Neutral earth bonding on backup systems.

[Justloadit]

In the case of a Deye or Sunsynk inverter, connecting the relay/contactor coil to the grid and using the N/C contact to bridge the inverter neutral to earth when the grid is off, means you might not have the inverter neutral to grid bonded during the delay period when the grid power restores which can be well over a minute. Would that be compliant and if so, why bother about bonding it all when there is no grid? With my Deye 8kVA inverter, I have the relay operated by the inverter and use a N/O contact to bond the inverter neutral to earth. For me this has worked without a problem for about 2 weeks now. I do understand that what works for me doesn't necessarily work for everyone.
Please feel free to correct me on the above.

Its about user safety, not having the Neutral/Earth bond during load shedding, means that the ELU will not detect a Live/Neutral to earth leakage fault, which may electrocute the user under certain circumstances if there is a faulty earth on any appliances. Anything more than a second in this situation could be fatal to a human.

The reason that ELUs work is that the Neutral on the input side is connected to earth, creating a reference level for any voltages on the output side of the ELU to detect any dangerous leakage voltages.

[Isetech]

If there has every been a so called grey area this has certainly topped them all. There seems to be 2 groups, one supporting the permanent bond and the other relay

Some say you should follow manufacturers recommendations, others say you should follow the regs.

Personally, after carrying out a few tests, I would say the relay as per manufacturers recommendation is the way to go.

My opinion, and it is just my opinion, I believe the confusion starts with the definition of an inverter. I dont believe an inverter should be classified as a generator. It is not a generator, you can connect a generator to an inverter using the gen ports, however it is not a generator and shouldnt be referenced as a generator. If anything, it is like a UPS. As mentioned in the video below, when connected to an electrical installation it must be converted from class II to class I. As mentioned, you cannot have 2 bonds in an electrical installation.

A bi-directional, hybrid inverter which at some point is linked directly to the grid supply, and only once it goes into islanding mode, once the grid power is switched off, at which point the bond is lost, not like a generator which will never run be connected to the grid power at any point in time (unlesss specifically designed for that application)

The solar industry has blown out of proportion in the past 2-3 years and I dont believe the regulations are ever going to catch up, by the time it does there will be new technology and new challenges.

As I mentioned this is my opinion, created after carrying out tests, speaking to a few electrical engineers, other electricians, trying to understand old regulations and watching videos. You need to make the decision yourself and not be blindly guided by others. You will have to answer for the decision you make, when you sign the COC.

Once the definition for an inverter is finalised, then we can move forward. I dont believe bi- directional, hybrid inverter can be defined as a generator, maybe one of those stand alone units you by from auto parts stores, wit ha manual bypass switch connected to a lead acid battery with no intelligence. It is like calling a type writer a laptop, or comparing a flooded lead acid battery to a lithium ion battery with a BMS.

https://www.youtube.com/watch?v=0Lpzwr4BIyo&t=725s&ab_channel=Sunsynk

[GCE]

Running a generator synchronized to the grid is becoming a common application to prevent stoppages especially during load shedding when you know what time it is going to happen

[Dave A]

Generators present a relatively simple situation because there's a clear crossover between municipal supply and generator as source. Even when syncing, it's a monitoring situation of two separate circuits, not two supplies being merged.
I suggest an inverter in bypass mode which then switches to battery power when the municipal supply drops presents a similar environment.

Where inverters present some careful thought is when they are in hybrid mode or are pushing back into their supply side.

One would hope that inverters that provide a contact to initiate a neutral-to-earth bridge have taken all the scenarios into consideration. But I suppose the only way to make sure if the manufacturer isn't saying is test. Test. Test.

[Isetech]

A generator also creates electricity using one rotary source.

An inverter also has multiple sources, grid, batteries and a generator all going through one device. It also converts power from DC to AC.


Then there is the class of device. Small mobile generators where never designed to connect to the electrical installation.

UPS units were also never designed to run lights and plugs for appliances in the house. they were designed to keep computers and servers and critical loads operating, hence the red dedicated plug.

Most people dont even know the difference between class I and class II.

[GCE]

Generators present a relatively simple situation because there's a clear crossover between municipal supply and generator as source. Even when syncing, it's a monitoring situation of two separate circuits, not two supplies being merged.
.

except when you are doing peak shaving

[Dave A]

[/B]

except when you are doing peak shaving

Fair enough.

[Actrox]

Hi. Can you please have a look at my proposed wiring diagram for my Neutral to earth bond in my system using a relay. Does this look correct?

[GCE]

[ATTACH=CONFIG]8748[/ATTACH]

Hi. Can you please have a look at my proposed wiring diagram for my Neutral to earth bond in my system using a relay. Does this look correct?

Struggle to see anything on the drawing to be able to comment

[Thys LOW Elektries]

Electronics fail, the software can be rebooted or reset, and so on. I put a bridge between the changeover neutral and inverter feedback neutral that way I know I have a bridge that won't fail me.

[Actrox]

Struggle to see anything on the drawing to be able to comment

DB Board.pdf

Let's see if this attachment is better.

[GCE]

Electronics fail, the software can be rebooted or reset, and so on. I put a bridge between the changeover neutral and inverter feedback neutral that way I know I have a bridge that won't fail me.

You cannot bridge incoming neutral to outgoing neutral of an alternative supply - 7.12.3.1.4

We have had an enquiry from Electricity department as to why sometimes they pick up a live neutral when changing meters - This could be one of the reasons


SANS 10142-1
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).
NOTE Where four pole switching is implemented, consideration should be given to use
overlapping neutral switching devices.
7.12.3.1.4 Where only part of an installation is switched to the alternative
supply in the same distribution board, the neutral bar shall be split
(see figures P.2 and P.3).

[GCE]

[ATTACH=CONFIG]8748[/ATTACH]

Hi. Can you please have a look at my proposed wiring diagram for my Neutral to earth bond in my system using a relay. Does this look correct?

The relay contact should be Normal open
The relay coil has no protection
you taking live from ELU and neutral from mains - it will trip
Inverter mains should not be from ELU
The individual inverters have no protection on incoming from mains or genset
The individual outputs on the inverters have no protection

Assuming you have just not shown protection on PV strings and batteries
Batteries should be on a common bus , I am saying that without reading the inverter manual

Rather get a contractor in to do the work

[Actrox]

The relay contact should be Normal open
The relay coil has no protection
you taking live from ELU and neutral from mains - it will trip
Inverter mains should not be from ELU
The individual inverters have no protection on incoming from mains or genset
The individual outputs on the inverters have no protection

Assuming you have just not shown protection on PV strings and batteries
Batteries should be on a common bus , I am saying that without reading the inverter manual

Rather get a contractor in to do the work

I Agree on everything you stated, except that the relay contact has to be N/C to operate correctly. If it was N/O and there was Eskom supply, I would be making the Neutral - Earth bond when the Inverters are NOT in island mode.
These inverters have the option of common battery or separate battery, when in parallel mode.

DB Board REV 1.pdf

Here is the revised drawing with the changes made.

[GCE]

I Agree on everything you stated, except that the relay contact has to be N/C to operate correctly. If it was N/O and there was Eskom supply, I would be making the Neutral - Earth bond when the Inverters are NOT in island mode.
These inverters have the option of common battery or separate battery, when in parallel mode.

Apologies - yes N/C