inverter earthing

[kwhkwh@hotmail]

hi all i am new here hope you are all keeping safe
i was reading an article regarding earthing inverters in a motorhome or caravan with various ideas one of which was connecting the main 230v earth to the van chassis and the negative of the battery and also the earth pin from the inverter socket earth pin and also the case then i could connect an rcd in the live output of the inverter socket would this work any ideas would be very helpful i have taken the case off the inverter and the socket earth pin is not connected anywhere thanks...kev

 

[DBK]

I'm a bit reluctant to give advice as I don't have the insurance to cover me if it goes wrong! But the normal way is to connect one side of the output from the inverter to the vehicle chassis. This makes that side of the supply equivalent to neutral and the other side becomes the live. The earth connects to the chassis too. Wired like this an RCD will work.

But I don't suggest you do this as inverter designs differ and yours may not take kindly to having this done to it and you may end up doing something dangerous.

If you do a bit of Googling on earthing inverter outputs you should get some ideas on how to do it.

Alternatively, just don't bother and assuming you only use double insulated appliances you should be safe. The reason for this is the inverter output is "floating" and you can't get a shock between the output and earth. You can only get a shock if you touch both outputs at the same time, which is normally difficult to do. I suspect the majority of inverter installations are not earthed.

 

[kwhkwh@hotmail]

thanks for your input i am confused should i earth and use an rcd or rely on no earth if one lead from a socket supplied by the inverter touched anything metal in the van and no connected rcd i/we could be fried thanks...kev

 

[pappajohn]

i/we could be fried thanks

As could the inverter

 

[kwhkwh@hotmail]

thanks for your reply pappajohn but if the inverter gets fried i buy another cant but cant buy another life no matter how much money is in the bank

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[68c]

If you have lots of money, and its your other half gets the hit, I think you will find them very easy to replace.

 

[DBK]

thanks for your input i am confused should i earth and use an rcd or rely on no earth if one lead from a socket supplied by the inverter touched anything metal in the van and no connected rcd i/we could be fried thanks...kev

This is where it gets tricky as I don't know the specifics of your inverter but generally if one side of the inverter output touches the vehicle or you nothing happens. The circuit is only completed if you also touch the other wire.

You can test this using a volt meter See if you can detect any voltage between the vehicle chassis and the inverter output. You probably won't, but it's worth checking.

 

[kwhkwh@hotmail]

also i have had an idea if i connected a relay to the earth lead of the earth ring connected to the relay coil and grounded to the negative battery terminal through a resistor with the relay controling the 230v out put from the inverter could this work

 

[kwhkwh@hotmail]

thanks dbk i am just looking for absolute safety if for a strange occurance i was stepping from the van holding on to the metal door frame which had been made live from a scuffed inverter lead and at the same time put my bare feet on the wet grass outside ?

 

[DBK]

also i have had an idea if i connected a relay to the earth lead of the earth ring connected to the relay coil and grounded to the negative battery terminal through a resistor with the relay controling the 230v out put from the inverter could this work

Not sure what you are suggesting but no I think. ?

thanks dbk i am just looking for absolute safety if for a strange occurance i was stepping from the van holding on to the metal door frame which had been made live from a scuffed inverter lead and at the same time put my bare feet on the wet grass outside ?

As I've suggested earlier, with a typical inverter you can't get a shock from its output by touching the vehicle chassis or the ground outside. This is because there is no return through the earth. If you Google "inverter floating neutral" as a starter you can fill your boots on various solutions especially if you want to incorporate an RCD.

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[kwhkwh@hotmail]

what if your wrong?

 

[DBK]

what if your wrong?

That's why I'm saying my views are only opinion. If you are unsure I can only suggest getting it professionally installed.

 

[kwhkwh@hotmail]

when i bought the inverter it was advertised as pure sine wave 50 htz when i opened the case i saw no earth connection to the socket and the two wires to the socket ( expected red and black or blue and brown ) were both red on the board connection marked ac1 ac2 ?

 

[bigtwin]

what if your wrong?

Why are you asking random folks on the internet for advice on electrics?

Can you rely on any advice you might get?

How will you know who to trust?

Ian

 

[Campervan_man]

Most inverter's have a small bolt / nut on the side to attach an earth lead to.
Normally this is then attached to the bared chassis point and then over coated with some sealant.
Eddecoa Inverters come with a small earthing lead with a ring terminal on one end and a crocodile clip the other end.
I have a 2KW petrol generator in My work Van for occassional emergency back up use.
I have earthed the generator to the chassis of the vehicle { long bolt and nut through the floor, the remainder of the long threaded bolt for other common Earth's if required, eg, leisure battery }.
I'm NOT an electrician so this is general advice, I have had some electrical training, if in doubt consult a Qualified 18th edition Electrician.
Most inverters instructions state connect the positive first as the other way round they tend to SPARK a bit.

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[Gromett]

It is not a simple question to answer. The output of the transformer in the inverter may be centre tapped so earthing to chassis may not be suitable.
Best to read the manual that comes with the inverter as a good quality inverter will indicate safety requirements.

You may find these two videos interesting as he does RCD tests...

 

[Gromett]

, if in doubt consult a Qualified 18th edition Electrician.

It's up to 18th already? Jeez, making me feel old. I did my apprenticeship under the 15th

 

[kwhkwh@hotmail]

thanks for all your replies have a long day ahead tomorrow doing little but working this safety problem out off to bed now keep safe all you people out there thanks will sleep on it and give you my thoughts tomorrow night ...kev

 

[DBK]

when i bought the inverter it was advertised as pure sine wave 50 htz when i opened the case i saw no earth connection to the socket and the two wires to the socket ( expected red and black or blue and brown ) were both red on the board connection marked ac1 ac2 ?

That's what I'm trying to put over. The concept of live and neutral doesn't apply to the normal inverter output, although models will differ. I can only suggest doing some wider reading. Best wishes. I used to be a member of what was called for most of its life as the Institution of Electrical Engineers and I have some random knowledge of things electrical but I don't have practical knowledge of specific inverters or even motorhomes which is why you need to find a professional if you are unsure of anything. An inverter involves potentially lethal voltages and very high DC currents which could potentially cause a fire.

 

[Richard n Ann]

DBK is spot on. Electricity only flows to earth because NEUTRAL is connected to EARTH at the local substation.
On an inverter or generator the earth is 'floating' and isn't connected to anything so neither of the outputs (both lives) will flow to earth. Don't worry and leave all alone it is safe as designed. ?

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