Grounding/earthing question on a RV

[Solarfun4jim]

When using an 'All in one' unit, when plugged into grid power, then i understand that the earthing is through the connecting cable. When no grid power connected, on the vehicle, where the engine battery is 12v negative earth, how is the earthing handled when the 'all-in-one' unit is connected to a 48v leisure(house) battery bank. I assume you cannot bond the negative busbar to the chassis as it could fry sensitive '12v' components, so i'm struggling to understand how to earth the bank in this circumstance?
Anyone care to enlighten this newbie?

 

[FilterGuy]

It is rather complicated.
https://www.rvtravel.com/rv-electricity-part1-abcs-campground-power/
https://www.rvtravel.com/rv-electricity-the-abcs-of-campground-power-and-grounding-part-2/

 

[John Frum]

Also this one hot skin and this one separately derived systems

 

[Geriakt]

You bond the negative 12 volt system to the metal frame rail of your rv as you do the 24 volt or 48 volt negative to the frame rail. Both positives from each battery system are isolated to each other. Electricity works as a flowing circuit. Your 12 volt system will only flow 12 volts when using that battery and appliances connected to it and the 48 volt systems will only flow 48 volts to those appliances.

 

[John Frum]

You bond the negative 12 volt system to the metal frame rail of your rv as you do the 24 volt or 48 volt negative to the frame rail. Both positives from each battery system are isolated to each other. Electricity works as a flowing circuit. Your 12 volt system will only flow 12 volts when using that battery and appliances connected to it and the 48 volt systems will only flow 48 volts to those appliances.

And you also bond the separately derived 120VAC system to the chassis.
The primary idea being to give the current a better "return" path than your body.

 

[Geriakt]

With regard to my 120vac green earth ground, mine is grounded to my Victron Multiplus 24/3000. I then ground the unit to the chassis negative ground. No everything is grounded.

 

[John Frum]

With regard to my 120vac green earth ground, mine is grounded to mt Victron Multiplus 24/3000. I then ground the unit to the chassis negative ground. No everything is grounded.

Yes and that means that 120vac fault current can return to the inverter via the chassis, no?

 

[Geriakt]

Yes and that means that fault current can return to the inverter via the chassis, no?

yes and when you are connected to shore power the green is now connected to a real earth ground.

 

[Geriakt]

My system is a 24vdc house battery and a 12vdc chassis battery system.

 

[John Frum]

My system is a 24vdc house battery and a 12vdc chassis battery system.

Great the point being that different sources of different volatages can use a common return media.

 

[Solarfun4jim]

Thanks guys for your replies. Somehow i had in my head that if a positive cable( carrying 48v 100A) shorted on the framework, that all the 12v components would be fried before the breaker tripped(simply because it was so much higher). This is why i love this forum....someone always comes along to dispel any crazy notions you might have.
Thanks for bearing with this non electrical newbie.

 

[John Frum]

yes and when you are connected to shore power the green is now connected to a real earth ground.

Well yes, but that is the secondary path back to the transformer.
Ground is bonded to neutral at the service entrance panel to give a much lower impedance path back to the transformer.

 

[Geriakt]

Well yes, but that is the secondary path back to the transformer.
Ground is bonded to neutral at the service entrance panel to give a much lower impedance path back to the transformer.

This is my limit of knowledge

 

[FilterGuy]

Yes and that means that 120vac fault current can return to the inverter via the chassis, no?

AC Ground and inverters get a bit complicated.

The general rule of thumb is that AC Neutral and AC ground should be bonded at the source and only at the source.

What does that mean when you have an inverter? Typically AC ground will be bonded to AC neutral at the inverter (The source)

Now, what about an inverter charger? In this case, the source is sometimes shore power and sometimes the inverter. A marine rated inverter charger is *supposed* to bond AC and ground when being powered by the inverter and disconnect the bond when on shore power. The problem is that it is almost imposible to find out what a particular inverter charger does by reading the published specs.