Grounded Vs Floating system do I need a RCD?

[fabio de sal]

In my RV I built a 12v System:

• I have 2 x 300AH 12V LiFePO4 batteries.
• 600W Solar & MPPT
• 1000W Giandel Inverter

I wired everything with positive and negative cables.
Everything works great but recently someone told me I:
1. need to ground my Batt. Negative to the chassis.
2. I was also told I need an RCD on the output of the Inverter.

Does someone know why?

I thought people only connect the negative to the chassis when the want to save on wiring cost and just use the chassis as the negative "wire" to the battery. I thought I have a "floating system"...

 

[DIYrich]

Many 3 wire devices expect negative and ground to be at the same potential.

I would not want to be shocked by touching the outside of an appliance and the chassis of the vehicle at the same time.

 

[mikefitz]

Does someone know why

Safety, reduces the possibility of electric shock in AC 220 v circuits and in DC circuits ensures protection devices, fuses or breakers, will protect against accidental unwanted current paths through the vehicle metal. Every DC positive cable requires overcurrent protection.

The AC system need for RCD protection depends on the inverter type and the instalation. If the inverter is installed as a 'permanent' device, wired into distributed outlets and appliances, then the inverter needs a neutral to earth bond and a RCD.
If the inverter is 'portable', with a single class 2 fully insulated appliance plugged directly into the inverter, you have a floating system, no RCD or earth neutral bond is needed. More than a single appliance, or extension cable, or class1 metal bodied apliance, plugged into the inverter increases the risk and ideally should have the neutral bond and RCD. Note that not all inverters can be neutral to earth bonded.

With any AC system, inverter or external AC 'shorepower', the protective earth must have a connection to vehicle metal.

 

[Q-Dog]

In my RV I built a 12v System:

• I have 2 x 300AH 12V LiFePO4 batteries.
• 600W Solar & MPPT
• 1000W Giandel Inverter

I wired everything with positive and negative cables.
Everything works great but recently someone told me I:
1. need to ground my Batt. Negative to the chassis.
2. I was also told I need an RCD on the output of the Inverter.

Does someone know why?

I thought people only connect the negative to the chassis when the want to save on wiring cost and just use the chassis as the negative "wire" to the battery. I thought I have a "floating system"...

You are confusing negative and ground. Yes, many systems use the chassis as the negative. Your system doesn't do that so should have a ground to the chassis.