Things You'll Need
A NEMA 6-50 plug has two straight hot prongs, running parallel to each other, and a horseshoe-shaped ground prong. The hot prongs on the 6-50 have different widths, with the large prong on the right. A NEMA 6-50 plug connects to a 250-volt 50-amp electrical circuit. A 50-amp electrical circuit needs 8-gauge or larger wires. The NEMA 6-50's round face measures 2-1/8 inches across, and it mounts in a standard wall-mount electrical outlet box. Some appliances, like electric welders with a 3 horsepower rating, connect to its power source with a NEMA 6-50.
Remove 3/8 inch of the insulation of the wires entering the NEMA 6-50 plug with either wire strippers or a utility knife. Often wire strippers will not work on the large braided wire that usually feeds a NEMA 6-50 plug.
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Loosen the NEMA 6-50 plug's wire terminal screws with a slotted screwdriver. Do not remove the screws.
Insert the ground wire into the NEMA 6-50 plug's ground terminal. The 6-50's ground terminal has a green screw. If the wire set has a black, red and white wire, use the white wire as ground. Otherwise, the wire set's wire without insulation or the wire with green insulation acts as ground.
Insert the stripped end of the black wire into the NEMA 6-50 plug's left-side wire terminal -- the terminal that connects to the small prong. Tighten the terminal screw with the screwdriver. If both remaining wires have black insulation, choose either wire.
Insert the end of the remaining wire into the NEMA 6-50 plug's remaining wire terminal -- the terminal that connects to the large prong. Tighten the terminal screw with the screwdriver.