Feeder Overcurrent Device Size

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The National Electric Code (NEC) calculation is based on continuous and non-continuous loads and what portion of total load each represents. When an overcurent device such as a molded case circuit breaker (MCCB) or a fuse is applied in an assembly, it must be sized at 125% of the continuous load. The calculation represents this and rounds up to the nearest standard ampere rating for fuses and inverse time circuit breakers as found in the NEC.

The National Electric Code (NEC) specifies the minimum size for cable tray systems which includes ladder, ventilated trough, ventilated channel, solid bottom and other similar structures. It’s important to note that cable trays are mechanical support systems and not raceways. Raceways are included in another section of the code.

Proper cable tray sizing is complicated and often existing cable trays are overloaded per the code. If you have questions or would like some engineering assistance to properly size your cable tray installation please contact us.

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