Hi Martin, 

a - I use 20A contactor

b- 2.5mm sq. for the NE bond

c- 0.75 or 0.5mm.sq for the contactor coil.

On 2023/06/27 at 8:15 AM, TaliaB said:

If you have a 5-wire system from the transformer (3 phase wires, neutral and ground), you should NOT have a neutral-to-ground bond in the service (just like in any other transformer to panel scenario). In fact, a 5-wire feed from the transformer is the BEST and safest electrical system possible. Hence the reason the Sunsynk 3 phase 5 wire inverter does not have a ATS

Just to be sure: you are saying that for a Sunsynk 12kW 3phase inverter, Earth-Neutral bond (when not connected to grid) is NOT required?

We are on a farm with Eskom supply. Transformer gets L1,L2 and L3 from the grid. Star point on transformer create the Neutral. Neutral is connected to an earth spike at the transformer to reference Neutral to Earth. Same Earth Spike becomes the Earth. (Armour of cable to house and shed)

15 hours ago, PieterLR said:

Just to be sure: you are saying that for a Sunsynk 12kW 3phase inverter, Earth-Neutral bond (when not connected to grid) is NOT required?

We are on a farm with Eskom supply. Transformer gets L1,L2 and L3 from the grid. Star point on transformer create the Neutral. Neutral is connected to an earth spike at the transformer to reference Neutral to Earth. Same Earth Spike becomes the Earth. (Armour of cable to house and shed)

It all depends on the method of your non essential setup. Normally 12kw inverter can deliver 52 amps at 230v so you don't always need to split neutrals for essential supply. If you run all your loads without splitting the neutrals you won't need to bond the earth/neutral because you already have the bond via the earth spike. To be sure when running in island mode(eskom off) measure between neutral and earth if 《5v you don't need to bond again if 》 5v bond.

On 2023/06/17 at 11:27 AM, BritishRacingGreen said:

Ok, so this new Axpert you putting in, what is the model? 

Morning All Axpert Cards"Voltronic has an onboard 30A relay to Do the same Function as the external Anti Island relay that needs to be installed on the outside of the SunSynk and Deya Inverters The Main test is to add battery voltage and test between output neutral and ground for resistance Pls remove The incoming cables before test The test indicates a dry contact between output neutral and ground 

On 2023/06/16 at 10:11 AM, Scorp007 said:

The E/N bond is only done at the inverter wires and it can be a relay in a DB. It is essential that this bond is only in place when running from battery. It is thus not a permanent bond. 

I know this is an older post, but I wanted to check. My installer appears to have bonded earth to neutral at my inverter - i.e. on site. Is this really bad practice?

Our local eskom tech says they treat N and E as the same thing, but likely because it's bonded in the distribution system. Is it OK to bond permanently at the inverter (Sunsynk 5k).

I had the Segen relay installed (same as the OP one - Weidmuller) but the installer removed it when he did my parallel upgrade and hardwired N to E on the inverter side.

Thanks

Edited September 6, 20232 yr by EastCoastRF

5 hours ago, EastCoastRF said:

I know this is an older post, but I wanted to check. My installer appears to have bonded earth to neutral at my inverter - i.e. on site. Is this really bad practice?

Our local eskom tech says they treat N and E as the same thing, but likely because it's bonded in the distribution system. Is it OK to bond permanently at the inverter (Sunsynk 5k).

I had the Segen relay installed (same as the OP one - Weidmuller) but the installer removed it when he did my parallel upgrade and hardwired N to E on the inverter side.

Thanks

Yes it is bad practise. If the munic loose their E-N bond or the forget to put it back after doing fault finding you become the transformers N-E and your wiring will melt during a big earth fault. 

The way I see it. 

With reference to MartinB on the size of the Earthing conductor.
Your earth wire size must be adequate to be able to conduct the "FULL" Peak Output Power of your inverter.
Most decent inverters are rated at around 200% (10 seconds), this is not fixed, and you have to verify the value from your inverter technical data.

If you have a fault, you can draw up to 7200W on a Sunsynk 5.5kW inverter.

Your N-E return path must be able to handle this current, about 32A at 230Vac, as a fault can cause the full current to flow in your Earth wire.
To me that imply that the relay used for N-E link must also be able to handle the "FULL" current.
If this is not done, you may create a scenario where the "touch" voltage of the faulty equipment is high enough to be fatal.

The term "Bonding" might be misleading.
The term bonding or electrical bonding, connecting and jointing two conductors (wires, pumps, machines, pipes etc) and metallic bodies (non-current carrying during the normal operation) permanently to equalize the potential difference on both machines or systems connected by bond wire.
Bonding wires tend to be a lot "thinner" as they do not carry any current.

If the wiring is done correctly the E-fault detection breaker trips within a small fraction of a second from a fault current of 30mA. It is normally rated 60A braking capability.

As another electrically inclined South African looking to stave off loadshedding and reliance on the incumbent utility,

I also find myself trying to make sense of the Earth-Neutral bonding story as it relates specifically to the Sunsynk/Deye devices but also all the inverter installs out there, here is my short answer conclusion (the looong answer follows):

The Load side Neutral bus should be bonded to the Earthing system bus ONLY when the inverter is operating in off grid mode, with a few very specific exceptions. The only sensible way to do this automatically is with an external N/O contactor powered by the ATS output (in the case of the SS/Deye system) or via a built in internal contactor (if the inverter supports it, not SS/Deye), or via a N/C contactor powered by the Grid side Live and Neutral (for all other inverter types without a E-N feature built in).

I come to my conclusion having read the SANS 10142-1 (specifically 2021 Edition 3.1) over and over trying to understand, and indeed trying to justify, why the majority of registered CoC grade electricians I have spoken to currently say they are making a permanent E-N bond at the inverter.

Unfortunately I still cannot justify their reasons, and I'm still trying to find out who gave this "directive" to do so, which to me seems to have become more of a broken telephone "it's what they say we must do" style argument. The best argument for permanent bonding I've heard is that relays/contactors are unreliable, which should not really be the case considering they are usually graded for hundreds of thousands of cycles and thousands of operations per hour. Nothing like what this E-N bond contactor should experience. I do agree that SS/Dey should have built in a monitoring system to ensure the E-N bond is made every time or disconnect the load, but that is not the discussion point I wish to raise.

 

Let me preface my research below with "I personally am not an electrician" and so do not have access to the "they's" of the registered electrician world, but I do have a background in engineering and enjoy a good deep dive into a subject to make sense of it, and this one is really getting to me.

I do hope that something definitive from a reputable source will come to shed light on this confusion once and for all (ie published officially in the government gazette or a letter penned and signed by a rep from Eskom or a large local South African municipal utility).

Until then, here are my arguments for using a the temporary bond including SANS references attached. Sorry if it is a  painfully long read.

 

My first reference is SANS 10142-1, page 231 section 7.12 Alternative Supplies.

The NOTE 2 in 7.12.1.1 states "This part of SANS 10142 does not cover the generation plant, integration and synchronising requirements of an alternative supply operating in parallel with the main supply to an installation"

The key word is parallel because this is EXACTLY what the SS/Deye units are. They have the capacity to run off-grid, but 99% of the time (well 60% in Stage 6) they are being utilised as an alternative device in parallel with the grid (ie grid-tied) not as an alternative device used "instead of" the grid (ie an off-grid device). A diesel generator that does not sync with the grid but is brought into use by a multi-pole change-over switch (break before make, auto or manual) is a good example of a "non-parallel" alternative energy device.

The regulations for a parallel (ie Grid-Tied) device appear to be contained in SANS 10142-1-2 "The wiring of premises
Part 1-2: Specific requirements for embedded generation installations connected to the low voltage distribution Network in South Africa". And the biggest problem with this is that 10142-1-2 is still, to the best of my knowledge, in the draft stages of publication (since 2020) . However it can be downloaded and read in draft form. And low and behold in SANS 10142-1-2 (Draft) page 43 section 6.1.5.2 "b) Where a system is designed to operate in Islanded mode, a neutral-earth switch shall be installed that forms a neutral-to-earth bond for the duration of the islanding operation only."

Now that should be the definitive answer right? ( ie use a temp not permanent bond for E-N when switching from island/off-grid to grid-tied/parallel modes), were it not for the fact that these regulations are still under draft review and therefore cannot be called definitive at this stage 🙄. In fact I may have been reading an older version of the draft and maybe this section has been or will be removed in the final print? Great.

 

So lets go back to SANS 10142-1:2021 Ed3, the current gazetted sparky bible for low voltage wiring of premises, and run through the scenarios for non-parallel alternative energy sources. Just to say we did.

Here we find:

Section 6.1.6 pg 79 (Installation requirements/General Circuit arrangements) "6.1.6 The neutral conductor shall not be connected direct to earth or to the earth continuity conductor on the load side of the point of control except as
allowed in 7.16.4."

Pretty straight forward, don't do it at the Load end of the line (ie after the house main incoming switch). But what of 7.16.4?:

7.16 relates to "Distribution systems as part of an electrical installation", ie complexes/multi dwellings where the utility (Eskom/municipality) supplies electricity to the complex and the complex submeters to each unit.

" 7.16.4 - Neutral Earthing

7.16.4.1 Whereas TN-C systems may be implemented along the distribution system backbone, the individual service connections at every distribution kiosk shall be TN-S.
7.16.4.2 From the point of supply to each user or part of a communal installation, the neutral and earth conductors shall be separate conductors""

7.16.4.6 A TN-S system shall not be converted to a TN-C system"

TN-S (Ground(terra)/Neutral-Separate) means the E-N is bonded at the source (usually transformer up the street, or at the diesel generator in the parking lot, ie at the source) and never again shall they be allowed to meet. TN-C (combined) means N & E are one wire from the source until it reaches a designated point down the line (designated by the system designer/utility at the design stage). This could be at the the kiosk in the street, at the entrance to the property or at the first/main distribution board of the dwelling, it is usually done as a cost saving measure (one less cable to run), somewhat at the expense of some safety. At that E-N bond point the N & E separate and become a TN-S system with the N & E never to again meet down the line (as affirmed in 7.16.4.6). Once a TN-S, forever a TN-S. Most urban dwellings are TN-S from the local substation, but more rural or older sites will be TN-C till the entrance of the property/building, where they split the N & E and become TN-S. Overall this is then referred to as a TN-C-S system. TN-S, TN-C-S systems pretty much cover household installations in South Africa, also I don't want to get into TT systems.

I digress, basically 6.1.6 says you shall not do an E-N bond on the Load end of the line and this is re-enforced in 7.16 where in fact you shall not do it at any location down line of the first E-N bond from the utility.

 

So why still the confusion, and willingness to violate the SANS code (under threat of a CoC fail)? Well here section 7.12 again makes it's appearance.

The part that seems to be causing the most confusion is on page 223 (10142-1:2021 Ed.3) section 7.12.3 "Earthing requirements and earth leakage protection" as it relates to "7.12 Alternative supplies" (remembering from 7.12.1.1 NOTE 2 that this section actually does not cover parallel/grid-tied alternative supplies, only non-grid-tied alternative supplies).

"7.12.3.1 Neutral bar earthing
7.12.3.1.1 Protection in accordance with the requirements of 6.7 shall be provided for the electrical installation in such a manner as to ensure correct operation of the protection devices, irrespective of the source of supply or combination of sources of supply. Operation of the protection devices shall not rely upon the connection to the earthed point of the main supply when the generator is operated as a switched alternative to the main supply."

So one cannot rely on the E-N bond that exists at the utility when running on an alternative off-grid supply, ie a new E-N bond needs to be made for the alternative supply. Makes sense, but how and where?

"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 and figure P.1). This earthed neutral bar shall be the only point at which the neutral of the installation is earthed. Any earth leakage device shall be positioned in such a way as to avoid incorrect operation due to the existence of any parallel neutral/earth path."

So indeed for an off-grid alternative supply the Neutral AND Earth from BOTH the utility AND the alternative energy supply can be bonded together in ONE location but ONLY if they are located NEAR to each other. This is the "few specific exceptions" I referred to earlier. This is pretty much never the case for an urban home looking to inject an inverter or install a backup generator into the house DB board. Read on..

7.12.3.1.3 Where alternative supplies are installed remotely from the installation, or from one another, and where it is not possible to make use of a single neutral bar or neutral conductor which is earthed, the neutral of each unit shall be earthed at the unit and these points shall be bonded to the consumer's earth terminal (see 6.12.4). The supply from each unit which supplies the installation or part of the installation, shall be switched by means of a switch that breaks all live conductors operating substantially together (see figures P.2 and P.4), to disconnect the earthed neutral point from the installation neutral when the alternative supply is not connected (see also 6.1.6)."

The "where it is not possible to make use of a single neutral bar or neutral conductor which is earthed" is the most common scenario encountered in the urban setting when alternative energy is wanted (diesel generator for example). In this case, each supply shall make an E-N bond themselves at their source, but they must have switches in place that only one of the suppliers E-N bonds gets connected to the essential load neutral bar at a time. 

To me it seems most likely that there is an earnest attempt make the info in 7.12.3.1.2 and 7.12.3.1.3 fit as the reason for permanently bonding the E-N at the outputs of an inverter that sits in parallel with the utility/grid. But:

a) the inverters under discussion are parallel tied inverters not off-grid, so 7.12 of SANS 10142-1 is somewhat irrelevant.

b) inverters in the domestic setting are usually nowhere near the main supply source (at best they may be near the TN-C -> TN-S bond, in a TN-C-S system) so bonding both supplies at the same source location is unlikely to be possible. If this were the case (maybe a farm with a transformer on a pole and the inverter sitting in a box next to the pole), then maybe the permanent E-N bond would be Ok (both supplies being E-N bonded all together on the SAME bar in the SAME location). 

c) where the supplies are not near to each other, they shall then each do their own E-N bond locally to their source, but they must be switched in such a way that the Utility/Grids Neutral (also the Inverter inputs neutral) and the Inverter output Neutral never share the same wire on the Load end of the installation. Figure P.2 shows this quite well where the the essential part of the DB sees only the Live/Neutral from the grid OR from the alternative supply, never at the same time. Since the Sunsynk bond the input and output neutrals when in grid-tied mode, this rule would be violated.

In conclusion, making a permanent E-N bond at an inverter tied in parallel down-line from the mains supply, on the load end of the line on a TN-S network to me seems to violate so many reasons that the Earth wire exists in the first place and a lot of SANS regs that relate to it. Why even have separate Earth and Neutral wires if we are just going to bind them together where ever we feel like it? There are very good safety  reasons to have a separate/redundant return path to supply source, which I don't want to get into. Every E-N bond done down line of the first one negates much of these benefits for all systems up line of that additional bond. There have also been good comments made that you risk becoming THE E-N bond for the entire are supplied by the substation should the sub find itself unbonded for "reasons".

The only way to satisfy 7.12.3.1.1 (no reliance on the utility E-N bond when islanding) and still run a parallel alternative supply device like the SS/Deye is with a temporary E-N bond that is only in effect when the device runs in island mode (off grid).

I have attached my references to SANS 10142-1 and 10142-1-2.

I do hope that SANS 10142-1-2 gets gazetted soon so that the debate can be concluded.

References SANS-10142 E-N Bonding.pdf

@WillHza great informative post!

I'm not in SA, but I solved the N-G/N-E bond using an NC contactor.

As my MUST inverter internally connects the AC input N to AC out N whenever grid (AC IN) is available (no matter what mode it's running in, be it bypass or battery mode), it works perfectly.

When grid goes down, the contactor engages immediately and inverter supplies loads from battery/PV.

When grid come back, the contactor opens immediately, but the inverter takes a few seconds to return to grid. This causes the output to be floating (no N-G bond) for a few seconds. This is a compromise I'm willing to live with, since I have a 30mA  RCD on the output, which should sense any imbalance.

I have a manual transer switch, to switch the loads between inverter output and grid. But this is only for maintenance purposes, to bypass the inverter. In usual operation, the inverter takes care if the switching. I did have a problem at first, when I had the N-G bond done AFTER the transfer switch, BEFORE the output RCD: When grid came back, it took the contactor a second (probably less) to open, so I had two N-G bond for a short time. This short time was enough to make my main RCD break open. 

The solution to this was to do the N-G bond at the transfer switch INPUT from the inverter. This way, only if inverter output is being used by the loads, the N-G bond exists.

Another solution to handle this would be to bypass the main RCD, and connect AC IN from the main MCB, before the main RCD (of course it should have its own dedicated MCB, from the main MCB).

I hope this helps someone.

Disclaimer: I'm not a certified electrician, so do at your own risk.

Edited September 12, 20232 yr by meetyg

 

Hi there,

I would like some advice on the Earth Neutral bonding for a Sunsynk 5kW inverter. There is a lot of debate surrounding using relay vs permanent bond. If using a relay for the bonding however, what rating should the relay be? I have seen a few photos where a 10A relay is used. Others suggested based on the inverter power (in my case then, 25A), although if current would flow between this bond, this should trip your Earth leakage, right? I was considering a 20 Amp DIN rail relay.

Additionally, what should the wire rating be for a) the wire creating the N-E bond (probably related to the relay rating).

So my questions are:

a) N-E bond relay A rating

b) N-E bond wire rating (probably depending on to the relay rating)

c) The rating for the wire that is used for the relay coil (connected to ATS 240)

Sunsynk did publish a document on the EN bond sizing in the past. Thankfully I downloaded it at the time, can't seem to find it on their website anymore. Here is a clip, the full document is attached.

The current draw for the Contactor coil should be negligible and so also the wire size from the ATS terminals, but consult the contactor spec sheet for actual draw if you are concerned or just use 1.5mm2 or the largest size the will fit in the terminals.

I would rate the actual bonding wire to the contactor size, since it will have to reliably handle a fault current up till, and a bit more than, the current rating of the CB on the inverter output.

The paralleling of the wires through the multiple contactors in order to increase the current rating of the unit is normally a bad idea for contactors that have to make and break on load (which is usually their purpose). The E-N bond use case is more of an off-load make/break and so IMO paralleling is not a sin in this case.

I do fear there is under sizing of these contactors taking place in the field and/or undersized contactors not making use of the the paralleling of the poles to increase their rating. This is possibly contributing to their designation as being "unreliable" as a form of E-N bonding (one fault and it's fried).

 

SS EN Bridge.pdf

Hi WillHza
I Agree with your statement of "Under sizing". I think that the SS guide is also too conservative in the contactor size rating.
If you look at the SS 8.8kW unit, it is rated for 16kW for 10sec.

Normally things go wrong is when high current is drawn, that is when you require the protection, and from what i read here and from installers i have spoken they are not applying this correct in the field.

Edited September 16, 20232 yr by Zodiac69

 

Hi WillHza
I Agree with your statement of "Under sizing". I think that the SS guide is also too conservative in the contactor size rating.
If you look at the SS 8.8kW unit, it is rated for 16kW for 10sec.

Normally things go wrong is when high current is drawn, that is when you require the protection, and from what i read here and from installers i have spoken they are not applying this correct in the field.

I agree it may be too conservative, or in this case too liberal? (IE the minimum size should be bigger).

In the SS-8KW case you may have a 50A CB on the inverter output and IMO the contactor should be able to handle this fault load for the full period of time before the CB trips.

If you had a 40A CB on the inverter output then a 15A 3pole E-N  contactor wired in parallel could give you the cover. Safer would be to oversize with a 20A 3pole (60amp effective) so that the contactor does not become the point of failure. 

Regarding what's in the field, I have not looked at all of the pre-assembled Segen style E-N bonding boxes that are for sale (there seems to be one for sale for each size of inverter out there), but the ones that I have seen with the single 10Amp relay contact, would mean the CB on the inverter should only be rated at 10amp max (pref less), which is likely far less than what the inverter is capable of. Seems more likely to be the Segen box has not been designed to handle fault loads (Eish?).

Some would argue that the earth leakage down stream will detect and take care of a fault to ground well before 10A is reached, but it is also very possible that the fault could occur before the earth leakage (an errant drill/ grinder/spade/pick hitting the the cable on the way from the inverter to the DB with the EL for example), or on a circuit without earth leakage protection .

This is my own logic, maybe others have a different opinion, which can be justified.

 

 

Seems more likely to be the Segen box has not been designed to handle fault loads (Eish?).

 

This is my own logic, maybe others have a different opinion, which can be justified.

I think you can get away with undersizing the contactor in the N-E bond, because it would normally not be required to break the fault current. I would expect the carrying capacity of a contactor to be substantially greater than its breaking capacity.

That said, I wouldn't do this myself. 

Edited September 27, 20232 yr by PierreJ

 

@Scorp007 confirmed that the Growatt SPF5000ES does the E/N bonding internally in an earlier post in this thread  

 

I am going to assume the Luxpower does the same, perhaps someone who has one could test and confirm?

So further feedback on this, it seems that not all of the Luxpower SNA5000 inverters have internal bonding.

 

Mine do not and they have the "SA Version" sticker on the side. Speaking to another forum member, it seems as if some of the SNA5000 inverters have the internal bonding and some have it physically missing.

 

So I will be installing a contactor to do the E/N bonding when there is no Eskom power.

I did noticed that on the Luxpower installer account, there is an option for the internal N-PE but on my unit it makes no difference whether it is enabled or disabled and when using a plug tester to test the earth leakage while Eskom is off the earth leakage does not trip.

 

Hope this helps someone out in the future and that they know to test and not just assume it has E/N bonding done internally.

Hi, guys.

Quick question. Does the relay and cable sizes change according to the inverter size?

How does one go about this?

Thanks!

11 minutes ago, mikaruthven said:

Hi, guys.

Quick question. Does the relay and cable sizes change according to the inverter size?

How does one go about this?

Thanks!

No need to change cable sizes for inverter size for the E/N bond or to choose relay based on inverter size. 

3 hours ago, mikaruthven said:

Hi, guys.

Quick question. Does the relay and cable sizes change according to the inverter size?

How does one go about this?

Thanks!

The relay/contactor must be able to handle the maximum fault current of the inverter, so yes, you should size the wires and contactor to exceed this value for the inverter in question. See my post above for Sunsynks minimum recommended contactor sizes based on inverter size. Wires should be at least the same size as the live wires coming from the inverter. Bigger is better for thermal loading and reliability.

On 2023/06/20 at 3:35 PM, PsyCLown said:

@Scorp007 confirmed that the Growatt SPF5000ES does the E/N bonding internally in an earlier post in this thread  

 

I am going to assume the Luxpower does the same, perhaps someone who has one could test and confirm?

Sorry to say --I did a test while system is drawing power from the grid and the voltage between N and E is 0v but if the inverter runs off batteries or just solar then 80v are present--so that tells me the inverter is not bonding the NE--Growatt SP5000ES 5KW

 

41 minutes ago, zs1ssm said:

Sorry to say --I did a test while system is drawing power from the grid and the voltage between N and E is 0v but if the inverter runs off batteries or just solar then 80v are present--so that tells me the inverter is not bonding the NE--Growatt SP5000ES 5KW

 

Let's get @zsde to join the chat. He is our resident Growatt specialist😀😀😀

54 minutes ago, zs1ssm said:

Sorry to say --I did a test while system is drawing power from the grid and the voltage between N and E is 0v but if the inverter runs off batteries or just solar then 80v are present--so that tells me the inverter is not bonding the NE--Growatt SP5000ES 5KW

 

The Growatt SP5000ES does not have a internal bond relay you have to use a 60A N/E relay and power it from the dry contact activate the dry contact relay in setting 24.

 

Just checked mine again, and I am running 2 in parallel.
The difference I think is that my system is off-grid, i.e. there is no grid power connection to the Inverters.
The internal bond works correctly. The reading between E and N is 0V
 

34 minutes ago, zsde said:

Just checked mine again, and I am running 2 in parallel.
The difference I think is that my system is off-grid, i.e. there is no grid power connection to the Inverters.
The internal bond works correctly. The reading between E and N is 0V
 

Yes you have a common output earth via an earth spike if you are off grid. The problem with floating neutral lies with TN-C-S grounding arrangement where the neutral is earthed at the sub or at the kiosk. If you would have TN-S grounding via Eskom you won't have a floating neutral either as the bond will exist at your point of consumption. I had the same issue with the Luxpower SNA5000 where i had to use a external bonding relay.

4 hours ago, zsde said:

Just checked mine again, and I am running 2 in parallel.
The difference I think is that my system is off-grid, i.e. there is no grid power connection to the Inverters.
The internal bond works correctly. The reading between E and N is 0V
 

@zsde  @TaliaB @Scorp007 I've just cheked, mine similar to zsed but grid connected, and I can confirm that the Growatt 5000 ES has internal earth bond relay, results of the test = with grid connected earth to neutral = 1,03 V, in island mode earth to neutral 0 V 

Edited January 9, 20242 yr by Antonio de Sa

4 hours ago, Antonio de Sa said:

@zsde  @TaliaB @Scorp007 I've just cheked, mine similar to zsed but grid connected, and I can confirm that the Growatt 5000 ES has internal earth bond relay, results of the test = with grid connected earth to neutral = 1,03 V, in island mode earth to neutral 0 V 

Thanks for sharing. You results are in line with what one would expect looking at the values between grid and island.