grounding confusion

wxh3
wxh3 Solar Expert Posts: 70 ✭✭✭✭
in Advanced Solar Electric Technical Forum #1
I am a bit confused about grounding in my small standalone system. I have a Morningstar ProStar charge controller and SureSine inverter. Both have grounding terminals and instructions stating the they should be connected to ground. The ProStar manual says that internally, its load negative, solar negative, and battery negative terminals are all connected. The SureSine does not say anything about its ground terminal other than the gauge should be larger than the power wires. I assume inside the ground is connected internally to DC negative?

Are there any problems connecting both to my ground bus? I have read in places that I should only connect my system DC negative to ground in one place. Maybe I am misunderstanding something.

Also, on the AC side I am planning on connecting one of the two power wires to my ground per Suresine instructions. Is it OK (and correct) to connect my A/C side ground to the same ground bus as my D/C side? I saw one place that said "NEVER" connect your AC and DC grounds...so does that mean they both must run out to a ground rod in separate wires? Or that there should be different ground rods?

I am also grounding my solar panel frames but that is a separate connection to my ground rod.

Sorry for all the questions. I get frustrated searching around for grounding advice...often the documents are a bit confusing to me and/or don't seem to apply to what I am doing. I need "Solar System Grounding for Dummies."
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  • wxh3
    wxh3 Solar Expert Posts: 70 ✭✭✭✭
    #2
    Re: grounding confusion
    wxh3 wrote: »
    The SureSine....ground is connected internally to DC negative?

    I now think I may be mistaken here...the SureSine ground terminal is probably just a chassis ground. Thus, I think there shouldn't be any problems connecting both devices to ground. Sorry for wasting bandwith in the "advanced" forum for this...
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  • nigtomdaw
    nigtomdaw Solar Expert Posts: 705 ✭✭
    #3
    Re: grounding confusion

    The main thing to avoid is having multiple separate earth points. Having a earth system for say your generator and a separate one for your inverter is bad.

    One earth ground system for all aspects of your install is the correct way as per Xantrex recomendations. I think it is acceptable to earth your PV array chassis separately if it is some way off your main system.

    Having separate earthing points can actually encourage lightning strikes between them because of potential voltage imbalances.

    I hope I have this right and please correct me if not
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #4
    Re: grounding confusion
    nigtomdaw wrote: »
    The main thing to avoid is having multiple separate earth points. Having a earth system for say your generator and a separate one for your inverter is bad.

    To put in layman terms, all of you DC grounds get tied together, then goto ONE grounding rod.

    I use the same grounding rod for my DC and AC systems.

    It is common on the DC side to have the negative of power tied to a ground lug.

    Also, you are not wasting bandwidth. We all start as noobs.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #5
    Re: grounding confusion

    Do a search here about ground loops in dc/ac systems. I don't remember the exact thread, but there is considerable conversation about damage to generator voltage regulators due to improper grounding of ac/dc systems.
    (I think this is the thread) http://forum.solar-electric.com/showthread.php?t=1623&highlight=generator+grounding

    Tony
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