What size conductors are needed for a 3 phase 800 amp service?

For a 3-phase 800 amp service, the conductor size will depend on various factors, including the type of conductor (copper or aluminum), the installation method, and ambient temperature. Generally, for copper conductors, you might need around 3/0 AWG to 250 kcmil, while for aluminum conductors, sizes typically range from 250 kcmil to 400 kcmil. It's essential to consult the National Electrical Code (NEC) and local regulations for precise sizing based on specific conditions and to ensure safety and compliance. Always consider factors like voltage drop and temperature ratings in your calculations.