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Hi I am installing an off grid solar system form my orchard and shed. Basically there are some pumps, lightning and some household appliances like refrigerator etc.

I have read many articles about grounding/earthing, I know what is EGC and GEC are but I cannot figure out the proper way of grounding my equipment.

I have attached a very crude drawing (sorry for my paint skills). From what I understand I have to connect all bare metal parts together with a copper conductor and connect that to Neutral Line (this is EGC). Also I have to connect the neutral to the earth through an electrode (this is GEC).

It puzzles me since if a lightning strikes to the metal frame of the pv array, all the EGC since all metal parts of all appliances plus the neutral line will be momentarily raised to the voltage of the lightning strike ?

Also if a lightning strikes to a conducting cable like the cable going to the motor the SPD will close and again the EGC voltage will be raised to lightning potential ?

If someone could point out the following questions I will be grateful.

1)There are 8 grounding points in the drawing. Which of them should be bond together ? 2) How many grounding rods I need ? 3) Where should I connect the Neutral Line to the Grounding Rod ?

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  • How are you planning to do DC ground fault protection in this system? – ThreePhaseEel Sep 10 '18 at 16:32
  • I forgot to ask that but I think DC negative should be connected to ground. I saw post where people advice against that claiming damage to their equipment by ground loop currents. I was thinking that using 2 pole circuit barkers will mitigate the problem but I could be wrong. – Samet Sevilen Sep 10 '18 at 16:50
  • You should thoroughly read Article 690 of the National Electrical Code. It may not be required in Turkey but it makes a lot of good sense. It is available to view for free on the NFPA web site. – ArchonOSX Sep 11 '18 at 7:54
  • Also @SametSevilen -- what voltage does your solar array (input side of the charge controller) run at? – ThreePhaseEel Sep 13 '18 at 4:25
  • Furthermore @SametSevilen -- what make and model is your inverter? (Some inverters will supply an internal N-PE bond depending on what grid code is configured) – ThreePhaseEel Sep 13 '18 at 14:44
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First off you should tell us where you are on the planet in order to get accurate answers.

1)There are 8 grounding points in the drawing. Which of them should be bond together?

All of them should be bonded so that they are at the same potential.

2) How many grounding rods I need?

There should be a minimum of one ground rod per location and possibly two. If all this equipment is in the same location two should suffice. If it is spread out over a large piece of property then I would judiciously add more rods. There is no exact answer here.

3) Where should I connect the Neutral Line to the Grounding Rod?

As close to the main service panel as possible.

Good luck!

  • Thanks for the answer. I live in Turkey but there is no utility around the shed and I have no connection to the grid. If I bond all the ground connections together what happens if a lightning strikes the PV array frame ? All the equipment is in the same location. Where should be the two ground rods located ? Should the nature line be connected to the ground rod before or after the main ac fuse? Should I connect DC negative to the ground ? – Samet Sevilen Sep 10 '18 at 16:36
  • If you have no connection to the grid and your PV array is your sole supply I would make sure the array frame is well grounded with a ground rod at either end of the array. Then carry a #6 AWG bond wire throughout your system with equipment ground wires bonded to that. You could add ground rods in other locations if you wish but they should all form one interconnected system. Also, surge protection is NOT lightning protection. If you are very concerned with lightning strikes you need a lightning arrest or on the system. If the PV array is on the roof it should have ground fault protection. – ArchonOSX Sep 11 '18 at 7:52
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First off, never connect the ground to the neutral line. This was a bad habit in the old days to save some wire, but is actually very dangerous and is now forbidden (at least in my country) and old houses had to be rewired.

The reason is that, if your neutral gets cut after the link ground-neutral, all your frames will be energized to your main.

For the grounding, it all depend of the distance between your different parts. As for the solar panels, as they are perhaps on your roof or farther away, it is recommended to directly ground them as close as possible.

If your other equipment is on a shed or placed closed by, you can use a star point to your grounding rod.

Also it depends if your device is at risk of lightening, which will require some more serious cabling than if you just protect against fault in the device that can energize the cabinet. I would not ground parts that are at risk of lightening to parts that aren't.

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    Where are you on this planet? IT grounding systems are very rare in residential work, and require specialized ground-fault detection to avoid an "invisible" first fault causing a shock hazard...normally, single-bonded TN-S or TN-C-S is used in the residential world to allow for single-fault disconnection on "hard" faults, instead. Or are you referring to a cross-connection of ground and neutral downstream of the system N-G bond point? – ThreePhaseEel Sep 13 '18 at 4:21
  • I guess those terms applies to your country, I'm in Europe, all Europe shares about the same rules. Also ground fault detector is required, my answer is about grounding path and of course correct protection circuit is also required. – Damien Sep 13 '18 at 7:22
  • IT/TN/TT is the IEC standard terminology for earthing (grounding) systems -- see IEC 60364 for details. – ThreePhaseEel Sep 13 '18 at 14:15

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