Grounding Solar Panels to Utility Ground or New Ground Rod?

[bob.longmire]

Hi All,

I live in a typical neighborhood subdivision in the American Southwest. I have a roof mounted systems with 20 panels. My house doesn't have a grounding rod that I can access without going into my main breaker panel for the whole house. It looks like the grounding wire leaves my main panel and goes into the same conduit my utility mains come from, so I'm not sure if my house has a grounding rod on the property or not.

Initially, I installed a new grounding rod about 50 feet away from my main panel and ran a ground/bounding wire from my panels to this rod (I also have lighting shunts on the DC output lines from the panels that tie into this ground before the DC wires run into the house and connect to the inverters). The panel frames are the only thing connected to this grounding rod, everything else uses the ground in my main electrical panel.

All of that to say, I noticed some of the other homes in my neighborhood with solar bring the grounding wire from the panels straight into the main electrical panel of the house. This seems crazy to me as it would invite the lighting right into the main electrical panel.

I get the logic to only have 1 source of grounding for a system. And I have that for everything except the panels on the roof.

Should I keep my current setup, or should I do what others in the neighborhood did and run the ground from my rooftop panels into my main electrical box and ground it to my house ground?

Thanks!!

 

[Quattrohead]

I would have done it like you did. Basically 1 ground for the DC side of the system and another for the AC side.

 

[EastTexCowboy]

I'm not a guru on this stuff but there are a number of threads on here about grounding and the consensus is you should have only one earth ground. That would indicate you need to ground back to the earth ground in your main panel. As for the lightning, you're probably going to want some kind of protection between the panels and your house no matter what you do.

 

[OilCan]

From the standpoint of lightning it still has a path into the house via the conductors of the PV panels, unfortunately the nature of high voltage. Grounding the panels is more for providing removal of static buildup and preventing shock by contact if a fault developed in the system and you happened to touch such a panel. My PV system is all ground mounted in two areas, each group has it's own driven ground rod, these are all bonded and grounded with their own separate ground back to the sub-panel and inverters. All are system grounded. Point is to try to keep everything at the same potential as possible. My home lightning rod system also has it's own driven grounds diagonally across the most distant corners that connect all lightning rods together, these are likewise bonded to the main service panel ground.

In addition to all of that for ham radio, besides the building service safety ground a RF grounding system is also employed to for communications use, RF grounding is a different animal because of the wide range of frequencies employed. Just the same it becomes system bonded with everything else. With a direct strike from lightning about the most one can do to avoid damage is not to be connected, for the most part you are protecting things from proximity strikes and static charges.

To minimize lightning strikes a well-designed lightning rod system can help minimize such an event because the lightning rod points will attempt to reach up above the structure about a 100 feet more or less and dissipate the "leader" before it makes contact with the structure to avoid damage.

That is a study in itself and the codes require all of this to be system grounded.

Not all methods of grounding are practical, so we attempt to do the best we can and pass any required inspections if needed.

Some concepts are covered in this article:

Top Band Hams - Proper Grounding for Safety and Lightning Protection

K3BM TOPBAND HAMS

topbandhams.com

 

[OilCan]

I'm not a guru on this stuff but there are a number of threads on here about grounding and the consensus is you should have only one earth ground. That would indicate you need to ground back to the earth ground in your main panel. As for the lightning, you're probably going to want some kind of protection between the panels and your house no matter what you do.

Well not sure where that consensus originates but I think what you may have in mind is "single point grounding", where all grounds will tie together at a single point. Depending on soil conditions some structures may use perimeter grounding to improve their ground conductivity, that cannot be accomplished with just one ground rod or plate in some cases. They will bury heavy bare cable, plates, rods around the perimeter of the building and all gets tied together at a single point.

 

[EastTexCowboy]

Well not sure where that consensus originates but I think what you may have in mind is "single point grounding", where all grounds will tie together at a single point. Depending on soil conditions some structures may use perimeter grounding to improve their ground conductivity, that cannot be accomplished with just one ground rod or plate in some cases. They will bury heavy bare cable, plates, rods around the perimeter of the building and all gets tied together at a single point.

Grounding is a much debated topic on here but I'm basing my assumption on info provided by @FilterGuy as well as several others on the forum. He has some excellent documentation on grounding in his Resources. When completely off grid I had two separate earth grounds but now I have everything grounded to a single earth ground, which is the original for the house. Along those lines, it seems to me if you have multiple earth grounds you're setting yourself up for a ground loop. I hate these grounding discussions. They always give me a headache.

 

[OilCan]

Thats the purpose of system bonding and grounding to eliminate loops which is essentially sounds like you did. As far as discussion I know what you mean. When you place your equipment "between" grounding points is the development of the loop you are concerned about. Bonding and grounding your equipment at the "end" point or "single point" eliminates that for the most part.