Grounding this setup?

How to ground this offgrid system? How does a simple groundrod sound to you guys? The manual for the tristar dictates that a GFDI must be installed, but how should it be wired in a small inverter-free system like this?
Anything else I should think of? The misc. small stuff is basically charging mobile phones a little now and then.

Comments

  • mike95490mike95490 Solar Expert Posts: 8,196 ✭✭✭✭✭
    Re: Grounding this setup?

    I'll assume the panels are mounted on metal and a metal pole in the ground several feet? That should ground the mount pretty well.

    What does the charge controller manual say?

    I don't see any lightning protection, is it needed in your area?
    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 ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

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  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Grounding this setup?

    Is this for an off-grid home/cabin or a mobile application like an RV?

    I wouldn't worry about the GFCI requirement (of NEC); many of us have been using off-grid power with the negative soundly bonded to Earth ground for years without any incident.
  • BB.BB. Super Moderators, Administrators Posts: 28,776 admin
    Re: Grounding this setup?

    To confirm, the two panels are wired in series? You are looking at ~1.4 volt drop. You could go 1 size larger for wiring--but it should work fine as designed.

    Do you have any plans to add more panels in the future? (panel wiring size).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • MisterBMisterB Solar Expert Posts: 156 ✭✭✭✭✭
    Re: Grounding this setup?

    Grounding is dependant on local conditions. If you drive a grounding rod into moist soft soil, 1 should be fine. If you are in a drier climate with dry ground, you will need more grounding rods and to connect them together with bare copper grounding wire. If you are grounding for lightning protection, you should have a good earth grounding connection and the more grounding metal you have buried, the better.

    I live in a very dry area with severe lightning at times and I have over 200 feet of copper buried on my property in a single point ground system. I have never had a lightning strike do any damage but several of my neighbors have.

    I'm also in charge of a small water system which is on the grid and it has for grounding at the pumphouse: 1 grounding rod which is bonded to the rebar in the concrete foundation and to all the pipes buried in the ground which includes a well casing that goes to a depth of 640'. I've seen lightning strike the power lines less than 1/2 a mile away from our system and do no damage. There are serious surge protectors in the pumping system but they depend on a good ground connection to work properly.
  • System2System2 Posts: 6,290 admin
    Re: Grounding this setup?

    This offgrid cabin system is currently under construction . The panels will be mounted, in series for a higher V, on a 9cm (diameter) 4mm (thick) 3,7meter tall steel pipe (½ under ground, ½ above). I'm from the northern part of Sweden (must've missed that part of the user registration) and lightning isn't particularly nasty around here, and besides, the location of the panels are lower than the house which in turn is situated lower than the surrounding forest. You don't have to worry, the house/forest won't obstruct any light.

    The tristar manual, page 5, http://www.morningstarcorp.com/en/support/library/TSMPPT.IOM.EN.04.pdf
    "This unit is not provided with a GFDI device. This charge controller must be used with an external GFDI device as required by the Article 690 of the National Electrical Code for the installation location."

    No expansion plans of the system exists, but who knows what can happen when the photonaddiction really kicks in. :P

    Thanks for the fast replies by the way =)
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Grounding this setup?

    I don't see anything wrong with the plan.
    Don't worry about the NEC GFCI requirement. Put the Earth ground rod in, attach the chassis ground of the controller & the (-) of the battery. Like Mike said the pole mount should provide sufficient ground for the array.
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Grounding this setup?
    .p.s. wrote: »
    This charge controller must be used with an external GFDI device as required by the Article 690 of the National Electrical Code

    I know what it says, but if you spend time around this form, you'll find that at best, these GFDI devices and the way they must be wired in, are at the very least, controversial, and at most, downright dangerous. I don't have one on my system, and from everything I've read on here by those far more expert than I. there's no way I'd install such a thing, especially on a smaller system. So my opinion? I agree with Cariboocoot, Don't worry about it. :D
  • MisterBMisterB Solar Expert Posts: 156 ✭✭✭✭✭
    Re: Grounding this setup?

    Noting that the original poster is in Northern Sweden:

    Northern Sweden in the forest will be a moist climate and grounding will be simple. The trees and vegetation will always keep the soil moist.

    GFDI is new to me. I just read the Outback pdf on it. Ground fault protection in DC circuits is something I haven't even thought of before. AC GFCI outlets are required by the American NEC in any area like kitchens or bathrooms where electrical equipment is likely to come in contact with moisture. The European equivalent, as far as I can remember, is called a "Differential Breaker" and is usually wired to the service entrance and protects the whole house or apartment, not just certain areas as in the American NEC. That being said, the only European countries where I have lived and looked at the way the wiring was done were Spain and Ireland and Sweden might have different code requirements.

    I have seen problems with GFCI outlets on off the grid systems. It usually comes from having the usual GFCI outlets in around the kitchen sink and bathroom and having one in the inverter. They don't like to be wired downstream from another GFCI outlet. In one instance, it created a phantom load of around 12 watts on the inverter. In another, pluging certain things in, like a big Mac computer, would trip the GFCI breaker at the inverter but it would work fine if the GFCI was removed.
  • BB.BB. Super Moderators, Administrators Posts: 28,776 admin
    Re: Grounding this setup?

    For computers, it is common to put AC input filter capacitors between line to line and line to ground... And it can create several milliAmps of current into the safety ground. And the AC GFI receptacles probably trip around 3-5 milliAmps.

    So, it is easy to see connecting a couple computer devices causing issues (computer, some sort of modem, printer, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Grounding this setup?

    AC GFCI is a whole different kettle of fish, generally work well, and do their job. The DC version as used on solar is something else and works in a totally different way.
    By the way, I like the European term Differential Breaker, because that's how they (AC ones) actually work. They monitor both lines for any difference in current flow, and finding a difference triggers it to disconnect.
  • MisterBMisterB Solar Expert Posts: 156 ✭✭✭✭✭
    Re: Grounding this setup?
    AC GFCI is a whole different kettle of fish, generally work well, and do their job. The DC version as used on solar is something else and works in a totally different way.
    By the way, I like the European term Differential Breaker, because that's how they (AC ones) actually work. They monitor both lines for any difference in current flow, and finding a difference triggers it to disconnect.

    I like the European term too. The main difference between the European and American implentations is where they are put--1 big one at the service entrance vs. several where they are most likely to be needed. A lot of inverters come with a GFCI outlet which is the European way of doing it and it makes sense if the inverter is going to be put in a boat or RV.

    Conceptually, the DC GFDI works on the same principle but the need for a ground fault protection in low voltage DC systems is not there as far as I can see. There might be a need in high voltage, high current systems but the safety issue would be more limited than in general household wiring. Unless you're actively working on the DC solar charge system, you're not likely to change anything in the electrical ciruitry but all you have to do on the inverter side is plug the wrong piece of equipment into the plug or get something wet to mess something up which is why both over current and and ground fault protection are required.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Grounding this setup?

    There's a fundamental difference between NA power and EU power: we use 240 VAC split with a neutral line and they use 230 VAC without any neutral. When they have a ground fault it's on a hot to hot circuit, so both L1 and L2 must be shut down. Over here it's usually L1 or L2 to N, so you need only kill the effected hot line; the rest of the service stays active. I'm not sure I'd be keen on shutting down everything because of a fault on one branch. Are you sure it isn't just 230 VAC ground-fault breakers on select branch lines?
  • BB.BB. Super Moderators, Administrators Posts: 28,776 admin
    Re: Grounding this setup?

    The 3-5 milliAmp current limit, in the US, only applies to branch circuits with plugs and consumer equipment (at least when I was designing equipment a decade or two ago).

    Larger circuits and hardwired equipment did not have AC GFI connected...

    One reason is that large equipment will have >>5 milliamps of leakage current--and you will have trips all the time. Normally, the system had to have locks or screws to keep untrained technicians out of hazardous areas.

    The 3-5 milliamp limit are to reduce the chance of stopping a person's heart when using tools/electrical devices in wet areas. I would doubt that you could detect 5 milliamps of leakage current on a whole house circuit reliably--There is just too much stray leakage current around.

    And, I would not want to kick a main breaker and loose all lights/other electrical items in a home... It would be like having a 15 amp branch circuit trip the main breaker of a home--pretty much a pain in the behind.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • MisterBMisterB Solar Expert Posts: 156 ✭✭✭✭✭
    Re: Grounding this setup?

    There is a lot of diversity within European countries in the way they do things. The standard European mains voltage is single phase 230v AC 50hz. They do use a neutral and ground in their wiring.

    The picture at the top of this article is pretty much what I saw installed at the service entrance of one apartment I lived in in Spain. I remember reading "differential breaker" on the label. This was around 1998. It is also a good overview of ground fault protection and how it works.

    http://en.wikipedia.org/wiki/Residual-current_device

    And for more on plugs and sockets worldwide and how they're wired:

    http://en.wikipedia.org/wiki/AC_power_plugs_and_sockets
  • System2System2 Posts: 6,290 admin
    Re: Grounding this setup?

    Allright, problemo solved.. much appreciated :)
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