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Doubts grounding an offgrid solar system

 
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Hi folks!

I just finished plugging in my panels to the inverter and now taking care of grounding and connecting AC to the house.

I got 3 grounding rods and was planning to place them as in the picture:


Does this sound a good idea or am I making some big mistake? I read somewhere that having multiple ground rods can actually be harmful, but in my case, they are all connected so it should act as just one, right?

Reason for this? Just playing safe and trying to get the best ground possible.

Thanks in advance for any tips/advice!

PS - this is a simplified drawing, obviously there are switchboards, fuses, batteries and all of that :)
 
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You can have as many supplemental ground electrodes as you like. Space them out and bond them together.

Usually having multiple supplemental ground electrodes is done where there are extremely sensitive electronics, (think cell towers. The grounding networks at these towers is comprehensive to say the least, im still hacking up cadmium..... probably!), high lightning occurance, extreme static or where ground conductivity is not sufficient for the purpose, rocky/sandy soil, shallow/no soil, low moisture in combination can cause issues and rods are added or horizontal solutions arise.

Mike Holt has some of the best lectures on grounding and electrical engineering in general which is valuable in re installations.

John Wiles should be referenced also.
 
frank li
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When wiring, it is best practice and should be s.o.p., all grounding landed first, especially before introducing live conductors.
 
Nuno Donato
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frank li wrote:When wiring, it is best practice and should be s.o.p., all grounding landed first, especially before introducing live conductors.



Hi Frank, thanks for the comments, much appreciated.

So I decided to bury only 1 rod for now, near the inverter, and test the system.

The output of the inverter, between live and neutral is 230V. But, oddly enough, when I measure between live and ground OR neutral and ground, I get a reading of approximately 110V!!

Any ideas what could be causing this? Or what kind of tests/checks I can do to diagnose the problem?
 
frank li
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You can get that anywhere the line is loaded. If you open a switch or breaker feeding that line, there should be nobody home.
 
Nuno Donato
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frank li wrote:You can get that anywhere the line is loaded. If you open a switch or breaker feeding that line, there should be nobody home.



but shouldnt hot to ground be the same (or nearly) as hot to neutral?
 
frank li
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What inverter do you have in place? With some inverters you will have an odd response.
 
Nuno Donato
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frank li wrote:What inverter do you have in place? With some inverters you will have an odd response.



It's an Axpert 5kva. Not sure if I should bond ground and neutral too... the manual doesnt say anything about grounding :/
 
frank li
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Oops, i didnt read well and diddnt see the split phase.
 
frank li
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Is it that your lines are split between services? Ther is something im not getting. I am unfamiliar with european electrical. Still.

Do you have 2 conductors and a ground?
 
Nuno Donato
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frank li wrote:Is it that your lines are split between services? Ther is something im not getting. I am unfamiliar with european electrical. Still.

Do you have 2 conductors and a ground?



I dont have any "services", its fully offgrid

AC output from the inverter is Line+Neutral.
 
frank li
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I guess i mean as far as european standard, even if you are off grid.

There should be only one place with a neutral ground bond in the building electric wiring system. This could be your distribution panel or the inverter and there are usually removable grounding screws or other devices for making one panel or the other, the one with the neutral-ground conductors bonded together.

When you test hot to neutral or the other hot or whatever you guys got going on over there! Im going to have to go back to school.... the ground is the neutral it seems. Ill go look and check on how that is done just so im not stammered. Never thought about it.
 
frank li
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I get it now. All should be fine. Just make sure you land the terminals with the right conductors indicated in the manual. Its like split phase no neutral. Except the ground. The ground is neutral. Do not short your inverter.
 
Nuno Donato
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frank li wrote:I get it now. All should be fine. Just make sure you land the terminals with the right conductors indicated in the manual. Its like split phase no neutral. Except the ground. The ground is neutral. Do not short your inverter.



So if I understood your reply correctly, there's nothing I should be doing differently and these readings are ok?
 
frank li
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Make sure protective earth is terminated with all equipment on one end and the ground electrode(s) on the other like a tail poked in the ground and it will be safe as can be so long as it has ground fault protection.
 
Nuno Donato
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frank li wrote:Make sure protective earth is terminated with all equipment on one end and the ground electrode(s) on the other like a tail poked in the ground and it will be safe as can be so long as it has ground fault protection.



Yeah I have a big rod where the ground wire connects to, on the other end of the wire it connects to a bus bar on my switchboard, where all other ground wires (coming from sockets and etc) will connect to.
 
frank li
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Ok, so it does have neutral.... still odd ducks to me. Ill listen for better comments.
 
frank li
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What i do is test continuity to determine that there is only one point where neutral is bonded. I just read that european standard has a neutral bonded to ground. This (edit, continuity test) is done at the inverter chassis/protective earth terminal and neutral output terminal. (Edit 2, and in all other panelwork where it could be done)



 
frank li
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I think you just divided it with the meter. Do check your wiring to be sure about the neutral/ ground bond location. It needs to be known regardless.

My replys look horrible, but im straightened out, i think. My house is wired in much the same way but at lower voltage. I have a single phase but at lower voltage. Our inverter is 120v and i jumper "L2" in  split phase panel and run all single pole breakers. I just had so many gaps about europe.....and it applies everywhere.

Your inverter could have the neutral ground bonded. If so you would get a fault as a result of a bond somwhere else, so long as its wired properly and that protection or indication is in place.

Ac disconnects, distribution panels, transfer switches, all the enclosures with the facility to have the neutral and ground tied together somehow, should be inspected and made sure to be only at one location within your system.



 
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