Inverter "ground terminal"

[peterc10]

The new Renogy inverter I have just bought has a "ground terminal", which my previous inverter didn't. It is shown on the diagram but no advice in the instructions as to what, why or how as to its use. Should I connect it and what is it for? If I do use I assume that I should attach it to a separate metal part of the chassis rather than the common negative pole on my shunt?

Many thanks

 

[tkk]

Cannot answer definitely, but somewhere on this forums “inverter threads“ is a post by someone who took off the casing and found that it connected to nothing but the case so I suppose it is the same as the grounding point on metal light fittings in A/c domestic setting just to protect you from live leak to the case.
Somewhere else on the Forum (cant pinpoint it) is a thread discussing how it isn’t easy to electrocute yourself with inverter output. I am unclear myself on the theory but someone will be along to clarify I hope. From the photos Ive seen on the Forum use of the earth point is rare.

 

[Boringfrog]

My Sterling inverter has a ground, I connected to a bolt near the handbrake.

 

[ctc]

Most motorhomes have rubber tyres, there is no "ground".

 

[peterc10]

Most motorhomes have rubber tyres, there is no "ground".

Two problems with that. It is "grounded" or "earthed" if plugged into the EHU I would guess.

And secondly I have metal hydraulic levelling jacks fitted to the chassis, so more than just tyres.

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[tkk]

Just to stir it, on one of the forum threads I mentioned raised the issue of earthing A/C output to the common earth of the D/C system. The situation discussed gets very complicated when you introduce earthed “shore “supply to the equation, modifications to circuit connections required , if I recollect correctly. If I find the thread Ill post. Also a lot of people use “metal steadies” even if they don’t have levelling jacks so its a common potential problem.

 

[tkk]

Thread started by kwhkwh@hotmail Aprril 2020 or search “inverter earthing” should bring it up

 

[peterc10]

Just to stir it, on one of the forum threads I mentioned raised the issue of earthing A/C output to the common earth of the D/C system. The situation discussed gets very complicated when you introduce earthed “shore “supply to the equation, modifications to circuit connections required , if I recollect correctly. If I find the thread Ill post. Also a lot of people use “metal steadies” even if they don’t have levelling jacks so its a common potential problem.

Thread started by kwhkwh@hotmail Aprril 2020 or search “inverter earthing” should bring it up

Thanks. Yes I also remember something on a thread, but it was more recent than that. Come to think of it, I think Raul contributed to it, so he may remember or be able to help

 

[Raul]

I can’t remember where I posted but tkk is right. Grounding PE to the chassis it’s ok if sistem functions in stand alone off grid mode. When shore supplied PE is connected, you end up with two bondings from neutral to earth. This is why multiplus has a relay for grounding the PE when stand alone, and opens the relay when detects ehu or shore power.

 

[peterc10]

I can’t remember where I posted but tkk is right. Grounding PE to the chassis it’s ok if sistem functions in stand alone off grid mode. When shore supplied PE is connected, you end up with two bondings from neutral to earth. This is why multiplus has a relay for grounding the PE when stand alone, and opens the relay when detects ehu or shore power.

Thanks. When we are away we rarely have EHU. But sometimes we do when away and always plugged in at home. So maybe I could use a manual switch. But what are the dangers if I just don't ground at all? Also what size should the ground wire be with a 2000W inverter

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[daveclare]

Watching this one and ready to buy a thicker wire than you! Just bought the 3000W Renogy inverter.

 

[Raul]

The danger of not grounding is electric shock if you happen to touch a life wire, or neutral.
There are sistems that work without ground, double isolated. If you touch one wire nothing happens as you don’t complete the circuit. Only if you touch both. But in this system you have no rcd.
The size of the ground should be close to equal to the life wire. On 1.5 life wire you can have 1mm PE.

I recommend you google for “victron wiring unlimited “, very nice explanation in there with schematics, better than me explaining.

 

[Jimbohorlicks]

The new Renogy inverter I have just bought has a "ground terminal", which my previous inverter didn't. It is shown on the diagram but no advice in the instructions as to what, why or how as to its use. Should I connect it and what is it for? If I do use I assume that I should attach it to a separate metal part of the chassis rather than the common negative pole on my shunt?

Many thanks

Hi peterc10 Did you fit a grounding wire to your renogy inverter or just left it as per your original inverter?

 

[peterc10]

Hi Jim, I did not fit a grounding wire to the Renogy inverter. Seems to work OK.

Now we are in Portugal with 240v, which those around us who have EHU do not have!

 

[Gromett]

I can’t remember where I posted but tkk is right. Grounding PE to the chassis it’s ok if sistem functions in stand alone off grid mode. When shore supplied PE is connected, you end up with two bondings from neutral to earth. This is why multiplus has a relay for grounding the PE when stand alone, and opens the relay when detects ehu or shore power.

I am a little curious about one point. If it is a standalone inverter with it's own built in sockets OR dedicated fixed sockets in the van is the earth/neutral disconnect still needed?

I understand the need for it in a Victron Multiplus or other combined charger/inverters. But is it still needed in a standalone inverter? Just my idle curiosity on this one.

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[Raul]

I am a little curious about one point. If it is a standalone inverter with it's own built in sockets OR dedicated fixed sockets in the van is the earth/neutral disconnect still needed?

I understand the need for it in a Victron Multiplus or other combined charger/inverters. But is it still needed in a standalone inverter? Just my idle curiosity on this one.

In stand alone if you have one socket only and the power does not go any further than 5m, or not taken outside, the a earth ground is not necessary, the double insulation of the inverter is enough protection. If you exceed those: more than one socket, and power goes outside or exceeds 5m circuit, then a neutral earth ground is mandatory with a 30mA RCD.

 

[peterc10]

I am a little curious about one point. If it is a standalone inverter with it's own built in sockets OR dedicated fixed sockets in the van is the earth/neutral disconnect still needed?

I understand the need for it in a Victron Multiplus or other combined charger/inverters. But is it still needed in a standalone inverter? Just my idle curiosity on this one.

Mine has a separate circuit I built in. The Renogy has the facility that when you are plugged in it will stop generating and instead allow the mains run the separate circuit.

 

[Jimbohorlicks]

Hi Jim, I did not fit a grounding wire to the Renogy inverter. Seems to work OK.

Now we are in Portugal with 240v, which those around us who have EHU do not have!

Well done. Where in Portugal are you.?

 

[autorouter]

I am a little curious about one point. If it is a standalone inverter with it's own built in sockets OR dedicated fixed sockets in the van is the earth/neutral disconnect still needed?

I understand the need for it in a Victron Multiplus or other combined charger/inverters. But is it still needed in a standalone inverter? Just my idle curiosity on this one.

This is all about whether you need to connect the neutral and earth together. If it's a stand-alone inverter using its own built-in sockets then there is no need to connect the neutral and earth. The live and neutral are isolated internally inside the inverter. Touching either a live conductor or a neutral conductor will not result in a shock. The system behaves like an isolating transformer, which is a good safety setup, as found in for example UK bathroom shaver sockets. It's not more widely used because powerful transformers are big, heavy and expensive. Obviously if both live and neutral are touched then a shock will result, as with any system.

If the inverter output is wired to the consumer unit, and distributed throughout the motorhome, then the neutral and earth should definitely be connected together when the inverter is running but the shore power is not connected. This is to protect against faults like a live wire touching some metal casing etc. However when the shore power is connected, that neutral/earth connection needs to be disconnected because there will already be a neutral-earth connection in the shore power, and two neutral-earth connections can cuse problems.

If the installation is somewhere between those two, say an inverter with a 4-way extension plugged into an inverter output socket, then it's a judgement call as to when the outputs become likely to touch exposed metal parts if a fault occurs.

Having said that,some inverters like the Renogy have an internal relay that can be set to automatically connect when the shore power is disconnected, and disconnect when the shore power is connected, as is required.

However to answer the original question posed by the OP, the metal casing of the inverter should in all cases be connected to the chassis metal somewhere. Usually it is stated that this AC chassis connection should be to a different place than the DC chassis connection, which is usually easy to do. Just find a different chassis bolt.