Neutral earth bonding on backup systems.

[GrahamH]

Not sure about the recent ruling but suppose that is interpretation - Has been out since at least 2008
Do not see how it can have an effect on the warranty - It has to comply otherwise you cannot use it into a fixed electrical installation - Then it should only have been used as a portable unit.

Thank you so much! I know I have mentioned this before... In my case, I bought a pre-assembled board from the supplier with the Deye 8kVA and associated breakers, fuses etc. already mounted and connected. After I received it, I pointed out a number of things that didn't look right, however, the supplier said that if we change anything on the board then they won't honour the warranty. The problems I see with board are: exposed AC wiring (ok, the wires are insulated but not in a conduit/duct etc everywhere), no provision for grounding the neutral when off grid, inline breaker of 32 amps (~7.36kW) which is less than the 36.4 amps rated output current (~8 kW) for the inverter and only two thirds of the 50 amp max continuous pass-through rating when connected to the grid. They don't seem to agree that the inverter power is added to the grid power when grid-tied for a total of 50 amps - which would be maximum load of 11.5 KW at a PF = 1.

[GrahamH]

There is a poll on social media, which indicates that more than 70% of inverter installations in SA have permanent bonds and only around only 30 % have a relay.

I stand to be corrected but I believe the majority vote on this platform is to install a relay.

Did someone mention grey area

The way I see it is that if you permanently bond your neutral to earth and it is also bonded at the substation, then some current will be flowing via a potentially naked earth whenever there is any current flowing through the neutral. In a normal single phase supply, the neutral current is the same as the live current. If the current from the substation is let's say, 50 amps at a given point in time and the neutral wire resistance is the same as the earth wire, then the current flowing through the earth would be 25 amps? And of course, for current to flow from point A to B there must be a voltage difference. Maybe I'm dumb, but I can't see that as being ok. Your neighbour's earth voltage could be different to yours, so never shake hands over the fence unless you're both wearing rubber gloves!

[Isetech]

I know where to get a T-shirt if I need one

What is important is to understand the operation of the inverter. Make sure you are aware if an internal relay is used and if it has fail safe protection.

As pointed out by GCE, isolated from the grid/mains.

Some inverters like Victron and Deye/Sunsynk have built in relays.

Older Axpert type inverters dont have a relay. Axperts are branded many other names, like Meccer, Kodak, MCE, RCT and many others.

Must inverters I ahve worked with dont have relays.

Growatt, Schnieder I am not familiar with this product, maybe someone can share.

[Isetech]

GCE, tell us more about being permanently isolated from the grid/mains.

An Axpert unit for example is not permanently isolated from the mains/grid. It would be like an online UPS which doesnt switch, instead it is isolated from the mains power via the internal components to product a clean pure sinewave ?

[GCE]

Some inverters like Victron and Deye/Sunsynk have built in relays.

.

Deye/Sunsynch - have an output that you configure , you have to fit the relay

[GCE]

GCE, tell us more about being permanently isolated from the grid/mains.

An Axpert unit for example is not permanently isolated from the mains/grid. It would be like an online UPS which doesnt switch, instead it is isolated from the mains power via the internal components to product a clean pure sinewave ?

If an inverter is isolated from mains it will normally tell you in the manual alternatively you will pick it up when you test with earth loop tester.

With an Earth loop on mains and you get good readings then the isolation is not there - If it is isolated your readings will not comply and the neutral will be " floating"

[Isetech]

From the little knowledge I have of Victron, the relay is integrated with the control of the inverter, which has fail safe protection for the relay, the power to the inverter switches off.

The way I understand the Deye/Sunsynk has relays in certain models (I dont know if they have built in fail safe protection) and the rest have a signal to a relay. The concern is what happens if the relays fails? What is the worse thing that can happen, or should I say what are the safety implications of a failed relay? The neutral will float creating a high touch voltage, making the installation dangerous ? If the neutral - Earht voltage exceeds 25 V , the installation should be shut down ? If you connect a device to monitor the neutral to earth voltage, if it exceeds 5 V it switches the power to the inverter off, problem solved and everyone is happy or not ?

Deye/Sunsynch - have an output that you configure , you have to fit the relay

[Isetech]

If an inverter is isolated from mains it will normally tell you in the manual alternatively you will pick it up when you test with earth loop tester.

With an Earth loop on mains and you get good readings then the isolation is not there - If it is isolated your readings will not comply and the neutral will be " floating"

I thought all inverters switched to "islanding mode" when the power is off, I wasn't aware that there are inverters that operate in islanding mode even with the power on. I have a lot to learn.

[Dylboy]

I want to add the Victron has the E N relay but it is not good, it is delayed and causes havoc with the earth leakage. Installers now install their own contactor... Basically their is a time delay before it operates and that is what causes the issue.

Also Sunsynk, of you use the signal thing it is also delayed and causes havoc, so again install contactor that switches with grid.

Sent from my CPH2197 using Tapatalk

[GCE]

The concern is what happens if the relays fails? What is the worse thing that can happen, or should I say what are the safety implications of a failed relay? The neutral will float creating a high touch voltage, making the installation dangerous ? If the neutral - Earht voltage exceeds 25 V , the installation should be shut down ? If you connect a device to monitor the neutral to earth voltage, if it exceeds 5 V it switches the power to the inverter off, problem solved and everyone is happy or not ?

We sometimes cannot avoid all issues or failures , same as when they steal the neutral earth bridge in the sub , or there is a cable fault in the street and you lose earth or neutral , or the overhead lines shorts earth to a phase.

If you have a D/Pole CB feeding the inverter and a D/pole out of the inverter and the relay does weld close and mains comes back then the D/pole CB will trip if the current draw on the neutral is excessive.
If you are using the normal open on the relay it will always close if the relay coil fails

Those measure should protect you , as the installer,

[Justloadit]

I want to add the Victron has the E N relay but it is not good, it is delayed and causes havoc with the earth leakage. Installers now install their own contactor... Basically their is a time delay before it operates and that is what causes the issue.

Also Sunsynk, of you use the signal thing it is also delayed and causes havoc, so again install contactor that switches with grid.

Sent from my CPH2197 using Tapatalk

I found this solution has its own issues, simply because there is a delay in the inverter before it changes over to the grid, which then trips the ELU.

[BEVIN]

Hi GCE :when mains fails and the generator supplies power you must earth the neutral - This is why you use a D/pole change over or 4 Pole change over .are we talking about earthing of the neutral of the gen here? Any possibility of a drawing please

[GCE]

Hi GCE :when mains fails and the generator supplies power you must earth the neutral - This is why you use a D/pole change over or 4 Pole change over .are we talking about earthing of the neutral of the gen here? Any possibility of a drawing please

It is late and drinking coffee to get to sleep - Drawing of what are you looking for

An inverter neutral earthing arrangement ?

[Isetech]

If you have a D/Pole CB feeding the inverter and a D/pole out of the inverter and the relay does weld close and mains comes back then the D/pole CB will trip if the current draw on the neutral is excessive.
If you are using the normal open on the relay it will always close if the relay coil fails

Those measure should protect you , as the installer,

You mean the N/C contact, to make it fail safe?

If it fails it becomes a permanent bond ?

Which is why I ask, is it really that dangerous either way, if it was the DOL would have already stepped in and cleared up the confusion and manufacturers wouldnt selling units in SA with and without relays.

I have had so many different responses from so many different people at all levels (from electrical engineers to electricians).

The AIA have threated court cases, I am so looking forward to them living up to their promises. It been 40 years in this industry and I still havent seen any light at the end of a very dark tunnel. I have tried been a member of associations for more than 10 years, dealt with technical advisers and all I see is a crippled industry with so many loop holes that the ship is going down just as fast as the bankrupt energy producer.

[GrahamH]

I found this solution has its own issues, simply because there is a delay in the inverter before it changes over to the grid, which then trips the ELU.

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.