Wiring a 3 prong 220 plug

[Tomeod00]

I am wiring a 3 prong 220 plug in a feeder panel with 12/2 wire. Should I hook the ground wire to the ground bus or to the neutral bus? The neutral bus is isolated from the ground bus and the panel box.

 

[Lucien Nunes]

Exactly what kind of outlet are you connecting?

If it is a NEMA 6 type which is a pure 220 or 240V outlet, then the centre prong is a ground which should be wired with the green / bare conductor and connected to the ground bus. There is no neutral in this type, only the two hots and ground, so it has no 120V functionality.

The historical NEMA 10 type (dryer) outlet which also had three prongs, was designated for 120/240 V circuits. The centre prong was the neutral and would be connected using the white wire to the neutral bus. There was no ground in this type, although it used to be permitted to borrow the neutral to ground the dryer chassis. This is no longer permitted.