Critical Power: Emergency Power

Electrical engineers must consider many factors when designing emergency power systems that include safety, maintainability, code compliance, and economics. Consulting-Specifying Engineer Magazine hosted a webcast with Page Principal / MEP Engineering Director Freddy Padilla, PE, ATD and Tom Divine, PE, Project Manager, Smith Seckman Reid Inc. It was such a popular event that some questions remained unanswered at the end so the panelists wrote responses for the remainder. To see what Freddy had to say, read on.

The webcast covered elements of generator systems for critical facilities, noting that specific requirements for emergency power vary based on building occupancy type, facility use, and critical function. When designing generator systems, engineers must ensure that the generators and the building electrical systems that they support are appropriate for the specific application. They must make decisions regarding generator sizing, load types, whether generators should be paralleled, fuel storage, switching scenarios, and many other criteria. NFPA 70: National Electrical Code (NEC) Article 700: Emergency Systems defines the category that applies to emergency generator power sources.

Afterward, Freddy answered whether fire pumps required to meet the requirements of NFPA 70-2017: National Electrical Code (NEC) Article 700, in addition to Article 695. He replied they are not, but a key point is that engineers should always check with their authority having jurisdiction (AHJ) to ensure that source or sources are per NEC Article 695.3. A related question asked whether fire pumps are legally required standby loads. Freddy explained they are not because they don’t need to comply with NEC 701.

A webcast participant asked how to classify mission critical projects if they are not required to have coordination protection. Freddy explained the reliability of mission critical projects is not regulated by the AHJ or the NEC. Selective breaker coordination is a requirement that needs to be discussed with the owner. There are several standards that recommend breaker coordination, such as Uptime Institute and TIA-942-A. Unless requested by the owner, these are only recommendation or good practices, not a requirement of the AHJ.

Freddy also answered other questions as did Tom Divine. To read the full question & answer session in CSE Magazine, click here.