Inverter 12V to 240 V AC How to earth?

[Cerebus]

I have learned from this forum that these devices need to be earthed as well as connected to an RCD type of thing available from caravan shops.

As far as I can make out from the posts I have read, the earth on a boat means a wire going from the inverter to a bolt (for example) through the hull and into the salty water (a “ water earth”).

Is that correct?

What about a caravan or camper van?

An earth can be used whilst stationary and on grass by ramming a rod into the ground and connecting the inverter’s earth connection.

An earth cannot be made easily whilst on the move though can it?

If parked upon concrete, I’d a wire laid upon the ground and a heavy stone or slab good enough?

 

[shanemax]

Is this a permanent use inverter or an occasional use inverter and how many watts can it produce.

 

[PaulRainbow]

Is this a permanent use inverter or an occasional use inverter and how many watts can it produce.

What relevance are Watts ?

 

[PaulRainbow]

I have learned from this forum that these devices need to be earthed as well as connected to an RCD type of thing available from caravan shops.

As far as I can make out from the posts I have read, the earth on a boat means a wire going from the inverter to a bolt (for example) through the hull and into the salty water (a “ water earth”).

Is that correct?

What about a caravan or camper van?

An earth can be used whilst stationary and on grass by ramming a rod into the ground and connecting the inverter’s earth connection.

An earth cannot be made easily whilst on the move though can it?

If parked upon concrete, I’d a wire laid upon the ground and a heavy stone or slab good enough?

Where are you going to fit an inverter, boat/caravan, or camper ? Exactly what make/model are you fitting ?

 

[Cerebus]

Where are you going to fit an inverter, boat/caravan, or camper ? Exactly what make/model are you fitting ?

Hi,
I would like to fit an inverter to my boat and also to a caravan.

I have not bought the inverter yet so make and model unknown.

Does make and model make a difference? Are the cheap ones inferior?

 

[PaulRainbow]

Hi,
I would like to fit an inverter to my boat and also to a caravan.

I have not bought the inverter yet so make and model unknown.

Does make and model make a difference? Are the cheap ones inferior?

Yes and yes.

For the boat the inverter must be capable of having the Earth and neutral bonded together. The Earth should then be connected to the boats AC Earth circuit, which in turn has to be connected to the water (for want of a better phrase). If you don't already have one, you will need to fit a galvanic isolator. I would recommend a Victron inverter. What sort of output are you thinking of ?

Someone will be along shortly to tell you that's all wrong, it doesn't need an Earth or a GI and you can wire it up with second hand speaker wire, with no fuses, because this always happens with inverter threads, I'd be inclined to ignore that sort of advice

 

[Sandy]

Someone will be along shortly to tell you that's all wrong, it doesn't need an Earth or a GI and you can wire it up with second hand speaker wire, with no fuses, because this always happens with inverter threads, I'd be inclined to ignore that sort of advice

I hear wet string, salt water rather than fresh, is the current wire of choice.

 

[Cerebus]

Yes and yes.

For the boat the inverter must be capable of having the Earth and neutral bonded together. The Earth should then be connected to the boats AC Earth circuit, which in turn has to be connected to the water (for want of a better phrase). If you don't already have one, you will need to fit a galvanic isolator. I would recommend a Victron inverter. What sort of output are you thinking of ?

Someone will be along shortly to tell you that's all wrong, it doesn't need an Earth or a GI and you can wire it up with second hand speaker wire, with no fuses, because this always happens with inverter threads, I'd be inclined to ignore that sort of advice

Thank you.

I have seen a friend’s inverter and it has an earth symbol on the back and a screw to connect a wire to.

I would not know if the neutral is bonded to the earth. Perhaps that is written in the paperwork that comes with purchase of an inverter?

I will do a bit of reading about GI because I have forgotten what I read about them on some thread a few weeks ago.

I won’t be using shore power ever, so my earth will be via the sea (and iirc from the post or thread on here that I need to find again) that earth is a through hull bolt. Have not added up the watts I need yet; 1000W may be enough for my modest needs.

 

[PaulRainbow]

Thank you.

I have seen a friend’s inverter and it has an earth symbol on the back and a screw to connect a wire to.

I would not know if the neutral is bonded to the earth. Perhaps that is written in the paperwork that comes with purchase of an inverter?

You need to find that out before buying an inverter.

I will do a bit of reading about GI because I have forgotten what I read about them on some thread a few weeks ago.

I won’t be using shore power ever, so my earth will be via the sea (and iirc from the post or thread on here that I need to find again) that earth is a through hull bolt.

If you never use shore power there is no need for a GI. Connection to the water can be the hull of a steel boat, a ground or an anode. If there are none of those available you can fit a small button anode. It won't act as an anode, just as a good connection point for the Earth.

 

[billcole]

I have learned from this forum that these devices need to be earthed as well as connected to an RCD type of thing available from caravan shops.

As far as I can make out from the posts I have read, the earth on a boat means a wire going from the inverter to a bolt (for example) through the hull and into the salty water (a “ water earth”).

Is that correct?

What about a caravan or camper van?

An earth can be used whilst stationary and on grass by ramming a rod into the ground and connecting the inverter’s earth connection.

An earth cannot be made easily whilst on the move though can it?

If parked upon concrete, I’d a wire laid upon the ground and a heavy stone or slab good enough?

Victron have a downloadable .pdf on their website..."Victron Wiring Unlimited" which has a lot of informationn and explanation on earthing inverters.

 

[Cerebus]

Victron have a downloadable .pdf on their website..."Victron Wiring Unlimited" which has a lot of informationn and explanation on earthing inverters.

Thank you

 

[Cerebus]

Victron have a downloadable .pdf on their website..."Victron Wiring Unlimited" which has a lot of informationn and explanation on earthing inverters.

What a document!

Confused me; not difficult to do.

I thought for a caravan a copper rod into soft ground would be the earth, but this quote implies something else:

“
7.5. Mobile installations
A mobile installation is an installation that operates independently from the grid. When it connects to AC power, it usually connects to the grid at different locations and/or generators. For example, boats, vehicles or mobile backup power systems. In this chapter, a boat installation is used. However, this information can be used for any mobile installation.
A mobile system does not have an earth stake. So, something else in its place is needed to create a central earth potential. All touchable metal parts of the boat or vehicle must be connected to each other to create a local earth. Examples of
metal parts in a boat or vehicle are: chassis, hull, metal fluid pipes, railing, engine, power socket earth contacts, lightning conductors and the earth plate (if present).
A mobile system typically connects to a variety of power sources. In these situations it is sometimes not clear which of the leads in the shore power supply is connected to earth or if the earth is connected at all. Also, phase and neutral may not have been wired correctly. Connecting a supply like this to a mobile system can potentially create a short circuit to earth. Or the earth is missing completely.
It also matters if the mobile system connects to power or if it is disconnected from power and running autonomously”



I don’t understand earthing to the chassis of campervan or caravan because of rubber tyres.

Taken from page 60 here:

https://www.victronenergy.com/uploa...imited_book/43562-Wiring_Unlimited-pdf-en.pdf

 

[ylop]

I don’t understand earthing to the chassis of campervan or caravan because of rubber tyres.

The function of the earth here is to protect you as the occupant of the van if a live connection some how comes into contact with the vans body work (say by chaffing as it crosses a rough edge). With no “earth” the vans body becomes 240V, and it you touch it and provide some means to close the circuit the experience will at best be unpleasant. Connecting invertor earth to the “van” and any other metalwork means if the van becomes live if should trip the inverter.

 

[PaulRainbow]

The function of the earth here is to protect you as the occupant of the van if a live connection some how comes into contact with the vans body work (say by chaffing as it crosses a rough edge). With no “earth” the vans body becomes 240V, and it you touch it and provide some means to close the circuit the experience will at best be unpleasant. Connecting invertor earth to the “van” and any other metalwork means if the van becomes live if should trip the inverter.

If wired correctly it will trip the RCD. This is why a decent inverter should be fitted, not some Ebay death trap that was bought because it was the cheapest one on the internet.

 

[PaulRainbow]

What a document!

Confused me; not difficult to do.

I thought for a caravan a copper rod into soft ground would be the earth, but this quote implies something else:

“
7.5. Mobile installations
A mobile installation is an installation that operates independently from the grid. When it connects to AC power, it usually connects to the grid at different locations and/or generators. For example, boats, vehicles or mobile backup power systems. In this chapter, a boat installation is used. However, this information can be used for any mobile installation.
A mobile system does not have an earth stake. So, something else in its place is needed to create a central earth potential. All touchable metal parts of the boat or vehicle must be connected to each other to create a local earth. Examples of
metal parts in a boat or vehicle are: chassis, hull, metal fluid pipes, railing, engine, power socket earth contacts, lightning conductors and the earth plate (if present).
A mobile system typically connects to a variety of power sources. In these situations it is sometimes not clear which of the leads in the shore power supply is connected to earth or if the earth is connected at all. Also, phase and neutral may not have been wired correctly. Connecting a supply like this to a mobile system can potentially create a short circuit to earth. Or the earth is missing completely.
It also matters if the mobile system connects to power or if it is disconnected from power and running autonomously”



I don’t understand earthing to the chassis of campervan or caravan because of rubber tyres.

Taken from page 60 here:

https://www.victronenergy.com/uploa...imited_book/43562-Wiring_Unlimited-pdf-en.pdf

It's worth noting, in the case of a metal hulled boat only a single connection should be made.

 

[Cerebus]

If wired correctly it will trip the RCD. This is why a decent inverter should be fitted, not some Ebay death trap that was bought because it was the cheapest one on the internet.

I get that the the inverter should go to an RCD (bought from caravan shop), but purely out of curiosity why would a cheaper inverter not work with the RCD appliance whereas a more expensive one would?

I will need to read up a lot more about the wiring before contemplating or hire a professional because it is obviously not a case of connect 12v domestic live and neutral to inverter and connect earth to a real earth (or salt water ‘earth’) and have output of inverter go through consumer unit (RCD).

 

[Cerebus]

The function of the earth here is to protect you as the occupant of the van if a live connection some how comes into contact with the vans body work (say by chaffing as it crosses a rough edge). With no “earth” the vans body becomes 240V, and it you touch it and provide some means to close the circuit the experience will at best be unpleasant. Connecting invertor earth to the “van” and any other metalwork means if the van becomes live if should trip the inverter.

Ok . I didn’t know inverters trip.

I thought connecting earth to chassis would leave vehicle live because of rubber tyres, so I thought a metal rod into soft ground would be the earth.

A lot of research needed.

 

[ylop]

Ok . I didn’t know inverters trip.

Well I think that’s Paul’s point. Make sure you buy a suitable one!

What are you intending to run off the inverter? At the risk of running the wrath of Paul’s opening comment - there are very small inverters usually intended to plug into a cigarette lighter socket which would commonly be used without an external earth. If you use them with caution and sense you should be able to avoid death! I installed an inverter when I bought the boat, sure I would need it, but have only used it for charging powerdrill batteries! A few good USB-C outlets might actually avoid a lot of the faff?

 

[PaulRainbow]

I get that the the inverter should go to an RCD (bought from caravan shop), but purely out of curiosity why would a cheaper inverter not work with the RCD appliance whereas a more expensive one would?

You need one where the Earth and neutral can be bonded at the inverter.

I will need to read up a lot more about the wiring before contemplating or hire a professional because it is obviously not a case of connect 12v domestic live and neutral to inverter and connect earth to a real earth (or salt water ‘earth’) and have output of inverter go through consumer unit (RCD).

Not sure why you need to do a lot more reading up, i've told you how to wire it.

Connect the DC positive and live to the inverter, with a suitable fuse close to the battery. Bond the Earth and neutral at the inverter. Connect Live, neutral and Earth to a consumer unit, fitted with a RCD and MCBs for individual circuits. Connect an Earth wire from the consumer unit Earth busbar to the water.

 

[PaulRainbow]

Well I think that’s Paul’s point. Make sure you buy a suitable one!

What are you intending to run off the inverter? At the risk of running the wrath of Paul’s opening comment - there are very small inverters usually intended to plug into a cigarette lighter socket which would commonly be used without an external earth. If you use them with caution and sense you should be able to avoid death! I installed an inverter when I bought the boat, sure I would need it, but have only used it for charging powerdrill batteries! A few good USB-C outlets might actually avoid a lot of the faff?

Good question, i did ask what sort of output the OP was planning to fit. Some more information would be useful.