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Data Centers and NEC 645

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by Cynthia Glendale on 22 June 2011

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Transcript of Data Centers and NEC 645

Data Centers & NEC Article 645 Dan Fanning, LEED AP, DC CEP, HCC
EDI Projects & Engineering Manager The Choice is Yours ARTICLE 645 Information Technology Equipment
645.1 Scope

This article covers equipment, power-supply wiring, equipment interconnecting wiring, and grounding of information technology equipment and systems, including terminal units, in an information technology equipment room. The Requirements of Section 645 "A means shall be provided to disconnect power to all electronic equipment. The disconnecting means shall also disconnect the battery from the load."
This has the obvious effect of protecting first responders from a disconnected UPS running on battery. Both the NFPA 70/NEC & NFPA 75 state: 645.10... The Purpose of the EPO In the event of an accident the fire personnel do not have the time to find, study, and understand the electrical system in an emergency situation.

The EPO provides a means of disconnect: ensuring first responders or the facility staff are not exposed to electricity and to remove power that maybe the cause of the event. The EPO provides Data Center Operators with a means to disconnect failing equipment as they exit the room. This becomes critical when fire or dangerous fumes are present. What if the accident involves a person being electrocuted by faulty equipment?
The EPO provides a safe and effective means to intervene and disconnect the power. In these scenarios the EPO's purpose is clear. Who Cares? You should, if you intend on using:

Unsecured flexible under-floor whips - 645.5 (D) (2)
Non-plenum rated cable in a (normally) plenum rated environment - Table 645.5 Second Most Common Violation Noted by the EDI Assessment Team? 645.15 Grounding.

All exposed, non–current-carrying metal parts of an information technology system shall be bonded to the equipment grounding conductor in accordance with Article 250 or shall be double insulated.

It is quite common to perform an assessment on a data center with little to no grounding. Along with the EPO, this is a life safety issue. Make sure your equipment, cabinets, racks, and cable trays are all bonded. Why this success? EDI Ltd.
http://www.ediltd.com/ From the NEC Requirements Grounding and Bonding 645.4 Special Requirements for Information Technology Equipment Room.
This article shall apply, provided all of the following conditions are met:

(1) Disconnecting means complying with 645.10 are provided. -- This is your EPO --

(2) A separate heating/ventilating/air-conditioning (HVAC) system is provided that is dedicated for information technology equipment use and is separated from other areas of occupancy. Any HVAC system that serves other occupancies shall be permitted to also serve the information technology equipment room if fire/smoke dampers are provided at the point of penetration of the room boundary. Such dampers shall operate on activation of smoke detectors and also by operation of the disconnecting means required by 645.10. -- Sealed Data Center perimeter and self contained mechanical system --

(3) Listed information technology equipment is installed. -- IT equipment --

(4) The room is occupied only by those personnel needed for the maintenance and functional operation of the installed information technology equipment. -- Don’t try to office your IT personnel in the data center --

(5) The room is separated from other occupancies by fire-resistant-rated walls, floors, and ceilings with protected openings. --Complete envelope and proper fire-stopping -- 645.10 Disconnecting Means.
An approved means shall be provided to disconnect power to all electronic equipment in the information technology equipment room or in designated zones within the room. There shall also be a similarly approved means to disconnect the power to all dedicated HVAC systems serving the room or designated zones and shall cause all required fire/smoke dampers to close. The control for these disconnecting means shall be grouped and identified and shall be readily accessible at the principal exit doors. A single means to control both the electronic equipment and HVAC systems in the room or in a zone shall be permitted. Where a pushbutton is used as a means to disconnect power, pushing the button in shall disconnect the power. Where multiple zones are created, each zone shall have an approved means to confine fire or products of combustion to within the zone.
Exception: Installations qualifying under the provisions of Article 685. (1) An orderly shutdown is required to minimize personnel hazard and equipment damage.
(2) The conditions of maintenance and supervision ensure that qualified persons service the system. The name(s) of the qualified person(s) shall be kept in a permanent record at the office of the establishment in charge of the completed installation. A person designated as a qualified person shall possess the skills and knowledge related to the construction and operation of the electrical equipment and installation and shall have received documented safety training on the hazards involved. Documentation of their qualifications shall be on file with the office of the establishment in charge of the completed installation.
(3) Effective safeguards acceptable to the authority having jurisdiction are established and maintained. EPO (Emergency Power Off) is specifically designed to override all redundancy and fault tolerance of the Data Center design. The EPO is used to:

De-energize all equipment within the IT area.
Close fire dampers, shut down ventilation, remove forced air, contain the fire, and maintain proper concentration of clean agent fire suppressant if installed.
Safely shut-down equipment during a flood or a sprinkler system discharge.
Protect first responders or others from electrocution when fighting a fire. Article 645 Best Practices Other Hints:

Do not show desks or work stations within the data center on construction drawings.
Limit egress into/out of the data center to the minimum required by code. Mechanical Best Practices:

Do not use data center air conditioning for conditioning adjacent space.
Compartmentalize support spaces.
Standardize on a fire-stopping system and implement a fire-stopping program.
Perform an annual perimeter audit under floor and above ceiling and seal new penetrations.
Ensure that fire dampers are included in an annual preventative maintenance. EPO Best Practices:

Provide training for all personnel with access to the data center in regard to the EPO and ramifications.
Include a complete EPO design in the electrical engineering firm’s scope of work.
Utilize an alarming and break open or latching EPO cover.
Utilize obvious surveillance in the EPO area in conjunction with signage.
Consider utilizing an Emergency Power Shutdown Management System.
Employ a dual activation switch.
Employ separate buttons for PDU/RPP, UPS, and mechanical systems.
Ensure that aspirating smoke detection is isolated from the EPO. Grounding Best Practices:

Ensure a proper grounding system is designed and installed; beware of VE options that reduce grounding scope.
Ensure that racks, cabinets, and cable trays are bonded together.
Avoid daisy chain grounding of cabinets to facilitate equipment moves.
Provide labels above the raised floor or below the ceiling where grounding buss bars are located.
Provide labels on grounding conductors.
Inform installers that all shavings and debris from the grounding installation are expected to be removed. Note: Article 685 will not help the typical Data Center escape the EPO requirement. All three of the following must be met to the satisfaction of the AHJ: Join the discussion or post your questions online @http://www.ediltd.com/ask-an-expert.html In order to reap the benefits of flexible under-floor electrical distribution, non-plenum cable, and unsecured communications cables, these conditions must be met. The grounding section of TIA-942 offers guidelines that meet the basic principles and add additional details specific to the modern data center environment. One important issue is the creation of electrical continuity throughout racks and cabinets. Because cabinets are powder-coated assemblies that are bolted together, electrical continuity, if it exists, will be minimal. Why is cabinet and equipment continuity important? For safety, electrostatic discharge (ESD) protection, and to ensure the proper grounding and bonding of your network equipment. The grounding system shall be intentional. Careful planning must be given to network grounding, just like any other system deployed in the data center. As the grounding system is no more reliable than its weakest link, only high-quality components can be used and trained professionals must make all connections. The grounding system shall be visually verifiable, from the equipment, to the rack, to the common bonding backbone, to the earth. The system can be inspected for degradation and should be accessible for implementing moves, adds, and changes, ensuring long-term system reliability and scalability. The grounding system shall be adequately sized. TIA-942 provides guidelines for the grounding system. Be aware that improper use of the guidelines can reduce network availability and cause premature equipment failure. The grounding system shall direct damaging currents away from equipment. A grounding system that complies with TIA-942 requires each rack to bond directly to the grounding grid or common bonding network, thereby directing current away from sensitive electronics. For instance, a common error is to daisy-chain racks together. All metallic components in the data center shall be bonded to the grounding system. The goal is to have all conductive materials at the same electrical potential to minimize current flow. Current flows when there is a difference in potential between components. If the current flows across a piece of equipment, damage may occur. Equipment, racks, cabinets, ladder racks, enclosures, and cable trays must be bonded to the grounding system. Compliant 645 Space Non-Compliant 645 Space No Yes Cabling installed below the raised floor that is used as an HVAC air path must be plenum rated?

Electrical raceways are limited to those that do not have a combustible outer covering and flexible metal conduit is limited to lengths of 4 feet?

All raceways and devices must be securely fastened?

Corded equipment receptacle connections must be made above the raised floor?

NEC 300.22 requirements for wiring in ducts, plenums and other air-handling spaces apply?

Cable tray may be used beneath the raised floor?

Raceways and devices are not required to be securely fastened?

Corded equipment receptacle connections may be made below the raised floor?

Requires an EPO? No Yes No Yes Yes No No Yes Yes No Yes No Yes No An Information Technology Room that is non-Article 645-compliant must meet the requirements put forth in Chapters 1 through 4 of the NEC. These requirements are cumbersome at best when applied in large IT spaces that utilize a raised floor for an air plenum and means of cable conveyance. The Choice is compliance between Chapters 1-4 or with Article 645. The AHJ (Authority Having Jurisdiction - i.e., electrical inspector or fire marshall) also cares, and their interpretation of the code will have an effect on your project. It keeps Data Center Operators awake at night. Fire! Fire! Fire! Most common violation noted by the EDI Assessment Team
is the lack of proper rated barrier. The two goals of the grounding system are to equalize electrical potentials and to create a low resistance path to ground. Drastically undersized main bonding conductor Homemade buss bar & field modified lugs Incredibly poor workmanship Thank you for your time. Article 645 is a trade off, it allows you to bypass some of the most cumbersome requirements of Chapters 1 through 4 if you implement strict fire safety and incorporate systems for immediate shutdown in an emergency. The choice is yours.

The Code is always subject to interpretation. Before designing a data center, determine the risks and advantages the NEC 645 provides and evaluate your design requirements with the local AHJ. After this evaluation, you may determine that Article 645 is not necessary for your project.

A wrong choice in IT space design could have long reaching effects on the installation, operation, and expansion capabilities. Fantastic labeling job by the EC! NEC Chapters 1 through 4 are required for the design of electrical distribution systems. Chapters 5, 6, and 7 are for SPECIAL conditions that apply to SPECIAL occupancies and equipment—hospitals, garages, bulk fuel storage, IT equipment, and classified areas. These SPECIAL spaces, in general, require a significant number of additional requirements to be code-compliant. By following the requirements spelled out in chapters 1 through 4, the electrical distribution system does not require an EPO. You and your electrical engineer must be aware of the special provisions that Article 645 allows. Then make an informed decision in regards to the installation of power and communication cabling under the raised floor before deciding to omit the EPO for the electrical distribution system. Chapters 1-4 vs Article 645 Yes No
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