Selection and Application Considerations for 100-Percent Rated Overcurrent Protective Devices

One hundred percent continuous load rated overcurrent devices are becoming more popular. Although for a specific current rating these devices usually cost significantly more than standard overcurrent devices (rated for 80 percent continuous load), the National Electric Code does not require them and the conductor they protect to be oversized to carry continuous loads. Thus when a significant continuous load is involved, the overall cost of conductor and overcurrent protection may be less, especially if there is a long length of conductor. However, the larger size conductor needed with standard overcurent devices, while more expensive, may have such compensating benefits as less power loss, which can result in energy cost savings, less voltage drop, longer life, and greater capacity. These benefits should be evaluated in the selection and application of 100-percent rated and standard 80-percent overcurrent protective devices.