Question

When calculating branch circuit capacity for a data center, which load type requires the highest derating factor?

Accepted Answer

When calculating branch circuit capacity for a data center, continuous loads require the highest derating factor. A continuous load is defined as a load that operates for three hours or more at a time. According to electrical codes, branch circuits supplying continuous loads must be derated to 80% of their rated capacity. This means that the circuit breaker or overcurrent protection device must be sized at least 125% of the continuous load. For example, if a branch circuit supplies a continuous load of 16 amps, the circuit breaker must be rated at least 20 amps (16 amps x 1.25 = 20 amps). This derating factor is necessary to prevent overheating and nuisance tripping of the circuit breaker due to the sustained load. Non-continuous loads, which operate for less than three hours, do not require this same level of derating. The high density of servers and other equipment in a data center often results in many continuous loads, making it crucial to properly derate branch circuits to ensure reliable power distribution.

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When calculating branch circuit capacity for a data center, which load type requires the highest derating factor?