Ground Rods

Crystal
Crystal Solar Expert Posts: 128 ✭✭✭
in Solar Beginners Corner #1
We have an off-grid solar system that is almost up and running. Just have a question about grounding.
Do we need three seperate ground rods at the panels, breaker box, and generator?
Thank you for your advice in advance.
~Crystal~
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Ground Rods
    Crystal wrote: »
    Do we need three separate ground rods at the panels, breaker box, and generator?

    No, you want one common grounding point for the whole system. Extra ground rods create alternate current paths, and you want to control where the electricity flows not let it find its own way (so to speak).

    A couple of other grounding concerns:

    MSW type inverters must not have a neutral-ground bond on the AC. They only want the (-) battery grounded, and inverter case if so design. Consult the manual for your particular inverter.

    Generators often come with "floating neutral" - no neutral-ground bond. This is good, as if your system should have the bond there should be only one. This is usually found in the AC distribution box. The gen may have a separate "chassis" ground lug which can be tied to the common ground of the system.

    Grounding is tricky stuff, and there are different opinions on what is "right". Also check local code if applicable.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,654 admin
    #3
    Re: Ground Rods

    As Marc says--tricky stuff...

    Generally, you want one ground rod at your AC panel next to your DC battery bank. Connect the neutral bond in the panel to the earth ground rod. Connect the DC ground bus to the earth rod. Connect any metal water pipes and gas lines to ground rod... Each items should have one and only one wire running to the earth ground rod.

    If you need more earth grounding for the main rod (rocky soil, etc.)--You can add more rods X feet (don't remember what code calls for X) way from center rod. Run ground wire from new rod back to "central rod".

    If you have a small genset (something like 3kW or less), most likely it has a floating AC neutral---Good. If the genset is larger, it may already have a frame to electrical neutral bond. Need to "remove" that bonding jumper. You can run a local ground rod to the frame ground of the generator.

    For the solar panels. If they are mounted on the home and it is straight run down the outside of the building to the central earth ground rod you did for your electrical grounds, you can run the solar panel frame ground to it.

    If the panels are mounted some distance away from the electrical panel earth ground, then you can drive a new ground rod for grounding the solar frames / mounting hardware to that local ground rod.

    Grounding is complex and before you do anything, need to make sure that "we on the forum" understand your setup.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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