NEC 645 covers details about the electrical systems (electrical equipment, wiring connections, and grounding) associated with Information Technology equipment (ITE) and systems in the ITE room. ITE room consists of computer-based systems and industrial equipment. Small terminals such as personal computers, cash registers in stores or supermarkets, and remote data terminals are not covered in Article 645.
NEC 645.5 covers supply circuits and interconnecting cables provisional requirements in ITE room. NEC 645.5(A) requires that branch circuit conductors supplying power to one or more units of ITE shall have an ampacity not less than 125% of the connected load. NEC 645.5(B) requires that branch circuits supplying power toITE shall be permitted to be connected by a power supply cord not exceeding 4.5 mts (15 ft). NEC 645.5(C) requires that separate ITE units are allowed to be interconnected by listed cable and cable assemblies. In this case, the power supply cord length not exceeding 4.5 mts (15 ft) as specified in NEC 645.5(B) is not applicable. NEC 645.5(D) requires that supply circuits and interconnection cables shall be protected against physical damage. NEC 645.5(E) requires power, communication, and interconnecting cables, cord & plug connections, and receptacles associated with ITE are permitted to be provided under the raised floor. Installation of supply conductors below a raised floor shall comply with NEC 300.11. Supply cords of ITE is allowed to run through the holes in the raised floor for connecting receptacles below the raised floor. Opening of the raised floor where cables or cords run through shall not be subjected to any lead abrasion of cables and cords. The underfloor area of ITE room is required to be provided with a ventilation system with approved smoke detectors. In case of any smoke detection due to combustion, air circulation shall be ceased. Interconnecting cables (other than branch circuit conductors) under raised floors satisfying NEC 645.5(E)(6) are to be listed as TypeDP cables. NEC 645.5(F) requires that power, communication, and interconnecting cables, connectors, plugs, receptacles, and other equipment part of ITE units shall not be required to be secured in place. NEC 645.5(G) requires that abandoned supply circuits and interconnecting cables which are accessible shall be removed unless they are contained inside the raceway. NEC 645.5(H) requires interconnecting cables and supply circuits which are identified for future use shall be properly marked with tag with good durability and contains information related to the date identified for future use, intended purpose, and other information about future intended purpose.
NEC 645.6 specifies that cables extended from ITE equipment room shall be required to comply with other relevant codes (Articles in Chapters 7 & 8 of NEC)
NEC 645.10 covers disconnecting means associated with ITE equipment room. An approved disconnecting means is required to be provided for disconnecting all electronic components in ITE equipment room or designated zones within the room. Dedicated HVAC systems serving the ITE equipment rooms or designated zones shall be disconnected from the power supply and all required smoke/ fire dampers shall be closed in case of any smoke detection due to combustion. NEC 645.10(A) requires circuits supplying power supply to ITE equipment room and the circuits supplying power to dedicated HVAC systems (for ITE rooms) are to be controlled through a separate disconnecting means. Operation of this disconnecting means can be from a single remote control device (push button). This disconnecting means isolate all the conductors feeding ITE equipment by cutting off the power supply from the source and all fire/smoke dampers shall be closed. When multiple zones are created, each zone has to be provided with proper means to limit the fire or products of combustion within the zone. Also, additional means shall be provided to prevent unintentional operation of the remote disconnection means. NEC 645.10(B) requires remote disconnecting means shall not be required to be provided for critical operation data systems. Proper approval procedures shall be available for removing the power supply and air movement within the ITE equipment room or zones. Qualified personnel shall be available to meet any emergency conditions and for advising methods for disconnecting circuit conductors supplying power to critical operations data systems. Smoke sensing/fire detection systems shall be available. An approved proper suitable fire suppression shall be available.
NEC 645.11 covers details about uninterruptible power supplies (UPS) systems installed within ITE equipment rooms. The disconnecting means provided in UPS systems for disconnecting power supply conductors shall comply with NEC 645.10 and it also shall isolate the battery from its load. The power supply circuits need not be required to comply with NEC 645.10 if the installation qualify Article 685 or power sources (UPS equipment or battery circuit integral of electronic equipment) limited to 750 volt-ampere or less
NEC 645.15 covers details about grounding requirements associated with ITE equipment room. All the exposed metal parts of the IT equipment system and signal reference structures shall be properly bonded to the equipment grounding conductor as per NEC 250 and shall be double insulated.