Off grid grounding.

[Ron Asbury]

I know there are many discussions on the topic but I am still confused.
This will be a 1st time install (DIY) in a totally off grid cabin. The system will be a SunGold Power 6548 inverter, 8x 415watt panels and 2x 48v 100ah server rack batteries.

Is this crude diagram of the grounding of the system safe? Grounding is the hardest part for me to understand.

 

[sunshine_eggo]

Assuming you're just grounding the PV frames, it looks good.

The only thing you're omitting is where the N-G bond is. The inverter should supply it when inverting, but it will open it when charging from generator.

Ideally, you would want to bond N-G in the AC panel, disable it at all times in the inverter, so that even when running on generator, the system will still have an N-G bond.

 

[Ron Asbury]

Thank you, that is the answer I was looking for. Yes, only PV frames grounded. Now to determine how to disable the N-G bond in the inverter. The user manual isn't clear or I cannot find it. Anyone who has disabled it in the SP6548 please let me know,

 

[sunshine_eggo]

Most voltronics type inverters have a bonding screw that you remove.

Try this:

 

[Ron Asbury]

Thank you, that helps a lot. I will contact Sun Gold Power to see if indeed the bonding screw has been removed.

 

[sunshine_eggo]

Thank you, that helps a lot. I will contact Sun Gold Power to see if indeed the bonding screw has been removed.

I think you need to open the unit and look for it. If it's there, you need to remove it if you want to provide the N-G bond in the AC panel.

 

[Ron Asbury]

Just a follow-up.
Reply from SunGoldPower.
https://signaturesolar.com/blog/dem...ng-in-solar-power-systems-with-eg4-inverters/Also found this at Signature Solar.

 

[Supervstech]

If this is the case, then all ya have to do is bond them on thw panel, and you are good.
The panel should come with a bonding screw, if not, just place a #4 solid copper wire between N bar and ground bar.

 

[Consumerbot3418]

Also, it's pretty easy to verify the N-G bond. With all power off, you should measure continuity from N to G, and after breaking the bond in the panel, there should no longer be continuity. Replace the bond, confirm continuity, and you'll know you've got it right.

 

[garetwo]

Just a follow-up.
Reply from SunGoldPower.
https://signaturesolar.com/blog/dem...ng-in-solar-power-systems-with-eg4-inverters/Also found this at Signature Solar.


View attachment 192295View attachment 192295
View attachment 192295

I received this from SunGold:

 

[garetwo]

If this is the case, then all ya have to do is bond them on thw panel, and you are good.
The panel should come with a bonding screw, if not, just place a #4 solid copper wire between N bar and ground bar.

We have a single SP6548 off-grid. We also have a generator. So, if we bond the Neutral to Ground on the 120VAC output side of the inverter (at the loadcenter) AND it is already bonded at the generator, should we have some way of easily breaking the bond at the loadcenter if we are in bypass mode on the inverter? Should we somehow automate the break? They told us "please do not bond the neutral to ground"....

 

[garetwo]

How we are proceeding, still with no neutral to ground bonding. Should I start a new string? This seemed a great take-off thread.

 

[garetwo]

If this is the case, then all ya have to do is bond them on thw panel, and you are good.
The panel should come with a bonding screw, if not, just place a #4 solid copper wire between N bar and ground bar.

We specifically were "asked" by SunGold not to bond the neutral to ground on their output side.

 

[Zwy]

Measure for continuity between N and G on the inverter, power off and no wires connected to input and output. Also, measure if continuity between N input and output.

Once you have those answers, you can determine what route to take. If genny is bonded, you might need a 3 pole transfer switch to break neutral if there is a service panel on AC input with N-G bond. Or remove the genny N-G bond.

N-G bond at only one location to prevent parallel paths.

Put up a wiring diagram showing service panel (if there is one),inverter and generator plus breaker panel.

 

[garetwo]

Thanks. They are two hours away but will confirm there is no bonding in the inverter, hopefully within the next few days. This is a sorta "as we go" image.

 

[Zwy]

Thanks. They are two hours away but will confirm there is no bonding in the inverter, hopefully within the next few days. This is a sorta "as we go" image.View attachment 250756

You can't feed generator power and grid power into the inverter at the same time, #3. You will need to isolate one from the other due to phasing. Transfer switch or double throw.

One thing about the Voltronic inverters is using a generator may not work out well if the generator doesn't provide clean power. You might need a Chargeverter instead. This would eliminate using a transfer switch. Generator power is sent to the Chargeverter and then to batteries. This would also eliminate removing N-G bond in the generator. What do you have for a generator?

Is there a service panel with grid power somewhere? Most likely this is where N-G bond is located.

 

[garetwo]

There is no utility power, I doubt they will ever have it. I will ask about the generator, I have heard that if the genset is too small it will not work well as the AC input.

 

[Zwy]

There is no utility power, I doubt they will ever have it. I will ask about the generator, I have heard that if the genset is too small it will not work well as the AC input.

That helps. As I stated previously, measure for continuity be N and G on inverter output, inverter off and no wires hooked to inverter. This will determine if N-G bond is present in the inverter. This will determine the next steps.

Yes, a generator too small or that is dirty power, such as fluctuating frequency will usually cause problems when wired to input side of an inverter. This is why the Chargeverter was created.

 

[glandpuck]

Hmm. Looks confusing to me. Off grid with hybrid inverter requires a grounding rod in the ground. A copper connection from this grounding rod to the ground buss bar of the inverter. The neutral ground connection would be kept in place. PV+ and PV- from panels into the inverter MPPT inputs. L1/L2/N/G outputs from the inverter to the panel. Breakers from panel to the outlets/appliances. The neutral/ground on the inverter is disconnected only if you have a grid tie connection that provides this proper neutral/ground in the main panel. ONLY ONE POINT OF NEUTRAL/GROUND CREATION IS ALLOWED ON THE COMMON WIRING.

The panels should be grounded by bonding them properly with the right connectors to make a frame contact through anodized aluminum. Then this grounding wire can travel in the conduit from the panels with the PV+ and PV- into the ground bar of the inverter.

The batteries should have their cases/cabinets/conduits etc. all grounded to the buss bar of the inverter.

Optionally, you could install a grounding buss bar from the ground rod and connect panels, batteries and inverter to this.

So the net result is that all items need to be grounded, DC and AC. A single point of ground is best if can be wired and built rather than multiple grounding points. Any generator should also be grounded. If using a free standing portable generator, the neutral/ground should be kept and the generator connected to a ground rod. If connecting a generator to the inverter and the inverter is supplying ground and neutral, then the generator does not need to have frame connected to the ground rod and and neutral/ground on the generator should be disconnected.

 

[Supervstech]

We specifically were "asked" by SunGold not to bond the neutral to ground on their output side.

This is insane.

They state their inverters do not have a neutral to ground bond, then they request you do not bond neutral to ground?
Anywhere?
The neutral MUST be bonded to the ground at one place. Usually at the first means of power disconnect.
You want the neutral to be close to the overload protection breaker.