Grounding victron Phoenix inverter

[gerry mcg]

The victron phoenix 12/500 inverter has the option to ground the neutral to the vehicle body via. It looks like it is 'optional' insofar as the standard configuration on the internal wiring is set up to not require it, and if you want to use it, you alter the earth cable connection on the internal circuit board and then connect an external earth.

None of the inverter installation video I've seen on YouTube for victron inverter or inverters from other manufacturers seem to use the external earth.
Am I OK not to ground the inverter

 

[Richard n Ann]

Haven't bothered with mine, it"s safe as it is

 

[Richard n Ann]

Generators are the same too, floating earth.

 

[Pausim]

It is perfectly normal to have floating neutral on inverters and generators but it is very important to understand that this means there is no positive and neutral wires, they are both live. Each wire is carrying 115V but out of phase, one wire is -115V whilst the other is +115V, which means that when you plug something in it gets 230V, this being the difference between the two wires. The wires rapidly swap between + and - to give the 50Hz 230V supply your device needs.

This 2x115V is considered safer than 1x230V where you have no proper grounding of appliances. When connected to an EHU the grounding comes through the 3 wire connection to the hook up. When using an inverter without hook up we do not have a grounding, unless we bash a big metal stake into the ground and bond it to the motorhome chassis.

UK mains sockets often have switches on them but this only disconnects the brown wire not the blue one, similarly if the plug fuse blows it will only cut off the brown wire. This is known as single pole switching. If you have a floating neutral inverter single pole switching does not make the device safe because the blue wire is still live, as one canal boater found out the hard way when he turned a plug off and opened up an appliance without unplugging it. You may have noticed that continental motorhome sockets do not have switches on them, they only allow 2 pole switching, which disconnects both wires.

It is also worth noting that many UK RCDs only have single pole switching so they are of no use with a floating neutral inverter. 2 pole RCDs can be found but I have yet to see one on a plug in RCD device. 2 pole switching is safer but unsurprisingly costs more.

In summary neutral bonding is safe but different.

 

[Raul]

What the appendix explains is how to bond the floating neutral to inverter chassis to create a protective earth, and a reference to a true neutral. You need this for rcd functionality weather is double or single pole. Without PE protective earth, the rcd will not trip. If you use double pole mcb and not rcd required, then this bond is not needed. In static installations, the PE is wired to a metal bar dug in the groud, soil, hence the name ground. In a vehicle is just bonding ground as all PE cables connected together. It’s not true PE but a work around.
If you really what to get the gist of it, I strongly recommend “wiring unlimited”, a pdf by victron.

^{_{Subscribers  do not see these advertisements}}

 

[Googlebot]

I was planning on earthing mine so the RCD I am adding inline functions as it distributes to all sockets.

Have I got this wrong? I was going to change it to a bonded neutral.

 

[Raul]

Not wrong. You have to bond the neutral to PE inside as shown per appendix, otherwise the rcd will not trip.

 

[tonyidle]

It is perfectly normal to have floating neutral on inverters and generators but it is very important to understand that this means there is no positive and neutral wires, they are both live. Each wire is carrying 115V but out of phase, one wire is -115V whilst the other is +115V, which means that when you plug something in it gets 230V, this being the difference between the two wires. The wires rapidly swap between + and - to give the 50Hz 230V supply your device needs.

This 2x115V is considered safer than 1x230V where you have no proper grounding of appliances. When connected to an EHU the grounding comes through the 3 wire connection to the hook up. When using an inverter without hook up we do not have a grounding, unless we bash a big metal stake into the ground and bond it to the motorhome chassis.

UK mains sockets often have switches on them but this only disconnects the brown wire not the blue one, similarly if the plug fuse blows it will only cut off the brown wire. This is known as single pole switching. If you have a floating neutral inverter single pole switching does not make the device safe because the blue wire is still live, as one canal boater found out the hard way when he turned a plug off and opened up an appliance without unplugging it. You may have noticed that continental motorhome sockets do not have switches on them, they only allow 2 pole switching, which disconnects both wires.

It is also worth noting that many UK RCDs only have single pole switching so they are of no use with a floating neutral inverter. 2 pole RCDs can be found but I have yet to see one on a plug in RCD device. 2 pole switching is safer but unsurprisingly costs more.

In summary neutral bonding is safe but different.

115v with reference to what? To behave as you suggest a centre-tap earth would be needed.

 

[Raul]

115v with reference to what? To behave as you suggest a centre-tap earth would be needed.

Indeed, the victron 230v are not center taped. The way victron works, is uses FET’s to create AC sine wave at about 8v and then upped to 230v by a toroidal. The American ones are centre taped.

 

[Richard n Ann]

You don't need an RCD though if you don't create a neutral. There is no voltage between either of the lives and chassis/ground/earth.

The only way you can get a shock is by touching both lives at the same time, and an RCD wouldn't protect you in that situation anyway (touching L&N at the same time)

Yes I know with some big installations stray capacitance comes into play.. Not relevant in Motorhomes.

^{_{Subscribers  do not see these advertisements}}

 

[Pausim]

My Victron Phoenix 12/500 is earthed to the motorhome chassis. I opened a plug and carefully took AC voltage readings between the brown and blue wires and as expected got 230V. I then took a reading between the blue wire and the green/yellow earth wire and got 115V. The reading between between brown and earth wire was 112V. This is entirely consistent with my explanation above.

I believe a 2 pole RCD should work because it is looking for an imbalance of power between the brown and blue wires. If either of the live wires (blue or brown) should leak to the chassis earth (perhaps through me when doing silly tests) the imbalance should trigger the RCD, which being 2 pole will interrupt both live wires.

 

[Richard n Ann]

My Victron Phoenix 12/500 is earthed to the motorhome chassis. I opened a plug and carefully took AC voltage readings between the brown and blue wires and as expected got 230V. I then took a reading between the blue wire and the green/yellow earth wire and got 115V. The reading between between brown and earth wire was 112V. This is entirely consistent with my explanation above.

I believe a 2 pole RCD should work because it is looking for an imbalance of power between the brown and blue wires. If either of the live wires (blue or brown) should leak to the chassis earth (perhaps through me when doing silly tests) the imbalance should trigger the RCD, which being 2 pole will interrupt both live wires.

I haven't done any tests myself but what springs to mind is that multimeter input impedences are very high, years ago on analogue ones it was 20,000 ohms per volt and I remember the new digital ones were said to be a lot higher.

So maybe your meter is picking up voltages that are so weak they wouldn't do anything like from stray capacitance... I may be wrong though.

 

[Googlebot]

Mind blown……

 

[Pausim]

So maybe your meter is picking up voltages that are so weak they wouldn't do anything like from stray capacitance...

There would have been a small load on the plug I was testing, sufficient to discharge any capacitors. I have no reason to doubt my meter readings, particularly as they were consistent with my understanding of what to expect from a floating neutral inverter. I do not like the term floating neutral because it seems to hide the reality that there are two out of phase live wires.

 

[Richard n Ann]

There would have been a small load on the plug I was testing, sufficient to discharge any capacitors. I have no reason to doubt my meter readings, particularly as they were consistent with my understanding of what to expect from a floating neutral inverter. I do not like the term floating neutral because it seems to hide the reality that there are two out of phase live wires.

No I mean stray capacitance.. Like from when 2 wires travel together and act as a capacitor.
Also do you mean floating earth? The two outputs are both lives until you connect one to the earth point to make the neutral.

Could do with a circuit diagram though before we can be sure of anything.

^{_{Subscribers  do not see these advertisements}}

 

[gerry mcg]

This is way over my head now!

 

[cmcardle75]

This is way over my head now!

It means that an RCD won't trip if you have a floating neutral. But this isn't so bad, as you can't get a electrocuted from such a system anyway, unless you have a live-neutral connection (which means you've contrived to touch TWO separates parts of your mains installation, which an RCD might not protect you from anyway).

 

[Pausim]

It means that an RCD won't trip if you have a floating neutral. But this isn't so bad, as you can't get a electrocuted from such a system anyway, unless you have a live-neutral connection (which means you've contrived to touch TWO separates parts of your mains installation, which an RCD might not protect you from anyway).

The test button on my 2 pole RCD makes it trip, presumably creating and detecting an imbalance between the two 115V live feeds. It would seem that I have a localised grounding arrangement between the power source (inverter) and the motorhome chassis to which it is clearly attached via the earth terminal on the device. I might have to set up some further tests to prove this point but will probably not be in a position to do so in the next few days. The one thing that is already clear to me is that both wires, brown and blue are live at 115V.

Having Googled “floating earth” it sometimes seems to have different meanings in different applications. I am not entirely sure how it is used in respect of Victron’s Phoenix inverters. However looking at the pictures in the op’s #1 post it seems to me that the earth wire is simply being moved from a centre tapped position on the transformer to an end tapping, thus creating a neutral earth bond. This would be consistent with my 2 x 115V connections.

 

[autorouter]

The test button on my 2 pole RCD makes it trip, presumably creating and detecting an imbalance between the two 115V live feeds.

Yes, the test button creates an imbalance inside the RCD, that triggers the trip mechanism. It is intended as a test of the trip mechanism only, not a test of the earth connection and the general effectiveness of the RCD within your wiring. In other words, the test button doesn't in itself prove you are safe.

 

[gerry mcg]

Only a slightly related note, I've got a victron Shunt installed to inform a Victron bms 700.
I take it I should connect the negative inverter cable to their downstream Shunt connection, rather than the negative battery terminal (as otherwise the Bms won't register the Inverter current draw)

^{_{Subscribers  do not see these advertisements}}

 

[Richard n Ann]

Yes

 

[Pausim]

Only a slightly related note, I've got a victron Shunt installed to inform a Victron bms 700.
I take it I should connect the negative inverter cable to their downstream Shunt connection, rather than the negative battery terminal (as otherwise the Bms won't register the Inverter current draw)

The only connection to the battery negative terminal should be one end of the shunt, everything else is connected to the other end of the shunt.

 

[Leighmeddle]

So in summary, after doing a lot of research myself, and also reading this thread, I should be fine not to ground the Phoenix inverter to the chassis as long as I am only using an extension lead straight from the inverter for my appliances?

 

[Diabalo]

So in summary, after doing a lot of research myself, and also reading this thread, I should be fine not to ground the Phoenix inverter to the chassis as long as I am only using an extension lead straight from the inverter for my appliances?

I could do with the answer

 

[DavidCh]

I think this is relevant to the discussion and I wonder if someone can tell me if I am wrong. I also have a victron inverter which was installed by someone else. They simply ran a lead from the ground terminal to the incoming earth from the incoming EHU which obviosly does nothing but is potentially (nice pun) dangerous. I am about to install a relay to automatically switch the invertor or the EHU to the internal sockets. As I see it I need two separate earth systems to the internal sockets. When the EHU is in use the earth on the electrical sockets should be connected to the incoming mains supply (which I assume is also linked to the chassis?) and when the inverter is in use the earth on the sockets should connect back to the inverter but the inverter should not be connected to the chassis so the inverter output is floating, which means an RCD on the inverter would do nothing. Or I could bond neutral and earth in the inverter and then the RCD would work but only if its connected back to the chassis? Or am I completly over thinking this?

^{_{Subscribers  do not see these advertisements}}

 

[Googlebot]

I connected the neutral to earth with the connector in mine. It now trips the RCD when I test it so I am happy.

 

[autorouter]

It may help to know that on the Victron Multiplus 2 inverter/charger, the inverter and charger are closely integrated. There is a built-in transfer switch to switch between grid power and inverter power, and even mix the two power sources together if required. For the earthing arrangement there is a relay that automatically connects the incoming mains earth to the socket earths and the chassis. When EHU is disconnected, the relay switches off and the inverter earth is isolated. There is an option to override this in the software controls.

 

[Raul]

The only think I can’t get my head round it it’s this scenario: chassis, ppl confuse vehicle chassis with equipment chassis. Having the earth conductor bonded to the equipment chassis it’s normal operation ( floating earth). Then ehu earth is isolated of the vehicle chassis. Fancy a earth fault current sent down from ehu to your van chassis without path to earth? On rubber tyres you don’t have any contact with earth. Yes the current will follow the least resistance, and will be sent trough a safe path back to source ehu. But, if ehu has a high resistance, or bad earth, those wet tyres in contact with grass, may be encouraged to create a second path. Therefore I’m thinking ehu earth conductor should be isolated of the vehicle chassis, same as boats.
Somebody put me straight on this.

 

[Googlebot]

I have even checked electricians forums for the answer on earthing.

Everyone has that one subject, for us it’s the CAMC or dogs. For sparkies it seems to be earthing…..

 

[Diabalo]

https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

On a thread in 2021 autorouter shared the link above to some excellent info, section 7 has all the relevent info around earthing, I'm slowly getting me head round it now.

I am slightly different to the OP in that the Renogy 2000W I have just bought does not have the option to fiddle internaly with the earthing, not that I want to. It's designed as a stand alone inverter to plug suitable domestic 240v appliances into, which is all I want to do as and when needed. I don't want to intergrate it with the EHU side. So regarding electrical safety it will be ok but (always one) there is a small ground terminal stud on the Inverter metal casing with no instructions, should this be connected to the vehicle chassis?

Now where's me paracetamol

^{_{Subscribers  do not see these advertisements}}