Flat maximum energy production

[scrambler]

For the shutdown of one inverter, I would do a few hours test rather than a few minutes
For the 2500W limit, you should do a full day test during a clear sky day to have clean data, especially the MPPT values

[smbunn]

its winter so cannot guarantee a long stretch of sunshine, not this week anyway

[smbunn]

So I have had quite a long run. Unit one with the 2,500 limit is clearly clipping at that limit regardless of what is going to or coming from the grid

solar2a.png

And unit 2 which has no limit is happily clipping along at 3,500 watts as we saw before

solar2b.png

Would you now agree that the clipping is not associated with my energy export?

[scrambler]

Can you share the data file of the 2500W clipping so we can check the MPPT values

[smbunn]

Here it is

[scrambler]

This seems to confirm that the MPPT raising voltage and dropping amps to do the clipping which is consistent with what we sam on the 3500W data.

If you did the test of shutting down one inverter and that did not affect the clipping on the other one, then the clipping is not at the grid level but at the inverter level.

So you are back to figuring out what is making the inverters do that...

As for your installer remark. You can tell him, that the sun makes an arc in the sky, and regardless of the season, on a clear sky day, this translate to a Bell curve for the solar radiation.
If all panels have the same exposure (which I understood is your case), they all have the same irradiation, and therefore the production curve will mirror the Radiation bell curve.
Depending on the Orientation, that bell curve can be skewed left or right, and depending on the season, the maximum reach will be higher or lower, BUT the curve will be a bell curve.

There is no natural phenomena that can make the solar radiation curve flatten (and therefore the production in your case). So something is purposely clipping your production and should not be any different when summer comes.

Good luck with them.....

[smbunn]

Awesome, thanks Scrambler

[scrambler]

One thing you could do to support your argument is use a Solar radiation monitor beside the Array, record that and put it in correspondence with the inverter solar production graph.

I had a bug in my inverter last year that the Provider refused to consider, but I have a small weather station that has a solar panel and records solar radiation during the day.
By graphing both Solar production and solar radiation together, it was clear the Solar production was not following solar radiation and so the inverter was up to something..

They finally agreed to look it up and did find a bug that was later fixed.

In your case I don't think it is a bug, but if they do not listen to a rational argument such as the one I mentioned previously, this could add some concrete element.

[J.P.M.]

One thing you could do to support your argument is use a Solar radiation monitor beside the Array, record that and put it in correspondence with the inverter solar production graph.

I had a bug in my inverter last year that the Provider refused to consider, but I have a small weather station that has a solar panel and records solar radiation during the day.
By graphing both Solar production and solar radiation together, it was clear the Solar production was not following solar radiation and so the inverter was up to something..

They finally agreed to look it up and did find a bug that was later fixed.

In your case I don't think it is a bug, but if they do not listen to a rational argument such as the one I mentioned previously, this could add some concrete element.

FWIW, I agree that irradiance monitoring is a good idea - I've got 1 minute monitoring records for almost 8 years continuous - but without care about how it's done in terms of instrument set up and then data interpretation and instrument calibration error it can create confusion, not to mention the lack of credibility if an installer knows anything about irradiance measurement/monitoring and it's not done right.

Can you describe what instrument you used, how you set it up, how the data looked and what it cost ?

Add: Given the cost and the likely fact that the problem is not the irradiance but clipping, seems to me that before the OP embarks on what could be a costly in terms of time/treasure and probably error prone quest to measure irradiance, it might be better to figure out where the clipping is coming from.

[scrambler]

Can you describe what instrument you used, how you set it up, how the data looked and what it cost ?

In my case it was part of an Ambient WS2000 weather station that has a small solar panel on top of it. Rough but still matches the Solar production pretty well.
Since then because I have two of my 20 panels on Enphase micro inverters, I setup monitoring of these two Enphase panel with an Emporia Vue 2 Energy monitor, and it gives me the perfect baseline for what the other panel should be producing

Add: Given the cost and the likely fact that the problem is not the irradiance but clipping, seems to me that before the OP embarks on what could be a costly in terms of time/treasure and probably error prone quest to measure irradiance, it might be better to figure out where the clipping is coming from.

I am definitely not suggesting to invest any significant amount of money on that. Just mentioned it in case he hits a wall with the installer.
The argument in itself should be sufficient. And at worst he can wait for summer to show his installer that his explanation does not hold...

[J.P.M.]

In my case it was part of an Ambient WS2000 weather station that has a small solar panel on top of it. Rough but still matches the Solar production pretty well.
Since then because I have two of my 20 panels on Enphase micro inverters, I setup monitoring of these two Enphase panel with an Emporia Vue 2 Energy monitor, and it gives me the perfect baseline for what the other panel should be producing



I am definitely not suggesting to invest any significant amount of money on that. Just mentioned it in case he hits a wall with the installer.
The argument in itself should be sufficient. And at worst he can wait for summer to show his installer that his explanation does not hold...

Thank you.

Yes, it will be a rough correspondence and not much use unless correction is made to convert the GHI (Global Horizontal Irradiance) the weather station measures to POA (Plane of Array) irradiance the array sees. That's one of several reasons why Smbunn's irradiance graph of clear day GHI included with his first post was mostly useless.

[oregon_phil]

My invoice from the installer just says '3 of tigo optimisers"

Nope, found a more detail info in the quote and it says Tigo TS4-A-O

Tigo still sells TS4-A-O, 500 watt, part number: 451-00252-32. 700 watt model is part number: 461-00252-32.

Is the part number on your bill of sale? Your installer should have installed the 700 watt model but you never know. The optimizer description is exactly the same.

Also, just to check, there is a power limits parameter in your Solax menu tree. It is proportional and I assume it should be set to 1. This is not the export limits parameter.

Just two WAGs.

[scrambler]

Good catch, although for Tigo even at 500W it should still not be an issue.

I assume you also verified the Model Number on your inverters faceplate, to make sure they actually installed 5kW models ....

[smbunn]

IMG_20210912_134115.jpg
IMG_20210912_134126.jpg

Checked both units faceplates. Both are SolaX Boost X1-5.0T rated at 4999 watts AC (5200 watts DC). It was something I considered as well.

[smbunn]

SOLVED: I finally got the SolaX company to respond directly. These units have dual string MPPTs. Each string has a maximum capacity of 3.5 kW. My installer has wired 5 kW to one string only in each unit.

The only solution is to split the panels so there is 5 panels per string (2.5 kW) and run 2 more twin core DC cables. Down the side of my 3 story house with no access now that the scaffolding my neighbour let me put on his driveway has long since gone. The ducting is 1 inch (25mm) so no room to get 4 sets of 4mm DC pairs plus a 6mm earth.

The installer is going to have a big cost to fix this. Not my problem and ready to sue if they don't step up.