That's what I'm saying. You can't get shocked by a ground fault on an ungrounded tool plugged into an ungrounded generator. But if you use a three wire cord that has a EGC bonded to the neutral in the generator, you have now forced yourself into contact with a wire referenced to the neutral.
So what is the fault path, even if you touched the hot? (Assuming you were not touching the ground/neutral). You are sitting in the dirt, the generator is up in the air. There is no fault path touching any single conductor. That same theory is at work in ungrounded delta that you might see in a critical application. You also see it in the little plastic box generators like the 2kw Honda. They may not bond the neutral and they get away with it because the generator is insulated. The ground at that point is antenna. OSHA says you have to put the bonding strap back. Any metal frame generator like you see on the job site is assumed to be potentially grounded by incidental contact so they do bond the neutral. If you connect to a ground electrode, you are an SDS. Rubber tire generators are like that Honda but 250.34 still says they bond the neutral. Bonding the neutral really only causes the breaker to trip but if the generator is truly isolated a phase to tool handle short is not going to kill you. Just don't cut the ground pin off and use it on a grounded system,
I see that this thread has developed quite much. I hope we may aggree in that electricution is dangerous! If you are insulated from ground, or other poles in the system you should be pretty safe. If the Generator (or transformer) is ungrounded, and well isulated from ground, both wires N an L will have a capacitive connection to ground, and the wires are twisted, they will have approxematly the came capacitive value, even with a looooooooong wire. The voltage measured between the wires and ground will be close to the half of the value measured between the wires. The current that may be possible to get between a wire and ground may increase bye the amount of wires in the system, and at a point it will be dangerous to touch ground and a wire. A GFCI close to where you are will protect you pretty good. This is one of the risks with the Norwegian system. 230V and no Neutral.
Last edited by dsk; 03/31/2405:49 AM. Reason: spelling
The service outlets in IBM mainframe machines were derived from an ungrounded secondary so on a scope, the two ungrounded conductors were roughly 60v above ground but the EGC was connected normally. Touching either conductor might give you a slight tingle but barely even noticeable. Certainly not enough to operate a GFCI. In the 360 days and before, the design specs were that no neutral was even brought to computer room panels. All loads were line to line, either 240 or 208, depending on the service.(delta or wye). The insulated neutral bus was used for the isolated ground that was only tied to the GEC in the service disconnect enclosure. All of that IG foolishness went away in our design specs in the early 70s when the 370 line was introduced. The legend that it actually fixed anything went on long after that. It turned out the "noise" they were trying to isolate was actually coming from the switching power supplies in our machines, not elevators fluorescent ballasts or any of the other usual suspects. I am not sure we ever admitted it tho. Anyone with an AM radio figured it out pretty fast.
I'm not arguing against any of that. I think my point is being missed because I'm not good at explaining things. My point, ultimately, is grounding things doesn't necessarily make them safer, much as ungrounded things doesn't necessarily make them dangerous. I sometimes get calls from customers about home inspections that note ungrounded receptacles. As much as I would like to say just rewire the house, honesty wins. I told one recently that it be ideal to have new wiring, but the reality is that it would be really hard to get shocked on a carpeted floor inside a house.
Add to that most equipment doesn't have a ground pin anyway. I lived the first 15 year of my life with 2 pin (NEMA 1-50) receptacles and never really even noticed.
My point, ultimately, is grounding things doesn't necessarily make them safer, much as ungrounded things doesn't necessarily make them dangerous.
One of the problems grounding the metal frames of residential lighting and appliances was supposed to address is Residual Current Leakage (RCD) or 'ground fault' conditions where a metal housing could be elevated to a voltage where touching it with wet hands could result in more than the amount of 'let go' current running thru a person.
In Europe and Japan they have more types of grounding systems than Canada & the US. But no matter what system they use they all employ RCD detection in all the branch circuit breakers. Given the RCD thresholds being equal in both systems there may not be much difference between grounded and ungrounded systems.
With 'standard' US and Canadian breakers that have no RCD protection a grounded system would be safer, as that offers a default RCD level thru the equipment grounding wire only.
For example if you have say a 5ma/25/ms RCD protection (AKA GFCI) gounded and ungrounded systems are the same and I think a 2-prong NEMA 1- or 2- receptacles would be just as safe as 5- and 6-
Interestingly Siemens and Eaton both manufacture a 'GFPE' breaker that has a 30ma/2000ms trip level, per some obscure super outdated UL standard. They can be identified by their 'red' test buttons.
If UL or CSA updated the standard for breakers to the more modern IEC standards for RCD 30ma/25ms they might be a good option for 2-prong NEMA 1- and 2- ungrounded receptacles and 240V equipment. But for now in the US the only RCD is a 5ma/25/ms UL Class A GFCI, which seems to nuisance trip due to the low 5ma trip level for wet locations.
However since per the NEC article 110.7, no proper functioning circuit should have "short circuits, ground faults, or any connections to ground other than as required or permitted elsewhere in this Code." thus not more the 30ma flowing on the Equipment ground (Earth Leakage) I am not sure why this GFPE breaker has not replaced the standard breaker (non GFCI ) where a standard breaker is permitted. At least in dry locations or fixed equipment in dwelling units.
I am familiar with the RCD systems and when NFPA gets done, I think our solution will be better but more expensive. Between the GFCI and AFCI that incorporates GFPE protection, every circuit will be protected. The main advantage is, when you get a ground fault, the whole house doesn't go black. That might be an Easter Egg hunt most of us would like to avoid. In most cases you will be in eyesight of a GFCI you tripped..
