What is is the cable size for 400 amps breaker

The cable size required for a 400-amp breaker depends on several factors, including the distance between the breaker and the load, the type of cable, and the voltage of the system. Here are some general guidelines:

• For a 400-amp breaker, the minimum recommended cable size is typically 4/0 (0000) AWG (American Wire Gauge) or larger. This is because 4/0 AWG cable has a current-carrying capacity of around 400 amps.
• However, if the distance between the breaker and the load is longer than 100 feet (30 meters), a larger cable size may be required to ensure that the voltage drop is within acceptable limits. In this case, a 250 kcmil (kilo circular mil) or larger cable may be required.
• If the system voltage is higher than 600 volts, a larger cable size may be required to ensure that the cable can handle the increased voltage.
• It's also important to consider the type of cable being used. For example, a cable with a higher temperature rating (such as THHN or XHHW) may be required for applications where the cable will be exposed to high temperatures.

Here are some examples of cable sizes that may be suitable for a 400-amp breaker:

• 4/0 AWG (0000) THHN or XHHW cable: This is a common choice for 400-amp breakers and is suitable for most residential and commercial applications.
• 250 kcmil (kilo circular mil) THHN or XHHW cable: This is a larger cable size that may be required for longer distances or higher voltage applications.
• 350 kcmil (kilo circular mil) THHN or XHHW cable: This is an even larger cable size that may be required for very long distances or high-voltage applications.

It's important to note that these are general guidelines, and the specific cable size required for a 400-amp breaker may vary depending on the specific application and local electrical codes. It's always a good idea to consult with a licensed electrician or electrical engineer to determine the appropriate cable size for your specific application.