DC grounding.......all electronics (AC&DC) mounted in same metal cabinet.

[pullin_gs]

My inverter and charge controllers do not have ground-lugs. I measured ~ohms between all DC-terminals and metal enclosures of inverter and charge controllers.
I still would like to ground metal chassis (by bolting on a ground lug of my own making) of inverter and charge controllers to a DC-ground bus bar inside metal cabinet (which is also grounded to same DC bus bar).

On the AC-side (output of inverter):
Inverter neutral and AC-ground are NOT bonded.......bonding will occur at main panel in which inverter AC-output connects via transfer switch.

I plan on bonding AC ground of inverter to the DC ground bus bar.

Does this sound like a safe plan?

I'm dealing with 150VDC and do not feel comfortable not having any of the metal chassis of the electronics components not properly grounded with metal cabinet (which is also bonded with house-ground) which houses everything.

PS: Within cabinet, all DC breakers and SPDs are housed in their own DIN enclosure, which is also bonded back to DC ground bus bar.

Thoughts?

 

[timselectric]

I still would like to ground metal chassis (by bolting on a ground lug of my own making) of inverter and charge controllers to a DC-ground bus bar inside metal cabinet (which is also grounded to same DC bus bar).

Please check your manual. Some tell you not to do this. It could cause catastrophic damage.
Especially if it's an AIO unit.

 

[pullin_gs]

Please check your manual. Some tell you not to do this. It could cause catastrophic damage.
Especially if it's an AIO unit.

Thanks for input. The manual is pretty sparse. Grounding is not mentioned at all. Only panel-DC-in and battery-charge-out.
Controllers and separate inverter enclosures are aluminum and floating (no continuity to respective + or - DC terminals).

 

[timselectric]

Personally
If it doesn't specifically tell you to, I wouldn't.
Unless it's a mobile installation. Then, negative battery to vehicle chasis is fine. (Not solar)

 

[Shimmy]

It is really confusing for systems that permit grounding on the DC side but do not require it. (Schneider XW-Pro)

When do you want to ground the DC system in general terms? If the systems are designed to run ungrounded do they have a built-in ground fault alarm?

As for a chassis ground, that is the minimum you want to do for sure.

 

[timselectric]

I never ground PV, unless it's required by the SCC manufacturer.
And only ground the negative of battery, if in a mobile application.

 

[Zil]

Does the inverter have three wires output? Line, neutral, ground? Black, white, green? If so where does the green connect?

 

[pullin_gs]

Does the inverter have three wires output? Line, neutral, ground? Black, white, green? If so where does the green connect?

Inverter is 120VAC. On AC side it has neutral, ground (unbonded) and hot.
Chassis of inverter is bonded internally to AC "green" ground.
This one is easy. I have indeed grounded chassis of inverter to ground bus bar (located inside cabinet).
Steel cabinet is also connected to ground bus bar.
The two charge controllers I am uncertain. Charge controller chassis is not bonded to DC "-"or DC "+" of either panel-in or battery-out terminal.
I want to connect charge controller chassis to ground because of unlikelyhood 150VDC (panel string voltage) making it's way it's ungrouned chassis (which resides in grounded steel cabinet along with other electronics.

 

[timselectric]

You can add a ground jumper to the SCC chasis.
But, if it's bolted to the grounded cabinet with at least 2 bolts. It's essentially grounded.

 

[pullin_gs]

You can add a ground jumper to the SCC chasis.
But, if it's bolted to the grounded cabinet with at least 2 bolts. It's essentially grounded.

Understood. Grounding each chassis back to copper bus bar in cabinet is something I had to do (even though rack-mounted w/multiple screws) building 48v PBX and server systems. Old habbits are tough to quit. Anyway I do want to

 

[pullin_gs]

Here is an excellent video I just found today which goes over grounding DC&AC covered in 2011 NEC 690.

 

[timselectric]

Here is an excellent video I just found today which goes over grounding DC&AC covered in 2011 NEC 690.

That's good to follow, with one change.
In 2014 or 2017 (I don't remember which), the NEC dropped the requirement for the extra ground rod. (Now called an auxiliary grounding electrode)
Because so many people were dead set on still doing it, it's still allowed. But the NEC didn't want the liability of requiring it. And for safety of the equipment, it's not recommended.

 

[SmittySmiles]

2014. I installed my DIY system with batteries, by the NEC and it passed inspection (with one ground rod). I currently sell power back to the utility (what I don't use). My Batteries (-) are grounded. If lightening strikes it will go through the batteries straight to ground. No problem. All ground connections including chassis, enclosures, should go to your electrical panel and ultimately to the ground rod. (IF THEY ARE NOT GROUNDED THROUGH SOME OTHER MEANS. Some stuff is internally grounded). Note: If you create a ground loop anywhere, you may burn your house down if lightening strikes, because current could circulate through the ground loop and melt your conductors, instead of dissipating through to the ground rod. Just something to look out for.

Only an opinion!

 

[timselectric]

I don't want lightning going through my batteries.
My only DC ground connection is through the inverter protection circuit. (House, not mobile)

 

[SmittySmiles]

You might find the negative side of your batteries are grounded through the inverter, already. My batteries are.

 

[timselectric]

You might find the negative side of your batteries are grounded through the inverter, already. My batteries are.

Yes, this is how it should be.

 

[pullin_gs]

Yes, this is how it should be.

Not with the inverter I use. Inverter ground (case) is not bonded with negative terminal of inverter input.

 

[pullin_gs]

I don't want lightning going through my batteries.
My only DC ground connection is through the inverter protection circuit. (House, not mobile)

I implemented SPD protection (surges redirect to ground) on each panel string where they terminate into cabinet before controllers.
Considering SPD on AC-side of inverter (inside cabinet) also.

 

[timselectric]

I implemented SPD protection (surges redirect to ground) on each panel string where they terminate into cabinet before controllers.
Considering SPD on AC-side of inverter (inside cabinet) also.

Good plan

 

[SmittySmiles]

I understand the apprehension. Consider a capacitor. The AC resistance of a capacitor = 1/2*Pi*Value of C*frequency. The higher the frequency the lower the AC resistance. Lightening is a very high frequency spike. Having said that, the batteries would be seen by the lightening as a short to ground (Extremely Low Resistance) and would right through them to ground.

But, I get it.