Wiring a 50-amp, 240-volt, double-pole circuit breaker is a relatively easy project, even for the beginner, but you do need to understand how to apply the rules and the tables found in the National Electric Code (NEC), so that your wiring meets the NEC standards. Also, you will need to apply for a wiring permit from the municipal building department before undertaking this project.
Turn off the main service disconnect and remove the cover to the service panel. Install the new circuit breaker. This breaker, depending on the make and model of panel that you are working with, may simply snap in or you may need to secure it to the Buss Bars by screws.
Remove a knockout from the side of the panel box by first using a screwdriver and hammer, drive it to a horizontal position and then wiggle it back and forth with Lineman's pliers until it snaps free.
Insert the cable connector in the hole left by the knockout that you removed. Secure it in place by screwing the lock nut tightly against the inside of the panel. Once finger tight, drive the lock nut an additional 1/4 to 1/2 turn using a screwdriver and hammer.
Route the cable from the panel box to the outlet box where you will connect the load. Route the cable along the sides of floor joists and wall studs and through holes drilled through them. Drill 5/8-inch diameter holes so that the near edge of the holes are at least 1 and 1/4 inches from the near edge of the framing members. Support the cable where it's run along the face of studs and joists with staples at intervals not exceeding 48 inches.
Cut the cable long enough so it will extend to the bottom of the service panel and at least 8 to 10 inches into the room where you will connect the load. Insert the cable into the service panel and secure in place by tightening the clamping screws on the cable connector.
Remove the cable's outer jacket with the razor knife being careful to not damage the insulation on the individual wires.
Route the white neutral wire and the bare copper grounding wire neatly down to the panels neutral and grounding bars. Cut them off as necessary to keep them neat. Remove 3/4 inches of insulation from the neutral wire with the wire strippers. Secure them using an empty compression hole connector.
Attach the red and black insulated wires to the terminals on the circuit breaker. Be careful when stripping wires to not nick them or cut grooves in the copper. Grooving them will create weak spots in the wire. Inspectors will make you redo any connection if they detect such damage.
Cap off the red, black, and white wires on the load end of the cable until you are ready to connect the load to be served by the cable. Tape the wire nuts in place.
Lock the new breaker in the off position. Turn on the main disconnect. Call for the required inspection before closing up panel.