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I have 3.2 kVA solar inverter with MPPT charge controller along with six 340 W solar panels installed. What I have noticed is that the inverter stops drawing power from PV though there is bright sun light. The inverter draw all power from utility only. In this phase, I have checked with the amp meter that there are no current even in wires coming from solar panels. But then I switch off utility to inverter and in few minutes inverter starts drawing power from PV and current come back in wires coming into inverter from PV modules.

This happens often during the day and I fail to understand why inverter is doing so because every time it is switched to utility all solar power is being wasted and I am still paying for utility.

Any suggestions would be appreciated.

PS: Inverter is set to draw power first from PV then battery and then utility.

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  • \$\begingroup\$ Are there any "price" or time settings causing the inverter to choose the utility by default? \$\endgroup\$ – Solar Mike May 16 at 10:25
  • \$\begingroup\$ A bit of a long shot but what is the open circuit voltage of the panels and what is the max accepted input voltage of your inverter? \$\endgroup\$ – winny May 16 at 10:36
  • \$\begingroup\$ Is the inverter getting too hot? \$\endgroup\$ – Solar Mike May 16 at 10:53
  • \$\begingroup\$ You need a circuit diagram. It is not obvious what voltage your load operates from and your description SEEMS to not make sense. You say "the inverter draws all power from utility only" - this seems to not make sense - if load is AC mains (230V? 110V?) then why is the inverter involved? \$\endgroup\$ – Russell McMahon May 16 at 11:01
  • \$\begingroup\$ Thanks for your answers, winny open circuit voltage are 46.2V each panel and i have 6 of them connected in parallel. \$\endgroup\$ – Fawad Pasha May 17 at 5:56
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  1. Usually MPPT charge controller have ability to select Main Source for their input. Make sure PV is the main option here and Grid Utility for backup. if you make sure this point is correct, then
  2. Input for MPPT must meet the minimum requirements. for example if you choose utility as the main source, say it's in 220V system, the MPPT will keep it as main source as long as the voltage not drop to lower than 170 or any number depend on your MPPT manual. So, in your case, maybe your PV has not meet the minimum voltage that MPPT want, maybe because of cable joint malfunction or something else. measure your input from PV to MPPT.
  3. Battery can also be a problem here, if the battery fail to suply power, because the voltage too low or another problem, MPPT will choose the safest way to feed their output. Measure your battery and make sure the voltage higher than 10.5 volt.
  4. Read MPPT manual :-)
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  • \$\begingroup\$ This is great you have highlighted few potential problems. I have 2 12 volts batteries connected in series and 1 of them is kinda weak so yes it could be a problem, i will get it checked. I have 6 solar panels connected in parallel each has 38.2V maximum power voltage and 8.9amperes. operating voltage of MPPT are 30-80Vdc and 50amperes. You think my connections could be a problem? i am using 6AWG wire and distance from solar panels to inverter is about 80 feets \$\endgroup\$ – Fawad Pasha May 17 at 6:02

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