Neutral earth bonding on backup systems.

[Thys LOW Elektries]

Sorry bad description. The inverter outgoing neutral I bridge to the earth bar.
Bridging different neutrals are dangerous, like bridging Eskom and inverter or generator and inverter.
I normally have a two-pole main breaker that supplies the ac out, from the inverter to the main db. From this breaker, I bond the neutral to earth.
Also neutral is potential life. It is always looking for a path to Earth, Unless the neutral has been isolated it will choke you from time to time.
City council normally only isolates live so the neutrals from the whole neighborhood see you as a "good" path to earth and will choke you.
Been there, done that and got choked.

[Thys LOW Elektries]

Oh yeah, I also forgot to mention that the neutral and earth are bridged at your LV side of the transformer, called a star configuration
Also, your older TNS systems the earth and neutral were bonded in the kiosk outside your house.
So strictly speaking, up to your earth leakage earth and neutral are common.
That is why plug testers can't tell you if you have a reversed neutral earth in a plug, but your earth leakage can see it and will trip

[Derlyn]

That is why plug testers can't tell you if you have a reversed neutral earth in a plug, but your earth leakage can see it and will trip

A plug tester will tell you if the neutral and earth are reversed in the socket outlet if you try and trip the earth leakage with the tester.

If the neutral and earth is reversed in the socket outlet, you will not be able to trip the earth leakage using the tester.
That's why it's important to trip the earth leakage from every socket outlet, especially on a new installation.

[GCE]

Sorry bad description. The inverter outgoing neutral I bridge to the earth bar.
Bridging different neutrals are dangerous, like bridging Eskom and inverter or generator and inverter.
I normally have a two-pole main breaker that supplies the ac out, from the inverter to the main db. From this breaker, I bond the neutral to earth.
Also neutral is potential life. It is always looking for a path to Earth, Unless the neutral has been isolated it will choke you from time to time.
City council normally only isolates live so the neutrals from the whole neighborhood see you as a "good" path to earth and will choke you.
Been there, done that and got choked.

Also not allowed with 2 regulations to back that up

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.

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.

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

[Thys LOW Elektries]

My permanent bridge is on the line side. My setup is as follows:
A main breaker, AC IN, supplies an inverter and changeover with electricity, from Eskom.
The inverter supplies a main breaker, AC OUT, and the changeover with electricity.
I can now choose if Eskom or the inverter must supply the house with electricity.
From the changeover, the electricity goes to the main breaker in the house.
From this main breaker, the electricity goes to an earth leakage and the various breakers then run from the earth leakage.

So putting the permanent bridge before the changeover is definitely on the line side and it can't interfere with the Eskom neutral.

Oops, I meant to say older TNC systems, not TNS systems since TNC systems have no earth from the transformer. and was only generated at some point on the network with a permanent bond between Earth and neutral.

[Isetech]

It seems the chief inspector cant make the decision, and cant issue a formal notice with the neutral/earth bonding, so the electrical police who have been appointed by the chief inspector, are making the rules as they go.

The good thing is that if it ever ended up in court, which will never happen, because of all the confusion, nobody could prosecute you either.

You could use the fact that the AIA have decided that it is safer to do a permenant bond than use a realy, and the regulation say you cant, and all the grey matte rin between.

Like the lithium battery installtions, you just have to go to social media to see how installing a lithium battery in any location is ok

I am going to say it again the electrical industry is a joke a minute.

[GCE]

My permanent bridge is on the line side.

So putting the permanent bridge before the changeover is definitely on the line side and it can't interfere with the Eskom neutral.

l.

Depending on the inverter it can interfere with the Municipal neutral - Some inverters the line side is isolated from live , I know the Imeon is - The Deye , Sunsync are not isolated from line side
Tesla powerwall is not isolated between live and line and has a contactor fitted internally

[Isetech]

You should send this to the chief inspector, clearly he has no idea what he is doing, relying on the AIA to make decision for him. You just have to look at the registration process and that would be regarded as a simple task.

I would have thought the chief inspector would be someone who has a little knowledge about the electrical industry and authority to tep in a set the record straight.

I am sure we will figure it out in the next 10 years

Also not allowed with 2 regulations to back that up

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.

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.

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

[GCE]

It seems the chief inspector cant make the decision, and cant issue a formal notice with the neutral/earth bonding, so the electrical police who have been appointed by the chief inspector, are making the rules as they go.

The good thing is that if it ever ended up in court, which will never happen, because of all the confusion, nobody could prosecute you either.

You could use the fact that the AIA have decided that it is safer to do a permenant bond than use a realy, and the regulation say you cant, and all the grey matte rin between.

Like the lithium battery installtions, you just have to go to social media to see how installing a lithium battery in any location is ok

I am going to say it again the electrical industry is a joke a minute.

The neutral earth bridge is being taken to SANS10142-1 technical workgroup to obtain a unified answer -
The utilities are not allowing permnent neutral earth bond on there networks and it is written as such by Nersa and the bylaws

NRS 097-2-1:2017 clearly states so in Annexure B - Pasted below

Annex B – Earthing system
(informative)
NOTE SANS 10142-1 does not apply to embedded generators (i.e. connected in parallel to the utility network). Annex B is provided as minimum requirements for earthing systems until the update of SANS 10142-1.
B.1 Application of SANS 10142-1
B.1.1 General
SANS 10142-1 applies to low-voltage wiring, earthing, bonding and safety. The requirements in B.1.2 to B.1.5 relating to earthing and to neutral and earth path connections apply.
B.1.2 Neutral conductor
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 (see 6.1.6 in SANS 10142-1:2012).

[Isetech]

Someone should tell the DOL policeman (AIA).

The fact that the AIA are suppose to be the people who know the regs, just make our industry look even more ridiculous

[Isetech]

We have establised that we are not going to get this right until the DOL steps in and provides an official statement, which I cant see happening anytime soon.

People are going to do both the a permenant band and some are going to install a relay, if you going to do either at least get it right, use the correct size wires and relay, a 10 map relay on an 8 kva unit is certianly not going to do the job.

What I would suggest, while the lads are busy with the new regs (there is talk of a 400 page document), that they add a clause which reuires the manufacturer to include a way to monitor the relay in case it fails, while in islanding mode and It should also detect high currents on the neutral earth if bridged in normal grid mode.

These inverters are smart enough, in fact the neutral earth should be built into the inverter, like they do on some of the inverters.

We are in for interesting times ahead, the cost to fix all the installations, once they decide which method must be used. The other one is the cost invloved in registering the SSEG's, I dont know the figure, but looking at the amount of units being installed, its going to be a lot of money to be made by registered engineers and the councils once they enforce registrations around the country.

People are in for a little awakening when they have to fork out another R10 - 15000 for the SSEG registration.

Not forgetting the lithium battery installation.

[NemesisXB]

So, on the relay spec. Should it be able to carry the entire load current? i.e. Should the relay for an 8kW inverter then be 40A? And what size wires should then be used to make the bond through the relay?
I have an 8kW inverter with a 25A relay for the bonding, and wire I am sure will not be able to carry the full load.

[NemesisXB]

With regards to the N E relay...

What size must it actually be ? I use 25A contactor with 4mm cable, sometimes 6.

In my eyes its to join them so that they are the same potential. No current is carried in the bridge other than in a Earth fault.

But some extra guideance would be great as I can't see in the book any thing abvious to me at the moment.


As I type this I think there is more to be discussed about how the bridge is done with what size relay and cable.



Sent from my CPH2197 using Tapatalk

Did you ever manage to get concrete info on the size of the relay to use?

[GrahamH]

So, on the relay spec. Should it be able to carry the entire load current? i.e. Should the relay for an 8kW inverter then be 40A? And what size wires should then be used to make the bond through the relay?
I have an 8kW inverter with a 25A relay for the bonding, and wire I am sure will not be able to carry the full load.

IMHO, the only time the relay contact would carry the entire load current would be if there was load-shedding (IE the relay is closed), a short from the inverter's live output to earth and the inverter's neutral is open circuit on the load side of the relay. IE. a double fault. I can't see that happening too easily, besides which, that should also trip the ELT on the main board if the short was on the load side of the board. My relay contact is also 25A and the contact is carrying only a few milliamps. I also have a red LED panel light across the contact which will light up if the bonding is not there, IE the inverter output is floating.

[Isetech]

How do you issue a COC if you measure 0- 10amps on a wire that is permantly bonded between neutral and earth on the UPS side of the inverter.

I did a number of tests on an inverter installation. A permanant bond, I get reading ranging form 0.5 -10 amps, while the grid connected. I have heard and read comments that indicate that the current is not really current, so what I would like to know, then what is it? Please share if you can answer this question. Someone mentioned that it has to do with the electronics.

A neutral/earth bond using a relay zero amps when connected to the grid.


6.12.1.9 An earth continuity conductor shall not be used to carry any current (other than fault currents).