grounding?

S.A.S.A. Registered Users Posts: 1
I am putting together a small 12V DC system powered via a 40W panel. It is powering an LED light and small consumer electronics at an absolute max of 10A. What type of grounding if any do I need for this type of system?

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  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: grounding?

    To review, grounding does several things.

    First, your cabin/home plumbing/gas lines, etc. are "naturally" at earth ground. If a 120 VAC hits one of those, and the Neutral is bonded to earth ground (and plumbing, etc. grounds), then a short circuit is created and it will pop the upstream circuit breaker.

    If you had "floating" plumbing fixtures, sinks, etc., a 120 VAC to sink would cause an electrocution hazard somebody has hand on sink and turn son metal faucet).

    Another issue is lightning/static discharge. If you have a chance of lightning in the area, any "ungrounded" electrical system (or metal for that matter) could be charged up and cause a shock hazard for somebody working in the building.

    For small off grid power systems (generally less than 3.5 kWatt for an AC generator) usually is "floating" (ungrounded). Not that anything is safer (or even more dangerous), it is just where the electrical code makes its cutoff.

    So--first question--This is a very small system and you have no 120/240 VAC power (just 12 volt DC, possibly a small AC inverter for power tools, etc. when needed). There is really no shock hazard/grounding required for this system. If you are permanently installing the battery+DC wiring and it will be near metal fixtures, metal bench, etc... You might choose to ground those to Battery Ground/negative bus. But a "floating" DC system is pretty safe too--A "single" short does not do anything (you need two connections, from + to - on the battery bank to get current to flow.

    Your bigger question is probably around lightning... If you do not have direct or nearby strikes in the area, then grounding will not be needed. If you have lightning in the area, then grounding the battery negative could help "control" where the excess static charge/lightning energy goes (to earth ground rod, metal water pipe, etc.).

    In the end, there is no "functional" earth ground needed (except for some florescent tube lights and other specialized items like HAM Radio or other stuff) for DC systems.

    A small floating power system is fine assuming neither of the above are issues.

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