Function of Portable Generator Outlet Ground

Hello, all. As most portable consumer-grade AC generators don't have their grounds (frame and ground prongs on their mounted AC outlets)
bonded to their neutrals, I was wondering what useful function having a 3-prong U-ground outlet on the genset performs (other than mating with appliance and extension cords). In a residence having the neutrals and green (grounding) wires connected together at the service entrance ensures that hot wire-to-exposed metal frame appliance faults (assuming appliance is using a 3-wire cord) will trip the appropriate panel breaker/fuse. This would not appear to be the case when using the portable generator. I'm only assuming that the generator is servicing 3-wire plugged-in appliances. I don't think it's a shock issue outdoors if a hot-to-ground fault in the appliance occurs, it may continue to function normally until it's subsequently plugged into a residential/commercial AC power outlet.
Of course the equivalent action in the residence could be had by bonding the generator's neutral to its frame ground. Your time and comment is greatly appreciated. Sincerely,
--
J. B. Wood e-mail: arl snipped-for-privacy@hotmail.com

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On Thursday, January 3, 2019 at 10:10:18 AM UTC-5, J.B. Wood wrote:

I came up short at your first assertion. In my 55 years of doing various forms of local power production installs I don't remember finding one off the floor portable generator were the neutral was not bonded to the frame.
--
Tom Horne

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On 1/4/19 12:35 PM, Tom Horne wrote:

Hello, and many thanks for replying. I think many of the Champion and Honda models have floating (unbonded) neutrals. The ground prong of the genset's utility outlets are still connected to its metal frame, however. If the frame of a bonded neutral generator is also connected to a conductive ground (e.g. earth via a driven ground rod), then the "hot" terminal of the genset is also "hot" wrt to earth. We now have increased the possibility for electrical shock when using an appliance with an exposed metal frame/shell without an intact ground (green wire) return to the genset to carry fault current. Sincerely,
--
J. B. Wood e-mail: arl snipped-for-privacy@hotmail.com

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wrote:

Honda inverters did not used to. Not sure about now but I think it makes the problem worse. Why would you create an extra path to kill someone if it did not exist before? (think ungrounded delta) They all have instructions to lift the ground if this is not going to SDS transfer equipment.
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On Friday, January 4, 2019 at 7:46:29 PM UTC-5, snipped-for-privacy@aol.com wrote:

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s forms of local power production installs I don't remember finding one off the floor portable generator were the neutral was not bonded to the frame.

If there is no connection between the Neutral and ground then the voltage r elative to ground is unknown and more importantly a fault between the energ ized conductor and ground does not create a shock hazard beyond a small cap acitive effect. If there is no path back to the generator winding from the earth because the neutral point of the winding is not connected to the ear th then in one sense there is a lower risk of an injurious electric shock.
I will admit that I never checked the bonding on the Honda Inverter Generat ors because I have never had to use one that was connected to a building wi ring system were the National Electric Code has specific requirements about the presence or absence of the neutral bond that have to be matched to whe ther or not the transfer mechanism transfers the neutral.
I find your experience with some of the Honda Inverter generators not havin g a bonded neutral disconcerting because without that bonding jumper there is no effective fault current pathway back to the source. I guess that it is fortunate that I always use a plug in Ground Fault Circuit Interrupter ( GFCI) cord set between Inverter generators or Inverters and the loads they supply. That is why we have to use Full Sign Wave Inverters. Cord set GFC Is cannot tolerate a non sinusoidal wave form without tripping.
Now I'm going to have to check the Honda Inverter Generators to see if they are bonded and correct that if they are not. Even if the GFCI protects th e user from an electrical injury that will not protect them from a startle reaction injury; which are a lot more common than most users are aware of; that may result from the brief shock sensation they would experience while the GFCI is tripping.
In all cases I want the Over Current Protective Device (OCPD) or the GFCI t o have opened the circuit in response to any current fault prior to any liv ing thing experiencing any degree of shock.
--
Tom Horne

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wrote:

The main reason we ground utility power is to deal with line transients like lightning strikes. This not much of an issue with a small portable and avoiding any ground connection at all is safer because there is no ground fault hazard. If the ground connection is not there I also see little advantage in bonding the neutral. I suppose you could do this
http://gfretwell.com/electrical/portable_generator_ground.jpg
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snipped-for-privacy@aol.com wrote in

I think that a genset must operate similar to a ground fault interruptor.
If a current gets detected on the fault return, the breaker for the generator feed opens.
Yes? No?
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On Sat, 5 Jan 2019 17:43:44 +0000 (UTC), DLUNU

If you bond the neutral and ground the generator a GFCI would work but without either of these, there is no way to create a ground fault. You could certainly create a fault from the ungrounded or even the grounded conductor to the EGC (center pin on a plug) as long as the neutral was bonded to the frame of the generator but if the generator is not grounded there is no fault path to earth. In my opinion that is safer than setting this up as an SDS (Talking about a "portable" generator. If it is fixed in place, you do need to ground the EGC. At that point we star asking about transfer equipment and the number of conductors that are switched to see if you bond the neutral.
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On 1/5/19 11:52 AM, snipped-for-privacy@aol.com wrote:

Hello, and as I pointed out previously (I don't think this is rocket science), having the neutral (one side of the voltage source) bonded with the EGC promotes tripping of the genset breaker if the "hot" wire should fault to the metal enclose of an appliance connected to the genset via a 3-wire cord (hot, neutral & ground wires). It can be a safety issue if the genset frame is also connected to a conducting ground plane (e.g. earth) and the EGC (green wire) from the genset is not intact to the appliance. In that case we could have line voltage existing between the appliance metal enclosure and the ground plane. Of course how much fault current would flow through the human body depends upon a number of factors such as soil resistance, distance from the appliance to the earth-grounded genset, etc. Sincerely,
--
J. B. Wood e-mail: arl snipped-for-privacy@hotmail.com

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On Mon, 7 Jan 2019 06:57:50 -0500, "J.B. Wood"

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All of that assumes the generator is grounded. Those little Hondas have a plastic can. I am not sure how you would ground one with a purpose built lug and a grounding electrode of some sort. Even my 5.5KW metal frame Briggs is sitting on rubber tires and rubber pads. If the neutral was not bonded and you did have a short to the EGC, I still do not see the fault path, even in the frame was grounded. Isn't that the object of using ungrounded isolation transformers in labs? There is no fault path to anything except the other side of the transformer.
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On 1/7/19 11:12 AM, snipped-for-privacy@aol.com wrote:

Hello, and that's because in that case there wouldn't be a fault path with a floating/unbonded neutral (not counting capacitive coupling, which is presumed to be inconsequential (but can be an issue on Navy ships, but that's another story). Sincerely,
--
J. B. Wood e-mail: arl snipped-for-privacy@hotmail.com

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On Mon, 7 Jan 2019 12:18:37 -0500, "J.B. Wood"

I am familiar with navy ships. I suppose that is why they use ungrounded delta for most if their distribution. They call the 120v "the deadly shipmate" because the neutral is bonded to the hull of the ship .
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snipped-for-privacy@aol.com wrote in wrote:

Consider this scenario:
Your device is a machine with a metallic case and that case is tied the what would be the neutral side of the 120V line cord. The third conductor in the line cord is what the industry terms as "the fault return line" and is designed to carry currents from an accidental "hot to case" failure mode inside the product during use. That is either supposed to cause a circuit breaker trip in the feed for the branch you are connected to, or at the very least clamp the voltage that would suddnely be [resent on the case with respect to Earth ground, where that power feed ties its "nuetral" side connection to earth. This protects users of AC powered electrical shock. It ONLY does this BECAUSE of the fact that the grid and all power has ground based fault return systems built in to the design.
A portable generator, ON THE OTHER HAND, does NOT tie either leg of its NON center tapped 240 AC feed to ground. It generates a fully floating AC power 'signal'. If there was a case where, as in the above example, a device with its "nuetral" attached to its case, experiences a situation where its internally connected "hot side" makes contact with the device case, and thereby the operator of the device. With no connection to earth, where is the danger that the operator is going to have a "hot" in one contact point and the earth in another (bare feet on concrete). Without the ground fault tie in this case, there would be no path to cause harm to the operator. Earth ground is not noly NOT a path for said fault, it is also not a path for the power feed, and is thereforee not how ANY gen set ground fault could or should be handled. Any that do will ALSO have a full transfer switch set up to the grid and standard AC power system.
For the most part if one side of the pair touches the other in a dead short (product case fault), the generator circuit interruptor should instantly trip.
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On 1/7/19 2:39 PM, snipped-for-privacy@aol.com wrote:

Hello, and sorry but that's incorrect (at least in the U.S. Navy). Neutrals (either from single or 3-phase generators) are never grounded (connected to the hull) on U.S. Navy ships (unless a fault occurs). This is to promote the operation of systems under electrical fault conditions (sometimes referred to as "battle short"). The ground prong, for example, on shipboard 120 VAC outlets is connected to the hull but unlike a residence connection if you were to measure the voltage with a high impedance voltmeter from either "hot" or "neutral" to ground you would observe 60 VAC. Because of capacitive coupling through equipment you still have to consider these voltages as potential shock hazards with respect to the ground plane (i.e. the steel hull). Sincerely,
--
J. B. Wood e-mail: arl snipped-for-privacy@hotmail.com

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