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Old 01-11-2021, 09:25 PM   #1
Mini-Skoolie
 
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To ground or not to ground.

I need help folks. I am completing my electrical setup and can't seem to find a clear answer on whether to ground my 120VAC to the bus chassis.

I am doing a 50amp 120VAC setup with a 100amp 12VDC power converter.

We will only have shore power and a generator. No solar.

Can AC and DC share ground without killing us? And if so would I ground my generator to the chassis also?IMG_20210103_134423.jpg
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Old 01-11-2021, 09:42 PM   #2
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Hello Neighbor. The AC panel and the DC can share the same ground. You have to check the generator manual as to the neutral vs the ground. All RV electrical systems are wired with their Ground and Neutral buses floated (unbonded from each other). There are lots of good reasons for this, most specifically that it’s an NEC and RVIA code requirement that the safety ground wire never carries any load current, and there can be only one Ground-To-Neutral bonding point in any distributed electrical system. The electrical pedestal at the rv park will bond them there. The RV electrical is basically a sub panel where you don't bond the neutral and ground. Your utility space looks nice.
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Old 01-11-2021, 09:58 PM   #3
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Thanks for the information s2mikon. I was thinking right along those lines.
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Old 01-12-2021, 01:18 AM   #4
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I understand the NEC requires bonding neutral to ground only at the point of service, but shouldn’t the panel in the bus have the ground going to the chassis? The DC is not a Hot and Ground. It is positive & negative. It is a closed loop system. Wouldn’t the 120 AC ground prevent “hot skin” ?
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Old 01-12-2021, 08:40 AM   #5
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Phatman, You are 100% correct. Maybe I should not have said "can" but must in post #2. The last thing you ever want to have happen is to have a hot skin situation.
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Old 01-12-2021, 09:07 AM   #6
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Remember folks, when working on the AC in our buses or anywhere else, never join the resistance and be forced to go underground
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Old 01-12-2021, 11:45 AM   #7
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I grounded my 120 to the body and when it rained i got shocked. Needless to say i ungrounded to threw body. That was 2 years ago
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Old 01-12-2021, 12:18 PM   #8
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The following is from "The no shock zone" and explains the RV grounding system very clearly. Also, check with your generator's mfg to determine if it is internally neutral/ground bonded. My Yamaha e3000iseb was not.
Jack

Generator Ground-Neutral Bonding - No~Shock~Zone
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Old 01-12-2021, 07:13 PM   #9
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Quote:
Originally Posted by Dead pirate View Post
I grounded my 120 to the body and when it rained i got shocked. Needless to say i ungrounded to threw body. That was 2 years ago
I’m not trying to start an argument with anyone ( here it comes....) BUT, the NEC, Article 551.56 (a) (b) requires all exposed Non-current carrying metal parts that ( could) become energized shall be effectively bonded to the groundING terminal or enclosure of the panelboard. A bonding conductor shall be connected between any panelboard and an accessible terminal on the chassis. The grounding conductor shall be a minimum of a #8 copper. Dead Pirate, if you were shocked when it was raining, you should go back over your system. You could be getting a back feed from a dc source. Something is not right somewhere.
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Old 01-12-2021, 07:25 PM   #10
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Dead pirate please don't try to live up to your name. You have a serious situation going on in your bus. Take a volt meter and set to AC and put the leads between the coach skin and a good ground where you plug in. In other words between both ends of your AC cord. You don't want AC going through you to the ground. I am not trying to start a forum war, but our buses need to be safe.

Remember folks, when working on the AC in our buses or anywhere else, never join the resistance and be forced to go underground
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Old 01-12-2021, 08:03 PM   #11
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Quote:
Originally Posted by mrlupr View Post
I need help folks. I am completing my electrical setup and can't seem to find a clear answer on whether to ground my 120VAC to the bus chassis.

I am doing a 50amp 120VAC setup with a 100amp 12VDC power converter.

We will only have shore power and a generator. No solar.

Can AC and DC share ground without killing us? And if so would I ground my generator to the chassis also?Attachment 52973
Mrlupr...... did you get my last post on your grounding/bonding to the chassis?
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Old 01-12-2021, 08:12 PM   #12
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Phatman, yes I read your post. Thank you for the detailed information. I am definitely going to ground everything properly.
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Old 01-12-2021, 08:17 PM   #13
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Quote:
Originally Posted by ol trunt View Post
The following is from "The no shock zone" and explains the RV grounding system very clearly. Also, check with your generator's mfg to determine if it is internally neutral/ground bonded. My Yamaha e3000iseb was not.

Jack



Generator Ground-Neutral Bonding - No~Shock~Zone
ol trunt, thanks for the link. It has a bunch of useful information.

My generator is a predator 3500 inverter. So now my next step is finding out if it has a floating ground or what.
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Old 01-12-2021, 10:21 PM   #14
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I looked up your generator and it is not neutral/ground bonded. Just to be sure for yourself follow the instructions Mike gives in the attached video.
Jack

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Old 01-12-2021, 11:03 PM   #15
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Quote:
Originally Posted by Phatman View Post
I’m not trying to start an argument with anyone ( here it comes....) BUT, the NEC, Article 551.56 (a) (b) requires all exposed Non-current carrying metal parts that ( could) become energized shall be effectively bonded to the groundING terminal or enclosure of the panelboard. A bonding conductor shall be connected between any panelboard and an accessible terminal on the chassis. The grounding conductor shall be a minimum of a #8 copper. Dead Pirate, if you were shocked when it was raining, you should go back over your system. You could be getting a back feed from a dc source. Something is not right somewhere.

No argument here! I'm just chiming in to emphasize that A) Phatman is right...and B) This is really serious stuff, which needs to be done right.


Edit to add credentials: I've taught NEC (electrical) code update classes for the IEC and the IBEW. I was even on an NEC code book update panel, a few cycles back, and at least one entry has wording I wrote. My area of expertise was the renewables sections (wind, solar, generators, grid connection) and not RVs. But I've read the whole code book. There's a ton in there and too much to memorize, so it's important to refer to the language often. A new book costs $120 or so. If you're not doing inspected work, and just want to be safe, you could get by with a used book from a recent prior edition. Like others here, I have a current NEC book as well as the relevant RVIA and ANSI books. We're all happy, I'm sure, to look stuff up for anyone here. As s2mikon said, more creatively, don't die. We'd miss you and fight over your bus.
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Old 01-12-2021, 11:50 PM   #16
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If your bus has a steel body (not fiberglass like a shuttle bus) the AC breaker panel needs to be grounded to the body in order for the breakers to work if an AC hot wire touches the body.

What confuses many is that "ground" is a different concept in AC and DC circuits. In a vehicle DC circuit the ground wire (or the body) simply completes the circuit similar to the neutral in an AC circuit. It will carry current whenever the circuit is powered on. In this case "ground wire" is a commonly used term that more accurately should be called a "negative wire"

An AC ground is a safety feature and normally doesn't carry current unless there is a shorted hot lead. Without a ground wire between the AC breaker panel and the body skin a shorted hot wire won't trip the breaker and touching the body could shock someone who's touching the metal body while standing outside the bus on wet dirt or pavement.

Your AC panel should have separate ground and neutral bus bars. Neutral and ground should only be bonded (connected) at the shore power panel.
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Old 01-13-2021, 12:21 AM   #17
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I get calls all the time out in the rural area that I live in From people getting shocked in their well house. It’s the same every time. Their pump motor is a 240 volt motor and they install a 120 volt light. You guessed it !! There is no neutral. They used the ground. It works but when that metal piped is pulled apart. BAM !! Hurts like hell. Most folks have no idea that neutral (white) wire carries current.
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Old 01-13-2021, 12:29 AM   #18
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Roach711, Thank you for the very good explanation. So many times people just get a nasty jolt and don't really think of the severe consequences of being electrocuted. I have a brother that was bit with 440 and lived. But it was a very close call. He was in a coma for a week. He won't get near high voltage now.

Remember folks, when working on the AC in our buses or anywhere else, never join the resistance and be forced to go underground
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Old 01-21-2021, 01:21 PM   #19
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OK... not to sound like a complete moron but can't you wire the AC and the bus DC completely separately? I have a 3000W inverter which runs an A/C unit and microwave but nothing else. The rest of the bus is geared for 12V DC such as the lights and phone charging stations. The only contact is the metal housing of the inverter being bolted to the metal of the bus body. The only thing else is a small solar setup tied to the batteries. Did I totally screw this up?
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Old 01-21-2021, 02:11 PM   #20
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If the metal of the bus is not grounded and an a/c load wire comes in contact with the bus metal then the metal of the bus is now hot. If your hands touch the metal and your feet touch the ground then you become part of the grounding system that was missing. If the bus metal is grounded and a load wire makes contact you trip a breaker. Now what would you prefer? A load breaker tripping, or joining the resistance and being forced to go underground?
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