Circuit Breaker Derating Guidelines

Recommended Circuit Breaker Stress Factor

Contact Application .. Contact Derating Factor
Resistive0.75 percent

Circuit Breakers should be operated at 20C below the maximum temperature specified.
Derating Factors [the numbers shown above] are used for many components and just mean that for a given application, the component should be derated by some percentage from its maximum operating limits. A dearting factor is always given in a percentage.

In this particular case the maximum limit to be controlled is current. So the recommendation in this case, for this component, is to never operate the device in a system that would require 100 percent of the current handling ability of the device. In other words, using the example above, if a circuit breaker is being used in a system with a resistive load, the load should be no greater than 75 percent of the maximum current the circuit breaker is designed to handle. So, for proper design never use a circuit breaker that indicates a 100 amp current rating in its data sheet for a circuit that requires 100 amps.
Unless indicated, contact current is assumed to be resistive.

Cut-away Circuit Breaker Drawing

Design Tags:
Rated Operating Temperature,
Maximum Rated Current,
Best Practices in circuit design

Related Vendor Topics;
Circuit Breaker Manufacturers
Fuse Manufacturers
Fuse Holder Manufacturers

Derating guidelines for components;
Recommendations on Derating Components

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Modified 6/13/15
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