Since we are taught that neutral and ground should only be on the same bus on the main disconnect, not even on the same lug, what are we supposed to say about bootlegging the ground to the neutral on a stove or dryer per manufacturer instructions on a 3 wire plug?
If the neutral shorted out wouldn’t the frame become energized ?
In a distribution panel/sub panel on a house or condo the neutral and ground are on separate buses. Why is it ok to combine the neutral and the ground on a 3 wire and plug it into a outlet in these instances?
It seems to me that the 3 wire plugs are very unsafe and I don’t see how they can even be used on a condo that has a distribution panel. Maybe I’m making a mountain out of a mole hill?
But how should I list these as a defect of at all?
For all listed appliances, you ALWAYS follow the manufacturer’s installation instructions.
If the appliance is straight 240V (i.e., no 120v clock/timers, etc.) there will be no current on the grounded/neutral conductor unless there is a fault.
Since the 1996 iteration of the NEC (IIRC) dryer circuits/plugs require four conductors, prior to that they had only three.
If a listed appliance is installed/wired in accordance with its installation instruction, it is most certainly NOT a defect. I do mention when there is an older three prong dryer receptacle because the client will need to purchase a three-prong cord retrofit kit if they buy a new electric dryer, but it is not a defect unless it’s of later vintage.
The reason you do not combine them downstream of the service equipment is that the equipment ground is intended for fault currents only. When combined downstream of the service equipment, you cannot prevent the ground/neutral return current from being carried on the equipment ground. In the case of a single phase 240V appliance, there is no current on the ground/neutral because the two 120V legs are 180° out of phase with each other and in the case of a three wire installation, there is no egc to carry it anyway. The ground/neutral is the only conductor available.
You may wish to consult an electrical engineer or research yourself for a more detailed explanation, however, as the NEC states: For listed appliances, the manufacturer’s installation instructions must be followed, regardless of whether it comports with your understanding of the prescriptive standard.