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Q: What size wire for a 250 amp 3-phase breaker?
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What size wire do you need to run a 220 pump 40 amp breaker 130 feet?

This is a tricky question to answer without all of the information necessary for calculations. A motor has to have a breaker sized at 250% of the motor's full load amps. Wire is sized by the amount of amperage that it is allowed to carry.If the breaker is sized at 250% then the motor's full load amperage must be 16 amps if this is the case then the conductor for 16 amps at 130 feet will be #12 copper or #10 aluminium. the insulation rating for the conductors must be 90 degrees C.If the motor's full load amperage is 40 amps then the conductors, both copper and aluminium must have an insulation factor of 90 degrees C ad the wire size will be #6. The breaker for this pump must then be a 100 amp breaker. The larger size breaker is used so that it does not trip due to the inrush current when the motor starts. It could be in the range of 300 to 600% of the motors full load amperage.


Convert 262 mcm to AWG?

Using the AWG for wire sizes only goes up to 4/0. After that the increases use MCM to size the wire. So your 262 MCM wire size will be same in AWG. There is no 262 MCM in the North American market place. It goes in 50 MCM increments starting at 250 MCM , 300 MCM, 350 MCM, 400 MCM right up to 2000 MCM cable.


What size breaker is needed for a 125 hp motor?

It depends on what the amperage of the motor is. The motors amperage depends on the voltage of the motor. The higher the voltage the motor operates on the lower the amperage. So unless the amperage from the motor's nameplate is stated an answer can not be given.Just remember that the feeder capacity to the motor has to be 125% of the motors full load amperage and the breaker protecting the conductors to the motor has to be rated at 250% of the motors FLA. This higher breaker size allows the motor to start without tripping a normal size breaker that is rated for the lower conductor size.


LRA is 134 AMPS. what size breaker should be used?

LRA (locked rotor amps) is not used to calculate the breaker size. Breaker's are used to protect the size of the conductor that is connected to it. Motor calculations are based on the motor's FLA (full load amps).Conductor size is 125% of the motor's FLA.Breaker size is 250% of the motor's FLA.This is the only occasion when the breaker is sized larger that the conductors maximum amperage rating. This is due to the motor drawing up to 300 to 600% of its FLA when starting.If you state the motor's wattage, voltage or amperage this calculation can be calculated here.


What size aluminum wire for a 220v 200a service in conduit undrreground at 180 ft?

250 MCM aluminum minimum