Master Electrician Exam (NEC)Special Occupancies, Equipment, and ConditionsHard
A master electrician is designing the electrical system for a new commercial building that will house a data processing (IT) center. The IT equipment includes multiple server racks and cooling units. According to NEC Article 645, which of the following is a specific requirement for the disconnecting means of the data processing equipment?
- AA single disconnecting means must be provided for all power to the data processing room, located within the room.
- BEach individual server rack must have its own dedicated disconnecting means, accessible only to IT personnel.
- CThe disconnecting means for the data processing equipment must be located outside the room to prevent accidental shutdown.
- DA disconnecting means must be provided to simultaneously disconnect all electronic equipment and the designated IT equipment cooling systems.
Show answer & explanationAnswer & explanation
Correct answer: D. A disconnecting means must be provided to simultaneously disconnect all electronic equipment and the designated IT equipment cooling systems.
NEC 645.10 requires a disconnecting means to be provided to disconnect the power to all electronic equipment in the data processing room and to the designated IT equipment cooling systems. This disconnecting means must cause simultaneous disconnection of all ungrounded conductors.
Why the other options are wrong
- A. While a main disconnect is needed, it must disconnect both IT equipment and cooling, and its precise location may vary based on facility design, not strictly 'within the room' for the *only* disconnect.
- B. Individual server racks typically have their own power distribution units (PDUs), but the NEC specifies a *main* disconnecting means for the entire room's IT and cooling loads, not individual racks.
- C. The disconnecting means must be readily accessible to the data processing room operators (645.10), and while it can be outside, it does not *have* to be, nor is the primary purpose to prevent accidental shutdown (it's for emergency shutdown).
Data Processing Room Disconnect (NEC)
The National Electrical Code (NEC) mandates a specific disconnecting means for data processing rooms that simultaneously cuts power to all electronic equipment and designated IT equipment cooling systems for emergency shutdown purposes.
- Disconnects IT equipment and designated cooling systems.
- Must be readily accessible.
- Causes simultaneous disconnection of all ungrounded conductors.
Memory trick: Data Room: Power and Cool, cut them ALL with one pull.