3 Phase Circuit Breaker Rating Chart

Circuit breakers are designed to carry 100 of their rated current while the nec dictates an 80 application.

3 phase circuit breaker rating chart. Full load current and circuit protection data for three phase ac motors. 75 c rating 30 c ambient wire size awg no. The next size up is 70a. Remember that 80 is the inverse of 125 0 80 1 divided by 1 25 and as such the rules are indeed identical in their end requirement.

Note that some types of single phase loads are routinely supplied by a 3 phase panel. Conduit sizes are for three conductors per circuit for three phase motors and two conductors per circuit for single phase and dc motors. If equipment terminations are rated for 60 c conductors only the 60 c ampacities. Maximum loading for any branch circuit is 80 of rating of circuit for ampacity of wire for any load.

A 3 poles circuit breaker can be used on 3 phase system using either 2 or 3 poles. A single phase circuit breaker can t be used for three phase supply voltage levels. Tripping characteristics bs en 60898 type b. A 3 poles circuit breaker can be used on 1 phase system only and only if indicated by the markings or instructed by user manual.

Wire size chart and maximum amp ratings. The wire size chart below shows allowable ampacities of insulated conductors rated up to and including 2000 volts 60 c through 90 c 140 f through 194 f not more than three current carrying conductors in raceway cable or earth directly buried based on ambient air temperature of 30 c 86 f. If your total 3 phase load in a 480v system is 50 000va what size breaker do you need. This applies to not more than 3 phase conductors in 1 conduit.

Use the correct size breaker. For 3 phase loads you divide the va by the nominal voltage and by the square root of three approximately 1 732. 1 25a 25mm 2. 50 000va 480v 1 732 60 2a.

Warning voltage drop nec 310 16 wire ampacity tables do not take into account voltage drop only thermal limit. Nec 220 2 use nec 310 16 for ampacity. Conduit sizes may need to be increased if equipment grounding conductors or neutrals are also installed in the conduit. Miniature circuit breakers ratings 1 to 63a breaking capacity 15ka 13 c60hb type b 3 5in applications protection and control of circuits against overloads and short circuits.

Magnetic setting between 3 and 5 in. The chart below displays information for motor wire size breaker size thermal overload ratings and other data for three phase ac motor circuit protection.