PV-ISO-PRO 01/02 Alarm

Ground faults are a notorious issue with PV installations. Essentially you have either a positive or a negative connected to ground. NUMEROUS causes can trigger a ground fault. DC wires pinched under the array, wires landed in the wrong terminals, precipitation triggering a ground fault, and on and on. 

The ground fault will need to be resolved before the system can be energized. 

PV-ISO-PRO01 - Negative wire is connected to ground

PV-ISO-PRO02 - Positive wire is connected to ground

If no ground faults are discovered then the fault is internal to the inverter and it will require an RMA. 

Troubleshooting (updated procedure)

  1. With the DC switch "OFF,"and the (+) and (-) homeruns landed in terminal blocks/fuseholders, measure and record DC voltage between (+) to ground, and (-) to ground for each home run.
    • If homeruns are being paralleled at the inverter MPPT(s), the homeruns must be isolated prior to troubleshooting.  When opening fuses to isolate strings, the technician must first verify that no current is flowing by using a DC clamp-on ammeter.
    • The measurements should bleed down to a safe level less than 10vDC, and eventually go to zero or close to it. If any of the measurements don't bleed down, or are greater than 50vDC, the system has a ground fault that should be investigated.
  2. If stable voltage higher than 50vDC between either (+) or (-) to ground is measured in Step 1, remove BOTH (+) and (-) homeruns from the terminal blocks/fuseholders on the MPPT, and repeat test.  If voltage to ground is still measured, a ground fault exists outside the inverter that should be investigated via visual inspection or with a megohmmeter (insulation resistance tester or "megger").
  3. If testing does not reveal ground faults from either the isolated DC homeruns nor internal to the inverter, but the inverter still displays a ground fault code, land the homeruns one at a time at the inverter and attempt to start it. If the inverter turns on with a known good DC input in every terminal, then there is no further issue, or the ground fault is intermittent and needs to be troubleshot under the same environmental conditions as when the fault is believed to occur.
Victor is the author of this solution article.

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