Grounding Generator

[Huck]

Do you ground your generator when camping?

[Steve L.]

Originally Posted by Huck

Do you ground your generator when camping?

No.

I do put it ON the ground, however.

[steve dunham]

If you wish to assure that your generator is properly grounded , you could drive 4- 12 ft ground rods around the generator perimeter approx 12 ft apart . With a #6 continuos solid copper conductor bond the ground rods together and connect the #6 to the ground lug on the generator frame .

Most people follow follow Steve L and set it on the ground

[Bruce H]

Has anyone here ever experienced a shock from an un-grounded generator? Or do you know anyone who has?



Those questions being asked, It is certainly prudent to avoid running a wet generator. Or running one in the rain, grounded or not.

[steve dunham]

A generator is a separately derived system .
The neutral is not intentionally or effectively grounded
There is basically no potential to ground or it can be described as a floating system
Running a portable generator with it just sitting on the ground poses no real hazard
The only time I was ever required to ground portable generators was at fairs where they were used to run amusement rides / equipment.

[Huck]

The reason I asked is harbor freight has their 2000 watt generator on sale for $449 through Sunday (12/9), and I am considering getting one. This is copied from the manual. I have never seen anyone ground their generator, so was interested in seeing if anyone here did.

Grounding

1.The Generator must be properly grounded in accordance with all relevant electrical codes and standards before operation. Have the unit grounded by a qualified electrician if you are not qualified to do so.
2.To ground the Generator, connect a #6 AWG grounding wire (not included) from the Grounding Terminal on the Control Panel to a grounding rod (not included). The grounding rod must be an
earth-driven copper or brass rod (electrode) which can adequately ground the Generator.
3.Refer to local regulations for ground source information

[steve dunham]

Check NEC Art # 445 ( Generators) and Art #250 ( Grounding)
Normally portable generators used to feed cord connected equipment can be frame grounded . Grounding a generator can introduce hazards if not done properly .

[Raspy]

Steve,

That Harbor Freight warning seems like CYA, but having never grounded a generator, and always being suspicious of anything electrical from Harbor Freight, I'm curious.

When you did ground one for use with an amusement ride, did you ground the ride itself, or the generator as previously described with a conductor between the generator and a ground rod? I seems like a hot wire shorted to the frame could lead to a shock on the ride, or a trailer, that would not be protected by a generator ground if there is no bond between the frame and the neutral, or the amusement ride frame and the generator frame.

[Steve L.]

If I were asked about grounding a generator tied into my house I would probably give a different answer but I'm not going around pounding 4-6' copper rods in my camp sites. I've read what Steve refers (post 7)to but I've never checked deeply enough to understand the cautions.

[steve dunham]

I purchased a Champion dual fuel generator this week for our hunting cabin
Printed on the face plate of the generator is “ Neutral is floating” or IE ; Not grounded .
If you take a meter and read from the line output to ground you would read 0 VAC.

[steve dunham]

Originally Posted by Raspy

Steve,

That Harbor Freight warning seems like CYA, but having never grounded a generator, and always being suspicious of anything electrical from Harbor Freight, I'm curious.

When you did ground one for use with an amusement ride, did you ground the ride itself, or the generator as previously described with a conductor between the generator and a ground rod? I seems like a hot wire shorted to the frame could lead to a shock on the ride, or a trailer, that would not be protected by a generator ground if there is no bond between the frame and the neutral, or the amusement ride frame and the generator frame.

We grounded the generator , associated equipment and the ride .
We usually drove two ground rods 8 ft apart and bonded all exposed metal / conductive parts .
There was no half way with grounding , you were required to comply with all relevant code articles. Since these rides were open to the public ( read children )
the State of Minnesota ( Inspectors )were extremely cautious .
Many of these rides came out of the Southern USA where the codes were often not strictly enforced so there was often some heated arguments between the ride owners and the local inspection authorities.

[CarlD]

Steve is on the right track here. If the generator is grounded and you happen to be grounded and accidentally touch the hot wire you will get a shock. If it is not grounded you may still get a shock however it will be a small shock from capacitive coupling. The down side is if you touch the neutral wire or the floating ground you may also get a small shock. The amount of shock is dependent on many factors such as the total mass of the electrical system and moisture. Since most people know not to touch the hot wire and all metal enclosures of electrical equipment are supposed to be grounded it is better to have a grounded generator especially if it is wet out. In reality if it you are in a dry environment a shock from capacitive coupling is relatively small, most of the time undetectable and grounding the generator is not going to significantly reduce a shock hazard.


As a side note: Those handy little pocket testers used to check for voltage use capacitive coupling.

[Casita Greg]

Along a similar line to the "grounding" issue relative to small generators, is that certain EMS, (Electrical Management Systems,) which many people incorrectly call "surge protectors," have a problem of not allowing power from some small generators to enter the trailer due to it having sensed a lack of a ground. Some larger generators, which don't have "floating grounds," can run the trailer effectively through the EMS, but many small generators do have floating grounds, and thus, won't work unless you trick it into believing that a ground exists. One easy work-around is to buy a simple 120 VAC male plug, and install a short jumper between the White (larger blade) silver terminal screw and the green Ground screw. DO NOT HOOK EITHER END OF THE WIRE TO THE GOLD "HOT LEG" SCREW (SMALLER BLADE.) Just plug this into one of the unused outlets on the generator and it will fool the EMS into allowing the power to come in. Understand, this is not a ground, it is just a device to fool the EMS unit by making the generator appear to be grounded.

[Casita Greg]

This is a little description of the N-G bond plug that I wrote some time back which I posted on some forums:

Portable Inverter Generators and Neutral-Ground Jumper for RV Use
While we're on the subject of portable generators, all RV electrical systems are wired with their Ground and Neutral buses floated, (un-bonded from each other.) There’s lots of good reasons for this, most specifically 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 in the USA. Now, when you’re plugging your RV into power from a building, such as your garage outlet or a campground pedestal outlet, your RV has its Ground and Neutral buses “bonded” (connected) together externally as part of the service panel’s earthed safety ground system. Again, lots of reasons for this, but the fact is you can only have a single G-N bonding point according to the National Electrical Code and RVIA building codes.

So when your RV is powered by a portable generator, and if you have an inline voltage monitor system from a manufacturer such as TRC or Progressive Industries, (like the EMS-30 that I installed in my trailer,) your voltage monitor is checking for the Neutral and Ground voltages to be very close to each other, probably within 3 volts or so. This works well if you’re plugged into shore power that’s properly grounded and bonded, but this voltage protector can be tripped off by plugging your RV shore power plug into a portable generator without an internal Ground-Neutral bond. If you don’t have a voltage protection device on your RV, then you may never know that your generator has a floated neutral (un-bonded G-N bus).

Contractor-type generators, such as a Coleman 5000 for example, are generally G-N bonded internally, which is why it runs your RV just fine. However, many portable inverter generators from companies such as Yamaha and Honda (such as a Honda 2000i or EU3000 for example) have floated Neutrals (i.e. no internal Ground-Neutral Bond) since they expect an external G-N bond to happen somewhere else. And while RV-approved generators may have an internal G-N bond, it seems that many of the most popular portable inverter generators from Honda and Yamaha have floating neutrals. So your 2000i or your EU3000 isn’t providing the Ground-Neutral Bond that your RV requires to think it’s getting properly grounded power, while a Coleman 5000 has a Ground-Neutral bond already so it operates your RV properly. Seems crazy, but that appears to be the scenario.

It’s pretty simple to wire a special “Ground-Neutral Bond” jumper cable for your Honda or Yamaha generator which will allow you to power your RV through its voltage protection device. You can obtain or make a dummy 15 or 20 amp “Edison” plug with the Neutral (white) and Ground (green) screws jumpered together with a piece of 12 or 14 gauge wire. This G-N jumper plug can be plugged into one of the generator’s unused 20-amp outlets, and the entire generator’s electrical system will be N-G bonded. You can then use the other 20-amp Edison outlet or the 30-amp outlet to power the RV.

Just be sure to mark this plug specifically for its intended purpose. It won’t really hurt anything if it’s plugged into a correctly wired home outlet, but it will create a secondary G-N bonding point that could induce ground loop currents and create hum or buzz in a sound system.

So this is a generator-only G-N bonding plug which should be only plugged into a portable generator while powering your RV.

What's going on inside the plug? Jumper wire between the silver screw terminal and the ground screw terminal. Be careful not to hook to the gold terminal screw. (Which is the "hot" prong and can be easily determined by looking at the two power prongs. The "hot" prong (usually the black wire,) will be the smaller of the two blades on the plug and is the power supply. Do not connect to this one.

[Raspy]

Back to the real world safety of a non bonded portable generator for just a moment. I'm still wondering. If there is a short to ground between the hot from the generator to the trailer frame, or through the coffee pot to the ground in the 120 volt trailer system, and no ground exists through bonding to the neutral or to an external ground at the generator, is there a shock hazard? I thought there was a bond between the trailer neutral and ground, in the trailer electrical panel, but maybe not. It seems there would be a shock hazard, but it must not be a realistic threat, since small generators are not grounded or bonded. My Yamaha 2000 runs my 2015 Oliver just fine and charges the batteries like one would expect, etc.

If there can be only one bonding location, does that mean there is no connection in common equipment between the neutral and ground? In other words, is there no N-G bond on the microwave or the coffee pot or the electric heater? If there is no N-G bond and there is a short from hot to the equipment frame (microwave box), how is one protected? Does it matter that those pieces of equipment are designed for use in homes and not trailers?

[steve dunham]

Originally Posted by Raspy

Back to the real world safety of a non bonded portable generator for just a moment. I'm still wondering. If there is a short to ground between the hot from the generator to the trailer frame, or through the coffee pot to the ground in the 120 volt trailer system, and no ground exists through bonding to the neutral or to an external ground at the generator, is there a shock hazard? I thought there was a bond between the trailer neutral and ground, in the trailer electrical panel, but maybe not. It seems there would be a shock hazard, but it must not be a realistic threat, since small generators are not grounded or bonded. My Yamaha 2000 runs my 2015 Oliver just fine and charges the batteries like one would expect, etc.

If there can be only one bonding location, does that mean there is no connection in common equipment between the neutral and ground? In other words, is there no N-G bond on the microwave or the coffee pot or the electric heater? If there is no N-G bond and there is a short from hot to the equipment frame (microwave box), how is one protected? Does it matter that those pieces of equipment are designed for use in homes and not trailers?

The neutral ( grounded conductor) in the trailer’s electrical panel is isolated from
the trailer and the equipment grounding conductor
The equipment grounding conductor is isolated from the neutral and is bonded to the panel and the trailer frame .
The only place these two wire connect / bond together is at the service entrance.

The neutral of a generator floats ( NOT INTENTIONALLY OR EFFECTIVELY GROUNDED)
Refineries at one time used a 120/240 VAC system where the transformer’s centertap was not intentionally grounded ( Referred to as a floating neutral ) If you took a meter and read from line /hot to earth ground you read 0 VAC because the transformer was not referenced to ground
Your generator is also floating and is not referenced to ground !

[redbarron55]

The generator is a separately derived system and needs to be grounded at the entrance of the power.
The generator should be grounded as the RV will not be connected to the RV park ground and the power is not coming from the park power system.
Ground the generator and the frame at the point of entrance to the "dwelling" in this case the RV.
When I worked in industry we had some older three phase systems that were ungrounded delta and over the years one leg had been shorted somewhere in the miles of power system unintentionally and it made for interesting troubleshooting!
Other delta systems had one leg intentionally grounded so that is another leg were grounded it would trip the circuit protection.
The problem comes in the case of the trailer if the hot leg "grounds" to the neutral or frame and makes the frame hot.
In this case the feeding circuit breakers should trip for the protection of personnel.
Ground fault breakers work similarly in that they have two paths to ground. The proper path is from hot through the device to neutral and then back to where the neutral is bonded to ground at the entrance.
If there is more than 5 ma. of current imbalance in the hot and neutral path from the breaker indicating that current is going through another path to ground (and neutral) it will interrupt the power and trip for safety.
By the way the ground fault breaker does not need to have an ground (as in the old two wire wiring) it will still trip if there is a 5 ma. imbalance between the hot and neutral without the ground present, but it will not "Test" since there is no ground to provide the test imbalance going to it. You can make a test fixture for it by plugging a grounded plug with a wire going to a source of ground so that pushing the test button can have a path to ground.
In short if you add a ground fault breaker, even if the ground is not proper it will still protect.

[CarlD]

John,


Here is another description of these wires. The hot and neutral wires are current carrying conductors. The ground wire is not. Because a separately derived system contains the neutral to ground bond you can not have a second one in the trailer. If you do the ground wire and neutral wires are connected in parallel between the two bond points. This will cause current to flow in the ground wire raising the voltage at the trailer bonding point and every point down stream which could be a safety issue. This will also cause a ground fault circuit breaker in the generator (if it has one) to trip immediately.



The ground only exists to provide a low resistance path to earth potential to prevent the voltage of an enclosure from becoming too high for too long during a fault condition.



As I stated before it is not really necessary to ground your generator if it is dry out. If it is wet you may want to. The reason I say this is because electricity needs a closed path for current to flow. If it is dry the resistance between the generator and ground is quite high AND your resistance to ground is quite high so very little current will flow even if you touch the hot conductor. Under these conditions capacitive coupling will draw the most current which is in the microamp range.


As mentioned earlier the easiest way to ground the generator in a stand alone scenario is to use a SWGS type system (many short rods interconnected by a wire. This is what the Marine Corp uses on the radars we designed for them. Also, if you ground your generator and it is dry then you will need to wet the area where the ground rod(s) are located with salt water to reduce the resistance and make it effective. If you don't do this you might as well not ground it. Kidney filtered beer can provide salt water if necessary!

[Raspy]

Thanks for the thoughtful responses guys. Let me see if I can accurately summarize:

My takeaway from this is that if there is a short from the hot wire to the appliance frame (coffee pot), in a floating system with no ground, I will not be shocked with more than a very small current because there is no ground path. Or, if there is a GFI breaker in the circuit, it will detect an imbalance and trip, even if there is no ground. And finally, if the conditions are wet and I touch the coffee pot frame that has shorted to hot for some reason, there is a shock hazard because I become the grounding conductor. There can be only one ground-neutral bonding location because if there are two, the ground wire becomes a current carrying conductor that runs parallel with the neutral and will cause a GFI to trip or be unsafe if touched.

Is that right?

As far as ground rods go, I've wondered for a long time how the simple ground rod can be approved for grounding in dry rocky ground where it seems incapable of delivering much amperage to earth. But if I anticipate a grounding load, I can run out there and take a leak on the ground rod right before the event, but not during the event! I have a ground rod at my little cottage and after driving it in I could turn it by hand. On the main house, I built a Uffer ground system that seems like it would have far less resistance and far more current carrying capacity.

My whole house frame is very heavy iron posts and trusses bolted down with long J bolts tied to a full rebar array throughout the floor, stem walls and footings. Two 20' pieces of #5 bar come together at one location, from opposite directions in the footings, where they are bent up, emerge from the concrete and become the grounding point for the house service panel. This is the best grounding system I could come up with and it did away with the ground rod idea.

[redbarron55]

The steel rebars in the concrete pad is a very good ground, however code may still require the ground rod (a made ground) at the entrance to the house (electrical service entrance)
Tie the ground rod to that ground from the pad and you are good.
In industry we often create a grounding grid throughout the plant with many ground points. In each case we install a triad (three ground rods driven to refusal) and cad weld everything together.