# 12 volt appliance earthing



## bigee (Oct 5, 2006)

I'm just in the process of buying an 07 reg panel van conversion based on a citroen relay. It's a new conversion and all the 12 volt appliances, compressor fridge, lights, waterpump, etc have been earthed to the vehicle chassis. I recently been told that its not a good idea to do this on newer vehicles as it could disrupt the engine management system, and they should be earthed straight back to the battery. Does anyone know for sure if this is right or not as i really don't want to have to rewire everything, but then i don't want any problems with the ems.


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## rayc (Jun 3, 2008)

Do you mean that the negative supply for the appliances is connected to the chassis which is the negative feed from the battery or that the metal parts of the appliances are bonded to the chassis forming no part of the supply?


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## loddy (Feb 12, 2007)

I would have put in a earth ring

Loddy


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## CliveMott (Mar 10, 2008)

Chassis and battery negative are bonded. Many equipment and appliance negative connections are direct to a local chassis connection. So what is your problem??

C.


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## rayc (Jun 3, 2008)

CliveMott said:


> Chassis and battery negative are bonded. Many equipment and appliance negative connections are direct to a local chassis connection. So what is your problem??
> 
> C.


I think his problem is that "I recently been told that its not a good idea to do this on newer vehicles as it could disrupt the engine management system".

I guess he wants reassurance that this is unlikely to happen.

Ray


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## rayc (Jun 3, 2008)

loddy said:


> I would have put in a earth ring
> 
> Loddy


It gets alittle confusing calling DC negative supply legs 'earthing'. Perhaps a negative battery supply ring would be a better way to describe it?
PS: I hope this response is not seen as negative.

Ray


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## loddy (Feb 12, 2007)

rayc said:


> loddy said:
> 
> 
> > I would have put in a earth ring
> ...


OK should have worded it " a negative battery supply " I thought most readers would have understood what I was trying to say, what if it's positive earth ??

After spending over 40 years in the motor trade and hours of tracing wiring/ connection faults that are nearly always due to bad earth, rust under earth rings, screws loose. Believe me its a good idea if you are doing it from scratch to put in a Wire That Goes to the Side of the battery that is earth

Loddy


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## Jezport (Jun 19, 2008)

As the +ve is going back to a separate battery (leisure) There is not a complete circuit back to the engine battery. So I think you have been misinformed.


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## loddy (Feb 12, 2007)

Engine and Leisure are connected via chassis connections


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## bigee (Oct 5, 2006)

Thanks for your replies lads. Yes ''rayc'' i meant the negative return cable back to the battery and not earthing of the appliance casings. Looks like the concensus is that it's ok to connect the negative returns to the vehicles chassis, looks like i was given duff imfo. I'll sleep better tonight without thinking of how the hell am i going to run new earth returns from the ceiling lights behind the insulated roof and wall panels without removing the shower cubicle and destroying the panels.


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## Mandale (May 18, 2011)

The negatives should be connected to the negative connection point on the motorhome power management system. We have been advised by the vehicle manufactures and VOSA that electric motors can confuse systems like ABS units. ABS sensors are basically magnets which rely on electrical pulses being sent back to a control unit, it is possible that electric motors can interfere with these signals.

The motorhome management system is connected to the vehicle battery and all the other base vehicle electrical systems, however between the connection is your leisure battery. The leisure battery and the vehicle batteries act like sponges soaking up all the interference thus preventing the pulses for effecting the base vehicle systems.


hope this is of help.


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## bigee (Oct 5, 2006)

Wow, now you have confused me. In simple language are you say ing that it's not ok to connect the leisure appliances earth returns to the chassis, or it is ok? And are you saying that it is only electric motors, like the water pump or fridge, that can affect the ems, so things like the lights will be ok? And can the motors only affect the ems when the engine is running, but would not cause a problem if the engine is switched off, which would obviously be the only time you would be running the water pump or fridge.


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## Mandale (May 18, 2011)

Hello, Bigee



EMS is different as it relates to radiated electromagnetic fields. Currently VOSA only require test data for their “normal IVA testing” and as motorhomes fall under “basic IVA” screening and testing is not required. 

The vehicle manufacturers are concerned about voltage pulses and spikes affecting or damaging the base vehicle electronics and have asked us the take steps to prevent this from happening. I can not comment on all habitation management systems however we do know that the system we use does regulate the voltage being supplied from the base vehicle battery. So by connecting the negative wiring of a compressor fridge to the vehicle chassis which means connecting it straight to the negative terminal on the vehicle battery is completing the circuit partially bye passing the habitation management system. The potential is there to reduce the effectiveness of the habitation system in preventing voltage pulses and spikes. Possibility and probability are two different things, so although the possibility is there, I could not say what the probability in doing this could result in damage to the base vehicle electronics. I would however conclude that I personally prefer all the appliance negative wiring to be connected to the habitation management system. 


Hope this is of help, Danny.


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## Mrplodd (Mar 4, 2008)

So what to the big manufacturers (Autotrail, Burstner, etc) do on their MH's ??

I bet they use the vehicle chassis/frame AND they have to guarantee the whole conversion !!!


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## Mandale (May 18, 2011)

Mrplodd said:


> So what to the big manufacturers (Autotrail, Burstner, etc) do on their MH's ??
> 
> I bet they use the vehicle chassis/frame AND they have to guarantee the whole conversion !!!


I can not comment on other manufacturers as I do not know.


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## Mandale (May 18, 2011)

bigee said:


> Wow, now you have confused me. In simple language are you say ing that it's not ok to connect the leisure appliances earth returns to the chassis, or it is ok? And are you saying that it is only electric motors, like the water pump or fridge, that can affect the ems, so things like the lights will be ok? And can the motors only affect the ems when the engine is running, but would not cause a problem if the engine is switched off, which would obviously be the only time you would be running the water pump or fridge.


Sorry Bigee,

I have misread your post regarding "EMS" engine management system, the first part on my post relates to "EMF" electromagnetic fields. Please disregard this part of the post as it so not what you asked.

Cheers, Danny.


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## loddy (Feb 12, 2007)

Sigh
:roll:


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## Glandwr (Jun 12, 2006)

I was confused recently when I fitted an inverter. Pos and Neg connections AND an earth connection. The earth had continuity with the metal case and the third pin on the plug socket. Is that what you mean?

As I only plan to use double insulated appliances in it that only have two leads anyway I ignored the earth. 

Dick


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## locrep (Dec 5, 2011)

Is it April the 1st already :?:


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## bigee (Oct 5, 2006)

Thanks for that everyone. I think it's all starting to get a bit confused. So is it a yes, i can connect to the chassis, or is it a no?


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## Mandale (May 18, 2011)

Have found this, it may explain why the vehicle manufacturers want us to insulate the habitation wiring from the base vehicle.

seems that new vehicles are less wired and more networked.

http://www.number66.net/an-introduction-to-can-bus/


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## bigee (Oct 5, 2006)

Thanks danny, that was interesting but a lot of it was a bit over my head. Surely a citroen relay van isn't as complex as a race car, and isn't wired via a CAN-bus system, is it? So the question remains, would i have problems with the vans electronics by connecting earth returns to the chassis, or not?


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## Mandale (May 18, 2011)

your local Citroen dealer can tell you if your vehicle uses can-bus


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## locrep (Dec 5, 2011)

You vehicle is wired with a central area network (can System) you can use the chassis as your Earth return with no problems, I have never worked on any F1 cars but I am sure they would use the same type of CAN system basics.

I would recommend you keep cable runs away from main van electrics where possible to avoid interference, do not splice into to any looms in the vehicle as this could cause a network problem, I would suggest fitting something like a Sterling B2B charging system as a split charge system may cause problems when it changes from main to leisure battery.


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## eddievanbitz (May 1, 2005)

rayc said:


> loddy said:
> 
> 
> > I would have put in a earth ring
> ...


I think that it was a very positive response. :lol:

Eddie


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## bigee (Oct 5, 2006)

Thanks for that 'locrep', think i'll be taking your advice, explained in plain simple english.


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## bigee (Oct 5, 2006)

Thanks for that 'locrep', think i'll be taking your advice, explained in plain simple english.


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## locrep (Dec 5, 2011)

Your welcome...


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