Grounding Multiple Systems

[teal95]

System 1 is a normal grid backup home system (at least for the US). 100 amp feed from the grid, SolArk 15k, 20 kW of panels and 30kWh of lithium batteries. Ground bonding is though the main grid panel with it being the only ground rod. Entire system is in a barn 200' from the house and main panel.

System 2 is for feeding 3 phase equipment in the barn. Currently 4x EG4 6400ex inverters with 2 more soon. At some point it will probably get more PV tied into them as the SolArk is already full.

The only connection between the 2 systems is the batteries. To me the 3 phase system should have it's own ground rod and bond in it's breaker panel. My electrician wants to tie all the grounds together including another ground rod in the barn.

Which is right or is there another alternative?

 

[timselectric]

One grounding system for everything. And only one connection point to the earth.
If the 3-phase system is not connected to the grid or any other system. It will need it's own N/G bond.

 

[teal95]

The only thing the 3 phase will be connected to is the batteries and the machines it's powering. From what I've seen of 3 phase breaker panels they don't have a neutral connection, or am I just not seeing it?

 

[timselectric]

The only thing the 3 phase will be connected to is the batteries and the machines it's powering. From what I've seen of 3 phase breaker panels they don't have a neutral connection, or am I just not seeing it?

3-phase wye has a neutral.
3-phase delta doesn't. (But can be corner grounded)

 

[timselectric]

What voltage 3-phase will you be using?

 

[teal95]

220 as the inverters can supply that and that's what the motors are spec'd for. Each inverter makes a leg at 127 volts with all the neutrals tied together. If I did my geometry right that's gives me 220v leg to leg, which I believe is what they are expecting.

I'm an EE but my specialty is microprocessor controls, so I only had one power class and that was 30 years ago. My electrician has never worked with 3 phase so I'm somewhat on my own. I did manage to find a guy at work who runs a similar home shop and he seemed to think I'm doing it right.

 

[timselectric]

Yes, 127/220v does have a neutral.
So you need a N/G bond for that system.
I believe that the Sol-Ark has a setting. Where it does it for you, internally.
If not, it's easily accomplished in the loads panel. Your electrician can verify which way to go.

I did manage to find a guy at work who runs a similar home shop and he seemed to think I'm doing it right.

The only problem with this is that it's based on the fact that he believes that his system is done correctly.

 

[teal95]

SolArk is only running the split phase, which in my mind is a separate system from the EG4's that are making the 3 phase. I don't have grid 3 phase available, that's the drive for this system.

I didn't asked the guy at work about grounding as I recognized that is was probably beyond his knowledge level.

 

[timselectric]

which in my mind is a separate system

They are separate systems.
The only thing common between them should be the grounding system.