ungrounded Rosie?

[BlackwaterPark]

Ok, so I've got a question here. I'm about ready to launch my secondary system, which will run side by side with my existing system. This new system will end up becoming my main system, with my existing setup becoming an auxiliary and back up to it. The new system is a Rosie with the E panel breaker box, running with a Hawks Bay 120 with its E panel as well, supporting 4 Powerflo 5.1s, and fed by an array of 16 415w bifacials split into 2 300v strings coming into the HB (I already know i'll be losing the full potential of that array running it all into the one HB). My first system, which I've run for about 12 years now, has never had a ground, and neither have my panels for that matter. It's never been a problem. I'm not interested in grounding my panels, lightning is rare where I am, and I'm likely going to just build a grounded lightning rod near the arrays anyway...just in case.  This brings me to how to deploy the new system. For the record, I am completely off the grid, as there isn't a utility pole within a mile and a half of me. Also, there's no need to comply with any codes other than septic where I live. Here's the question.... can the Rosie run fine without incorporating a ground to it?  This inverter is a fair bit more sophisticated than my up and running unit, so i'm uncertain if a lack of ground will cause issues of any sort.  To be comprehensive here, my plan on using my older system in a support role is to run the 240v output into a breaker box that will then hook into the Ac input side of the rosie, to be triggered when the powerflo bank drops below a roughly 20% SoC voltage threshold. Thoughts?

[Brucey]

Ok, so I've got a question here. I'm about ready to launch my secondary system, which will run side by side with my existing system. This new system will end up becoming my main system, with my existing setup becoming an auxiliary and back up to it. The new system is a Rosie with the E panel breaker box, running with a Hawks Bay 120 with its E panel as well, supporting 4 Powerflo 5.1s, and fed by an array of 16 415w bifacials split into 2 300v strings coming into the HB (I already know i'll be losing the full potential of that array running it all into the one HB). My first system, which I've run for about 12 years now, has never had a ground, and neither have my panels for that matter. It's never been a problem. I'm not interested in grounding my panels, lightning is rare where I am, and I'm likely going to just build a grounded lightning rod near the arrays anyway...just in case.  This brings me to how to deploy the new system. For the record, I am completely off the grid, as there isn't a utility pole within a mile and a half of me. Also, there's no need to comply with any codes other than septic where I live. Here's the question.... can the Rosie run fine without incorporating a ground to it?  This inverter is a fair bit more sophisticated than my up and running unit, so i'm uncertain if a lack of ground will cause issues of any sort.  To be comprehensive here, my plan on using my older system in a support role is to run the 240v output into a breaker box that will then hook into the Ac input side of the rosie, to be triggered when the powerflo bank drops below a roughly 20% SoC voltage threshold. Thoughts?

My Rosie M is running ungrounded (floating ground). It's not connected to the grid. No issues at all.

[BlackwaterPark]

[
My Rosie M is running ungrounded (floating ground). It's not connected to the grid. No issues at all.

Is the M version needed to establish a floating ground, or can the RE version do this as well to your knowledge? My existing system has a floating ground and would like to keep it that way.

[Wizbandit]

I would advise against "Floating Ground" systems.
DC on the PV Side is least concern but still a concern as a ground fault will just maybe cause a fire and burn up the PV modules or the building they are on.

The AC side is a human safety concern. The "Floating Ground" depending on what devices are not grounded could be energized to upwards of 200VAC or more from the MOV's (surge devices) inside the Inverter as they are referenced to the ground system.  Any MNSPD's will also "bleed" energy continuously to the floating grounds.

To avoid this you will need to remove the Surge Protection Devices from the AC lines and possibly clip out the MOV devices and maybe some RFI noise capacitors that are across the AC in and OUT to ground. Good luck with the next close lightning strike...

AC devices should all be bonded together to the ground bar in the AC distribution panel and to a ground rod(s) outside.  The PV ground system should be connected to the AC ground system.  You achieve nothing but troubles by not engaging a complete safety ground system...

[BlackwaterPark]

I see so much conflicting and contradictory information on all this in regards to grounding. It gets very confusing, and my takeaway is that no one really knows. There are a lot of "experts" that advise against grounding to earth your inverter...even Prowse says it's foolish to do in most cases. Then there are many "experts" that say it's stupid NOT to do. My own experience is that I've had a floating ground system for almost 13 years and that about four years back, we had an extremely close ground strike that actually traveled through my black iron LP pipe (presumably through my buried gas line) and manifold on the exterior of my house and sparked right off my stove while I was about four feet away...startled the @*#& right out of me. System and panels were completely untouched. I don't have any SPDs installed, and I don't know about the other components you mentioned. I know RVs, boats and other mobile systems are never earth grounded, so i've got to wonder what the difference is then?

[Brucey]

[
My Rosie M is running ungrounded (floating ground). It's not connected to the grid. No issues at all.

Is the M version needed to establish a floating ground, or can the RE version do this as well to your knowledge? My existing system has a floating ground and would like to keep it that way.

The M has an additional relay for the neutral ground bond (disconnecting when connected to ac input), but otherwise identical to my understanding to the RE.

[aaapilot]

Midnite designs and builds the Rosie, requires an earth ground in residential, non-mobile applications.  Whizbandit lists some of the issues that can happen and HAVE happened without a ground.  If your experience has been acceptable without grounds and you don't want to follow the manufactures instructions, then do as you see fit, at your own risk.  Every electric code since the 1960's requires electrical equipment to be grounded, so if one guy on YouTube says its not required and you choose to follow that advice, well ... ok.  I'm guessing you don't use GFCI plugs or CB,s for your kitchen/bath circuits as well if you follow this line of thinking?

There were no seat belts in cars when i started riding in them.  I never had an accident where i was thrown thru the windshield, so my experience suggests i shouldn't wear one now, but i do.  What I'm saying is just because it hasn't happened to you YET, doesn't mean it's not a good idea and our collective knowledge is built on accidents that have happened to others.


Dave

[BlackwaterPark]

Midnite designs and builds the Rosie, requires an earth ground in residential, non-mobile applications.  Whizbandit lists some of the issues that can happen and HAVE happened without a ground.  If your experience has been acceptable without grounds and you don't want to follow the manufactures instructions, then do as you see fit, at your own risk.  Every electric code since the 1960's requires electrical equipment to be grounded, so if one guy on YouTube says its not required and you choose to follow that advice, well ... ok.  I'm guessing you don't use GFCI plugs or CB,s for your kitchen/bath circuits as well if you follow this line of thinking?




Dave

So how would you ground the system I've detailed out above? There will be two systems operating side by side, and the details of the system already in place which will serve as a backup "grid support" to the rosie os as follows:

Genetry solar GS6000 (a highly customizable 6kw LF 48v 240vac inverter)

2 Kilovault HaB 7.5kwh 48v batteries

Midnite classic 150

EG4 Chargeverter

PV array ~98v, 30a

Any guidance would be helpful. There are zero contractors in my area that are not booked into next year, so this is all on me.

[ClassicCrazy]

Midnite designs and builds the Rosie, requires an earth ground in residential, non-mobile applications.  Whizbandit lists some of the issues that can happen and HAVE happened without a ground.  If your experience has been acceptable without grounds and you don't want to follow the manufactures instructions, then do as you see fit, at your own risk.  Every electric code since the 1960's requires electrical equipment to be grounded, so if one guy on YouTube says its not required and you choose to follow that advice, well ... ok.  I'm guessing you don't use GFCI plugs or CB,s for your kitchen/bath circuits as well if you follow this line of thinking?




Dave

So how would you ground the system I've detailed out above? There will be two systems operating side by side, and the details of the system already in place which will serve as a backup "grid support" to the rosie os as follows:

Genetry solar GS6000 (a highly customizable 6kw LF 48v 240vac inverter)

2 Kilovault HaB 7.5kwh 48v batteries

Midnite classic 150

EG4 Chargeverter

PV array ~98v, 30a

Any guidance would be helpful. There are zero contractors in my area that are not booked into next year, so this is all on me.

Why can't you put a ground rod outside and run the AC grounds to that ?
It seems pretty simple to do and at least that part of  your system will be safer.
Larry

[BlackwaterPark]

Why can't you put a ground rod outside and run the AC grounds to that ?
It seems pretty simple to do and at least that part of  your system will be safer.
Larry
[/quote]

Thanks for the reply Larry. If I did that, what exactly gets grounded to rod? Just the AC breaker box? For whatever reason, the whole subject of grounding is a rather confusing one, and the more videos I reference, the more confusing it becomes. On the AC side, from what i'm gathering, you can only get dangerously shocked if you are touching the live and neutral at the same, and i'm not sure under what conditions that would occur outside of getting your hands in the internals and not paying attention, but as soon as you ground it to earth, you can complete the circuit by touching it, potentially to lethal effect, unless I'm grossly misunderstanding this video:

https://youtu.be/5czI7-9CVrU?si=oBIMXtTxJAMAJDLk

this is the big part that's got me wondering.

[aaapilot]

Anything metal in your system should be grounded. You are totally off-grid if I remember right.  When you installed the main CB panel for the house, that panel has, or should have, a ground lug.  I would either start there, or your main power source if it's not co-located, I.e. your inverter, start with the ground lug on that. Whichever is easiest to get to an outside ground bar.  From that point, you simply run a ground wire to any metal box connected to the system.  Ensure the size of the grounding wire is appropriate for the largest size of the wire you are using in your system.

[ClassicCrazy]

Why can't you put a ground rod outside and run the AC grounds to that ?
It seems pretty simple to do and at least that part of  your system will be safer.
Larry


Thanks for the reply Larry. If I did that, what exactly gets grounded to rod? Just the AC breaker box? For whatever reason, the whole subject of grounding is a rather confusing one, and the more videos I reference, the more confusing it becomes. On the AC side, from what i'm gathering, you can only get dangerously shocked if you are touching the live and neutral at the same, and i'm not sure under what conditions that would occur outside of getting your hands in the internals and not paying attention, but as soon as you ground it to earth, you can complete the circuit by touching it, potentially to lethal effect, unless I'm grossly misunderstanding this video:

https://youtu.be/5czI7-9CVrU?si=oBIMXtTxJAMAJDLk

this is the big part that's got me wondering.

If there is a short and you have it wired up correctly to a ground, the breaker trips. If it isn't grounded and nothing to trip the breaker and there is a problem the current goes through you to ground . That isn't a good deal !
I am not an expert but know standard AC wiring . At the point of first AC entry is the only place where ground and neutral are bonded together.  No where else in the house are ground and neutral bonded together. In an AC circuit all the current will be going through the hot and back through the neutral . No current is going on the ground.
If someone has the power coming in from grid - and it goes right to breaker box inside the house that is the point of first disconnect so that is where neutral and ground are connected to each other. There is a green screw in boxes that is either put in to bond or left out to keep them separate. So for instance if there is the meter from grid outside and it goes to a switch outside and then to the breaker box inside, that switch outside is the point of first disconnect and then that is where the neutral and ground are bonded together . In that case the breaker box inside does not have the neutral and ground bonding screw . 
But then what does an off grid guy like me do when I have an inverter ? I guess that is the voltage source instead of the grid coming in and would I would still ground the neutral and ground in the AC box after it. But I have a newer different brand inverter that has an integral breaker and the inverter has an option to do an internal bonding inside it of neutral and ground. Then when it goes to my AC box since that is already bonding inside the inverter , no bond in the breaker box.
So it really depends on your system and what you have . I don't have a Midnite Rosie or the other newer other AIO midnite inverter so don't know what options they have or what is right to do for those.
Yeah it can be a bit confusing and I hope I stated all of the above correctly or if I am wrong someone will let us know.
It gets even more confusing if you try to define what a ground is in electronics ! I watched a presentation about that but we are just talking about AC wiring for now.
I am not so well versed on grounded DC systems and if they share the same ground, if you have to bond the grounds between something like PV racks and inverter case grounds, etc. I know how I did my system and hopefully it is right.
I do know that the other day I was adding a new battery on my system, using a metal ratchet on the positive buss bar, and my hand touched the side of some foil lined foam insulation around the battery box and I felt a nice electric tingle in my hand . I think there was a metal shielded cable from my AC system that was in contact with the foam board foil, and that made some kind of connection from the positive 55 volts of the battery to through my hand to ground . Somehow those two grounds are connected I guess - might be something like Jim talked about with surge protector MOVs to ground etc. I haven't analyzed this yet . I checked with a meter from positive to foil on my insulation and it showed the battery voltage and like I said the only culprit grounding that foil is a mc metal shielded AC cable in contact with it.
Electrons go where they will even if you don't want them going through you to do it !
Larry 

[BlackwaterPark]

Anything metal in your system should be grounded. You are totally off-grid if I remember right.  When you installed the main CB panel for the house, that panel has, or should have, a ground lug.  I would either start there, or your main power source if it's not co-located, I.e. your inverter, start with the ground lug on that. Whichever is easiest to get to an outside ground bar.  From that point, you simply run a ground wire to any metal box connected to the system.  Ensure the size of the grounding wire is appropriate for the largest size of the wire you are using in your system.

yes, completely off grid, not near any poles at all actually. Question...if your objective is to connect every piece of metal to a ground bar, why can't you locate the ground bar indoors near your gear and then run a single lead to the rod?  Wouldn't this save on copper and time? Also, the thickest wire in my system is OO for the battery leads (oversized for sure).... surely I wouldn't need a grounding lead of that heft...?

[Brucey]

Anything metal in your system should be grounded. You are totally off-grid if I remember right.  When you installed the main CB panel for the house, that panel has, or should have, a ground lug.  I would either start there, or your main power source if it's not co-located, I.e. your inverter, start with the ground lug on that. Whichever is easiest to get to an outside ground bar.  From that point, you simply run a ground wire to any metal box connected to the system.  Ensure the size of the grounding wire is appropriate for the largest size of the wire you are using in your system.

yes, completely off grid, not near any poles at all actually. Question...if your objective is to connect every piece of metal to a ground bar, why can't you locate the ground bar indoors near your gear and then run a single lead to the rod?  Wouldn't this save on copper and time? Also, the thickest wire in my system is OO for the battery leads (oversized for sure).... surely I wouldn't need a grounding lead of that heft...?

I would suggest reading the Rosie manual it goes into great detail on system grounding and equipment grounding, starting on page 22:

https://www.midnitesolar.com/pdfs/10-432-1_Rev_C_(MNROSIE7048_Manual)_22MAR2024.pdf

[ClassicCrazy]

Also one thing that can get confusing is that some people refer to everything as grounding when there may be two different concepts at play - grounding and bonding .

from ARRL book in link below
AC safety: Protect against shock hazards from ac-powered equipment by providing a safe path for current when a fault in wiring or insulation occurs.

Lightning protection: Keep all equipment at the same voltage during transients from lightning, and dissipate the lightning's charge in the Earth, away from equipment.

RF management: Prevent unwanted RF currents and voltages (also known as RF interference or RFI) from disrupting the normal functions of equipment.

https://home.arrl.org/action/Store/Product-Details/productId/133989

Larry