Greetings All,

 

This is my second post to the forum after joining 2 days back.

I'm currently running a small off-grid DIY Solar System using an Infinisolar super 4 and I'm perplex on the safety and compliance of the system. I have drawn a schematic (see attached picture for illustration AND take note on the Question marks) on the following:

1. (?) - Is this how I must do my Neutral-Earth bonding - tap it on the input N of the Earth leakage?

2.(??) - is is the right way to Earth my PV array - tap it off from the SPD the run it to my PE on DB?

3. (???) - Is the inverter Chasses also connected to the same (PE in the DB)

so effectively this means the PV array frame, inverter chassis, Output Neutral and Output earth are interconnected ALL go to the earth spike?

 

advise before I procced further with the connections.please

please note that I have omitted some components to simplify the drawing.

 

Please advise before I procced further with the connections.

Regards

Have you had any other feedback on this?

I'm also a relative newbie but as I understand:

1. Many inverters already connect Neutral and Earth internally. You should test this with an Ohmmeter. If they are not connected then yes you need the Neutral Earth Bond to the ELCB in your diagram. You should only have one Earth/Neutral bond connection in your system. Either through the Invertor or in your DB board before the RCD/ELCB. You won't need the yellow link back to your inverter. https://www.victronenergy.com/media/pg/The_Wiring_Unlimited_book/en/ground,-earth-and-electrical-safety.html#UUID-7790f868-512d-9080-00fb-c272426e66c5 

2. Victron recommend that your battery negative is also grounded. https://www.victronenergy.com/media/pg/The_Wiring_Unlimited_book/en/ground,-earth-and-electrical-safety.html#UUID-63a9c710-66e2-2c63-0d7c-d9345826267b.

3. Some people recommend not Earthing your panels:

   a. Because they are double insulated and it is not necessary, (unless they are at risk from hail damage etc.) and

   b. Because they may instead actually become a "target" for lightning! Perhaps have an independent lightning conductor higher than your panels if lightning is a risk.

   c. This is a complicated area and some might recommend that you still ground your panels as well. What is the experience of other people out there?

   d. Your SPD will need to be earthed though.

4. Being off-grid this is a so-called "TT" earthing system. Make sure your earth rod is more than 10m away from any other earthing systems or pipes etc. as any faults there may be picked up on your earth and fed into your system.

5. As always get an electrician in to check your installation out and to give you a Certificate of Compliance. May be needed for insurance purpose as well. They should also test that your earth rod is in spec.

I hope this helps? If anyone has constructive advice on the above please assist. And be gentle please. 🙂

Regards

Edited May 21, 20233 yr by TonyB

2 hours ago, TonyB said:

Have you had any other feedback on this?

I'm also a relative newbie but as I understand:

1. Many inverters already connect Neutral and Earth internally. You should test this with an Ohmmeter. If they are not connected then yes you need the Neutral Earth Bond to the ELCB in your diagram. You should only have one Earth/Neutral bond connection in your system. Either through the Invertor or in your DB board before the RCD/ELCB. You won't need the yellow link back to your inverter. https://www.victronenergy.com/media/pg/The_Wiring_Unlimited_book/en/ground,-earth-and-electrical-safety.html#UUID-7790f868-512d-9080-00fb-c272426e66c5 

2. Victron recommend that your battery negative is also grounded. https://www.victronenergy.com/media/pg/The_Wiring_Unlimited_book/en/ground,-earth-and-electrical-safety.html#UUID-63a9c710-66e2-2c63-0d7c-d9345826267b.

3. Some people recommend not Earthing your panels:

   a. Because they are double insulated and it is not necessary, (unless they are at risk from hail damage etc.) and

   b. Because they may instead actually become a "target" for lightning! Perhaps have an independent lightning conductor higher than your panels if lightning is a risk.

   c. This is a complicated area and some might recommend that you still ground your panels as well. What is the experience of other people out there?

   d. Your SPD will need to be earthed though.

4. Being off-grid this is a so-called "TT" earthing system. Make sure your earth rod is more than 10m away from any other earthing systems or pipes etc. as any faults there may be picked up on your earth and fed into your system.

5. As always get an electrician in to check your installation out and to give you a Certificate of Compliance. May be needed for insurance purpose as well. They should also test that your earth rod is in spec.

I hope this helps? If anyone has constructive advice on the above please assist. And be gentle please. 🙂

Regards

I know nothing about Victron except that it is a Low Frequency, transformer based inverter. So I cannot see what their reasoning about grounding battery  terminal is. 

But most mainstream residential inverters are High Frequency, transformerless systems, NEVER earth any battery terminal or PV terminal here!!!!!  And in the case of earthing the PV side will result in destruction of the machines DC-AC converter. So its not an option to consider.   What most of us mean by PV earthing, iis the earthing of the metal frame, not the energy carriers. 

 

Thanks for the feedback. Yes, I had meant the PV frames and not the energy carriers. 

I'm also planning an off-grid (TT) installation in a rural area. I'll be using an earthing rod. Maybe several connected together depending on resistance.
The PV panels will be fused, with DC isolators and grounded Surge Protection Devices.
I assume then that the panel frames and the SPD's and the system PE would all be connected to the same earth rods(s)?
If the panels were hit by lightning would the whole system be sufficiently protected?

Thanks.

 

Edited May 21, 20233 yr by TonyB

1 hour ago, TonyB said:

assume then that the panel frames and the SPD's and the system PE would all be connected to the same earth rods(s)?

No, the frame must be connected to earth rod. 

The pv spd earth must be your elecyrical system earth, ie the inverter's earth. The reason for this is we want to protect the inverter inputs, not the panels. 

32 minutes ago, BritishRacingGreen said:

No, the frame must be connected to earth rod. 

The pv spd earth must be your elecyrical system earth, ie the inverter's earth. The reason for this is we want to protect the inverter inputs, not the panels. 

Hi, Thanks

Sorry for the ongoing questions. Being an off-grid (TT) installation the only earthing available is via earth rods to be stuck into the ground. 
The inverter would be operating in TN-S mode though with the Earth connected to the Inverter and the PE earth bar before the RCD.
(I'll add an MCB before the RCD and probably a Surge Protector in the DB board as well.)
If the panel frames were connected to another separate earth rod nearby that would surely cause a problem, in the event of a fault or lightning strike, with the potential difference between the two, and the other rods picking up the fault? I assume the whole system needs to be grounded to the same earth rod(s).

(Earth rod is bottom left in picture)

Inverter setup:

Edited May 21, 20233 yr by TonyB

I see, ok you have pure offgrid. 

Yes, you can use same earth, you will make majority of members very happy, there has been numerous debates before, including  videos of the charismatic Mike Holt, earthing guru. 

I have my own opinions, but they are opinions. 

What I would suggest though is you keep the route from panels to rod private, short as possible, 6mm thick wire minimum,  surface mount (avoid going in roof). 

Route your system earth from the rod, dont tap off from the panel earth. 

But, please invite one more member to view an opinion on this. 

EDIT : and of course, dont be shy on the size and length of that rod, and investigate quality of good soil. As they say, size matters😊

 

Edited May 21, 20233 yr by BritishRacingGreen

20 minutes ago, BritishRacingGreen said:

I see, ok you have pure offgrid. 

Yes, you can use same earth, you will make majority of members very happy, there has been numerous debates before, including  videos of the charismatic Mike Holt, earthing guru. 

I have my own opinions, but they are opinions. 

What I would suggest though is you keep the route from panels to rod private, short as possible, 6mm thick wire minimum,  surface mount (avoid going in roof). 

Route your system earth from the rod, dont tap off from the panel earth. 

But, please invite one more member to view an opinion on this. 

EDIT : and of course, dont be shy on the size and length of that rod, and investigate quality of good soil. As they say, size matters😊

 

Thanks a mill. When you say "private", does that mean a direct connection to the rod from the panels with no other wires feeding off it?
ie: As you say, to connect the system earth directly to the rod as well.

I have another question: I may want to extend this to provide power to a (metal) caravan more than 30 metres away. 
This is outside the "equipotential" zone. ie: If there was a fault in the caravan and the metal became live and I was standing on the ground there, I could get a big shock... There would be a 30mA RCD there coming from a 100mA RCD in the main supply though. I understand that I could just put another grounding rod attached to the caravan and the caravan DB Board Earth Bar before the RCD too, to minimise the voltage difference between the earth under the caravan and the supply earth?

Should I start another thread on this rather?

29 minutes ago, TonyB said:

When you say "private", does that mean a direct connection to the rod from the panels with no other wires feeding off it?
ie: As you say, to connect the system earth directly to the rod as well.

Yes

 

30 minutes ago, TonyB said:

I have another question: I may want to extend this to provide power to a (metal) caravan more than 30 metres away. 
This is outside the "equipotential" zone. ie: If there was a fault in the caravan and the metal became live and I was standing on the ground there, I could get a big shock... There would be a 30mA RCD there coming from a 100mA RCD in the main supply though. I understand that I could just put another grounding rod attached to the caravan and the caravan DB Board Earth Bar before the RCD too, to minimise the voltage difference between the earth under the caravan and the supply earth?

@TonyB I can see you are doing your homework properly , as it should.👌 As a result , you are coming up with some good and 'nasty' questions. This one I had my head scratching , again !  Never given thought to this before , but let us analyze this from reasonably first principals , and see where it takes us , not least to attract guru's on this subject :

1. Logic tells me , and as Mike Holt says , current will flow only if it has a path to return to the source . The source in your case is the Neutral at the inverter , which is anchored to earth via the earth rod near vicinity of the panels.

2. The quality , or the resistance of local earth at the caravan in relation to the earth rod , to me , is neither here nor there.  I mean you have factory floors and large homes , where distances can easily reach 30m and more.  The bottom line is that the caravan local earth may be very low in relation to the earth rod , or it may be very high . Lets look at the implications of both , and for that matter anything in between :

3. If the earth is low , i.e. same as earth rod , that's good , meaning any diversion from live to earth will be well detected and earth leakage at the inverter will trip.

4. if earth at the caravan is high , then the return path to source is compromised , and no current or very little can flow thru you when you touch live. Remember you are lethally shocked  by a current exceeding a certain minimum (say 30mA) . If the earth is  high , that current will not be reached. If the earth is perfect in relation to earth rod , you will be shocked but the 30mA will be drawn , and RCD will trip.

5. This brings me to a question that many people have : why then bond the neutral in the first place ?, just leave it floating , then no one will ever  get shocked !!!! Unfortunately this is not a perfect world , and inadvertent earth leakages between cores and connections and insulation and earth will always be found  , un-deterministic 'bonds' . And many such  small  'bonds' will be in parallel  and will eventually constitute small enough impedance to allow human to get shocked. In this case its best to take one feed from the generator and earth it hard , and let it henceforth be named as Neutral . The remaining feed will henceforth be labelled as Live. Then force upon our beloved ones the deterministic RCD or ELD. 

6. For all these reasons , you need to carry the system earth from the rod , all the way with live and neutral , and install surge protection etc at the caravan , with reference to this system earth.

This is my 2 cents , so I invite members to comment , please because @JohnB needs practical answers . @Modina , @Scorp007 et al.

21 minutes ago, BritishRacingGreen said:

Yes

 

@TonyB I can see you are doing your homework properly , as it should.👌 As a result , you are coming up with some good and 'nasty' questions. This one I had my head scratching , again !  Never given thought to this before , but let us analyze this from reasonably first principals , and see where it takes us , not least to attract guru's on this subject :

1. Logic tells me , and as Mike Holt says , current will flow only if it has a path to return to the source . The source in your case is the Neutral at the inverter , which is anchored to earth via the earth rod near vicinity of the panels.

2. The quality , or the resistance of local earth at the caravan in relation to the earth rod , to me , is neither here nor there.  I mean you have factory floors and large homes , where distances can easily reach 30m and more.  The bottom line is that the caravan local earth may be very low in relation to the earth rod , or it may be very high . Lets look at the implications of both , and for that matter anything in between :

3. If the earth is low , i.e. same as earth rod , that's good , meaning any diversion from live to earth will be well detected and earth leakage at the inverter will trip.

4. if earth at the caravan is high , then the return path to source is compromised , and no current or very little can flow thru you when you touch live. Remember you are lethally shocked  by a current exceeding a certain minimum (say 30mA) . If the earth is  high , that current will not be reached. If the earth is perfect in relation to earth rod , you will be shocked but the 30mA will be drawn , and RCD will trip.

5. This brings me to a question that many people have : why then bond the neutral in the first place ?, just leave it floating , then no one will ever  get shocked !!!! Unfortunately this is not a perfect world , and inadvertent earth leakages between cores and connections and insulation and earth will always be found  , un-deterministic 'bonds' . And many such  small  'bonds' will be in parallel  and will eventually constitute small enough impedance to allow human to get shocked. In this case its best to take one feed from the generator and earth it hard , and let it henceforth be named as Neutral . The remaining feed will henceforth be labelled as Live. Then force upon our beloved ones the deterministic RCD or ELD. 

6. For all these reasons , you need to carry the system earth from the rod , all the way with live and neutral , and install surge protection etc at the caravan , with reference to this system earth.

This is my 2 cents , so I invite members to comment , please because @JohnB needs practical answers . @Modina , @Scorp007 et al.

Thanks a mill! Without the Grounding Rod at the Caravan the Voltage difference from a "live" fault on the Steel Frame to the real Earth could be massive, like 100V+, so it's only the RCD saving you really. If you also have a local Earth (rod) then the Potential difference is very small and you will only feel a buzz but not a shock. Thata's also why EV chargers can be dangerous...

I see in Australia they use the MEN System. (Multiple Earthed Neutral) with Ground Rods at each outbuilding and the Neutral connected to Earth as well at each DB Board. In fact most utility companies do this all the time. (Mike Holt) ie: Grounding the Neutral at multiple points from the main sub station.

This seems to be fine! See links and image..

One does have to be careful where you put the rods. Mine is rural off-grid so no issues but if you put the rod near your neighbour's water pipe and they have a fault it will come over to your place too!

https://memberarea.necawa.asn.au/Admin/ViewContentPage?uniqueName=multiple-earthed-neutrals-men 

https://electricians-success-academy.com/learn/what-is-men-system 

 

Edited May 21, 20233 yr by TonyB

If PV panels are electrically isolated from the frames, what is the purpose of earthing the frames?

21 minutes ago, TonyB said:

"live" fault on the Steel Frame to the real Earth could be massive, like 100V+

that may be true , but if there is high voltage , it also means that the source impedance of that high voltage is high. If there was low impedance between inverter rod earth and caravan earth , then of course you will not see a big voltage difference. With the exception of course if there is lightning surges.

 

21 minutes ago, TonyB said:

I see in Australia they use the MEN System

I copy . This will of course be fine , as long as the multiple earth system is within a controlled environment in terms of safety . But the moment you interface from there to the user/consumer  domain, you can only have one neutral that is earthed at one point . Otherwise the RCD will not be able to work at the point of interface if you have further downstream earth connection to that  neutral. Otherwise you need isolation transformers.

Edited May 21, 20233 yr by BritishRacingGreen

6 minutes ago, BritishRacingGreen said:

Otherwise the RCD will not be able to work at the point of interface if you have further downstream earth connection to that  neutral. Otherwise you need isolation transformers.

Ok, I'm not sure I fully understand. The MEN system (in the image) has downstream connections. I would have thought that in any event the RCD would see an imbalance between Live and Neutral and trip? Other than selectivity issues and false tripping maybe from the downstream one? And if the upstream one trips on a downstream fault that's ok for now. As long as something trips 🙂

If I did feed any other outbuilding I would in any event take it from the main board, to another DB Board with MCB and RCD etc in the outbuilding.so hopefully this is not an issue.

5 minutes ago, TonyB said:

Ok, I'm not sure I fully understand. The MEN system (in the image) has downstream connections. I would have thought that in any event the RCD would see an imbalance between Live and Neutral and trip? Other than selectivity issues and false tripping maybe from the downstream one? And if the upstream one trips on a downstream fault that's ok for now. As long as something trips 🙂

If I did feed any other outbuilding I would in any event take it from the main board, to another DB Board with MCB and RCD etc in the outbuilding.so hopefully this is not an issue.

I will draw you a schematic tommorrow. In short, if you earth the neatral on  more than one point, say on point A and Point B. Now between A and B there are two return paths from live, that is a path thru neatral AND a path thru earth. Now depending on the impedance of earth between A and B, and the impedance of neatral carrier between point A and B, the return current is shared between the two paths. Now guess what, you have created an unwanted fault current path thru earth, and whats more, your RCD  connected between A andB will ALWAYS trip. 

Earth should only be there as fault paths, not as a nominal carrier. 

2 minutes ago, BritishRacingGreen said:

I will draw you a schematic tommorrow. In short, if you earth the neatral on  more than one point, say on point A and Point B. Now between A and B there are two return paths from live, that is a path thru neatral AND a path thru earth. Now depending on the impedance of earth between A and B, and the impedance of neatral carrier between point A and B, the return current is shared between the two paths. Now guess what, you have created an unwanted fault current path thru earth, and whats more, your RCD  connected between A andB will ALWAYS trip. 

Earth should only be there as fault paths, not as a nominal carrier. 

Thanks! As far as I can see the Neutral has minimal impedance so virtually all of the current will go back via there. If, however, there is a live short to Earth then some of that current will be absorbed by the "real" earth. (Me touching the Caravan). The RCD will see an imbalance in the Live and Neutral currents and trip. I can't see how a downstream earth could cause an imbalance between live and neutral?

1 hour ago, BritishRacingGreen said:

3. If the earth is low , i.e. same as earth rod , that's good , meaning any diversion from live to earth will be well detected and earth leakage at the inverter will trip.

4. if earth at the caravan is high , then the return path to source is compromised , and no current or very little can flow thru you when you touch live. Remember you are lethally shocked  by a current exceeding a certain minimum (say 30mA) . If the earth is  high , that current will not be reached. If the earth is perfect in relation to earth rod , you will be shocked but the 30mA will be drawn , and RCD will trip.

ps: just further to your comment. The issue with a remote distribution point is about the potential difference in Voltages between the Earth and Neutral  - as far as I understand, hence the need for a local grounding rod. I'll research some more and get back on this.... 

Edited May 21, 20233 yr by TonyB

9 hours ago, TonyB said:

ps: just further to your comment. The issue with a remote distribution point is about the potential difference in Voltages between the Earth and Neutral  - as far as I understand, hence the need for a local grounding rod. I'll research some more and get back on this.... 

Here's a good video that shows the potential difference between a Live casing and the Ground (at 0V) because of the impedance going back to the supply Earth. In the event of a fault, and you are touching the case and the ground, this could cause a large current to flow through you, because of the large Voltage drop. This current would likely be insufficient to trip the breaker, but you would get a big shock. So, an RCD is definitely required. 

And, in order to reduce the Impedance back to the supply, and hence the large Voltage drop and current, a local Earth connected to Neutral would mitigate this and have minimal voltage drop, and thus minimal current flowing through you. The RCD would still pick up the imbalance between Live and Neutral as some of the return current is going back via the "real" Earth.

Oh dear, I've just looked deeper into multi-earths. Utilities do this all the time, all the way down your street, but it IS a hazard.
So, what's the solution? Relying on an RCD only? Go full TT (with RCD's) throughout without exporting the Earth? ie: The Inverter supply is TN-S but everything downstream is TT.  ie: Local Earth not connected to Neutral. As in the picture below? Anyone have a better / safer solution?
https://www.ecs.csun.edu/~bruno/MultiGroundedNeutralFinal_4-17-7.pdf

And the Pro's and Con's of Single vs Multi: https://www.csemag.com/articles/grounding-points-single-or-multi/#:~:text=Single-point grounding means exactly,are grounded at multiple points.

RCD Video and Potential Difference:
https://www.youtube.com/watch?v=XN7s4ge1FoQ

 

TT Installation:

Edited May 22, 20233 yr by TonyB

On 2023/05/21 at 2:20 PM, TonyB said:

Have you had any other feedback on this?

I'm also a relative newbie but as I understand:

1. Many inverters already connect Neutral and Earth internally. You should test this with an Ohmmeter. If they are not connected then yes you need the Neutral Earth Bond to the ELCB in your diagram. You should only have one Earth/Neutral bond connection in your system. Either through the Invertor or in your DB board before the RCD/ELCB. You won't need the yellow link back to your inverter. https://www.victronenergy.com/media/pg/The_Wiring_Unlimited_book/en/ground,-earth-and-electrical-safety.html#UUID-7790f868-512d-9080-00fb-c272426e66c5 

2. Victron recommend that your battery negative is also grounded. https://www.victronenergy.com/media/pg/The_Wiring_Unlimited_book/en/ground,-earth-and-electrical-safety.html#UUID-63a9c710-66e2-2c63-0d7c-d9345826267b.

3. Some people recommend not Earthing your panels:

   a. Because they are double insulated and it is not necessary, (unless they are at risk from hail damage etc.) and

   b. Because they may instead actually become a "target" for lightning! Perhaps have an independent lightning conductor higher than your panels if lightning is a risk.

   c. This is a complicated area and some might recommend that you still ground your panels as well. What is the experience of other people out there?

   d. Your SPD will need to be earthed though.

4. Being off-grid this is a so-called "TT" earthing system. Make sure your earth rod is more than 10m away from any other earthing systems or pipes etc. as any faults there may be picked up on your earth and fed into your system.

5. As always get an electrician in to check your installation out and to give you a Certificate of Compliance. May be needed for insurance purpose as well. They should also test that your earth rod is in spec.

I hope this helps? If anyone has constructive advice on the above please assist. And be gentle please. 🙂

Regards

Hi TonyB,

With the help of youtuber content creator: "Roland W" I ended up connecting the system as depicted above, except that I omitted the earthing of the Solar panel frames.

1. Yes my inverter has the capability of N-E built in, but I disabled it and opted for the DB one.

2. I've only connected the earth of the battery chassis, not the terminal themselves.

3. I didn't earth my panels yet, or won't until I'm certain of the standard and yes my SPD is connect to earth.

4. Noted

5. Noted

Thanks.

 

 

@DMAC thanks for the feedback and keep us posted!

Yes, I've been following a bit of Roland W except I play his videos at 150% speed 🙂.The TN-S picture I posted above comes from his YouTube channel.

As mentioned above, only ground the frames of your PV panels and not the DC current (negative or positive) at all.

And also don't connect any battery wires to earth. The frame is ok I suppose but I'm not sure how the inverter would handle it if there were a short?

Edited May 26, 20233 yr by TonyB

 

On 2023/05/21 at 9:31 PM, chrisc said:

If PV panels are electrically isolated from the frames, what is the purpose of earthing the frames?

If they get physically damaged by hail or something and then, especially if they have water on them, the frame could have a high voltage on it and be dangerous.