I have a question that I am struggling with. If an electrical service panel is not grounded properly and I have a hot wire that shorts against the panel box, am I to assume that a person can be electrocuted and the fuse or breaker will not trip
Short answer is yes. Are you an inspector?
No not yet. Getting ready to take the National Exam.
Let’s look at that question a little deeper…from a CMP 5 perspective shall we.
Here was the question “If an electrical service panel is not grounded properly and I have a hot wire that shorts against the panel box, am I to assume that a person can be electrocuted and the fuse or breaker will not trip”
I think if you substitute the word “grounded” for the term “bonded” then you would be more accurate. If many conceive the notion of “grounded” to mean something associated with the Grounding Electrode System with ground rods and such then the answer would be NO…but if you ensure that a Main “Bonding” Jumper is properly installed and the “grounded” conductor is intact…then an OCPD will serve it’s roll.
Yes the potential is there. Remember, the current is going to be looking for ground. So if you are the grounding source yes. If you are lucky and the circuit is on a GFCI breaker the breaker should trip.
That being said, my rule of thumb is always assume there is something wrong with a panel until you rule it out. I always touch a panel cover initially with the back of my hand. IF the panel is hot your muscles will contract and pull away. DON’T just grab the panel latch and pull.
Ad as I am sure you know you should NEVER have an ungrounded panel.
Hope this helps.
Current is never looking for “ground” my friend. Current is a result of electron flow and resulting differences of potential. The current theoretically is looking to return to the source of its creation…ie Transformer, Generator…and so on.
Current is never looking to get to ground specifically. When we provide an effective ground-fault current path we are simply providing one path (of many paths) that would constitute a low-impedance path for the elevated current to flow back to the source…and allow the OCPD to activate accordingly. You break that path or provide an inefficient path then you risk OCPD’s not activating or lagging in their activation.
The current want to complete its path so it can get back to the source. So given the generator or transformer is grounded at the far end, the current needs to get back there.
In the scenario described the hot panel case and the person touching it will complete the path (circuit) for current to get back to its source through the ground. So yes an electric current could flow through your body, since you now serve as the wire between the hot panel case and the ground. In other words YOU completes the path (circuit).
The resistance of earth is too high to complete the path back to the source and trip a breaker. You can place a hot directly on a ground rod and probably never trip the breaker. You will receive a shock due to the potential difference.
As Paul said, the breaker needs the neutral bond to trip the breaker.
The OP had two questions instead of one as he said.
Am I to assume that a person can be electrocuted and the fuse or breaker will not trip?
I was answering the portion about the electric shock. Breaker would not trip but the free electrons in his body would start moving in an organised way.
I came across this youtube video that has a helpful summary of some of the info you’re looking for. https://www.youtube.com/watch?v=7mtROtuUwfA