Unable to get Solar to start

General Troubleshooting

Last Post by fkitzmann 5 days ago

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fkitzmann

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April 8, 2026 5:49 pm

(@fkitzmann)

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System Hardware - FlexBoss21, GridBoss, 23 PV panels

Symptom & troubleshooting, This is a new, recently installed system that the PV never starts up. PV panels can be configured as two banks or one complete bank. Initially tried two banks connected to PV inputs 2 & 3 where PV 2 had ~220VDC on it's input and PV 3 had ~ 180VDC. The MPPT's would never start up, i.e. no PV current pulled by inverter on either input (measured with external voltage and current meter). Also, no PV voltage displayed in any PV (1,2,3) Data, Chart, Voltage measurement. I can physically measure voltage at each PV 2 & 3 inverter input terminals but yet no voltage measured by inverter other than small accuracy related fluctuations. In knowing that this inverter has a MPPT start up voltage of 200VDC. The thought was that I was right at it's minimum so I also lowered the Start PV Voltage to 170V. Still no go. I then configured the two strings into one complete string. This now has a voltage of ~380 - 400VDC. I then transferred this to MPPT 1's inputs. This did not work any better and I still could not see any voltage on PV 1's Data Voltage measurement. I have checked all settings under the maintenance tab and everything appears correct. Even the advanced settings -

Note that other than the above PV issue, all else appears to be working. Batteries can supply power to EPS loads & can be charged from grid.

Eric - I can DM you with system access and other information if you want to look at it.

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PV won't start.

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EG4 Eric

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April 15, 2026 8:04 pm

(@eg4eric)

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@fkitzmann
Yes, please send me your inverter's serial number so I can look into this for you.

Posts: 65

fkitzmann

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April 20, 2026 8:55 pm

(@fkitzmann)

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He is using the wallmount indoor 280Ah Lithium Battery. Is has since discharged so I know that the inverter side is working. Let me know if you need SN’s. The solar should still be hooked up with voltage on the PV terminals as I stated originally I.e. ~380 - 400vdc. Although I can’t measure right now to confirm, but it should be that. I’m wondering if the MPPT circuit has an issue. I should be able to verify the PV voltage later today.
Eric, This is the current status. I have separated the PV's into two banks from what I had before (One complete string). These are connected to PV1 and PV2's inputs on the inverter. These are now physically measuring 207.5VDC (PV1) and 173.7 (PV2).

Note also that I'm currently charging the batteries and that works -

And again, No voltage or current present on solar, other than some small residual voltage -
Go ahead and take a look now if you can.
Some additional information on the set up. The system originally consisted of a Solivia 7.6TNAG4TL Model GPI76212032 inverter with 22 solar panels of unknown manufacturer and model. Also at the panel are N number (possibly 4), of Delta Smart Rapid Shutdown System modules Model GPI00012105. I removed the Solivia inverter and wired the existing panels with Delta RSS into the new FlexBOSS21. When I first powered up the EG4 FlexBOSS21 inverter, I was expecting that it would send out the RSS signal and turn on the power from the panels. At that time, there was no power out putted from the wires from the panels. I then went into the inverter settings and enabled the RSD control. Reset the inverter. Still no PVDC voltage on either PV wires (2 Banks). I then tried PV Arc & PV Arc Fault Clear. Still no PVDC voltage. I then assumed that the RSS controller in the FlexBOSS21 may not be supporting the Delta Smart RSS modules Model GPI00012105. I then connected the original Solivia to the PV wires so it could generate the RSS signal and turn on the panels. Note that I made sure that the DC power switch on the Solivia was turned off so no solar current can go into it's inverter but yet would still generate the RSS signal and turn on the DC from the panels. This worked and I now had DC power applied to the FlexBoss inverter. This is where the system currently sits with the connections. As you can see in my prior post. There is DCPV power applied to the PV1 & 2 terminals of the FlexBOSS. Again, None of the PV power is actually going to the Solivia inverter. It's only being used to turn on the RSS controller modules up at the panels. Unfortunately I can't physically get to the RSS controller modules on the roof and try disconnecting them, but I don't believe that this is causing any problem with the FlexBOSS at this point.

Also, this is only a temporary solution. The final solution could be one of two solutions. Assuming that there could be a mis-match in the RSS protocol between what EG4 is sending verses what the Delta RSS controller is expecting. Maybe EG4 can update their RSD protocol to include what is expected by the Delta RSS module. The other alternative is to replace the Delta RSS modules with something like Tigo RSD. Do you know what RSD manufacturer's are supported with the FlexBOSS21?

See a snip of the Delta RSS specs - See Rapid shutdown line