Question about generator grounding - 2 chassis bonds going to different grounding points

Re: Question about generator grounding - 2 chassis bonds going to different grounding po

vtmaps wrote: »

So true. After the GFP trips, all neutral DC wiring can be hot and unfused with respect to ground.

There is a simple solution for one controller... use Outback's 3 pole GFP device to disconnect both PV pos and PV neg when a fault is detected.

For two controllers you would need a 5 pole GFP (one pole being the ground fault detector and the other 4 disconnect pos and neg from two arrays), but I don't think they make one with that many poles.

--vtMaps

And the three+ pole DC GFI only works for DC shorts on the PV array side of breaker (i.e., a DC PV short to earth that draws more than 1 amp) because the breaker only cuts off the PV source of power.

If there is a DC to earth fault anywhere else in the system (battery to earth, inverter to earth, MPPT charge controller to earth, any other wiring fault to earth)--There is no other two pole breaker to stop those sources of power at all (i.e., short the battery + to earth, DC GFI does nothing to "interrupt" the source of the fault's power).

Just a big mess--There are a dozen major fault situations where DC GFI does not work or causes more problems than it fixes).

The only reason DC GFI even sort of works--There is a 1 amp fuse between DC Return and Earth Ground that stops current flow... But, in normal AC and DC wiring with single pole breakers/fuses, placing a fuse between return and safety ground is never a supported configuration (except in solar power systems). If you have a (now) floating power system, you need two pole ganged breakers on every power source to "safe" the system if there is a fault.

Which then would add costs (more breakers with slave trips) and--If there is ever a hot to earth fault anywhere in the DC power system--It kills power to the entire DC power system.

Just as bad as slaving the Main House Breaker to every breaker in the panel--Any fault kills the power to the whole home--killing power/lights everywhere in the home and making it very difficult for fault isolation.

When design larger Computer/communications systems, putting fuses in the return/safety ground leads would have made my job a lot easier--The customers a lot less safe and the systems much less reliable.

-Bill