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Old 11-01-2018, 05:18 PM   #1
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120 volt AC breaker box: ground to chassis or not?

I'm sure this is beating a dead horse but I am getting conflicting information from different sources.

Do I need to ground my 120 volt AC to the bus?

As of now, all my breakers run to a single grounding busbar inside the work center. This includes both breakers on either side of my inverter and my breaker for my rooftop a/c which is on a completely separate input system. I have gone as far as running a ground wire from each metal breaker box to the grounding busbar on the breaker box.

My question is: Do I need to run a ground wire from this busbar to my chassis/frame?

If my understanding is correct, grounding all of these will prevent "hot skin" if there is a break/loose HOT wire that comes in contact with the bus. I then read it's the opposite? Help me skoolie-wan, your my only hope!
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Old 11-01-2018, 05:20 PM   #2
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Extra info:

I have kept all neutral wires on a separate busbar from the grounds. My inverter has automatic transfer switch.
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Old 11-01-2018, 06:17 PM   #3
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Get an experienced pro to help with shore power stuff.
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Old 11-01-2018, 06:38 PM   #4
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Well, the electrician's I talked to didn't know. From reading a different thread it's not ground the box to the bus but grounding the bus to box. I'll run my ground a ground to the chassis/frame.
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Old 11-01-2018, 06:52 PM   #5
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The info you're looking for should be in here somewhere- http://http://noshockzone.org/rv-ele...0%93-hot-skin/
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Old 11-01-2018, 07:24 PM   #6
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Hello, My name is Kevin, I'm currently in my 5th and final year of my union inside wireman apprenticeship. Sitting here in class, working through a code lesson and had to look it up.

Found this info in my 2017 NEC book. 551.56 Requires bonding of all exposed non-current carrying parts that are likely to become energized shall(must) be effectively bonded to the grounding terinal or enclosure of the panelboard There is an exception to NEC code 551.56.

Any recreational vehicle that employs a unitized metal chassis-frame construction to which the panelboard is securely fastened with a bolt(s) and nut(s) or by welding or riveting shall be considered to be bonded.



If your panel is not bonded by any these means, you shall(must) run a bonding wire from the chassis to the grounding terminal in your panel.

The bonding conductor shall be solid or stranded, insulated or bare, and shall be 8 AWG copper minimum.
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Old 11-01-2018, 07:30 PM   #7
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Originally Posted by EastCoastCB View Post
The info you're looking for should be in here somewhere- http://http://noshockzone.org/rv-ele...0%93-hot-skin/
Good info!

It is correct to ground your 120V panel to the chassis of the bus.

Also, make sure that the neutral bus in your breaker panel is NOT bonded to ground. Many breaker panels (load centers) come out of the box with a bonding strap between neutral and ground. This should be removed.


However..... When you connect to generator power you will will need to bond ground & neutral.

Ground and neutral should only be bonded at the source. IE: generator or shore power connection.
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Old 11-01-2018, 08:45 PM   #8
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This seems right but have to wonder 120ac grounded to the bus, and 12 volt dc grounded to the bus, just seems this would do something not good. On my bus both are grounded, so clearly it works.

Anyone have an explanation as to why this does not create a problem being ac/dc plus different voltage?
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Old 11-01-2018, 09:29 PM   #9
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Thank you for the help all.

Just reread the hotskin article ECCB,.great info. I should buy that book.

PNW-Steve, thanks. I made sure to keep ground far from neutral in the main panel.

Helio- great info. I'll step up.my wire size for.the ground connection. I have some spare 8 ga laying around from the old bus electric.

Now, I just need to.call champion and find out about my Genny and if they bonded ground to neutral or not. My inverter has the auto transfer switch but my rooftop doesn't run off the main panel or the inverter and j want to make sure that's plugged in correctly as well.

Thanks again!
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Old 11-01-2018, 09:42 PM   #10
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Quote:
Originally Posted by Ronnie View Post
This seems right but have to wonder 120ac grounded to the bus, and 12 volt dc grounded to the bus, just seems this would do something not good. On my bus both are grounded, so clearly it works.

Anyone have an explanation as to why this does not create a problem being ac/dc plus different voltage?

The confusion arises because the term "ground" doesn't mean the same thing in AC and DC circuits.



A DC ground completes the circuit, just like an AC neutral wire. The AC ground wire is a safety feature that only carries current momentarily when there is a fault in the system like a loose hot wire touching metal. Without the ground connection between the bus body and AC breaker box there would be no way for the breaker to sense a hot wire touching the bus body. That would mean the breaker would not trip and the bus body would be energized. A shocking situation!
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