EG4 › GridBOSS/FlexBOSS parallel link
Rapid shutdown cuts the whole home, or only one inverter responds
reported in the field
Symptoms
- Testing RSD/ESS behavior turns up results the installer or owner did not expect: on two paralleled 18kPV inverters each wired to an independent Tigo rapid-shutdown module, only one inverter at a time registers an RSD event, so the pair cannot demonstrate the NEC-compliant rapid shutdown EG4's own certification claims
- On a GridBOSS+FlexBOSS21 whole-home backup system, pressing the RSD button cuts power to the entire home, including cameras, alarm and fridge on backup loads, even though the GridBOSS was deliberately left out of the RSD circuit with its jumper still in place
- And testing RSD/ESS shutdown with the grid connected causes the grid to repeatedly cycle on and off, cycling power to the house and inverters, instead of a clean backup shutdown. EG4's own training videos and independent install videos show the same surprises: a system that goes into rapid shutdown the moment it powers up, an RSD test that pops every battery breaker, faults the BMS and drops the backed-up loads panel for about ten seconds, and a display left flashing 'hybrid, no grid' until the batteries are cycled
Alerts and codes
flashing hybrid, no griderror fault grid boss breaker open
The cause and the fix
Subscribers see the cause, the fixes that worked and who did them, part numbers and recent prices when a part is involved, and the field reports behind this entry.