RV Grounding

[deacon st. john]

Long time reader of the message boards, first time poster.
I have a question on my RV 5th wheel solar install. Use of this system is aimed at running the 3 way refrigerator on 12V and powering all the 12v loads with bonus of some 120v convenience items while winter camping in the desert. I’ve added in a magnum 2000w 12v inverter for boondocks trips. I have added 1200w of solar and 600AH of lifepo4 batteries. Midnite charge controllers and midnite solar breakers, battery discos, fuses etc.

Question is about grounding the 12v side of everything. I have removed the 5 OEM chassis grounds traced down for the DC side that all tied back to a common OEM grounding terminal/negative bus. This is where all the OEM equipment DC negatives tie in as well.
Grounds all were on frame at various different places. Appear to have been multiple ground (from my understanding of the subject) loops from the OEM. Grounds here, there and everywhere for the DC side with no rhyme or reason. Even found 2 #8 awg ground wires that weren’t even properly connected to the frame, just a sheet metal screw with wire wrapped around it. Go figure lol. AC panel/converter box only had one single #4 awg bare to proper chassis lug so it was left alone.

I installed a new single 4/0 awg chassis ground. Sanded to bare metal, copper washers on terminal, and 3/8” bolt through frame with sealant to prevent corrosion. This 4/0 goes to the new Victron 600AMP DC negative bus bar.

For the grounding lugs on the charge controllers, dc combiner boxes, solar panels, inverter etc do these equipment grounds need to tie back to the DC negative bus bar or direct to the chassis? I’m assuming direct to the DC negative bus is the proper way? I’m planning on using #4awg for the ground connections and to tie in the OEM DC negative bus to my new bus bar with #4awg as well. Any help is greatly appreciated!

 

[Cal]

The frame is an excellent way to conduct current as it has lower resistance than cable. My RV battery is connected directly to ground. Solar charge controller ground, converter ground, etc. are connected to chassis frame. Cable routings are minimized while getting better performance.

 

[12vDC]

I don’t even have one, but do you have a diagram for your system?

if you’re planning to use a shunt to monitor voltage and current, then all of your grounds should eventually tie in to the shunt which, presumably, would be fed by the DC bus Bar.

 

[deacon st. john]

The frame is an excellent way to conduct current as it has lower resistance than cable. My RV battery is connected directly to ground. Solar charge controller ground, converter ground, etc. are connected to chassis frame. Cable routings are minimized while getting better performance.

Yes, this is why I took the “shoddy” oem connections off and put in 1 good connection to the chassis. Most of the oem grounds were degauged too, where someone on the assembly line got a little too aggressive with wire stripping tools and only left 2 or 3 strands per cable that were actually connected.
My 4/0 ground is only 3ft length from chassis to negative DC bus bar.

Still unsure of best practices for all the solar components to share the same ground for bonding the equipment cases.

 

[deacon st. john]

I don’t even have one, but do you have a diagram for your system?

if you’re planning to use a shunt to monitor voltage and current, then all of your grounds should eventually tie in to the shunt which, presumably, would be fed by the DC bus Bar.

I can draw a basic diagram later today.

 

[scrubjaysnest]

This grounding method is typical for the rv industry. I ran mine all to a common buss bar then trough the shut to the frame. Been working fine since 2016, used the same method on the previous rv.

 

[Vigo]

Chassis ground is fine for everything UNLESS you use a 'positive ground' PWM charge controller, of which there are many many many. But they are usually the bottom of the barrel cheapy stuff, so that warning probably doesn't apply whatsoever to someone who is fastidious enough to chase out all the factory grounds and replace them with a 4/0!! Bravo btw, sounds like you are going to end up with something really nice.

 

[deacon st. john]

Chassis ground is fine for everything UNLESS you use a 'positive ground' PWM charge controller, of which there are many many many. But they are usually the bottom of the barrel cheapy stuff, so that warning probably doesn't apply whatsoever to someone who is fastidious enough to chase out all the factory grounds and replace them with a 4/0!! Bravo btw, sounds like you are going to end up with something really nice.

Using midnite solar kid charge comptrollers! Hope that’s not bottom of barrel lol, the price wasn’t!
In all reality the OEM wiring in this RV is really sketchy. So many loose connections, poor workmanship on the electrical side. I’ve done more repair work to the factory wiring than time I’ve spent on the solar install!
Another example; The 10-2 romex wire from the shore plug had damaged outer jacket and damaged insulation on hot conductor, OEM just wrapped with tape. I cut and replaced the entire section back to the converter panel.

Moral of story, check other peoples wiring, you probably care more about it than they did.