Grounding question - RV Build

[Firetodd]

I’m am putting together the components to install my solar system into a new 5th wheel RV while my 16 280ah cells are on order. My RV is also being built and won’t be here for another month....

Anyway, I will be building a solar generator that will be mounted in the compartment below my pin box. I will then be plugging the shore power umbilical cord into this system. My panels will be mounted on the roof. Here is what the compartment looks like: (spare tire will be moved lol)

 

[Firetodd]

Here is my system layout:

 

[Firetodd]

The thing I am confused about is grounding the system. I have searched the forum and found this link: https://diysolarforum.com/threads/grounding-check.15442/

 

[Firetodd]

I was not planning on installing a negative buss bar or running anything to the chassis. But now after reading I’m thinking that perhaps I might need to?

 

[Firetodd]

My LV6548 says this in manual:

 

[Firetodd]

My portable generator says this:

 

[Firetodd]

So do I need to run a ground to the chassis, and if so, from where? Secondly, if I hook up my generator to the LV6548, do I need to do something about ground?

 

[Firetodd]

I see @Will Prowse installed the LV6548 on his solar trailer, but can’t see that he installed a chassis ground. Perhaps I am missing something.

 

[Hedges]

Proper and safe mobile setup has neutral AC wired to "ground" or RV chassis while running off inverter/generator. It disconnects that ground connection and makes use of shore power neutral/ground bond when plugged into shore power. Some shore power just might be wired backwards, with the "hot" pin of the AC plug grounded and the "neutral" pin hot. Caveat Camper. Best if you test the outlet before plugging in, and have a way to swap wiring to what is correct.

There is some UL listing number for inverters that take care of neutral/ground bond/isolate automatically when plugged into shore power.
Some inverters and generators tolerate having their neutral bonded to ground, but some do not. This is addressed in threads on this forum.

 

[Firetodd]

If I understand correctly, the MPP LV 6548 is UL 1741 “compliant.” Which means:

“UL1741-listed inverters must allow for the neutral-to-ground bond to only occur at the main AC service panel.” https://www.sigineer.com/news/difference-ul458-ul-1741-power-inverters/

So I I were to plug the MPP LV6548 into a utility power power source I would be kosher. But if I’m just using solar and the batteries, or a portable generator, what is the proper wiring? Do I need an AC ground buss and then run a chassis ground to it? Also do I need a DC ground buss wired to chassis?

 

[Hedges]

"As required by NEC and UL specification 458, inverter / charger installations in the U.S. that are used in RV or Marine applications should be provided with a“Neutral to Ground Bond Switching Relay”to switch bonding of the Neutral Output Connector of the Inverter Charger"

https://www.samlexamerica.com/support/documents/13009-0612_NeutraltoGroundSwitchinginRVandMarineApplications.pdf

Me, I would just mount a dead outlet with neutral wired to ground, and plug the power cord into that when not connected to shore power.
Hopefully no one gets electrocuted in the time it takes me to move the cord.

I'm not using a mobile inverter, but some guys on the forum are; try searching the topic.

 

[Firetodd]

@FilterGuy what’s your take?

 

[Hedges]

I don't think the " @FilterGuy " syntax actually pings him.
I've stumbled across postings under "What's new" that referenced me, without having been alerted by a message.

Might be better to "Start Conversation" with him or find a thread addressing similar topic that he or another has already responded to; you could provide a link back here.
Software, you know. Never can trust it.

 

[Firetodd]

Thank you Hedges!

 

[FilterGuy]

Nope.... I did not get pinged.

Lets start with the MPP. I do not have data on that model, but I am reasonably confident it will be similar to this:


If the MPP LV6548 is the same as the LV2424, then you are good for having the Ground-Neutral bond on either battery or shore power.

Now we go to the generator.

I found this in the Generator Manual.

That means there is no Ground-Neutral bond in the generator. If you use it as-is, the system will work but it is dangerous because if a hot lead from the 120 shorts to grounded metal it won't pop the breaker.

As @Hedges said, the easiest way to deal with this is with a plug that ties the Neutral to ground.
Plug it into one of the spare plugs on the generator and it will create the Neutral-Ground bond. Then you can use your shore-power cord to plug into the Camper.

You can buy one pre-built (https://www.amazon.com/gp/product/B07F4R7BDL/)
Or you can build one.

Here are pics of one I built a while back. (I used a 15A plug on this because that is what I had on hand... normally I would use a 20A plug just so it is obvious it is 'special'.)




I would not worry about the chassis ground lug on the generator. Leave it unhooked If you have the above plug set-up.

BTW: I have heard that some inverter-generators have safety circuits that will not let them opperate if they do not see a G-N bond on the AC.

 

[Firetodd]

Wow! Thank you so much! Will I need a DC ground to chassis between my battery and the LV6548?

 

[Hedges]

My idea wasn't a plug with neutral tied to ground.
Rather a socket with neutral tied to ground.

If you stick such a plug in an outlet and forget to unplug when using shore power, you have neutral bonded to ground in two places.
With a socket, you either plug your inverter AC input cord into shore power, or into the (unpowered) socket which performs ground bonding.

Generator could be hardwired to such an outlet (or same outlet; powered it generator running)

 

[Firetodd]

I camp about 50-60 days a year for the past 20 years and have always boondocked. The only time I ever hook into utility power is when I am at home. In that case my system would be grounded at my house. If I left the plug installed on the generator, then I should be covered?

 

[FilterGuy]

Wow! Thank you so much! Will I need a DC ground to chassis between my battery and the LV6548?

On a 48V system, there should be a bond between the DC and Ground. I assume the LV6548 does not already provide this connection, but it would not hurt to check with an ohm meter before you hook up the inverter.

 

[FilterGuy]

I camp about 50-60 days a year for the past 20 years and have always boondocked. The only time I ever hook into utility power is when I am at home. In that case my system would be grounded at my house. If I left the plug installed on the generator, then I should be covered?

Yes.... you should be covered. @Hedges does have a point though.... you need to be sure to never plug the NG-plug into a system that already has a Neutral-Ground bond. If you do, things will mostly work (Except for GFI breakers) but there will be current on the equipment grounding wire and there are several safety issues with that.

BTW: It looks like your Gen-set has a 20A receptacle. If you build the NG-plug out of a 20A plug you are a less likely to plug it into anything else but the generator cuz 20A receptacles are not very common.