diy solar

diy solar

Off-grid farm/cabin - Please check my grounding diagram!

pappitattoli

New Member
Joined
Aug 13, 2021
Messages
1
Hello everybody!

please forgive me if any of this sounds stupid, but I'm new to this world.
I'm designing the off-grid system for my farm. The final diagram is 90% complete, but I'm stuck with the grounding.

I understand that grounding changes a lot depending on the components and other variables, so I thought I'd draw a diagram for the whole grounding system.

Consider the following:
  • It's a split phase with two 120V Victron Quattro inverters. There will be both 120V and 240V appliances
  • The inverters will get absolutely no AC inputs. They will be powered exclusively by the battery bank (BYD LVL 15.4)
  • The Quattros have an automatic Neutral/Ground bonding inside, when no AC input is used. Here's the manual:"The Quattro is provided with a ground relay (see appendix) that automatically connects the N output to the casing if no external AC supply is available."
I've been looking at this diagram for the past few hours, and I can't find any mistakes. But it's impossible that everything is right!

My doubts are the following:
  • where/how does the RCD/GFCI come into place?
  • does it make sense that inside the breaker box there's no bonding between neutral and ground? From what I understand, the neutral/ground bonding should be made in only one point for the whole system, and that's where the Quattro's internal bonding comes into play, together with the main ground busbar
  • for each Quattro, the AC output has three terminals: Line, Neutral and Ground. As I said, Neutral and Ground are automatically bonded together by the inverter, so does that mean that the Ground terminal has no wires connected to it? It seems that I can use the ground lug (chassis) and that would be enough.
  • the attached diagram has been made by me based on what I could read online for the "standard" setups, but I'm not quite sure that it would work for a split-phase system (I could't find a lot of examples for this kind of setup)

So please help me find out if something is wrong!
 

Attachments

  • grounding - small image.png
    grounding - small image.png
    1 MB · Views: 41
Not from US but I would say:
  • Quattro has an incoming line and ground too I think (AC in). Connect ground there to the incoming ground
  • Because off-grid Quattro will bond your incoming ground to outgoing ground and outgoing neutral
  • is not enough, bond both inverter's outgoing neutral and the outgoing ground together (this is your main bond)
  • after that comes the RCD to the lines and neutral
  • ground goes directly to panel

From what I understand, the neutral/ground bonding should be made in only one point for the whole system, and that's where the Quattro's internal bonding comes into play, together with the main ground busbar

On one level I would say :).
Can happen that you have more bonding between neutral and ground. Like here inside the inverter and you need to do outside too.
Victron has some docs about it. I think it was in a marine scenario. The level means that they are both before the RCD.

Also check your ground rod resistance. Here it has to be better than 10 Ohm. You even can have more rods connected together.
In off-grid you do not have the excellent grid provided ground, so you have to make a good one for yourself.
 
Back
Top