Originally Posted by P-J
Well apparently you are not aware of the way clothes dryers and electric ranges were set up pre 2002 code changes. Or for that matter how a power feed is delivered to a barn and then setup for 240-120V power.
In trying to be a peacemaker, I'm wondering if both of your are right if viewed from different angles.
I don't know the NEC code, but I was trying to understand how the idea of creating a 4-wire circuit from a Spa Panel that's connected to a 3-wire Dryer outlet would be grounded. Somewhere in the Electrical Primer I read how appliances such as dryers and ranges got away with a 3-wire plug because the appliance is the ONLY thing on the circuit.
In the case of the 4 wire spa panel being "derived" from the 3 wire dryer receptacle, I'm wondering if the "purpose" of this is more to provide "protection" in lieu of a "true" ground.
In the case of this single appliance, the brew rig, that, like a dryer or range, contains both 220V and 110V circuits . . . if something happens that causes current to flow into the green wire in the rig, the GFCI inside the spa panel will detect this within the required amount of time and, as a result, trip the circuit. Even though the green wire between the e-control panel and spa panel isn't a "true" ground, it performs enough of the "function" of a ground wire to trip the circuit should current find its way to ground.
I still may be confused, but in my non-electrician understanding, it appears that grandequeso might be correct in the "strict" sense in that a ground that terminates onto the neutral away from the main panel is not truly a ground according to the Code, yet P.J. is correct in the "functional" sense in that this pseudo-ground wire will serve the purpose of giving the GFCI within the spa panel something to monitor such that if something abnormal happens to shunt current into the ground wire, it will sense it, trip, and thereby protect the brewer.
BTW, another question just hit me: if the spa panel is connected into the 3-wire dryer circuit and mounted outside the house AND you run a wire from the grounding lug inside the spa panel to a piece of pipe stuck into the ground, would you be "truly" grounded?