Lets kill the guy that asked yet another ground question

Re: Lets kill the guy that asked yet another ground question

JESSICA wrote: »

I have to ground my panels frames, via a 6 or 4 awg attached to a copper ground rod inserted 10 feet in the ground/soil;
I have to attach to THE SAME ROD ALL the following ground cables/wires:

1. a cable from the chassis of my mx60 controller;
2. one from the negative post of my battery bank;
3. one from the chassis of my inverter;
4. another one from the negative terminal of my inverter;

Note that #2 and #4 create a "ground loop". A picture of this would look like:

[FONT=Fixedsys]

Battery Negative=================Inverter Negative
                 |             [COLOR=Red]|[/COLOR] 
                 |             [COLOR=Red]|[/COLOR]
                 -------[COLOR=Red]--------[/COLOR]
                       |
           Ground Rod
[/FONT]

The "RED" portion above is what creates a "ground loop"--a parallel path for current to flow between the inverter and the battery. And, depending on the current involved, you could cause problems (i.e., your inverter can send 200 amps down your very heavy battery cables, but you are only using 6 awg wire for grounding--you may over heat the ground cable.

So, don't do #4.

Regarding the grounding of the Outback charge controller--it is probably OK--but always read the manual. The MX has a separate grounding lug attached to the chassis that (I don't believe) is attached to the battery negative terminal.

More important (in my situation): Can/should I use THE SAME GROUND ROD I have in the ground for lightning protection, the one that is attached (now) via # 4 bare copper wire, to another rod in the roof?

Lightning is not "simple". It flows according to a different set of laws (AC/high frequency rules--basically radio frequencies). So, having rounded/large diameter bends (not square corners, but something like > 18" diameter--if I remember correctly).

In some ways, it is like water flowing through a pipe... Nice rounded bends, the water flows without turbulence. A sharp 90 degree square bend, there is turbulence--and with lightning, it will find a different path to follow.

And, because of this (plus the high current, and the fact that ground and wires do not carry radio frequency energy very well) how close or far apart things are makes a difference too... If all of your major ground bond connections can be made within 10' or so of the ground (AC mains, battery bank ground, charge controller ground, etc.)--then sending them all to one rod is fine.

If your AC/earth ground rod is one end of the home, and 50' away is your solar equipment--then running all of the wire to the far ground rod may not be the best choice.

Here, drive a second ground rod near the solar equipment for your DC and Array Frame Grounds.

Personally, I would also connect this second ground rod to the closest metal water pipe (if you use metal water pipes in your home) too. And, if possible, I would run a 6 awg or heavier ground wire from the 2nd rod back to the first ground rod (although, I could understand if others here with more knowledge would disagree with this suggestion).

If I recall correctly, you have an MSW inverter, so do not ground reference your AC output (i.e., ground the neutral wire) at the MSW inverter (unless the manual tells you it is OK/Recommended--MSW inverters typically will get a "dead short" if the battery negative and MSW Inverter AC output are grounded together).

-Bill