Beach system without Ground

lazza
lazza Solar Expert Posts: 336 ✭✭✭
in PV Installers Forum - NEC, Wiring, Installation #1
HI All

we are about to do some events on the beach :D with PV panels and a typical off-grid set up.

There will be no possible ground connection for the AC side.

I am therefore thinking of connecting the default Neutral to Ground connection to the "Dummy" terminal within the Victron inverter (see page 8 and Appendix B of the manual http://www.victronenergy.com/upload/documents/Manual%20-%20Phoenix%20Inverter%20Compact%202000%20-%20rev%2002%20-%20EN%20NL%20FR%20DE%20ES%20SE.pdf)

.. this will be in order to leave the whole system "floating".

I will then put in a GFCI (RCD) and bi-polar circuit breakers in order to protect both the neutral and live sides, as in fact there wont really be a neutral.

For safety purposes, is this the best system that I can install bearing in mind the lack of a ground connection?

Thanks
Larry
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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Beach system without Ground

    There's no point. Without an actual Earth safety ground you don't have any grounding and no way to make the neutral "safe". By making the neutral-ground bond anywhere all you will be doing is energizing the grounded portion of the system, i.e. every metal case in the place will be live. So don't do this.

    Using a GFI outlet is a good plan, in that if someone touches either hot wire and creates a grounding path to the sand it should kill the power on both sides and make things safe again. Test the outlet to make sure both sides go dead when the GF is tripped. There's some cheap junk out there.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #3
    Re: Beach system without Ground

    Can't you just drop a line in the sand ?
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #4
    Re: Beach system without Ground
    mike90045 wrote: »
    Can't you just drop a line in the sand ?

    Or at least draw one.:D
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  • lazza
    lazza Solar Expert Posts: 336 ✭✭✭
    #5
    Re: Beach system without Ground

    Wouldnt it be hard to make a good ground connection doing that? I'd rather have a floating system than a badly grounded one
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: Beach system without Ground

    if this is temporary one can throw a metal plate or screening of over say a square meter or so of ground and connect to that as a temp ground.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,639 admin
    #7
    Re: Beach system without Ground

    Get back to the fundamentals. Why do you ground.

    Lightning, electric shock, reducing chance of electrolysis, are a few that I can think of...

    So, first, do you have a chance of lightning (afternoon thunder storms, etc.)? If you do, then grounding a system with lots of wiring (i.e., more than just powering a few loads close to the system) is still very important. Buried metal plate (Niel's suggestion), burying some lengths of bare copper wire, etc. would all be a help (comprehensive lightning protection is complex). But that still leaves as an issue a bunch of people exposed to lightning conditions--Suggest looking at lightning alert equipment so you can evacuate before a first strike.

    second, electric shock. An isolated AC output system (usually a TSW inverter has an isolation transformer) is actually pretty safe. Unless an AC output wire gets shorted to ground somehow (failed insulation, etc.). Then, a safety ground of some sort is important. If this system will be powering, for example, sound system for a stage (as an example)... You have lots of equipment, people, and widely distributed equipment. Even if you cannot get an "earth safety ground"--That is really the wrong thing to focus on. Instead, look at carrying the green wire from the inverter case (and battery ground) to the major metal objects (stage, equipment racks, equipment green wire ground, etc.). What you want is a green wire path back to the TSW inverter (and the white wire/neutral green wire connection) to safely "short" any AC (or DC) hot wire to metal ground connections (blow fuse, pop GFI) instead of causing something to become electrified (i.e., somebody grabs a mike stand while holding a metal rail on stage).

    Other things (electrolysis, hard starting of some florescent tube fixtures, spark ignition for some stoves) can also be affected by lack of grounding--but they are more rare and usually not major safety issues.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
    Re: Beach system without Ground

    If you are going to try this with a "portable grounding system" (flat grounding plate buried under wet sand) take a couple of extra precautions: check the outlet with a plug-in tester after you connect everything up to see that you actually have a viable ground and if not, be able to disconnect the neutral-ground bond to return the system to "floating". Not perfect, but every little bit helps.

    You are quite right that floating is better than a bad ground.
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