Grid Connect Solar Troubleshooting


    I thought I might spend a little time discussing some basic troubleshooting with Grid Connect solar systems. I seem to spend a lot of time talking with people who are concerned their Grid Connect solar array is not function as they had expected. So lets start at the beginning.

    How much Energy should my System produce?

    For an indepth technical discussion on this issue go here (Estimating Solar System Yields). If you dont want to be bored to tears then read on.

    The basic rule of thumb (the magic formula) is:

    System Size x 5 = Avg Daily Yield.

    So how does this work... lets assume Joe Bloggs has a 2kW Grid Connect solar array installed at his house. Assuming the panels are facing North and there is no shading he should expect his system to produce at least 2 x 5 = 10kWh of energy most days.

    Before you shout me down hear me out.. On a full sun day in summer he should be expecting more than this, on a cloudy day in winter he should expect it to be well below this. But if Joes system rarely produces the 10kWh then there is a problem. The formula above is easy to remember and gives a reasonable estimate on what a healthy Grid Connect Solar system should be producing.

    I was told my Grid Connect System will Produce a lot more than that?

    It might be possible that your grid connect system will produce a little more than what the above formula estimates during different seasons, but over the entire year the above formula has proven to be right more times than it is wrong. I am not saying it will estimate it to the last kWh, but give or take a bit it is pretty close.

    So the moral to this little story is if you were told it will produce a lot more.. somebody has not been truthful.


    Your System doesnt produce what the Magic formula says it should!

    Then chances are there is a problem. In my experience the problem will either be in the Solar Panels, or with the main power lines. An inverter will generally be working, or not at all, there is no in between, this shouldnt be a surprise, safety is of the utmost importance when designing a Grid Connect Solar inverter so if something goes wrong the inverter is quick to shut down.

    Is the problem with the main power lines?

    What I am talking about is main grid voltages. All inverters in Australia are programmed to shutdown if they detect the main grid voltage rise a little over 260V. What happens in some places is the main grid voltage is very high (255+V) to start with, then when your solar system starts to put power back into the system it pushes the voltage even higher, causing it to go higher than the inverters upper threshold, so the invert will disconnect. Once the inverter disconnects it will wait a little while, during this time the voltage drops back again, the inverter connects back onto the mains and starts producing power, it raises the voltage again and disconnects.

    So why havent you noticed this? well chances are it is happening around midday when you are at work, early in the morning and in the evening lots of people are using electricity so the voltages are lower than normal, and during this time the suns power is not as strong as it is at lunch time so you are not putting much power into the grid anyway. Many intelligent inverters will detect the pending voltage problem and start to reduce the amount of power it puts into the Grid, just so that it can stay connected, sometimes the only warning you get is a small message on screen.. very easy to miss.

    How do you test for Grid Problem? I would start by checking the Grid voltage reading on your inverter at lunchtime one day, if it is in the 255V or higher then you need to investigate further. By investigate further I mean pick a bright sunny day during the working week and try and catch it in action.

    If you do catch the mains voltage rising above the 260V and the inverter disconnects then its time to call the energy company... good luck.

    Is the problem with the solar panels?

    Lets start with the things you can do yourself...

    On a bright sunny day just before midday read the amount of power coming into the inverter, most inverters will have this figure somewhere. If this figure is less than 80% of the rate system size then there is a problem somewhere (so with Joes System the rated size was 2kW, so 80% of this is 1.6kW). If the day is a really hot one (ie temps in the low 30's or above) then expect the system to only be 70% of the rated size.

    So you have performed your calculations and the system is a lot down on what it should be, here are the things to check:

    1. Are the solar panels dirty.. ie is there a lot of bird deposits and dust/dirt... if so clean them with warm soapy water and a soft sponge.
    2. Is there any significant shading.. a small sharp shadow covering part of one panel can be just as damaging as a gentle shadow covering a lot of area. If you have shading then short of moving then panels there is not much that can be done.
    If none of the above options are the problem then you really need to call in a professional to look at it. The kinds of things we do to track down problems are:
    • Thermal scan the panels and all DC wiring looking for failures.
    • Verify the wiring configuration of the panels is optimal.


    I hope some of this was helpful. If you are still concerned there is a problem dont hesitate to call us. A solar array that has solar panels starting to fail can be a serious fire risk so dont leave it, get somebody in to look as soon as possible.


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