How to Ground a Simple Shore Power Hookup

[SmoothSailing]

Hello all, a little over a year ago I picked up a completed conversion. Only recently have I been able to use it, and what I have discovered is that the original builder seems to have wired the AC hook up incorrectly.

The system is a simple shore power plug directly into a conventional sub-panel with 4 breakers.

- There is no inverter in the system
- There is no generator in the system

Currently this is what the panel looks like (pic attached)

Problem: My understanding is that the bonding of the neutral and the ground wire as shown in the attached picture, is unsafe, and that this bonding should only occur at shore source.

Solution: My plan is to buy an additional isolated busbar, then screw it inside the panel and hook the main ground form shore to it, and then route all of the ground wires for each breaker to this isolated bus bar.

Is this a safe and correct way to wire the setup?

Thank you so much for your input!

 

[DeMac]

Add-A-Bus

Hello all, a little over a year ago I picked up a completed conversion. Only recently have I been able to use it, and what I have discovered is that the original builder seems to have wired the AC hook up incorrectly.

The system is a simple shore power plug directly into a conventional sub-panel with 4 breakers.

- There is no inverter in the system
- There is no generator in the system

Currently this is what the panel looks like (pic attached)

Problem: My understanding is that the bonding of the neutral and the ground wire as shown in the attached picture, is unsafe, and that this bonding should only occur at shore source.

Solution: My plan is to buy an additional isolated busbar, then screw it inside the panel and hook the main ground form shore to it, and then route all of the ground wires for each breaker to this isolated bus bar.

Is this a safe and correct way to wire the setup?

Thank you so much for your input!

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That's right.
Reroute the Grounds to a new, panel-bonded Grounding busbar. The neutral bar is already isolated.

If you buy a Ground bar from the same manufacturer as the panel, the mounting holes will align with the existing prepunched holes. Otherwise, you'll have to drill at least one hole.

If you cannot thread or tap the holes, use nuts (torqued) on the back, then cut off the remaining threads. Lockwashers are allowed.

Self tappers are NOT allowed to be used to mount ground bars.

More about adding a bus here:
skoolie.net/ceiling-framing-and-electrical-rough-in

 

[Danjo-SKO]

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That right. If you buy a Ground bar from the manufacturer, the mounting holes will align with the prepunched holes in your panel. Otherwise, you'll have to drill at least one hole.

If you cannot thread or tap the holes, use nuts (torqued) on the back, then cut off the remaining threads. Lockwashers are allowed.

Self tappers are NOT allowed to be used to mount ground bars.

Hey I thought it is the Grounded Conductor, aka the Neutral that should be isolated and that the Ground Fault wire, the green or bare wire should always be bonded to the chassis, no? Please someone correct me if I misunderstood this.

Anyway, for the OP and anyone else interested, the NEC covers recreational vehicles in article 551. Here’s a link I found. It’s not the original source and I didn’t check version so YMMV and IM NOT AN ELECTRICIAN

https://up.codes/viewer/minnesota/nfpa-70-2023/chapter/5/special-occupancies#551

 

[SmoothSailing]

*Accidental reply*

 

[SmoothSailing]

------------------------

That's right.
Reroute the Grounds to a new, panel-bonded Grounding busbar. The neutral bar is already isolated.

If you buy a Ground bar from the same manufacturer as the panel, the mounting holes will align with the existing prepunched holes. Otherwise, you'll have to drill at least one hole.

If you cannot thread or tap the holes, use nuts (torqued) on the back, then cut off the remaining threads. Lockwashers are allowed.

Self tappers are NOT allowed to be used to mount ground bars.

More about adding a bus here:
skoolie.net/ceiling-framing-and-electrical-rough-in

Thanks for the confirmation DeMac! Also thanks for the tip on self tappers!

I am guessing the reason self-tappers aren't allowed because of they are not viewed as "permanent" fasteners?

 

[SmoothSailing]

Hey I thought it is the Grounded Conductor, aka the Neutral that should be isolated and that the Ground Fault wire, the green or bare wire should always be bonded to the chassis, no? Please someone correct me if I misunderstood this.

Anyway, for the OP and anyone else interested, the NEC covers recreational vehicles in article 551. Here’s a link I found. It’s not the original source and I didn’t check version so YMMV and IM NOT AN ELECTRICIAN

https://up.codes/viewer/minnesota/nfpa-70-2023/chapter/5/special-occupancies#551

Danjo, I believe your statement only applies when there is power generation on board (generator/inverter).

For a strict shore-power setup the ground should go back to the shore, so to speak.

I'm not an expert, maybe DeMac can answer.

 

[SmoothSailing]

DeMac, I just realized your example has a non isolated ground bar.

I was going to use an isolated ground bard, this one pictured below.

Is this bar ok to use?

 

[DeMac]

Chassis Bond

Hey I thought it is the Grounded Conductor, aka the Neutral that should be isolated and that the Ground Fault wire, the green or bare wire should always be bonded to the chassis, no? Please someone correct me if I misunderstood this.

Anyway, for the OP and anyone else interested, the NEC covers recreational vehicles in article 551. Here’s a link I found. It’s not the original source and I didn’t check version so YMMV and IM NOT AN ELECTRICIAN

https://up.codes/viewer/minnesota/nfpa-70-2023/chapter/5/special-occupancies#551

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The definitions, which use the root word ground*, can be confusing to the novice installer, so I don't muddy the waters when they have a crystal clear understanding of the labor which must be completed, before the over current protection devices will work properly. Safe

Click here for more on
Bonding:

I bored a hole through the sole plate, sill plate & steel floor

Bare Solid Cu #6 through floor, outside the chassis rail. Plenty to bond to the chassis & still extend it via Cu split-bolt

*Ground, Ground Wire, Grounded Conductor, Ungrounded Conductor, Grounding Electrode, Ground Bar, Ground Lug, Ground Bus, Ground Rod, Equiptment Ground....

Awesome of you to mention Bonding to chassis, though. You're number one.

 

[DeMac]

DeMac, I just realized your example has a non isolated ground bar.

I was going to use an isolated ground bard, this one pictured below.

Is this bar ok to use?

---------------------
NO. Not at all good.

Use a Ground bar which is made for the panel you have. Check the cover for the manufacturer's name model number. Then goto electrical supply house, pull up this thread & show them.

The Ground bar Bonds to the panel. Metal to metal. Not isolated. Use the machine screws which come included with the bar. They will thread the factory ground bar holes for you.
Currently, you have NO Ground bar or panel Bond grounding your panel. This only happens via the ground wire in the SO cord which travels back to the power pedestal, outsode your bus.
The neutral ought Not be bonded to the grounds or the panel's chassis. The Neutral bus Currently installed on your panel IS isolated from the panel (perfect). Remove the Grounds Only and mount them to the new Bonded bus bar. While you are purchacing the bar, purchace feet of solid #6 or #8 and a #6 Ground Lug to mount onto your (grinder to clean metal) chassis rail.
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I followa code made bu many other who walked this path before me. Like Moses list, I do no stray and make my own list of "okay for DeMac" list.
Self justifying self-righteous, I am not.

Improperly bonded panel is dangerous.

Nothing spent yet. Why buy the wrong crap? Panels are always sold without the ground bars and lugs. Most folks already know this and purchace all the parts together as the grounds are installed first, not last.

 

[Booyah45828]

I think either will work, so long as if it's an isolated bar that is used, you add a wire between the panel chassis and the ground bar so that the panel chassis is grounded.

Using a non-isolated bar would do that by default I believe.

 

[Danjo-SKO]

DeMac, from the photos you posted it looks like the white wire is isolated. Is this the case?

 

[SmoothSailing]

Oh dear.. I thought that if there was no inverter or generator on board then there was no need for a ground to chassis?

I thought my whole system should just be wired like an extension of the shore power and in turn using it for ground.

This why I went for an isolated ground bar.

 

[DeMac]

DeMac, from the photos you posted it looks like the white wire is isolated. Is this the case?

Sure, the Neutral bus is isolated from the grounds, panel steel, etc..

Neutrals are Grounded Conductor, however...

There are two Conductors, one Ungrounded Conductor (commonly called hot, black) and a Grounded Conductor (commonly called neutral, white). The Ground system is entirely separate from these two, but bonded to everything metal and typically unused by the user. Saftey devices use the Ground, path of least resistance.

The neutral is NOT bonded to the Ground or panel chassis in the sub panel. It is Bonded to the grounds way back at the first Main Breaker, where the power company's meter is. This is the only place where the neutral and grounds are bonded. After this point, every metal raceway, metal box, panel, bottom wire in the recepticals and into ypur bus via the cord connection. They'rre all Bonded via the grounding wires. A network of Copper bonded every where but receives no current, normally. It's the baseline which is used to measure impedance for comparison. Your safety devices use this measument to protect the occupants and thier property.

 

[DeMac]

I Thought...

Oh dear.. I thought
(........)
This why I went for an isolated ground bar.

--------------------
(.........) as didn't wanna repeat this part

I appreciate your honesty as to the souce.
Do you have another source, other than your thoughts referenced above?
Maybe you know something I don't. I'm willing to learn, if you can teach me. This sort of stuff can change. I simply prefer to read the language which has been voted on by a large panel of fire industry leaders. ("only"?)

I witnessed something entirely different, when I read from a Power Greater Than Myself (the group of folks who wrote all these NFPA codes, that is my great power) I really don't have a need to quote verse & chapter as I've posted the souces for grounding chassis in 120v AC systems many times before.
But, us humans have grey matter, so we think, instead. Me too

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RV manufacturers & RV parks must adhear to these standards. We can do as well or better or we can do good-nuff-for-me then sell our rigs to the next guy.
Oh....

 

[Danjo-SKO]

Oh dear.. I thought that if there was no inverter or generator on board then there was no need for a ground to chassis?

I thought my whole system should just be wired like an extension of the shore power and in turn using it for ground.

This why I went for an isolated ground bar.

Ive just now started to understand this.

Just like any metal box, metal conduit, appliance, motor case, and etcetera in typical construction, the Equipment Grounding Conductor is bonded everywhere and is continuous. And just like typical construction the Grounded Conductor that is the normal return path is only bonded to the Equipment Grounding Conductor at the main breaker, which your vehicle does not have since it is effectively a sub panel. The Main Breaker is at the electrical source. This is also the place where everything is bonded through a grounding rod to Earth Ground

 

[SmoothSailing]

Ive just now started to understand this.

Just like any metal box, metal conduit, appliance, motor case, and etcetera in typical construction, the Equipment Grounding Conductor is bonded everywhere and is continuous. And just like typical construction the Grounded Conductor that is the normal return path is only bonded to the Equipment Grounding Conductor at the main breaker, which your vehicle does not have since it is effectively a sub panel. The Main Breaker is at the electrical source. This is also the place where everything is bonded through a grounding rod to Earth Ground

Hi Danjo,

Are you in agreement with my original thought that no chassis ground is required if no power source is on board or are you saying a chassis ground is required no matter what?

I follow your logic, I'm just not quite understanding what you are concluding.

Thanks for your input!

 

[Booyah45828]

Oh dear.. I thought that if there was no inverter or generator on board then there was no need for a ground to chassis?

I thought my whole system should just be wired like an extension of the shore power and in turn using it for ground.

This why I went for an isolated ground bar.

You still ground every panel/box/switch/outlet in the system regardless of power source. Using an isolated ground bar, you'd still have to come up with a way to ground the panel to the bar. Whereas a non-isolated unit would have the panel chassis grounded through the screws holding the bar to the chassis.

It's also not a bad idea to attach a wire between the bar and bus's chassis, which is what DeMac showed in post 8.

What changes between inverter, mounted genset, portable genset, shore, etc is where the ground-neutral bond occurs. Moral of the story is that the bond should occur only once, and only at the power source. If you're connected to a home outlet, it should be bonded in the home's panel. If you're connected to a genset, and that genset doesn't have a bond where you plug it in at, you need to create one (generator bonding plug).

In your picture, your neutral is isolated from the panel's chassis, which is what you want. Some panels aren't isolated like that, which is where you would install that isolated bar and then use it for your neutrals, using the non-isolated bar as your ground bar.

 

[Danjo-SKO]

Hi Danjo,

Are you in agreement with my original thought that no chassis ground is required if no power source is on board or are you saying a chassis ground is required no matter what?

I follow your logic, I'm just not quite understanding what you are concluding.

Thanks for your input!

Just to clarify, when you say “ground” I’m interpreting that to mean “Equipment Grounding Conductor” in other words, the emergency path back to ground in the event something goes wrong, the “green” wire.

The normal path back to the source is the “Grounded Conductor” the “white” wire.


As I understand it, the “Grounded Conductor” needs to stay isolated until it makes it back to its source which is Earth Ground which in the case of an RV is outside of your bus, back at the main source panel, where the circuit that feeds the RV site’s pedestal originates. It is at this point that the “Grounded Conductor” and “Equipment Grounding Conductor” are bonded.

In any case, you shouldn’t trust me. Read NEC Article 551 and then ask an electrician.

 

[SmoothSailing]

Thank you DeMac, Booyah, & Danjo!

I'm going to run to the hardware store and get a non-isolated grounding bus bar that will match my panel like DeMac said.

I'll run the shore power ground to that new ground bar, then I will run all the breaker grounds to the ground bar, finally, I will also run a #6 or #8 ground wire from that grounding bus bar to the bus chassis.

After that is done I will test all outlets and check for a "hot skin" condition

 

[Booyah45828]

Sounds like a winning plan to me.