Portable generator and grounding

[PamW]

Those of you with portable generators mounted on their travel trailers. Do you ground them? Do you have a ground wire attached to the trailer frame? Do you dangle a wire to ground when in use? Do you ignore it?

Attaching ground to the trailer frame seems to make the most sense, but is the trailer actually grounded? I mean, it’s sitting on rubber wheels. The stabilizers are sitting on plastic pads. The jack is sitting on either plastic pad or pieces of wood. Seems pretty isolated from ground as a whole to me.

Thoughts?

[chily3]

We just use the three wire cord. No other grounding

[wahoonc]

Most portable generators don't require grounding under most applications. For the RV I wouldn't worry about it too much. When I had my Airstream with the dual Honda setup we didn't bother to ground anything, just plugged it and used it.

Aaron

[MartyG]

There is a point to be made here. The chassis ground of a generator is not normally tied to the neutral side of the voltage output, like it is in a house or camper pedestal outlet. There are lots of stories why this is so, but the end result is that when you plug your shore power plug into a generator outlet, the chassis ground is not connected to the return (white wire) in an AC outlet. That can cause problems for voltage and circuit monitors, like surge protectors. To overcome this, it is common to wire the ground (green) to the neutral (white) in a regular 120 volt, 15 amp, 3-prong plug, and plug it into the generator's 110Volt outlet. That will tie the two together and alleviate these malfunctions. Just a simple plug, with a 1" jumper inside, marked as "Grd to Neu connector" or words to that effect.

[PamW]

Thank you folks. I play electrical engineer during the day and tend to overthink things occasionally. I also make clear to anyone who listens that I play engineer, not electrician. I know theory (mostly), not real life installation! I assumed no ground was necessary, until the instructions suggested otherwise.

Found this, which makes me more comfortable.

2014 NEC

250.34(A) Portable Generators.
The frame of a portable generator shall not be required to be connected to a grounding electrode as defined in 250.52 for a system supplied by the generator under the following conditions:

1. The generator supplies only equipment mounted on the generator, cord-and-plug-connected equipment through receptacles mounted on the generator, or both, and

2. The normally non-current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacle are connected to the generator frame.

Marty, thank you for your input I'll know what's wrong if my gfci at my sink keeps tripping after forgetting the trick with the plug!


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[wahoonc]

Check out the specific generator, some are bonded neutral, others are floating neutral. The bonded ones will play fine with a GFCI.

Aaron[emoji41]

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[PamW]

Originally Posted by wahoonc

Check out the specific generator, some are bonded neutral, others are floating neutral. The bonded ones will play fine with a GFCI.

Aaron[emoji41]

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Mine is a cheap no name brand. I'll assume the worst! [emoji6] But I probably won't do anything about it until I see problems because, well, memory. [emoji23]

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[wahoonc]

Originally Posted by PamW

Mine is a cheap no name brand. I'll assume the worst! [emoji6] But I probably won't do anything about it until I see problems because, well, memory. [emoji23]

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Define "cheap no name brand"...

Aaron[emoji41]

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[PamW]

Wen 2000w

Inverter style, bought from Woot.com for $330.

At least no-name to me at the time.

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[PamW]

Originally Posted by PamW

Wen 2000w

Inverter style, bought from Woot.com for $330.

At least no-name to me at the time.

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http://www.wenproducts.com/store/gen...nerator-56200i


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[wahoonc]

Originally Posted by PamW

Wen 2000w

Inverter style, bought from Woot.com for $330.

At least no-name to me at the time.

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I will check it out tomorrow. I have heard of it, but I am not familiar with them.

BTW... I am a lot of design engineers worst nightmares... I am the guy in the field that installs it AND makes it work! [emoji3]

Aaron[emoji41]

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[PamW]

Originally Posted by wahoonc

I will check it out tomorrow. I have heard of it, but I am not familiar with them.

BTW... I am a lot of design engineers worst nightmares... I am the guy in the field that installs it AND makes it work! [emoji3]

Aaron[emoji41]

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When I used to do a lot of construction administration the first thing I would say upon meeting a contractor for the first time was, "just because it makes sense to me in black and white on paper doesn't mean it necessarily makes sense in real life"! (but that doesn't mean I was a pushover either!)

I just noticed a wiring diagram in the user manual, let's see how good and confused I can make myself! (and I wonder how accurate it is, or if it's made like our Colemans! [emoji6])

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[PamW]

Originally Posted by wahoonc

I will check it out tomorrow. I have heard of it, but I am not familiar with them.

BTW... I am a lot of design engineers worst nightmares... I am the guy in the field that installs it AND makes it work! [emoji3]

Aaron[emoji41]

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If I'm reading it right... On the plug it's showing hot to hot, neutral to neutral and ground to ground to the ground screw on the front of the unit.

I suppose I could send them an email and ask...what a concept!

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[MartyG]

I found the article which taught me about Ground-Neutral Bonding. As you read the comments at the end, there is an on-going discussion as to why, but most agree to do it.
As to Wen, I had one of their soldering guns way back in the 60's. They've been around a long time, have a respectable web site and line of electrical tools.

Here's the grounding link: Generator Ground-Neutral Bonding | No~Shock~Zone

[Firstime RVer]

Not sure if I can make this simple..


Grounding connections are to take any stray current caused by bare wires or dripping water etc. and run it safely to ground along the path of least resistance. This keeps you and me from being the path of least resistance to ground.


If you picture your generator as a battery. You can touch the positive or negative terminals of the battery without getting shocked.. Touch both terminals at the same time and it would be a shocking experience..


Now if you connected the negative terminal to a rod in the ground (called an earth ground) and touched the positive terminal with one hand, and the ground with the other, you will get zapped because you are the path of least resistance to ground.. The ground connections inside your rv protect you inside the trailer. So connecting the generator ground to earth ground doesn't really buy you anything inside or outside the trailer..


On shore power since the neutral is connected to earth ground thru your power cord, there is now a risk outside your rv. That's why GFCI's are used..


hope this makes sense

[MartyG]

I was with you until the last two sentences:

Originally Posted by Firstime RVer

....The ground connections inside your rv protect you inside the trailer. So connecting the generator ground to earth ground doesn't really buy you anything inside or outside the trailer..
On shore power since the neutral is connected to earth ground thru your power cord, there is now a risk outside your rv. That's why GFCI's are used..
hope this makes sense

The TT is only designed for shore power, unless it has a built-in generator. Using a portable generator is not within their design. As such, the chassis of the trailer is indeed tied to the chassis of the generator, through the ground prong of the connector. However, none of it is directly grounded. Thus, stray voltage can find a path somehow to ground, and it's dangerous if that path is through a human body. That's why (although nobody pays attention) that every portable generator owner's manual says to ground the generator chassis to an earth ground.
There are other reasons, previously noted, for tying neutral to ground. But you're off a little on the purpose of a GFCI. They work by measuring the current coming in from the hot side, and flowing out the neutral side. They should be the same. If the two vary by just a few milliamps, the voltage must be going somewhere else, rather than the desired path. It could be a leak to chassis ground, but more dangerously, through a human to get to that ground. The GFCI trips when the "in" and "out" don't match, within some given tolerance.
Finally, I agree that when you are plugged into a properly-wired outlet, that the pedestal, or house wiring effectively bonds the neutral to the ground, and extends that ground to the TT chassis. But I do not understand your statement, "...there is now a risk outside your rv. "

[Firstime RVer]

Hi Marty,
I don't think we are disagreeing.. I was trying to make the point that since a generator that is not grounded to earth has a floating ground that stray currents between the generator power and earth ground don't represent much of a risk.
On shore power the risk of stray currents to earth ground are much higher..
In both cases GFCI's are lifesavers...
All the best.
Pat


Ps I prefer, not being able to reset a GFCI as an indication of a problem, to the "tingles" we used to get in the old days when something was wrong...

[MartyG]

Pat, you are correct; we are not disagreeing. I hear you more clearly now. You're saying that a generator, not grounded to earth, (and I guess) especially when the neutral is not tied to chassis ground) then a hazardous path to ground is less of a threat. Interesting point of view. Will welcome the opinions of others on that. We agree on the benefits of GFCIs, and yes, I remember the "tingles!" Best to you, too!

[Firstime RVer]

I'm no expert, which becomes more obvious to me with each passing day..
So I'd also like to get other opinions as well..

[wahoonc]

Even the 'experts' can't agree. My company dictates that ALL generators in use on a job site WILL be grounded. Some manuals say you have to, some manuals say per the local codes, same don't say at all. I have worked on sites all over the country, some want generators grounded some will tell you not to. Just for the record we have everything from 1500 watt Honda inverters all the way up to a couple of 17kw 3 phase diesel monsters.

On a personal level I think grounding is a probably a good idea, however a true grounding rod according to the NEC has to be driven in the ground and has to be at least 8' long... NEC 250.52(A)(5) states: “Rods and pipe electrodes
shall not be less than 2.44 m (8 ft.) in length.” Now how many of you are lugging around an 8' grounding rod and a means to drive it 7'+ into the ground.

When working on buildings we can usually get our hands on a good ground via the steel frame, the lightning protection system of even the building electrical ground. Cold water pipes used to be a good ground, not so much anymore since they have switch to plastic plumbing.

Aaron