I received this question recently:
I have posted it here with the permission of my friend Tim.
Hello mr Bill
Hope this finds you well during this covid crisis, bet distancing not a problem on the Canadian prairies, we’ve managed to avoid it, or was asymptomatic. Carol showed a pic of the siblings, fine looking crew. Unemployed at moment working on final stages of my off grid retreat. Hope you’ll entertain few technical questions.
Primary power is my gen but wanting to add some batteries and inverter for nighttime lights, tv etc.
Online literature said neutral/ground bonding should be at generator L(0), not load center, seems to be working fine, Plan on installing sub panel at ground level connecting to batteries/inverter and back feeding load center when needed. Wondering if bonding at generator will suffice for grounding or could this possibly damage gen. Gen will be isolated by disconnect at load center and breaker on gen itself. Or do I need alternate grounding/bonding when using batteries. Typically you bond at load center and run to ground rod as I understand it. I ran another line from ground bus bar back to gen L(0) then to ground rod. Should I ground sub panel? Also inverters usually 120 volts, can I install 240 breaker at sub panel with a jumper to energize both hot buses at load center
Had been looking at Used EV lithium batteries For 25$ each but seems that charging and fire hazards beyond my understanding, will use deep cycle marine or golf cart batteries and figure on changing out every couple years
In regards to grounding.
First, there are two systems under grounding that should be understood.
Equipment bonding/grounding.
All exposed electrical equipment should be/must be bonded or connected to ground.
This includes all metallic panels and junction boxes.
This includes the frame of the generator.
This includes the enclosure or chassis of any inverters.
The ground grid.
This may be one ground rod, a buried bare cable, a grounding plate, or other types of grounding electrode.
All of the rods, cables, plates and other grounding electrodes must be connected together.
The code requires and there are several good reasons that there is one and only one connection between the neutral and the grounding system.
My preferred location for this connection is in the main panel.
Your main panel typically is supplied with a green screw, that is often shipped loose.
You install the screw to make the connection between the bonding system.
If the panel is used as a sub panel, the screw is not installed.
If the screw is missing you may use a #8 jumper from the neutral bus to the ground bus to make the one connection between the neutral and the ground system.
The generator.
Some generators are shipped with a jumper connection between the neutral and the generator frame.
In my installs, I remove the jumper at the generator and ground the neutral at the main panel.
Inverters:
I did a similar system in the Yukon territory many years ago.
Rather than an inverter we used a large generator and a much smaller generator for night-time use.
It worked well.
Of course if you are using solar or wind energy this won’t fly.
When you run the cable to the generator, include a grounding cable to ground the generator frame.
You may add an optional ground rod at the generator, connected to the generator frame and to the grounding conductor running to the main panel.
I can’t say definitely yes or no on this without knowing a lot more about your layout.
“Online literature said neutral/ground bonding should be at generator L(0), not load center, seems to be working fine,”
This is okay, but with more than one source (generator and inverter) I prefer to make the ground to neutral connection at the main panel.
“Plan on installing sub panel at ground level connecting to batteries/inverter and back feeding load center when needed.”
A suggestion.
I would use the sub panel for just those lights and plugs that are intended to be used with the inverter.
I would install a transfer switch so that the sub panel may be fed from either the main panel (generator source) or from the inverter.
You may install your jumper on the inverter side of the transfer switch, so that the sub panel gets 240 Volts when fed from the generator and runs on only 120 Volts when fed from the inverter.