Potential Voltage Rise issue - Temperature derating

Hi I have a new 6.6kwh solar system and it’s been super clear sunny conditions but in the middle of the day it’s dropping significantly everyday. See t attached.

Installer says it fine, after some advice?

Inverters will often derate power when they are working in a very hot environment. Is your inverter exposed to the sun?
Also, if they do not have adequate cooling (space around for airflow), they will get very hot and derate output.

Gday, the inverter is outside but in the shade. I wouldn’t have thought it would get that hot.

That said it’s 29 degrees C atm and internal temp is 67 already.

Max being 70 it could be that I’ll keep an eye on it,

Interesting, what brand inverter is it? Does it have any active (fan-forced) cooling? You could try using a small fan and see if this improves the performance.

Also, what grid voltages are you seeing? Anything above 253V will generally result in reduced output as required under the AS4777.2 inverter standard.

Huawei Sun2000 no fan just Natural Convection haha just realised the installer had the manual sitting on top of it could have been restricting air flow!

See how it goes tomorrow.

How did you go? If something blocks airflow around the rear heatsink, it could definitely cause it to run hotter and derate the output.

Still issue’s unfortunately Huawei logged in said everything looks fine but can’t explain the dip in output.

They also said it’s not getting hot.

See voltage below seems ok.

Is there anything on the roof that could be casting a small shadow over some of the panels during this time? Even a very small air-vent can have a big impact

This was taken during one of the dips interestingly there has been one or two days where it hasn’t dipped.

I might put a pedal stool fan on the inverter today just to be sure lots not temperature.


The basics: What inverter do you have? What panels do you have? How many panels? Do you also have batteries hooked up? Where roughly do you live and what is your grid interconnection agreement? Do you have any rapid shutoff or balancing devices? How many strings or are you using micro inverters? Anything else you can tell us about your system? Also how much experience does the installer have? Do you have a copy of the design calculations for your system?

Divide things up: Is it the panels, the grid, the inverter or what? After collecting as much useful information about your system, suggest cooling the inverter first, just to try and rule that out. A fan pointed to it might do the trick, or a pan of ice near it. Does the inverter have any way to tell you what it thinks, like error messages or status messages? It’s useful to have some intel coming from your array. If you don’t have that, how much would that cost to add? … and i don’t know, i’m sure there are other ideas of how to approach this…

  • 16 x Astro 415w panels 6.64kw - 25 years product warranty
  • 1 x Huawei hybrid inverter 5kw

No batteries or micro inverters - 2 strings pv2 has more panels on it due to roof layout.

No errors installers say everything OK.

Tried the fan didn’t seem to help,

Cloudless sky today and still a massive dip between 12-1300.

It appears PV2 is hitting its max input current (13.5A) just before the dip, could that be the cause?

They put more panels on PV2.

The 13.5A input current shouldn’t cause a problem. The max input current (Isc) is 19.5A, and it’s well below this.

However, the MPPT voltage could have an impact if it gets close to 140V, which is the minimum operating MPPT voltage. The string voltage will drop in hot sunny weather, especially on still (windless) days.
What was the weather like on the days that this problem didn’t occur? If it was colder sunny days, then this might be the issue.

I think you might be on to something I’ll need a few more cool days to be sure as It’s been steady over 30 in Perth since it’s been installed (some days windy though which cools everything, however today it’s only been 29 and it’s looking heaps better!

I’m guessing nothing can be done about it?

Yeah much cooler day today and just a tiny dip. Thanks for your help. Case closed.

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Great to hear. However, I’m surprised the dip was that great, considering the MPPT voltage appeared to be well above 140V? :thinking:

Although, I could be wrong. It would be interesting to know what MPPT string voltage you record on a hot day? MPPTs ramp down as they approach the lower limit, but it’s not always clear at what voltage this actually starts.