Inverter earth confused

Hi Pixiemops ................

Not really my field, but isn't the trailer insulated from EARTH by the tyres and jockey wheel ??? Unless it is still connected to the vehicle .................

Agree, this 12v stuff is very confusing for us lay people !!

Hi pixiemops

This may get the right reply

But Earth means earth, if your car trailer has rubber tires then it's not earthed' But for better protection hook the wire from the earth terminal to any metal part which is attached to the negitive battery terminal.

Richard

You cannot die ("maybe") from 12 volts

Please do not try this at home

First off... yes you can die from 12v :-(

Run the Pos+ cable to the Pos+ battery terminal.
Run the Neg- cable to the Neg- battery terminal, NOT the body.

Only use secured fittings.

Remember you are now 'playing' with 240 VOLTS

For an inverter used in a camping situation there is no need to earth it. It is arguable that doing so increases the risk of electrical shock.

Mike Harding

Hi Pixiemops

Don't be scared of 12V unless there is high amps. DC current can be dangerous when the amps are increased or like already mentioned it is turned into 240v.

1 or 2 automotive batteries is safe to work with.

There is no need to earth the unit but it is 240V so same rules apply as at home.

No water, rain and handle with care.

Regards

Derek.

Hu pixiemops

I don't want to delve into the possible safety aspects of your query but I had an inverter that I used in a cabin cruiser to run a 240V stereo. There was a lot of static in the radio reception.

I was advised to connect the earth to an earth point. Hey Presto! Static dissapeared.

Anyhow, that's my contribution.

My inverter came with one positive wire and two negative earthing wires. One to the negative battery terminal and one earthed to metal in vehicle body frame.

Hi

Don't shoot the messenger but some of you won't like what you read below.

The purpose of the inverter is to provide 240 volt AC energy. This is the same as you get out of a power point at home. 240 Volt AC is the same and can kill no matter how it is produced!

Australian Standard AS3000 Series describes how earthing of electrical installations is to be carried out. As far as I am aware, compliance to AS 3000 is a legal requirement in all Australian States and Territories. In certainly is the case in NSW, Queensland and the A.C.T. Failure to comply can be a criminal offence.

All installations and servicing of 240 volt AC electrical equipment and appliances must be carried out and tested by a licensed A Grade Electrical Fitter or Mechanic (Electrician).

A normal domestic safety switch typically disconnects the supply in 40 milliseconds (0.04 s) for a leakage of 30 milliamps because it has been found that currents higher than 30 milliamps passing through human beings can kill.

Don't forget that very young children's soft moist skin is highly conductive and they are could easily touch the side of a caravan while standing bare footed on moist ground.

So the safe thing to do with an inverter is to drive an earth stake into the ground and connect it with a suitable cable to the earth terminal on your inverter because when using a 240 volt AV appliance supplied by an inverter it is important to ensure that the electrical potential of the accessible metal casing of the appliance and the inverter is zero.

Simply put, a car, metal caravan or trailer can be classed as an appliance if 240 AC is distributed and used within the vehicle. There is an Australian Standard for 240 volt AC installations in a mobile vehicle, caravan and trailer.

If in doubt go and discuss this with your Electrical installation Inspector at your local Electricity Supply Organisation.

Cheers
Phil
Licensed A Grade Electrical Fitter and Mechanic (Electrician)

Hello Mike

The majority of scientists now believe death is permanent.

I realise I have opened up the proverbial "can of worms".

I do know what I am talking about as I was once employed working with Electrical Inspectors.

I wrote my response because there is a potential danger, it may only be 10,000,000 to 1, of receiving a severe electrical shock. About as much chance of winning lotto but then someone must win lotto sometimes.

I can assure you that if there was an accident, the police would call in the OH&S authorities, ( Workcover or Worksafe or whatever it is called in the State or Territory) and the Electrical Installation Inspectors would become involved.

The AS 3000 series has many standards on electrical subjects. Have a look at the ones about earthing and earth bonding of mobile and stationary generators and other electrical equipment and the standard on electrical installations in mobile homes and caravans.

Cheers
Phil

I am very definitely with Mike on this one. Earthing an inverter or generator either to ground or metal chassis of vehicle just gives you a far greater chance of a person becoming the circuit in the event of a fault in an appliance attached to the device. As Mike explained you have to touch both an active and an inactive point on AC to form a circuit. Highly unlikely with an internal fault in an appliance that you would be able to do that, but if its "earthed" then highly likely that you could form a circuit (from "earth" to appliance.

Another issue is that a large number of inverters do not have an electrically isolated 12 volt section. I understand that this IS an OH&S issue. To my knowledge the Jaycar ones are isolated, dont know of any others.

This is my view only, I do not have any formal qualifications in this area, but plenty of practical exposure.

Regards avro

Thnaks alot guys for all your responses. Yesterday I phoned about 5 different auto-electricians and from them got the following suggestions.

1. All we do here is wire the earth to the negative terminal of the battery. Another auto sparky said that is a no no.

2. Another suggested just wire the earth to a metal part of your car. Someone else said that is not right as the earth in 12v ie the car is very different to the earth in 240v .

3. Another suggested use the earth stake and a shop that specialises in inverter sales says he has never heard of anyone having to earth an inverter full stop and didnt think it necessary.

So now I am very confused even the auto electricians seem not to give a definite answer. I think I will use a stake . It will be a long way from the inverter and trailer up near the tow bar. Maybe there needs to be some very clear guidlines for people like me and the auto sparkies as well on this one.

thanks

Hi Pixiemops

Follow up from my other responses, I have just found the instructions to my inverter which confirm that the inverter must be earthed. I quote "WARNING: BEFORE USING THIS INVERTER YOU MUST PROVIDE A GROUND CONNECTION TO THE INVERTER".

They then describe how it is done, by connecting a heavy duty queen-insulated wire to the wing nut connection on the inverter which is connected to the earth terminal of the outlet.

The heavy duty queen-insulated wire should be connected to a metal earthing stake driven into the ground to a depth of 1.2 metres or more.

hope this helps
Cheers
Phil

Hi Phil

>It takes a very low number of milliamps to cause a serious accident.

It’s actually about power rather than current; which is why you can touch a 12V battery with a couple of thousand amps capability or a coil ignition system with 25kV but a very low current capability without harm… however don’t try touching a 25kV, 2000A power supply! :)

>1. A possible dangerous situation could be a faulty inverter
>e.g. the active shorting to the metal case

That would cause one of the inverter fuses to rupture or destroy the output stages of the inverter, it would not cause any part of the installation to become live at 240V relative to the planet earth.

>and an appliance with loose or broken earth and neutral wires
>and poor insulation resistance to the metal case

If the appliance has a broken earth it doesn’t matter what you do! If it has a broken neutral then it simply won’t work. If it’s leaky from the appliance active to the appliance case then providing you _don’t_ earth the inverter you won’t receive a shock because there is no way for that leakage current to return to the neutral pole. This is exactly the situation in which earthing the inverter raises the danger level.

>Like a home installation

That’s the thing Phil – an inverter (gen) in a camping situation is nothing like a domestic installation because it’s not bonded to earth and does not need to be.

>I have just found the instructions to my inverter which confirm
>that the inverter must be earthed. I quote "WARNING: BEFORE
>USING THIS INVERTER YOU MUST PROVIDE A GROUND
>CONNECTION TO THE INVERTER".

They say that as a legal getout in case the inverter is (as they often are) used in conjunction with a solar system and the domestic mains, in that case there is good reason to earth the inverter or standby generator – in a camping, or stand-alone, situation there is not.

Phil: do you agree that with a non-earthed inverter or gen one could stand on the ground and touch the active connection and not receive a shock?

Mike Harding

mike_harding@fastmail.fm