When do I need a neutral on a 240V branch circuit?
A nema 6 outlet has two hots and a ground, it is used for pure 240V equipment.
A nema 14 outlet has two hots, a ground and a neutral. It is used for equipment that has both 120V and 240V components.
A nema 10 outlet nominally has two hots and a neutral but no ground. However in practice the neutral pin is used as a combined neutral and ground conductor. Nema 10 outlets are forbidden in new work, but existing range and drier installations that were correctly installed to the code of the time are grandfathered and new appliances can be fitted with 3 wire cords and nema 10 plugs for connection to existing installations.
Combining the neutral and ground functions is problematic because if the combined neutral and ground wire breaks, the appliance case will become live. The system is therefore not &quot;single fault safe&quot;.