If you are installing a 50 amp circuit breaker, the size of wire you should use depends on the allowable ampacities of the aluminum and copper wires. Based on these ampacities, you should use 6 AWG copper wires or 4 AWG aluminum wires for a 50 amp circuit breaker that runs for 100 feet or less. For runs larger than 100 feet, you should account for voltage drop and use larger cables. For example, you should use a 3/0 AWG copper wire or a 4/0 AWG aluminum wire for a 200ft cable run.

Its important to note that 8 AWG copper wire and 6 AWG aluminum wire are not recommended, despite having the 50 AMP-60 AMP ampacity rating, because the National Electrical Code (NEC) states that the maximum loading capacity of the electrical circuit should not exceed 80% .

If you are running a 50 amp RV plug, the size of wire you need will depend on the amperage requirements of your RVs 2 A/C unit and voltage of your electricals. For a 300-foot run, you will need to upgrade to 4 or even 2 gauge wire.

In summary, the size of wire you need for a 50 amp circuit breaker depends on the allowable ampacities of the aluminum and copper wires, the length of the run, and the amperage requirements of your appliances. Here are the recommended wire sizes for a 50 amp circuit breaker:

• 6 AWG copper wires or 4 AWG aluminum wires for a 100-foot run or less
• 3/0 AWG copper wire or 4/0 AWG aluminum wire for a 200-foot run
• 4 or even 2 gauge wire for a 300-foot run