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Article 646

Modular Data Centers

Part I. General

  1. Scope. This article covers modular data centers.Informational Note No. 1: Modular data centers include the installed information technology equipment (ITE) and support equipment, electrical supply and distribution, wiring and protec‐ tion, working space, grounding, HVAC, and the like, that are located in an equipment enclosure.Informational Note No. 2: For further information, see NFPA 75 -2017, Standard for the Protection of Information Technology Equipment, which covers the requirements for the protection of information technology equipment and systems in an informa‐ tion technology equipment room.
    N Table 645.10(B)(5) Cables Installed Under Raised Floors
    imageCable Type Applicable SectionsimageBranch circuits under raised floors 645.5(E)(1)Supply cords of listed information technology equipmentClass 2 and Class 3 remote control and PLTC cables in other spaces used for environmental air (plenums)Optical fiber cable in other spaces used for environmental air (plenums)Communications wire and cable, cable routing assemblies, and communications raceways in other spaces used for environmental air (plenums)Coaxial CATV and radio distribution cables in other spaces used for environmental air (plenums)645.5(E)(2)(a), 300.22(C)
    725.135(C) and Table 725.154
    770.113(C) and Table 770.154(a)
    800.113(C) and Tables 800.154(a), (b), & (c)
    820.113(C) and Table 820.154(a)
  2. Definitions. The definitions in 645.2 shall apply. For the purposes of this article, the following additional definition applies.Modular Data Center (MDC). Prefabricated units, rated 1000 volts or less, consisting of an outer enclosure housing multiple racks or cabinets of information technology equip‐ ment (ITE) (e.g., servers) and various support equipment, such as electrical service and distribution equipment, HVAC systems, and the like.Informational Note No. 1: A typical construction may use a standard ISO shipping container or other structure as the outer enclosure, racks or cabinets of ITE, service-entrance equipment and power distribution components, power storage such as a UPS, and an air or liquid cooling system. Modular data centers are intended for fixed installation, either indoors or outdoors, based on their construction and resistance to environmental conditions. MDCs can be configured as an all-in-one system housed in a single equipment enclosure or as a system with the support equipment housed in separate equipment enclosures.Informational Note No. 2: For information on listing require‐ ments for both information technology equipment and commu‐ nications equipment contained within a modular data center, see UL 60950-1-2014, Information Technology Equipment — Safety— Part 1: General Requirements, and UL 62368-1-2012, Audio/ Video, Information and Communication Technology Equipment — Part 1: Safety Requirements.Informational Note No. 3: Modular data centers as defined in this article are sometimes referred to as containerized data centers.Informational Note No. 4: Equipment enclosures housing only support equipment (e.g., HVAC or power distribution equip‐ ment) that are not part of a specific modular data center are not considered a modular data center as defined in this article.
  3. Other Articles. Circuits and equipment shall comply with 646.3(A) through (N) as applicable. Wherever the requirements of other articles of this Code and Article 646 differ, the requirements of Article 646 shall apply.
    1. Spread of Fire or Products of Combustion. Sections 300.21, 770.26, 800.26, and 820.26 shall apply to penetrations of a fire-resistant room boundary, if provided.
    2. Wiring and Cabling in Other Spaces Used for Environmen‐ tal Air (Plenums). The following sections and tables shall apply to wiring and cabling in other spaces used for environ‐ mental air (plenums) within a modular data center space:
      (1)Wiring methods: 300.22(C)(1)
      (2)Class 2, Class 3, and PLTC cables: 725.135(C)and
      Table 725.154
      (3)Fire alarm systems: 760.53(B)(2), 760.135(C)and
      Table 760.154
      (4)Optical fiber cables: 770.113(C) and Table 770.154(a)
      800.154(a), (b), and (c)
      1. Communications circuits: 800.113(C) and Table
      2. CATV and radio distribution systems: 820.113(C) and Table 820.154(a)
      Informational Note: Environmentally controlled working spaces, aisles, and equipment areas in an MDC are not considered a plenum.
    3. Grounding. Grounding and bonding of an MDC shall comply with Article 250. The non–current-carrying conductive members of optical fiber cables in an MDC shall be grounded in accordance with 770.114. Grounding and bonding of communications protectors, cable shields, and non–current-carrying metallic members of cable shall comply with Part IV of Article 800.
    4. Electrical Classification of Data Circuits. Section 725.121(A)(4) shall apply to the electrical classification of listed information technology equipment signaling circuits. Sections 725.139(D)(1) and 800.133(A)(1) (c) shall apply to the electrical classification of Class 2 and Class 3 circuits in the same cable with communications circuits.
    5. Fire Alarm Equipment. Parts I, II, and III of Article 760 shall apply to fire alarm systems, cables, and equipment instal‐ led in an MDC, where provided. Only fire alarm cables listed in accordance with Part IV of Article 760 and listed fire alarm equipment shall be permitted to be installed in an MDC.
    6. Cable Routing Assemblies and Communications Wires, Cables, Raceways, and Equipment. Parts I, II, III, IV, and V of Article 800 shall apply to cable routing assemblies, communica‐ tions wires, cables, raceways, and equipment installed in an MDC. Only communications wires and cables listed in accord‐ ance with 800.179, cable routing assemblies and communica‐ tions raceways listed in accordance with 800.182, and communications equipment listed in accordance with 800.170 shall be permitted to be installed in an MDC.Informational Note: See Part I of Article 100 for a definition ofcommunications equipment.
    7. Community Antenna Television and Radio Distribution Systems Cables and Equipment. Parts I, II, III, IV, and V of Article 820 shall apply to community antenna television and radio distribution systems equipment installed in an MDC. Only community antenna television and radio distribution cables listed in accordance with 820.179 and listed CATV equipment shall be permitted to be installed in an MDC.
    8. Storage Batteries. Installation of storage batteries shall comply with Article 480.Exception: Batteries that are part of listed and labeled equipment and installed in accordance with the listing requirements.
    9. Surge-Protective Devices (SPDs). Where provided, surge- protective devices shall be listed and labeled and installed in accordance with Article 285.
    10. Lighting. Lighting shall be installed in accordance with Article 410.
    11. Power Distribution Wiring and Wiring Protection. Power distribution wiring and wiring protection within an MDC shall comply with Article 210 for branch circuits.
    12. Wiring Methods and Materials.
      1. Unless modified elsewhere in this article, wiring methods and materials for power distribution shall comply with Chapter 3. Wiring shall be suitable for its use and installa‐ tion and shall be listed and labeled.Exception: This requirement shall not apply to wiring that is part of listed and labeled equipment.
      2. The following wiring methods shall not be permitted:
        1. Integrated gas spacer cable: Type IGS (Article 326)
        2. Concealed knob-and-tube wiring (Article 394)
        3. Messenger-supported wiring (Article 396)
        4. Open wiring on insulators (Article 398)
        5. Outdoor overhead conductors over 600 volts (Arti‐ cle 399)
      3. Wiring in areas under a raised floor that are constructed and used for ventilation as described in 645.5(E) shall be permitted to use the wiring methods described in 645.5(E) if the conditions of 645.4 are met.
      4. Installation of wiring for remote-control, signaling, and power-limited circuits shall comply with Part III of Arti‐ cle 725.
      5. Installation of optical fiber cables shall comply with Part V of Article 770.
      • (6) Alternate wiring methods as permitted by Article 645
      shall be permitted for MDCs, provided that all of the conditions of 645.4 are met.
    13. Service Equipment. For an MDC that is designed such that it may be powered from a separate electrical service, the service equipment for control and protection of services and their installation shall comply with Article 230. The service equipment and their arrangement and installation shall permit the installation of the service-entrance conductors in accord‐ ance with Article 230. Service equipment shall be listed and labeled and marked as being suitable for use as service equip‐ ment.
    14. Disconnecting Means. An approved means shall be provi‐ ded to disconnect power to all electronic equipment in the MDC in accordance with 645.10. There shall also be a similar approved means to disconnect the power to all dedicated HVAC systems serving the MDC that shall cause all required fire/smoke dampers to close.
  4. Applicable Requirements. All MDCs shall:
    1. Be listed and labeled and comply with 646.3(N) and
  5. through 646.9, or

Informational Note: For information on listing requirements for modular data centers, see UL Subject 2755, Outline of Investi‐ gation for Modular Data Centers.

  1. Comply with the provisions of this article.
  1. Nameplate Data. A permanent nameplate shall be attached to each equipment enclosure of an MDC and shall be plainly visible after installation. The nameplate shall include the information in 646.5(1) through (6), as applicable:
    1. Supply voltage, number of phases, frequency, and full- load current. The full-load current shown on the name‐ plate shall not be less than the sum of the full-load currents required for all motors and other equipment that may be in operation at the same time under normal conditions of use. Where unusual type loads, duty cycles, and so forth, require oversized conductors or permit reduced-size conductors, the required capacity shall be included in the marked full-load current. Where more than one incoming supply circuit is to be provided, the nameplate shall state the preceding information for each circuit.Informational Note No. 1: See 430.22(E) and 430.26 for duty cycle requirements.Informational Note No. 2: For listed equipment, the full-load current shown on the nameplate may be the maximum, meas‐ ured, 15-minute, average full-load current.
    2. For MDCs powered by a separate service, the short-circuit current rating of the service equipment provided as part of the MDC.Informational Note: This rating may be part of the service equipment marking.
    3. For MDCs powered by a separate service, if the required service as determined by Parts III and IV of Article 220 is less than the rating of the service panel used, the required service shall be included on the nameplate.Informational Note: Branch circuits supplying ITE loads are assumed to be loaded not less than 80 percent of the branch- circuit rating with a 100 percent duty cycle. As an alternative to the feeder and service load calculations required by Parts III and IV of Article 220, feeder and service load calculations for new, future, or existing loads may be permitted to be used if performed by qualified persons under engineering supervision.
    4. Electrical diagram number(s) or the number of the index to the electrical drawings.
    5. For MDC equipment enclosures that are not powered by a separate service, feeder, or branch circuit, a reference to the powering equipment.
    6. Manufacturer’s name or trademark.
  2. Supply Conductors and Overcurrent Protection.
    1. Size. The size of the supply conductor shall be such as to have an ampacity not less than 125 percent of the full-load current rating.Informational Note No. 1: See the 0–2000-volt ampacity tables of Article 310 for ampacity of conductors rated 600 V and below.Informational Note No. 2: See 430.22(E) and 430.26 for duty cycle requirements.
    2. Overcurrent Protection. Where overcurrent protection for supply conductors is furnished as part of the MDC, overcur‐ rent protection for each supply circuit shall comply with 646.6(B)(1) through (B)(2):
      1. Service Equipment — Overcurrent Protection. Service conductors shall be provided with overcurrent protection in accordance with 230.90 through 230.95.
      2. Taps and Feeders. Where overcurrent protection for supply conductors is furnished as part of the MDC as permitted by 240.21, the overcurrent protection shall comply with the following:
    1. The overcurrent protection shall consist of a single circuit breaker or set of fuses.
    2. The MDC shall be marked “OVERCURRENT PROTEC‐ TION PROVIDED AT MDC SUPPLY TERMINALS.”
    3. The supply conductors shall be considered either as feed‐ ers or as taps and be provided with overcurrent protec‐ tion complying with 240.21.
  3. Short-Circuit Current Rating.
    1. Service Equipment. The service equipment of an MDC that connects directly to a service shall have a short-circuit current rating not less than the available fault current of the service.
    2. MDCs Connected to Branch Circuits and Feeders. Modu‐ lar data centers that connect to a branch circuit or a feeder circuit shall have a short-circuit current rating not less than the available fault current of the branch circuit or feeder. The
      short-circuit current rating of the MDC shall be based on the short-circuit current rating of a listed and labeled MDC or the short-circuit current rating established utilizing an approved method.
      Exception: This requirement shall not apply to listed and labeled equip‐ment connected to branch circuits located inside of the MDC equipment enclosure.Informational Note: UL 508A-2013, Standard for Industrial Control Panels, Supplement SB, is an example of an approved method.•
    3. MDCs Powered from Separate MDC System Enclosures.
    Modular data center equipment enclosures, powered from a separate MDC system enclosure that is part of the specific MDC system, shall have a short-circuit current rating coordinated with the powering module in accordance with 110.10.Informational Note: UL 508A-2013, Standard for Industrial Control Panels, Supplement SB, is an example of an approved method for determining short-circuit current ratings.
  4. Field-Wiring Compartments. A field-wiring compart‐ ment in which service or feeder connections are to be made shall be readily accessible and comply with 646.8(1) through(3) as follows:
    1. Permit the connection of the supply wires after the MDC is installed
    2. Permit the connection to be introduced and readily connected
    3. Be located so that the connections may be readily inspec‐ ted after the MDC is installed
  5. Flexible Power Cords and Cables for Connecting Equip‐ ment Enclosures of an MDC System.
    1. Uses Permitted. Flexible power cords and cables shall be permitted to be used for connections between equipment enclosures of an MDC system where not subject to physical damage.Informational Note: One example of flexible power cord usage for connections between equipment enclosures of an MDC system is between an MDC enclosure containing only servers and one containing power distribution equipment.
    2. Uses Not Permitted. Flexible power cords and cables shall not be used for connection to external sources of power.Informational Note: Examples of external sources of power are electrical services, feeders, and premises branch circuits.
    3. Listing. Where flexible power cords or cables are used, they shall be listed as suitable for extra-hard usage. Where used outdoors, flexible power cords and cables shall also be listed as suitable for wet locations and shall be sunlight resistant.
    4. Single-Conductor Cable. Single-conductor power cable shall be permitted to be used only in sizes 2 AWG or larger.

    Part II. Equipment
  6. Electrical Supply and Distribution. Equipment used for electrical supply and distribution in an MDC, including fittings, devices, luminaires, apparatus, machinery, and the like, shall comply with Parts I and II of Article 110.
  7. Distribution Transformers.
    1. Utility-Owned Transformers. Utility-owned distribution transformers shall not be permitted in an MDC.
    2. Non-Utility-Owned Premises Transformers. Non-utility- owned premises distribution transformers installed in the vicin‐ ity of an MDC shall be of the dry type or the type filled with a noncombustible dielectric medium. Such transformers shall be installed in accordance with the requirements of Article 450 . Non-utility-owned premises distribution transformers shall not be permitted in an MDC.
    3. Power Transformers. Power transformers that supply power only to the MDC shall be permitted to be installed in the MDC equipment enclosure. Only dry-type transformers shall be permitted to be installed in the MDC equipment enclosure. Such transformers shall be installed in accordance with the requirements of Article 450.
  8. Receptacles. At least one 125-volt ac, 15- or 20-ampere- rated duplex convenience outlet shall be provided in each work area of the MDC to facilitate the powering of test and measurement equipment that may be required during routine maintenance and servicing, without having to route flexible power cords through or across doorways or around line-ups of equipment, or the like.
  9. Other Electrical Equipment. Electrical equipment that is an integral part of the MDC, including information technol‐ ogy equipment, lighting, control, power, HVAC (heating, venti‐ lation, and air-conditioning), emergency lighting, alarm circuits, and so forth, shall comply with the requirements for its use and installation and shall be listed and labeled.
  10. Installation and Use. Listed and labeled equipment shall be installed and used in accordance with any instructions or limitations included in the listing.
    Part III. Lighting
  11. General Illumination. Illumination shall be provided for all workspaces and areas that are used for exit access and exit discharge. The illumination shall be arranged so that the failure of any single lighting unit does not result in a complete loss of illumination.Informational Note: See NFPA 101 ® -2015, Life Safety Code, Section 7.8, for information on illumination of means of egress.
  12. Emergency Lighting. Areas that are used for exit access and exit discharge shall be provided with emergency lighting. Emergency lighting systems shall be listed and labeled equipment installed in accordance with the manufacturer’s instructions.Informational Note: See NFPA 101 ® -2015, Life Safety Code,Section 7.9, for information on emergency lighting.
  13. Emergency Lighting Circuits. No appliances or lamps, other than those specified as required for emergency use, shall be supplied by emergency lighting circuits. Branch circuits supplying emergency lighting shall be installed to provide serv‐ ice from storage batteries, generator sets, UPS, separate service, fuel cells, or unit equipment. No other equipment shall be connected to these circuits unless the emergency lighting system includes a backup system where only the lighting is supplied by battery circuits under power failure conditions. All
  14. ARTICLE 647 — SENSITIVE ELECTRONIC EQUIPMENT

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