FAQ: How do you fit solar panels?

Posted On 05-09-2017

By Bart van den Bosch – product manager Libra Energy
Step-by-step plan for connecting and checking solar panels

  1. Check the string layout in the drawing.
  2. Make a note of the serial numbers in the drawing (IN THE LAYOUT PLAN).
  3. Lay the wiring from the panels to the inverter as per the drawing.
  4. Mark the wires with positive or negative string number and inverter number (if so desired, input number MPPT 1 etc.)
  5. Always check polarity (positive and negative to the right connectors) before connecting.
  6. Ensure the string is connected and that the open-circuit voltage is correct (number of panels in series x Voc). If the strings are connected parallel, the parallel voltage needs to be measured. Therefore, always take measurements of single strings. (CAUTION! THESE ARE HAZARDOUS HIGH VOLTAGE DC CURRENTS)
  7. If the voltage is not what it should be, check all connections in the string.
  8. If required, each panel can be checked individually. In this case you are measuring the Voc voltage.
  9. Check the polarity and the Voc voltage of all strings.
  10. Measure the operation of the switch. If it is in the ‘on’ position, you are measuring the voltage of the cables from the string distributor to the power module or MPP connection on the inverter.
  11. Measure the Voc voltage and polarity so you know for certain that nothing has been swapped over during the connecting process.
  12. If this is as it should be, turn the DC switch to ‘off’. Now you can connect the string wiring to the power module or MPPT input on the inverter.
  13. Leave the AC side off and start the inverter using the DC switch. An error message should now appear because there is no mains power.
  14. Turn the AC isolating switch on. The inverter will now start.
  15. Measure the string voltage. It will be lower than the Voc voltage (MPPT voltage of the string).
  16. Use a current clamp to measure the different strings. Now you are measuring the MPP current. The current must be about the same for each identical string.
  17. On the AC side, use a current clamp to measure the current that is fed back into the grid.
  18. On power modules with equal numbers of panels, this must be about equal.

If the above is working, then the system is operational. Make a note of all measured values and record them in a delivery document. This document will be essential in the event of a warranty claim.

Download your sample document here.

You can also refer to NTA 8013:2003 for checking PV systems.

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