Rosie Breaker Box with Hawks Bay Controller

[aaapilot]

The breaker box for the Rosie has a DIN rail for Controller PV plus and Battery breakers, while the Hawks Bay breaker box shows a circuit breaker for BOTH PV plus & negative, as well as the battery breaker.  So, question:  Why does the Hawks Bay box include a negative circuit breaker? In my previous systems, I have never used a breaker/fuse on the negative lead.  If I have a Rosie inverter and breaker box, do I need the Hawks Bay breaker box as well?  Would I need to add a negative PV breaker to the Rosie, though the Rosie manual does not show it?

[ClassicCrazy]

I think that negative breaker  you see is part of the remote trip breaker. I think there is some  electrical engineering to break both the positive and negative at the same time for higher voltage DC. 
I made a series of videos of my Hawkes Bay hookup - this is one part where I show my final PV in connection. https://youtu.be/7t7lw8ryIxA?t=910
I had a resistance heater on the same pv with a single breaker and it had flames coming out of it from arc when I shut it off - but the double breaker of both positive and negative breaks the load fine. Could also be that the single breaker wasn't as good but you only see PV disconnects on the market doing both positive and negative.

Larry

[boB]

Breaking both positive and negative was, as far as I remember, due to NEC newer regulations for GFP/GFI.

Remember the older solar GFP breaker system that disconnects negative from ground (and PV plus) being possibly dangerous ?  And also all of the transformerless  (non-isolated)  PV grid tie inverters ?  This should take care of both situations.

I didn't think of the arcing and sparking thing but I guess it can help that as well.   If both breakers are wired backwards, maybe it can technically still arc with polarity sensitive breakers ?

Connecting the PV positive to the plus end of a single PV breaker SHOULD open without any arcing though.

boB

[aaapilot]

Thanks ClassicCrazy and boB!  I have a Kid that only requires a cb/fuse on the PV+ and a Midnite breaker box for a Magnum inverter that specified the same.  But these are not as high a voltage as the Hawks Bay capability.  Can't say that I know newer NEC solar requirements that well to have caught a requirement to break the PV- after a certain voltage or amperage :/

[boB]

Thanks ClassicCrazy and boB!  I have a Kid that only requires a cb/fuse on the PV+ and a Midnite breaker box for a Magnum inverter that specified the same.  But these are not as high a voltage as the Hawks Bay capability.  Can't say that I know newer NEC solar requirements that well to have caught a requirement to break the PV- after a certain voltage or amperage :/

Breaking of the PV- line came with the non-grounded (transformer-less) PV systems.

The PV minus can be permanently bonded with ground for MPPT controllers like the Kid and Classic but their internal GFP will not work then.

The Classic and Schneider MPPT 60 (and others ?)  have an internal GFP that connects the PV minus to ground through either a fuse or a resettable fuse (Classic)  and has a particular name for grounding...  When there is current through that fuse exceeding around 1 amp, it opens up and the controller senses this and turns off.

But disconnecting that negative from ground that can make things dangerous.  This wasn't really discussed or thought about until just a few years ago (less than 10 yrs ?)...   So disconnecting both plus and minus lines is really the best way to go and works for both grounded and ungrounded PV systems.

Not sure what was supposed to be done for GFP when Sun Power had their PV modules that needed to be positive grounded to work rightl.

This gets kind of convoluted for me some times.

boB

[aaapilot]

Very interesting, boB.  If I still owned my last home in Northern CA, think I'd modify the 3 systems I had running there and break/fuse the PV- legs.  Now that I'm starting from scratch, I'll incorporate this going forward.  I did bring a spare Kid with me and I'm looking to incorporate a Rosie & Hawks Bay at our new place we just built in OKC.  I've got 20 - 370W and 16 - 260W panels sitting in my garage soaking up shade waiting!!  This city requires a licensed electrician to even APPLY for a building permit to erect ground mount solar, so it's a bit harder for a DYI type.  Still looking for an independent electrician that isn't associated with an all or nothing solar company.