.

If it is in the location the diagram says it's in, it will be fairly easy to get to.
I don't necessarily trust the correctness of the diagram yet.
If not, I'll have to search out the panel.
I may need to take the panel loose to find the SN and check out the connections.

I would think an upscale VOM would allow me to pinpoint whether the panel or the inverter was the source of the problem, if they were still out with good connections.

If the foregoing is workable, it would be much easier and cheaper that your suggestion.
Thoughts?

[bob-n]

You suggest that there is a risk that the panel locations are not correct. An easy way to check that is to get a large piece of cardboard and cover the suspect panel, then check your generation. If no change, that's the location. You can then move the cardboard to any other location and look at the web to see if the right panel goes dark.

Next, you need to find out if it is the cable, panel, or microinverter that is bad. A VOM can tell you the open circuit panel voltage, but that isn't enough to tell you whether the panel is good or bad. Ideally, you would swap two panels. If the problem stays put, it is the microinverter or cable. If the problem moves, it is the panel.

If the cable is suspect, replace it. It isn't feasible or dependable to clean those contacts if they are corroded, and more likely, the housing is damaged.

If the microinverter is bad, you can get used M250 on ebay or other places. You can also replace it with a modern microinverter from the same manufacturer such as the IQ7. They play well together and will report just like the M250. But the IQ7 uses a different connector than the M250, so again you'll need new cable.

The cabling should be locked together, requiring a small plastic tool to separate. Some people do it with a couple of tiny screw drivers. Others just break off the locking tabs. But I suggest the right tool.

You didn't talk about panel mounting hardware, but that is often also very easy to remove and replace. Just torque everything to factory specs when reinstalling. A $10 Harbor Freight 1/4" torque wrench is fine for this job.

[voyager]

You suggest that there is a risk that the panel locations are not correct. An easy way to check that is to get a large piece of cardboard and cover the suspect panel, then check your generation. If no change, that's the location. You can then move the cardboard to any other location and look at the web to see if the right panel goes dark.

Next, you need to find out if it is the cable, panel, or microinverter that is bad. A VOM can tell you the open circuit panel voltage, but that isn't enough to tell you whether the panel is good or bad. Ideally, you would swap two panels. If the problem stays put, it is the microinverter or cable. If the problem moves, it is the panel.

If the cable is suspect, replace it. It isn't feasible or dependable to clean those contacts if they are corroded, and more likely, the housing is damaged.

If the microinverter is bad, you can get used M250 on ebay or other places. You can also replace it with a modern microinverter from the same manufacturer such as the IQ7. They play well together and will report just like the M250. But the IQ7 uses a different connector than the M250, so again you'll need new cable.

The cabling should be locked together, requiring a small plastic tool to separate. Some people do it with a couple of tiny screw drivers. Others just break off the locking tabs. But I suggest the right tool.

You didn't talk about panel mounting hardware, but that is often also very easy to remove and replace. Just torque everything to factory specs when reinstalling. A $10 Harbor Freight 1/4" torque wrench is fine for this job.

Thanks bob, that gets me started on fixing this.
Plus, going hands-on gives me much info about making this work without needing to bring an installer in to do it.

The cardboard is a good idea.
Reminds me of the "electrician's" problem.
He wasted over a couple of hours because the dead panel would move around as he laid down on and covered different panels.
Plus, he just slammed the panels back on the mounts with no rhyme nor reason to the order.

I'll start out locating the panels and placing them in the order on the diagram.
While doing that, I can locate any bad panels or microconverters.
If I need to replace any microconverters I think I can get them through Enphase.
Might cost a little more,but I'll get a guarantee for it to do the job.
Connections, cables, and everything else will get a good look-over too and replaced if needed.
Little doubt I have most if not all the tools needed.

Your post seemed to cover everything + that I was already considering.

[Mike90250]

When you pull the panel mounting hardware off, it's likely to seize and break, so have fresh SS hardware, and maybe some anti-seize goop to butter the threads with. It may be worth buying a couple of boxes of the correct sized SS hardware if you have more than a couple panels to sort through. Local hardware store might have enough to do one panel, but not for all .I like to suggest McMasterCarr for good hardware, shipped in a day.

https://www.mcmaster.com/screws/material~stainless-steel/

but they only have 17 grades of stainless steel, chose carefully

[voyager]

When you pull the panel mounting hardware off, it's likely to seize and break, so have fresh SS hardware, and maybe some anti-seize goop to butter the threads with. It may be worth buying a couple of boxes of the correct sized SS hardware if you have more than a couple panels to sort through. Local hardware store might have enough to do one panel, but not for all .I like to suggest McMasterCarr for good hardware, shipped in a day.

https://www.mcmaster.com/screws/material~stainless-steel/

but they only have 17 grades of stainless steel, chose carefully

HI Mike,
To be honest, I've never looked closely at the fastening and mounting gear.
It is new to me.
Not sure if the clamps are alum or SS.
Alum would be more likely to gall.
I'll probably oil all clamp screws before trying to remove them.
When they removed and replaced them a couple of years ago after at least 4 years in service, I don't think they had any problems with them.
Hopefully all will be OK this time too.
Will be ready to deal with them if not.
Thks