Neutral Earth bonding of inverter

**Dylboy** · 19-May-23, 02:30 PM

For the VoV one when doing a DB tie or whatever, don't use the earth of the output and then bridge the Neautral and Earth on the "supply side" so basically not shorting the VoV.

So using the Line and Neutral only from the inverter and joing the out going supply Earth to the Neutral.

That is how I see it can be done on a VoV.

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**JackC** · 20-May-23, 08:36 AM

Thanks everybody for your contributions. I will try to digest the information and try to come up with possible solutions.

I anyway decided not to bond neutral and earth on the output of the inverter, therefore I will keep my trolley as a portable solution. But I will try to make it as save as possible by introducing an ELU.

Once I am done with possible solutions, I will publish the diagrams on this forum for discussion.

One lesson that I however learned so far is to me thorough when buying online.

**Dave A** · 20-May-23, 08:49 AM

Originally Posted by Derlyn

That's a VOV output. You cannot just bridge neutral to earth on that output.

Not just a floating neutral?
Or did you check the specs on the unit?

**Derlyn** · 20-May-23, 10:28 AM

Originally Posted by Dave A

Not just a floating neutral?
Or did you check the specs on the unit?

The specs on these types of inverters only give the live/neutral voltage output.

I was probably a bit hasty with my VOV reply. Its just seldom that one measures a floating neutral scenario so close to exactly half the supply voltage. ( possible, but seldom )
Of course the correct way, as with a generator as well, is to connect a load to the output before taking voltage measurements. I use incandescent light bulbs.
I was under the impression that the author had done this.

Had he not, it will be interesting to know the outcome after doing so.

**Isetech** · 20-May-23, 10:47 AM

This is the way I understand the logic, right or wrong, I am sure someone will correct me.

Genrators, UPS, inverters and the like are designed for a specific application, which is why they are class 11 devices, not orginally designed to be connected to fixed electrical installation.

A class 11 devices doesnt have a floating neutral, it has 110 VAC on each leg, which reduces the voltage to make it a little safer for mobile use.

A floating neutral is a floating neutral in a 3 phase supply which creates an extremely dangerous situation, in the past neutral condustors have been stolen in sub station because the thief has learnt that they will not get electricuted if they cut it.

IF you are an electrician and been called out for a burning smell in a property, or burnt plug tops, ballasts and the like, you would have carried out tests and realised that the power had to be switched off asap, why because the voltage measured would in some cases be as high as 600-700 VAC

**Justloadit** · 22-May-23, 09:22 AM

Originally Posted by JackC

But I will try to make it as save as possible by introducing an ELU.

An ELU will not work if you do not earth the inverter 'output Neutral', as there is no return path for the detection coil to operate.
I suspect that with all these inverters, there is usually a small value capacitor connected between the inverter output and the 'Neutral' leg of the output plug.
This capacitor cause the typical readings that you get with your multimeter when measuring the output of the inverter.

**Derlyn** · 22-May-23, 10:58 AM

@ Justloaded. The way I understand it is that the earth leakage will work if the neutral and earth is not bridged on the output.

If someone were to shock down to earth , then the difference in currents between the live and neutral will be detected by the earth leakage and it will trip, much the same as if one shocks down to earth from a double insulated appliance that is fed with live and neutral only, excluding an earth.

However, should the output of the inverter be in a vov configuration, then the earth leakage wont trip.

Correct me if I'm wrong.

**Justloadit** · 22-May-23, 11:28 AM

@ Derlyn. The inverter shown by the OP does not have a VOV. They have a booster circuit multiplying the 12V Battery through a transformer to 230V AC out. So the battery and earth is effectively isolated by the transformer. If the Inverter Neutral output is not connected to earth before the ELU, the the ELU will not work. Of course the "Earth" connection is important, not only to the metal housing of the inverter, but also to the 'House' earth, as one would expect this to be a good earth point.

I can not vouch for the VOV, in which the 'O' connection is earthed, if it would trigger the ELU. Theoretically it should.

**Derlyn** · 22-May-23, 12:09 PM

Thank you, my brother, much appreciated. 👍👍

**JackC** · 23-May-23, 03:15 PM

"Of course the correct way, as with a generator as well, is to connect a load to the output before taking voltage measurements. I use incandescent light bulbs"

I done it with a small hair dryer as load, the voltages remain the same as tested previously. I also tested the current with a clamp meter both on live and neutral (basically the same 2.3 Amp) and when I include both neutral and live in the clamp meter I get a reading of 0.07 Amp. As explained by various forum members it seems like an inverter developed specifically for mobile use.