You are an electrician working in a industrial plant.The company is constructing a maintenance shop located 225 feet from the main plant electrical system.You are to install a 400 ampere three phase wire system in the new maintenance shop.The service is supplied by the existing plant service.The voltage is 480 volts and the voltage drop is to be kept at 3% or below at full load.The conductors are to be aluminum.What size conductors should be install for the new service?

 

There is missing information such as required maximum demand for the installation, allowable voltage drop and whether the cables are enclosed or buried etc....

 

Depends on the amperage your needing to supply, what electrical code calls for, and some headroom calculation in the event additional amperage is needed due to future equipment upgrades.

Also, if a lot of amperage is required, it might be better to run high voltage wire to the shop area and then feed it into a step down transformer.