Is Generator Grounding Necessary?

Thank you so much for finding the answer to the question, ng and Bill.

OK, after reading through this post, the majority consensus is that grounding is probably not necessary.

But just in case I do decide to ground my generator, I have a question:
I understand that sand is not a good ground. That being said, if I place a ground rod a foot or so into the sand, wouldn't it "probably" follow that ground instead of me touching the generator in the case of a catastrophic failure of the generator wiring. Doesn't ground usually follow the path of least resistance, and hopefully that being the rod in the sand instead of me standing on top of the sand somewhat insulated by shoes??

Thanks to all for a great thread here.

Chap

One foot is not going to be deep enough for an effective ground.

All that said, a caution. First, if there is anything in the stuff your connecting that is also grounded, you need to tie any grounds you have together properly (with thick wires) - otherwise the second ground will actually *increase* your risk of fire and shock danger.

The reason the ground won't do any good is that the generator isn't producing electricity relative to ground. Electricity needs a complete circuit to flow - basically, a simplified view is to think that the electricity needs to end up where it starts via some sort of path. So, with a commercial power station, which is grounded (as is your neutral wire in your breaker panel at home), a path such as "power station hot wire to person to bathtub cold water pipe to power station grounding system" is a complete circuit. However, your little generator isn't connected to ground, so even if you held onto the "hot" wire from the generator in one hand, and a cold water pipe in the other, you wouldn't get shocked - there is no way for the ground to connect back to the generator.

Now, as mentioned, your house is grounded. That's why the NEC says you have to ground a generator powering your house - if you don't, and something goes wrong in the generator (or elsewhere), it's possible for someone touching a ground and the generator to get shocked (let's say the hot wire was "lighting up" the outside of the generator; the path would be "generator case hot to person to ground to neutral bonded in the breaker panel to generator"). But if there is no ground connection (and that's easy to verify with your trailer, hard to verify with your house) you won't get shocked.

I hope my convoluted explanation makes sense. The short of it is that if you are in a trailer, the ground rod won't ever be the path of least resistance to complete the circuit. It would never have current flowing across it.

Fortunately, your generator probably has a GFI in it - that means if any generator casing or the third prong ever senses voltage, the generator will quite sending power.

Originally Posted by mtnguy

OK, after reading through this post, the majority consensus is that grounding is probably not necessary...

Depends on what you mean by grounding. You want to bond your generator ground to the trailer, not necessarily drive a rod into the ground. Go back and read posts 5 and 6 in this thread. Post 6 really deals the most with what the NEC is trying to accomplish.

What you are getting confused about is driving the ground rod into the ground. What the NEC is trying to prevent is getting a charge riding on the trailer and the appliances contained witihin, should something happen to the wiring. Bonding the ground gives the system a low impedance path back to the generator ground.

A ground rod is going to be hard pressed to supply a 25 ohm or less path back to generator ground. Bonding the trailer to the generator ground does supply that path.

The operative phrase to remember is that a generator connected to travel trailers is called separately derived. That is why the wiring conventions for wiring a generator to the house is different than the wiring to travel trailer.

[TM Pilot]

The first issue is grounding. I have a Champion 3100 watt Inverter Generator (Model 75531i). On Champion's FAQ page, here is what they recommend concerning use of a grounding rod: http://www.championpowerequipment.com/faq/

5) I am confused about the recommendation of a grounding rod attachment.

The recommendation for a grounding rod is best used for a permanent location, such as outside of your house for emergency use. A copper rod driven into the ground and a copper wire attached from the rod to the generator frame will give you solid protection against electrical shock. A GFI (Ground Fault Interrupter) is also another attachment that is effective against electrical shock. It is recommended to speak with a licensed electrician if you are considering this type of permanent installation. If you are running your generator in shallow water areas, it is a must to attach the generator to a grounding rod.

Here are two good articles from OSHA:
Grounding Requirements for Portable Generators: https://www.osha.gov/OshDoc/data_Hur..._generator.pdf
Portable Generators and OSHA Construction Regulations: http://oshaprofessor.com/Portable%20...rds%203-05.pdf

When I apply these two articles to my Champion 3100 Watt Inverter Generator, what they say is that I don't need a grounding rod and I don't need GFCI outlets installed on the generator.

The last issue (bonding) is the most controversial. Since my generator will be used to power my TM (a separately derived system) and has a floating neutral, do I need to bond the neutral to the generator frame/ground? Since my generator does not produce 240 volts - it is optional. Read the next article:

https://www.osha.gov/pls/oshaweb/owa...ONS&p_id=21184

A 120/240 volt system has a neutral and therefore must be bonded to the generator frame. A 2-wire 120 volt system has no neutral and therefore bonding is optional. Recall that neither side of a 2-wire derived system is a neutral and when one grounds either side, it becomes a grounded terminal or conductor, but it is not a neutral.

Since bonding the neutral and ground is optional, there are strong opinions for which is safer. For now, I'm going to keep my inverter generator in the floating neutral configuration (the entire separately derived electrical system [TM & Inverter Generator] is "floating." ).
Additional/related info: http://www.trailmanorowners.com/foru...light=champion

[Padgett]

I always thought of a house as being fed 240vac which is split into two 120vac circuits at the fuse box by tieing each side to ground (neutral). It is important that the ground be a real ground since otherwise what you would have would be a split 240vac line with no reference

With a floating ground as long as the loads on both sides are the same you are fine but if the load gets unbalanced then it will pull the neutral to one side or the other and there will be a difference between neutral and ground.

This is why sometimes in an old house when the furnace comes on the lights may get bright for a moment.

OTOH most small generators are a single phase 120vac circuit referenced to itself. You can tie either side to ground if you wish just don't become one.

ps a TM GFI detects differences between "ground" (really the coach frame) and neutral. Like a car, "ground" or "earth" is just a term and not reality.

[Bill]

Actually, GFI does not look for a difference between ground and neutral. It detects a current difference between hot and neutral. Ground does not enter into the operation of a GFI, and no ground is necessary for a GFI work properly.

Bill

[TM Pilot]

When one decides that they want to bond the neutral and ground on a generator with a floating neutral - what is often done is that a bonding plug is installed in the 120V outlet. That method works, but it uses up a perfectly good receptacle. Here is another method that doesn't waste a good receptacle:

https://www.youtube.com/watch?v=PrXGFZxuxpU&t=115s

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As I've studied the floating neutral vs bonded neutral debate when hooking up a TT to a generator, it seems that the big issue is what provides better electrocution protection.

The bonded neutral crowd says that since the generator ground (3rd prong) attached to the generator's metal frame in a floating neutral generator isn't connected to the generator's CB on the hot/neutral circuit, then if a short happens then the generator CB might not trip. The metal skin of the appliance plugged into the generator (ex. a Trailmanor TT) and the generator's metal frame becomes energized via the 3rd prong ground wire. And without the CB popping - you would never know that there is a potential problem. If you bond the neutral and ground in the generator via a plug or jumper cable on the 120v outlet, then the CB will pop if there is a short and you will know that there is a problem. Plus, the CB popping will protect you from getting electrocuted. It's a win-win situation. Ohh, wait....not so fast:

The floating neutral crowd responds and says that that's all true, but even if an appliance plugged into the generator (ex. a Trailmanor TT) and the generator's metal frame are both electrified (via the 3rd prong ground wire) due to a short somewhere - one could touch the appliance and/or the generator frame plus be standing in a water puddle outside and never get electrocuted because they are not a part of the circuit back to the AC coil of the generator because the neutral isn't attached to the ground on the generator's frame. No completed circuit via one's body = no electrocution if the CB doesn't pop.

If anyone is worried about 'hot skin' on their Trailmanor - a better way to test for it is using a non-contact volt tester (ex. Southwire 40150N) instead of waiting for a CB to pop or you getting french fried.

Personally, I prefer not getting electrocuted by not completing a circuit instead of betting my life on a CB popping (isn't that why we sometime upgrade to GFCIs?). Therefore, my generator that I use for my Trailmanor will stay floating. However, both floating and bonded neutrals are safe...safe in their own way.

I also know of another issue of floating -vs- bonding neutrals where some fancy surge protectors will not accept power from a floating neutral generator. In that case, you're stuck with having to bond the neutral to the ground on the generator to get the surge protector to work. But if you do, do you need a ground rod too?

P.S. The YouTube video linked above from Champion said to use a grounding rod when modifying a generator's floating neutral to a bonded neutral. So that brings us full circle in the grounding rod and bonding debate. Be safe.

[Bill]

TM Pilot -

Thanks for that post. Digging up real information about RV generator grounding can be tough, and you have found a lot.

Over the years, I have come to rely on information from Mike Sokol, an RV electrical expert who writes for RVTravel. He uses the RV section of the National Electrical Code for a lot of his information, and though the Code can be hard to read, there is no better source. He also uses his own lab and equipment to illustrate some of the tougher concepts. I have dealt with him directly on several topics, and have always found him polite, helpful, and deeply knowledgeable. You have pulled up a lot of the same info. Readers can start here.
https://rvelectricity.substack.com/p...ng-and-bonding

In addition to grounding to earth, Mike also discusses bonding of a generator's neutral to its frame (not the same as earth ground). Bonding has some applications, but is not a safety item. One place where he differs with you is the need for an earth ground for a portable generator, which is defined in the NEC. I downloaded a copy of the relevant portion of the code, worked through it, and to my surprise, ended up agreeing with him.

As I recall, the difference between commercial power (from the power lines) and generator power is that for good reasons, utility power has a ground connection, which establishes a path for a fault. A portable generator does not have a ground reference, and adding one doesn't accomplish anything.

Somewhere I have a collection of notes from Mike' site and my conversations with him. I'll have to dig it up.

Bill

[TM Pilot]

I'm not saying that I agree with Champion's video about the need for always using a ground rod when converting the floating neutral generator to a bonded neutral. Seems if you hook up the generator to a floating non-bonded subpanel (like a trailmanor TT) - a grounding rod isn't needed (I believe this is also Mike Sokol's position). But if you hook up the generator to a home's bonded main panel during a power outage - then a grounding rod may be needed??? However, on this forum, I only care about how to set up the generator for a Trailmanor TT and don't want to go down the home backup power via a transfer switch rabbit trail...