Hey everyone, I'm based in the US and I'm working on the wiring diagrams for my inspector. I want to confirm whether I need a neutral connection between the GridBOSS and FlexBOSS units. The manual states "only connect the inverter's grid port to the GridBOSS hybrid port," and the wiring diagrams only show a link between the inverter port and the grid port. The neutral bus layout suggests they aren't expecting three #2 AWG neutrals for a fully loaded FB21 setup, especially since there are only two lugs for that size cable. However, I'm concerned about how to manage unbalanced loads. Should I consider using #4 cable for the neutral run instead?
1 Answer
Honestly, this really had me scratching my head too! I just connected a #2 Neutral from the FB21 to the GridBOSS and a #8 ground without even considering the need for a neutral. But after thinking it over, I don't see the necessity for it. The FlexBOSS doesn't supply 120V to any loads; it provides DC to the batteries and 240V AC to the GridBOSS. So all AC loads are supposed to connect to the GridBOSS instead. Your question is definitely valid, though!
Exactly! When the grid is on, it takes care of any imbalance. If there's no grid, the ground-bonded neutral at the GridBOSS should handle it, making a neutral to the FB unnecessary. I might go ahead with a #4 neutral to each FB, given the limited lugs for #2 neutrals at the GridBOSS, unless I hear differently from EG4. Plus, I'd love to know what the tolerance for imbalanced loads is on the FB!