Lots of misunderstanding here. Let me try to simplify it:
Back in the 2 prong days, ground was indeed tied to neutral. So the chassis would be tied to the neutral. If it wasn’t, then if a hot wire touched the chassis, the chassis sat at 120V and shocked you. Some components were wired like this. Us old guys remember that often you’d get a shock from a metal part. Now we still have some 2 prong plugs, why? they are generally on simple components and the UL code allows 2 prong if they have double insulation and meet certain requirements. and I haven’t been shocked by them.
The neutral "theoretically" doesn’t need to be tied to ground. it goes all the way back to the power plant and completes the circuit....but for various reasons, if you don’t tie it to ground, it can float above ground. So your 120V outlet turns out to have 190 volts on the hot wire and 70 volts on the neutral wire (I just picked 2 numbers). So if everyone ties their neutral to ground, that never happens, and it was codified.
Problem is, with multiple unbalanced loads on a circuit, especially a long and fully loaded circuit like we used to see more of, the neutral can float above ground in certain locations locations in the house, even if tied too ground in at the box. So now maybe your chassis has 10V on it and gives you a little tingle when you touch it.
So we went to 3 wire. The ground has one function, to keep the chassis or other grounded points well connnected to a 0V ground so that if a hot wire touches the chassis, you have a path back to ground and breaker will trip (usually). a bad connection to the chassis can result in less current than will trip the breaker and you have constant current flow to ground. In this case there will be very little voltage on the chassis, just the voltage loss back to the ground. since ground wires are generally robust, that should be less than a volt and not dangerous. But if you have wet feet standing on a concrete floor you can make a good path to ground and get shocked in this scenario. that doesn’t happen very often. Safety has some components of probablility.
Now if you had seperate ground rods in the earth for neutral and ground, everything will work the same. But theoretically, the circuit sould be back to the power plant, not to ground. so I'm sure the code requires the ground to be tied to the same ground rod as the neutral.
Jerry
