3 Phase Circuit Breaker Rating Chart

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.

3 phase circuit breaker rating chart. This applies to not more than 3 phase conductors in 1 conduit. 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. The chart below displays information for motor wire size breaker size thermal overload ratings and other data for three phase ac motor circuit protection. Conduit sizes may need to be increased if equipment grounding conductors or neutrals are also installed in the conduit.

For 3 phase loads you divide the va by the nominal voltage and by the square root of three approximately 1 732. Warning voltage drop nec 310 16 wire ampacity tables do not take into account voltage drop only thermal limit. Full load current and circuit protection data for three phase ac motors. Tripping characteristics bs en 60898 type b.

Magnetic setting between 3 and 5 in. Wire size chart and maximum amp ratings. 1 25a 25mm 2. Maximum loading for any branch circuit is 80 of rating of circuit for ampacity of wire for any load.

Circuit breakers are designed to carry 100 of their rated current while the nec dictates an 80 application. 50 000va 480v 1 732 60 2a. A single phase circuit breaker can t be used for three phase supply voltage levels. The next size up is 70a.

Conduit sizes are for three conductors per circuit for three phase motors and two conductors per circuit for single phase and dc motors. 75 c rating 30 c ambient wire size awg no. A 3 poles circuit breaker can be used on 3 phase system using either 2 or 3 poles. This rule states that an ocpd can be loaded to only 80 of its rating for continuous loads.

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. Use the correct size breaker. If your total 3 phase load in a 480v system is 50 000va what size breaker do you need. Dual element time delay ul class rk5 fuse used with properly sized o l relay circuit breaker instantaneous trip circuit breaker continuous amp rating single phase units 115v 8 4 14 15a 15a 208v 230v 4 4 4 2 14 8a 7a 7a 115v 11 12 15a 15a 208v 230v 5 5 5 4 14 12a 10a 15a.

In applications with general load characteristics. Nec 220 2 use nec 310 16 for ampacity.