Always an interesting topic... 

From what I have read on other forums/groups: A poll was created and more than 60% of installations make use of permeant bond. 

Would love a final answer on this - from all the reading it seems some authorities will fail a COC if there is a relay...

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We have dyn11 system in sa with a earthed neutral . So every alternative supply neutral must be bonded also

 

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7.12.3.1.2 In an installation that is supplied from a combination of transformers and alternative supplies located near to each other, the neutral points of each of these items SHALL be connected to a single earthed neutral bar (see P.1). This earthed neutral bar shall be the only point at which the neutral of the installation is earthed. 

 

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The inverter is a new supply and has a new and extra point of control.

So if you read 6.1.6 it doesn’t say on the entire installation. It just says neutral shall not…

So what do you do if you are supplied a tnc system? You create an earth before the point of control in the budgy box.

Inverter is a tnc system. You have to create an earth return path. In both cases. The reason we say the relay is not sufficient is because code also says you shall not make a tns or tncs a TNC system under any circumstances. If you use a relay, you are making a tncs system to a tnc system. If you do a permanent bond it cant happen

 

Edited June 28, 20232 yr by spotity

58 minutes ago, spotity said:

From what I have read on other forums/groups: A poll was created and more than 60% of installations make use of permeant bond. 

Probably, if we create a different poll, we will find out that more than 80% of today's installers are not enough qualified and don't understand the system and standards properly 🙂

Since when polls dictate, what is done according to the standards and what is not?

 

Edited June 28, 20232 yr by PowerUser

This is where I believe the confusion arises, when the grid and inverter are operating together,  you never bond the neutral/earth after the "point of supply" or at 2 points in an electrical TN-S installations.
While your essential supply (output of the inverter) is connected to the grid, there should never be a bond between neutral and earth.
The only time there should be a bond between neutral and earth is when the inverter is in islanding mode (disconnected from the TN-S system) at which point you create a TN-C before the essential DB, (output from the inverter) , at the essential DB, you would then create a TN-S system and at no point after the DB, should the neutral earth be bonded again. Like i previously said the biggest problem with bonding earth and neutral while on mains is that if the star point at the minisub comes loose your star point could be the point for the complete minisub .
That 6sqmm or 4sqmm wire could look like a glow plug if you become the star point on an 800KVA minisub

Edited June 28, 20232 yr by TaliaB

Maybe some installers are talking about the permanent neutral-earth both bond in the main DB at the point of entry and that confuses a lot of people. They probably think, this is the bond on the Load side of the inverter. Just guessing...

56 minutes ago, PowerUser said:

Probably, if we create a different poll, we will find out that more than 80% of today's installers are not enough qualified and don't understand the system and standards properly 🙂

Since when polls dictate, what is done according to the standards and what is not?

 

Not the point of the post, but rather supporting your point of installers not being qualified or the standards not being clear

Edited June 28, 20232 yr by spotity

South African regulations forbid connecting the Inverter output neutral to the earth permanently. No power generator may connect the output neutral to ESKOM neutral permanently. Some inverters like Sunsynk have terminals that can drive a relay when on islanding mode. The relay then connects the Inverter output neutral to an earth spike and house earth. Other inverters connect the inverter output neutral to earth internally. The manuals should provide that information.

If an inverter doesn't have terminals to drive a relay or internal neutral bonding then a relay can be installed as shown below.

2 hours ago, TaliaB said:

This is where I believe the confusion arises, when the grid and inverter are operating together,  you never bond the neutral/earth after the "point of supply" or at 2 points in an electrical TN-S installations.
While your essential supply (output of the inverter) is connected to the grid, there should never be a bond between neutral and earth.
The only time there should be a bond between neutral and earth is when the inverter is in islanding mode (disconnected from the TN-S system) at which point you create a TN-C before the essential DB, (output from the inverter) , at the essential DB, you would then create a TN-S system and at no point after the DB, should the neutral earth be bonded again. Like i previously said the biggest problem with bonding earth and neutral while on mains is that if the star point at the minisub comes loose your star point could be the point for the complete minisub .
That 6sqmm or 4sqmm wire could look like a glow plug if you become the star point on an 800KVA minisub

Correct @TaliaB

Let me try -

Your Municipality supply is TN-C (N + E combined) at your supply point.

Then become TN-S (N + E separated throughout the rest of the house - Neutral not connected to Earth) 

Disconnect / Cut your Municipality supply cable and dig it out. Sell the cable.

You are now fully Off Grid. (Island mode)

Now your inverter lost this original TN-C connection from the Municipality supply.

Now, and only now, you must create a NEW TN-C connection at your NEW supply point. (Inverter output) as you will have a floating Neutral (Voltage between N + E. )

Then again it must be converted to a TN-S system throughout the rest of the house.

The moment you reinstall and reconnect the Municipality cable because Swambo is de M...... in with you, you need to remove the Inverter from its TN-C supply point that you created and reinstate the original TN-C supply point from the Municipality.

Now you don't want to do this exercise on a regular basis (Load shedding) Thats why you install the relay to do the work for you.

Permanent bond between Neutral and earth on the Inverter supply/load side means you have two TN-C points while the grid from Municipality is available = Illegal in ZA.

Hope I did not confuse myself now!

Edited June 28, 20232 yr by VirWat

2 hours ago, TaliaB said:

The only time there should be a bond between neutral and earth is when the inverter is in islanding mode (disconnected from the TN-S system) at which point you create a TN-C before the essential DB, (output from the inverter) , at the essential DB, you would then create a TN-S system and at no point after the DB, should the neutral earth be bonded again

Yes sir. Of course apart from the bonding of neutral to earth in island mode, the grid neutral and inverter output neutral  must also be disconnected, but this is autmatically done by the inverter itself. 

3 minutes ago, BritishRacingGreen said:

Yes sir. Of course apart from the bonding of neutral to earth in island mode, the grid neutral and inverter output neutral  must also be disconnected, but this is autmatically done by the inverter itself. 

Don't we have to be specific on this per inverter. 

I thought not all inverters will be doing this automatically? 

19 minutes ago, Scorp007 said:

Don't we have to be specific on this per inverter. 

I thought not all inverters will be doing this automatically? 

Really, ok I can only speak for inverters I have been confronted with, the Axperts, Deye and Sunsynk. 

I will be surprised if there are  some that don't. In that case the external bond relay should have an additional contact to disconnect the incoming neutral from inverter.  That is by the way how Axpert does it internally, in this case via a full changeover relay contact. The contact wiper  connected to load neutral, the NO contact connected to mains neutral and the NC connected to earth. 

The Deye and SS do disconnect the neutrals internally, but does not do the bond to earth, hence the need for external bonding. This is also true for axperts older than generation 3.

Edited June 28, 20232 yr by BritishRacingGreen

40 minutes ago, BritishRacingGreen said:

Really, ok I can only speak for inverters I have been confronted with, the Axperts, Deye and Sunsynk. 

I will be surprised if there are  some that don't. In that case the external bond relay should have an additional contact to disconnect the incoming neutral from inverter.  That is by the way how Axpert does it internally, in this case via a full changeover relay contact. The contact wiper  connected to load neutral, the NO contact connected to mains neutral and the NC connected to earth. 

The Deye and SS do disconnect the neutrals internally, but does not do the bond to earth, hence the need for external bonding. This is also true for axperts older than generation 3.

Thanks a lot. I knew we can get a specialist answer from you our expert. 😄😄😄😄

Now another question. What causes a Axpert to have a voltage of 40-70V on N to E when the grid is off and output is from battery? 

Edited June 28, 20232 yr by Scorp007

42 minutes ago, Scorp007 said:

Thanks a lot. I knew we can get a specialist answer from you our expert. 😄😄😄😄

Now another question. What causes a Axpert to have a voltage of 40-70V on N to E when the grid is off and output is from battery? 

007, that on face value is a dead giveaway that the machine under test has no internal bonding. Which is true for those axperts before generation 3, ie the olders ones. 

A simple test will reveal this omission. If you disconnect all incoming and outgoing AC  connections on the machine, then test for continuity with your multimeter between IN neutral and OUT neutral. If none, test between OUT neutral and case earth. If none, there is no internal bonding. In this case you need to follow the nice procedure compiled by @Andrewj (CORRECTION @Eurard) which is available in this thread. It involves an external 10A rated bonding relay, operated by incoming mains. 

Edited June 28, 20232 yr by BritishRacingGreen

31 minutes ago, BritishRacingGreen said:

007, that on face value is a dead giveaway that the machine under test has no internal bonding. Which is true for those axperts before generation 3, ie the olders ones. 

A simple test will reveal this omission. If you disconnect all incoming and outgoing AC  connections on the machine, then test for continuity with your multimeter between IN neutral and OUT neutral. If none, test between OUT neutral and case earth. If none, there is no internal bonding. In this case you need to follow the nice procedure compiled by @Andrewj which is available in this thread. It involves an external 10A rated bonding relay, operated by incoming mains. 

By the way, if I understand and follow @Coulomb correctly, he has actually made Voltronics aware of the lack of bonding on older machines, which affected a design change on later models. Which is pretty cool  to say the least, and illustrates the level Coulomb has made his presence felt in this industry. 

Edited June 28, 20232 yr by BritishRacingGreen

14 minutes ago, BritishRacingGreen said:

By the way, if I understand and follow @Coulomb correctly, he has actually made Voltronics aware of the lack of bonding on older machines, which affected a design change on later models. Which is pretty cool and illustrates the level Coulomb has made his presence felt in this industry. 

In turn, I am also of opinion that in South Africa, because islanding is more of a rule than exception, the wrongdoings of bonding during islanding  have manifested itself big time.  It stands out like dog pooh in vanilla icecream factory. 

Edited June 28, 20232 yr by BritishRacingGreen

On 2023/06/26 at 7:16 PM, TaliaB said:

I also check each plug point on the essential side with plug tester with mains power switched off and then do tripping time with multitester on RCD (20-35ms on times 5 scale) ( 120-350ms on times 1 scale) and tripping threshold normally between 16-22ma.

@TaliaB how would a laymen check if his system has been installed correctly re E-N bonding when in Island mode?

3 hours ago, FixAMess said:

@TaliaB how would a laymen check if his system has been installed correctly re E-N bonding when in Island mode?

Get a socket tester and plug it in when Eskom power is off, inverter in islanding. Use a socket connected to the essential side ( inverter output. )

Tester to use below, plug it in and check the 3 led lights on this tester L-ON N-ON Earth-Off.

OR check with a multimeter between N and Earth should be 0V.

 

 

First signs of something wrong is when you notice Ghosting or a floating Neutral.

Look for some low wattage LED's etc lights.

When Eskom is off, and you notice a very faint glow even when the light is off, it means that power is somehow being fed to it at a low voltage, too low to light it up, as if it was on.

I have always had this and never knew why, until I became familiar with the issue.

I tested the Voltages from my inverter out L/N and Earth, when Eskom was on and when it was off, any boom. Yup confirmed. When Eskom was on there was Zero Voltage from my inverter out between N and E, but the moment we went to load shedding, I had a 82V reading, as well as a 132 V reading between L and E.

Voltages from Mains when Eskom was on was L-N (230V), L-E (230V) and N-E (0V), same with the inverter output when not load shedding.

After the neutral earth bond relay was connected, the readings are now the same whether Eskom is on or off, meaning when we are load shedding, I have my bonded Neutral Earth back, and readings between Inverter Out N and Earth is 0V.

and you guessed it, that faint glow from the LED lights are gone, all good.

 

I actually noticed this at my neighbour as well when we were load shedding and their outside external LED security lights at 5pm (before they come on) were faintly glowing.

On 2023/06/28 at 11:53 PM, BritishRacingGreen said:

if I understand and follow @Coulomb correctly, he has actually made Voltronics aware of the lack of bonding on older machines, which affected a design change on later models.

I can't take the credit for that one. I actually try to keep a low profile with Voltronic Power, though I've tried to have the premature float bug fixed by my supplier years ago (MPPSolar). You can tell that didn't work out.

It was actually a colleague on the Australian Electric Vehicle Association that convinced them that they really needed this. Perhaps the combination of it being a safety issue and also being fairly inexpensive to fix (just make one relay a double pole type and add a little printed circuit board trackwork), it was done fairly quickly and has been in every model since.

On 2023/06/28 at 3:13 PM, Scorp007 said:

Thanks a lot. I knew we can get a specialist answer from you our expert. 😄😄😄😄

Now another question. What causes a Axpert to have a voltage of 40-70V on N to E when the grid is off and output is from battery? 

The battery 48VDC is converted to 220VAC by the inverter. The 220VAC Neutral on the output is isolated from the Grid during islanding. Normally the neutral is connected to earth in the substation. That is why the neutral floats in reference to earth. Hence anti islanding needs to be installed to pull the neutral down to earth potential.

On 2023/06/28 at 1:55 PM, TonyH said:

South African regulations forbid connecting the Inverter output neutral to the earth permanently. No power generator may connect the output neutral to ESKOM neutral permanently. Some inverters like Sunsynk have terminals that can drive a relay when on islanding mode. The relay then connects the Inverter output neutral to an earth spike and house earth. Other inverters connect the inverter output neutral to earth internally. The manuals should provide that information.

If an inverter doesn't have terminals to drive a relay or internal neutral bonding then a relay can be installed as shown below.

I would avoid the time delay relay.

I would use a standard NC relay/contactor. The reason being, is that you don't know for sure, how much time it takes for the inverter to re-sync to grid power.

While 30s seems enough, it could actually be less than that I suppose. It could also be more for some reason (let's say grid isn't stable when it returns). What will happen then, is that you have two N-G bonds in your system, for a short while. As we know this could cause various problems, including tripping some RCDs.

I think it would be better to immediately open the output N-G bond when grid power comes back. Yes, then you have a floating output for a short while. But if you have an RCD on the output of the inverter, it can still detect an imbalance between L-N. The only downside is that if there is some sort of fault, it has to find a path to be imbalanced. Let's say a person touched the enclosure of the faulted device, only if there is a current path (to ground, via the person) then the RCD will trip.

I think this is still fairly safe, having that you have a proper RCD on the output (30mA leakage detection at most), and having that most of the time, our bodies aren't touching real ground. Also, most devices with metallic casing are also grounded, so I would think the RCD would trip anyways in case of a fault.

Then when Inverter goes back to grid power, we are fine. So this "hazard" is only for a short while, but we don't know for sure how long (depends on inverter synchronization to grid).

Can anyone confirm my assumptions above? @Coulomb what do you think?

Edited July 2, 20232 yr by meetyg

7 hours ago, meetyg said:

@Coulomb what do you think?

I don't know the inverter involved, but the only proper way to do it is to bond only when the incoming mains is not providing the bond. So basing the bond on the presence of the grid seems wrong to me.

I'm also not used to neutrals being switched at all. So sorry, I'm not the right person to ask.

13 hours ago, meetyg said:

But if you have an RCD on the output of the inverter, it can still detect an imbalance between L-N.

That is exactly the problem if you have a floating neutral on the inverter output due to the lack of bonding there is no refrence point to earth,should there be a faulty appliance( live or neutral shorted to metal casing) the RCD will not detect the fault current as it cannot create an imbalance between live and neutral to activate the RCD. You touching the metal case provides a path for the fault current to flow to earth only then might the RCD trip hence the reason 30ma is used in domestic applications should it be 100ma @50hz it could be fatal. 

44 minutes ago, TaliaB said:

That is exactly the problem if you have a floating neutral on the inverter output due to the lack of bonding there is no refrence point to earth,should there be a faulty appliance( live or neutral shorted to metal casing) the RCD will not detect the fault current as it cannot create an imbalance between live and neutral to activate the RCD. You touching the metal case provides a path for the fault current to flow to earth only then might the RCD trip hence the reason 30ma is used in domestic applications should it be 100ma @50hz it could be fatal. 

IIRC we do have a safe voltage one can touch as well as current through the body and above these levels it can be fatal as mentioned. 

Edited July 2, 20232 yr by Scorp007

On 2023/06/26 at 10:16 AM, TaliaB said:

The Luxpower does the neutral/earth bond internally i have installed quite a few of the SNA 5000 and all checks show no floating neutral when islanding. I also check each plug point on the essential side with plug tester with mains power switched off and then do tripping time with multitester on RCD (20-35ms on times 5 scale) ( 120-350ms on times 1 scale) and tripping threshold normally between 16-22ma.

I have installed a LuxPower SNA5000 on Friday and found a NEV of 82V.

I am beginning to wonder if there is an earthing problem on site which carries through to the inverter output. The earth wire shouldn't disappear during load shedding?

 

So, just wondering if there has been a consensus reached as to what is the correct way to establish the Earth/Neutral bond on a SS/DEYE inverter, or are we still in disagreement between hard bond vs a relay? 🙂 

My inverter was installed with a hard bond and wondering if I need to change it.