Inverter must have separate ground?

Re: Inverter must have separate ground?

It looks like I need to run a separate "DC grounding conductor", #8, from the inverter to the existing home grounding rod outside.

So the "AC grounding conductor" then can be the usual ground wire that is bundled with standard electrical wiring?

Re: Inverter must have separate ground?

mike90045 wrote: »

Q) What kind (Brand, Model) of inverters are you using ?

Xantrex GT3.3 (240)

mike90045 wrote: »

Be cautious, as inverters generally work OK without a ground, and that one of the house wires (usually white, on the wide blade of an outlet) is tied to ground. You don't want to inadvertenly get both inverter wires hooked to ground.

Right. The neutral and ground are bonded only at the main service/breaker panel outside the home. The Xantrex has a ground bus bar, and the diagrams depict DC and AC grounds tying to this point. What I would like to make sure of is that I need to continue the DC ground (coming from array) with a separate conductor to the grounding electrode.

Let me see if I can make an ASCII diagram of the grounds:
For simplicity, I'm showing one inverter (there are two).

Here's what I think I'm supposed to have:

[[Array] [Inv.] [subpanel] [main svc] [gnd]
AC ................x________x______x_________X
DC x________x_____________________X


Here's what I have right now:

[[Array]] [Inv.] [subpanel] [main svc] [gnd]
AC .................x_______x_______x_______X
DC x________x


The ____ is a ground wire, 'x' is a bonding point, and '...' is nothing; it's the only way I can make white space (a 'tab') using this editor.

Re: Inverter must have separate ground?

Thanks for the reply. I understand how they work and how they must be connected, but I'm trying to clarify the grounding requirements.

The diagrams show all grounds (DC and AC) bonded at the ground bus bar provided in the Xantrex wiring box. So my particular question is, although these grounds are bonded at this point, do I still need to run two separate ground wires from the inverter to the building ground electrode?

It seems to me that, due to the ground bus bar in the inverter, having two ground wires makes little sense (electrically). Once the grounds are bonded, then any wires running from that point (inverter) to another common point elsewhere (building ground) are simply parallel conductors. It doesn't hurt anything, but is it really necessary? Is it "one of those things" in the code that you do because it says so?

A related part of this question is where these ground conductor(s) are allowed to run. One of them, no doubt, is the bare ground wire on the AC side that comes with standard house wiring (Romex, NM-B, etc.), and this obviously runs right along with the wiring. Where can the DC ground run (if required)? If the inverter is mounted outdoors, then you normally run a ground conductor from the inverter down the side of the building to the nearest grounding point. If it is indoors, however, (as is the case here) where can I run this ground conductor? Do I need to bust through the nearest exterior wall, or can I run it alongside the AC wiring, which goes through the attic before it finally exits the building?

Cheers,
AJB