# Grounding/Earthing in the motorhome



## aivlys (May 1, 2005)

Hi again,

I have been reading the fitting instructions for my new inverter and noted that it should be 'grounded'. I then searched the forum to see how this might be done and found a trail 'Auto changeover relay for inverter' asking a similar question but tapered off.

If the MH is grounded via the battery do I need to do any further grounding? The instructions indicate I should attach the cable to the lug at the back of the inverter and attach it to the vehicle chassis. Which is a bit odd because the chassis goes to four rubber tyred wheels as opposed to being 'grounded'...... I hate electics - so confusing - I just find it difficult to understand.

Thanks again.

Sylv


----------



## selstrom (May 23, 2005)

It needs to be connected to the chassis.


----------



## Razzo (May 1, 2005)

I have taken mine back to the leisure battery where I took the feed from. I know I will always get a better connection there than getting one on the Chassis. As my cables are very thick and only a metre of length, I do not suffer any additional voltage drop. If it was at the other end of the van then I might consider going to the chassis, but I like to keep the circuits separated.

Brian


----------



## aivlys (May 1, 2005)

Thanks for above response.

I have a metal bar which keeps the battery in place, can I earth back to this bar, if not should I then wire to the red or black post connection?


----------



## philoaks (Sep 2, 2008)

aivlys said:


> Thanks for above response.
> 
> I have a metal bar which keeps the battery in place, can I earth back to this bar, if not should I then wire to the red or black post connection?


Sorry but this will probably sound really rude but if you have to ask this question I think you ought to get someone with a little more knowledge of "electrics" to connect this up for you.

Whilst 12v may not be as dangerous to the touch as 230v it is still lethal if an accessory isn't connected/fused correctly.


----------



## aivlys (May 1, 2005)

philoaks said:


> aivlys said:
> 
> 
> > Thanks for above response.
> ...


You are probably right and this is my intention, but costs nothing to ask the question - everyone starts somewhere to learn even if only asking, listening and watching .....


----------



## pippin (Nov 15, 2007)

Just to reinforce philoaks post.

If you had taken the earth to the red terminal (battery positive) there would have been an almighty explosion with sulphuric acid everywhere, physical damage to everything around (incuding you) and probably a fire.

A shorted lead acid battery is a fearsome beast. :firestarter:

PS: Again, no disrespect is intended - just helpful education.


----------



## listerdiesel (Aug 3, 2012)

There is some confusion here as to exactly what is to be grounded.

The inverter input is connected to the battery, so no need for anything extra there.

The inverter case should be grounded/earthed to the input negative, but some have it grounded/earthed to the output earth, which is not a good idea in my view.

The actual output conductors should be free-floating and neither be connected to earth or ground.

As an isolated power source it should remain isolated.

There are a few that carry the 12V negative through to the 230V socket ground, which I can live with as long as the 230V connections are floating.

Peter


----------



## philoaks (Sep 2, 2008)

aivlys said:


> philoaks said:
> 
> 
> > aivlys said:
> ...


I quite agree that we all need to start somewhere and the more we learn the more we understand. From your post I took it that you intended to do all the work yourself and I was honestly concerned for your safety and that of your van. There would be nothing wrong in you doing all the prep work for the installation and then getting it checked over before the final connections were made. That would both reduce your costs and ensure a safe installation.

I've spent a lifetime working in and around electrical things (albeit mainly low voltage comms stuff) and have seen enough accidents/incidents to know that even the experts get it wrong sometimes. I include myself in that as once I inadvertently disconnected a battery from a charger without switching the charger off first. The resulting spark ignited the hydrogen gassing from the battery and blew it apart. Not pleasant, as pippin says, a fearsome beast!!

I have also seen a spanner glowing red when it got shorted between the battery live and a car body (not guitly of that one) and a colleagues finger virtually severed when his wedding ring got shorted between a 50v bus bar and earth. All low voltage stuff but scary to see.


----------



## Camdoon (Sep 21, 2012)

Was following a car on Sunday and it had a small doll dangling from the rear bumper. I wonder whatever happened to those rubber "grounding" strips which were prevalent dangling from cars around the mid eighties(?)?


----------



## pippin (Nov 15, 2007)

More carbon in the tyres?


----------



## Glandwr (Jun 12, 2006)

On my Waeco inverter I pondered about the earth connection. Did a bit of research and found that it had been factory modified for the UK market and the symbol /UK stamped into the metal case after the serial number. The modifications? Our 3 pin plug and the crudely fitted case earth connection. Did I run it to earth? No. figured that if there was 240 volts at the case the best thing was to leave it there rather than connect it to the chassis  

Dick


----------



## pippin (Nov 15, 2007)

A bit puzzled here Dick.

"_Our 3 pin plug_"

I assume you mean "socket".

Again:

"_the crudely fitted case earth connection._"

Can you describe what that is?

I wouldn't be happy if the case potential was at 240V.


----------



## Glandwr (Jun 12, 2006)

You are right Pippin it was a socket. The earth connection was a simple bolt soldered awkwardly on to the inside of the metal case with a sticker showing the earth symbol. All other labling was done by stamping into the metal. Considering the general standard of design in the unit it looked a very gauche addition. I presumed (rightly or wrongly?) it to have been an add on purely to serve UK regs. Along the lines that any device with a metal case that contains 240 volts should have a means of earthing the case.

What do you think I should have done?

Dick

editted to add Do 

pps there was no continuity between the earth pin in socket and case.


----------



## DABurleigh (May 9, 2005)

I have derived from first principles a single equation governing the whole of electricity, magnetism and electromagnetism. I understand it.

I have written on motorhome earthing many times, consistently.

I can't add to this post, many years ago:
http://www.motorhomefacts.com/ftopicp-432637.html#432637

Dave


----------

