Neutral/earth bond for inverters

[Isetech]

If you installed an Axpert type inverter, chances are you have bonded the neutral to earth, between the inverter output terminal and the top of the output earth leakage unit, and you dont have an earth earth leakage on the inverter supply. The debate about supplying the inverter via an earth leakage would be an interesting one.

I will soon be adding a Sunsynk 5 kva inverter to my workbench, this is were it gets a little complicated. I have been doing some research into this inverter (for about 2 years) because I just dont have the funds to outlay on a Victron unit yet, maybe once I get my Bugatti, all the blue will blend together in the garage.

It seems people use an external neutral earth bridge connected using a relay. The sunsynk is a hybrid which complicates things a little, capable of receiving and send power back to the grid. There seems to be a lot of confusion about this.

Anyone has a simple explanation which is easy for everyone to understand.

[Justloadit]

A statement by someone about Sengen -

I spoke to the guys from Segen who are also selling the Sunsync now. They said the inverter has a built in earth neutral bond and that bonding is only recommended at one single point and that a permanent bond can cause impedance issues.

[Justloadit]

Check this video
Automatic Neutral Earth Bonding

Do a google search on SunSync videos, lots of training materials.
I have the Deye which is made in the same factory, can state that I am very happy with it, and it does what the manual says.
Since installing it, I save about 50% on my electricity bill, but bear in mind, that my 2 geysers geysers is running on my own designed Dual Usedasun Geyser System so is not even part of the savings

[Dave A]

I suspect hybrid inverters have to deal with the neutral-earth bonding issues. My Growatt certainly does too, so add that to the list that "just works". Probably due to the "complexities", as you say.

I did have a plan as to how to deal with the issue if I had found the neutral was floating at any point (using a relay to drop out the bond when the municipal supply is on), but happily not an issue.

I have no idea why the supply to the inverter would need to be on earth leakage. Surely what you want protected by earth leakage is what the inverter supplies...

[Derlyn]

I have no idea why the supply to the inverter would need to be on earth leakage. Surely what you want protected by earth leakage is what the inverter supplies...

What happens if you use your earth leakage tester on the output of the invertor ?
Does the earth leakage relay on the input side ( supply) trip ?

[Isetech]

I suspect hybrid inverters have to deal with the neutral-earth bonding issues. My Growatt certainly does too, so add that to the list that "just works". Probably due to the "complexities", as you say.

I did have a plan as to how to deal with the issue if I had found the neutral was floating at any point (using a relay to drop out the bond when the municipal supply is on), but happily not an issue.

I have no idea why the supply to the inverter would need to be on earth leakage. Surely what you want protected by earth leakage is what the inverter supplies...

Been watching the Sunsynk training videos, Keith mentions certain countries require RCD protection on the input side of the inverter.

This external neutral relay sound like a dangerous option, especially if the relay fails or doesnt switch fast enough or too fast, it will result in the supply E/L unit tripping. It could explain why there are so many queries about E/L unit tripping when the power switches to backup then back to power.

Throw in a hybrid inverter and many different type so electrical system and you have a task trying to find the right solution for that specific application.

I had to remove the earth/neutral bond to prevent the supply E/L unit from tripping.

[Isetech]

What happens if you use your earth leakage tester on the output of the invertor ?
Does the earth leakage relay on the input side ( supply) trip ?

Without the neutral/earth bridge.

With the mains power on - both earth leakage units trip. The E/L unit in the Workshop DB and the E/L unit on changeover panel.

With the mains power off - only 2 lights are on the plug tester and the E/L units feeding the essential circuit does not trip.

If you fit the neutral/earth bridge between the inverter output and the input side of the E/L unit, you cant switch on the workshop E/L unit, until you remove the bridge. If you add a relay with a neutral/earth bridge, it could get rather interesting.

I have sure there must have been a lot of research into this neutral/earth bridge, we just need to find the documentation.

[Derlyn]

So in other words with mains power off, there is no earth leakage protection on the inverter output circuits.

[Justloadit]

So in other words with mains power off, there is no earth leakage protection on the inverter output circuits.

You use the ELU after the inverter for the loads.
If there is no Neutral Earth bond when there is a Mains failure, then the Neutral and Live will slowly increase in potential to earth due to high frequency switching inside the inverter. This could rise to a few thousand volts, now if you touch Neutral and Earth, you could get a fatal discharge of this built up static charge. By connecting the Neutral to Earth with a bond, you prevent this static build up from occurring.
This is the reason that if you do not use the Earth Neutral bond, and the Neutral/Live load has built up a charge, and then gets connected to Mains, the ELU will see the discharge as an Earth fault and trip.

[Tang]

Someone connected a sunsynk inverter without the external N-E relay and that caused some alarm and camera power supplies to blow.
I suspect the output is similar to the vov generators without the neutral to earth bonding. Just my opinion.

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[Dylboy]

Yes without it if I recall correctly i would measure 98 volts around there of N to E. So I can see that cussing issues for electronics and also the ELU won't work.

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[Alfred M]

What happens if you use your earth leakage tester on the output of the invertor ?
Does the earth leakage relay on the input side ( supply) trip ?

The reason is that all inverters have capacitors to earth from both neutral and live. These are to mitigate EMI/RFI from the switching transients. These capacitors cause current in the earth conductors: transient currents, plus some milliamps of 50 Hz current. Both of these make a Residual Current Device before the inverter more likely to nuisance trip. You can still have them, but not the usual 30 mA ones. But then of course, there is less protection so what is the point

[Isetech]

Note the reference to class I and class II products.

Something else the I am still trying to wrap my head around, how I will fit a changeover/bypass switch in this system and as he mentions is not required.

https://www.youtube.com/watch?v=QtDblj7MMjY&ab_channel=Sunsynk

[recre8]

What I did with my Sunsynk/Deye inverter was to ignore the "island" output of the inverter you would normally use to power a relay to do the earth-neutral bond. Instead I installed a Hager 25A 1NO+1NC contactor in the DB. The contactor will close whenever grid power is lost and bond neutral to earth - and obviously when power restored, the contactor will open and break the bond. No particular reason other than it being neater in my opinion having it in the DB vs having it in the inverter cubby. Another reason I prefer doing it this way: The contactor will open immediately when grid power is restored whereas with the inverter, it will keep the relay powered (and thus the bond) until it synchronizes with the grid. By default configuration that is 60 seconds.

As for my earth leakage. I have two earth leakages. One for the grid, and another for the UPS output of the inverter. Both having their own separate neutral bars. The automatic transfer switches that I use will then switch the relevant circuits to either UPS Live+Neutral or Grid Live+Neutral.

[Isetech]

Why a neutral/earth bond relay is used in conjunction with RCD's

https://www.youtube.com/watch?v=mQR5VKdlshE&ab_channel=Sunsynk