Grounding Questions, 24V Hybrid Inverter, 24v to 12V RV System

[TinMan6294]

First build, first post. I’ve looked at other threads and I cannot find one that addresses my concerns.

I'm installing a solar system in my RV. It's been overwhelming. The closer I get to wiring it all in, the more intimidated I’m getting. And I’m not an easily intimidated guy.

I'll end up having 4 panels that will be providing around 790 watts in 24-volt configuration. Two 195w 12v panels in series and two 200w 24v panels in parallel.

I'm installing a 24v Hybrid inverter/controller which will be attached to periodic SP/Generator as well as 24v DC battery power. The inverter has 120v AC output.

Because my RV is 12v, I'll be installing a 24/12 70 70 amp Victron DC reducer.

My questions are in regard to grounding. The SP/generator "IN" has three prongs (neutral, hot and ground). The existing wiring to the AC panel in the RV also has three wires. The inverter AC "IN" and AC "OUT", however, only have two wire connections.

So, my questions are:

1. Can I ground three different voltages to the same RV chassis?

2. Right now, I plan on putting a ground buss bar on the mounting board and using it to ground the inverter, and the ground wires that should be accompanying the 10 AWG stranded that I’m using to connect the AC IN and OUT to the inverter. This ground buss bar will be grounded to the RV chassis.

3. Can I ground the negative buss bar to the ground buss bar mentioned in #2 or should it have its own ground to the chassis?

4. Rather than wire nut the ground 10 AWG stranded to the existing SP/generator IN ground post, and run the wire to the mounting board ground buss bar, can I just ground it to the chassis where the AC IN comes in?

5. Similarly to Question #3, can I ground the existing ground wire that goes to the RV AC panel right to the chassis rather than running a ground 10 AWG stranded to it from the ground buss bar?

I’m attaching a sketch of what it looks like in my head right now. I did not include all of the breaker/switches and fuses in the sketch but I will be using a 160 amp breaker/switch for the battery wires and 30 amp breaker/switches for everything else. I'm also putting a 200 amp fuse right at the positive battery terminal.

My mounting board is plywood covered with metal roof thickness sheet steel. I was worried about mounting things that could overheat or spark to wood.

Any input, advice, criticism is welcome, please.

 

[time2roll]

1) yes.
2) Inverter chassis ground should be an independent #8 wire to the vehicle frame.
3) best to have a separate negative bus for each voltage if needed. With each having an independent connection to the frame.
4) On-board generator ground needs to connect to the distribution panel ground. Not sure what this question is saying.
5) The RV AC panel should have a ground bus that is already bonded to the frame.

 

[TinMan6294]

1) yes.
2) Inverter chassis ground should be an independent #8 wire to the vehicle frame.
3) best to have a separate negative bus for each voltage if needed. With each having an independent connection to the frame.
4) On-board generator ground needs to connect to the distribution panel ground. Not sure what this question is saying.
5) The RV AC panel should have a ground bus that is already bonded to the frame.

Thanks so much for the reply and info.

As far as having a separate bus for each DC voltage, the Victron reducer that I bought has only one negative pole. It has a 24v positive 'in' and a 12v positive 'out' but it appears that the negative uses the same connection. I plan on running pos & neg #8 AWG stranded to my DC panel from the reducer. It will already be connected to my DC negative bus.

As far as my question #4, I drew the accompanying sketch to try an illustrate what I mean a little better. White won't show up on a white board so imagine the red as the white. My SP/generator IN plug has white, black and ground. From that plug, it used to go to the AC panel via what looks like 12/2 Romex that was installed at the factory. I simply disconnected the Romex from the plug and I'll run 10 AWG stranded from the IN plug right to the AC 'IN' on the inverter/controller. Then I'll be running 10 AWG stranded from AC 'OUT' on the inverter/controller back to the existing Romex that goes to the AC panel. BUT, the inverter does not have a ground IN or OUT so I'm struggling with what to do about the ground connection on the SP/generator plug and the ground wire on the existing Romex. I thought about putting a ground bus near the inverter and grounding it to the chassis with #8 like you said and then grounding the IN and OUT AC grounds to the same bus. Or, can I just ground the plug and the Romex ground wires right to the chassis? I just don't know what to do with those two ground connection since the inverter doesn't have a connection for them.

Thanks again, so much.

 

[time2roll]

If the inverter has only Hot and Neutral in/out then just put a wire nut on the ground (in-ground direct to out-ground) so it can go past the inverter.

Assuming SP = Surge Protector it does the same thing. The ground just goes straight through inside the box.

 

[filippomasoni]

1) yes.
2) Inverter chassis ground should be an independent #8 wire to the vehicle frame.
3) best to have a separate negative bus for each voltage if needed. With each having an independent connection to the frame.
4) On-board generator ground needs to connect to the distribution panel ground. Not sure what this question is saying.
5) The RV AC panel should have a ground bus that is already bonded to the frame.

On this resource: https://diysolarforum.com/resources/grounding-made-simpler-part-4-mobile-systems.159/ it actually says to only ground the entire system to chassis in one place, otherwise there's a risk of ground loops.

 

[TinMan6294]

If the inverter has only Hot and Neutral in/out then just put a wire nut on the ground (in-ground direct to out-ground) so it can go past the inverter.

Assuming SP = Surge Protector it does the same thing. The ground just goes straight through inside the box.

No, I used SP to mean Shore Power

 

[time2roll]

Either way the ground from shore power or generator feed continues past the inverter to the ground bus in the electric distribution panel.
Electric panel will have a bond to the frame from the ground bus.