Codes & Standards - Lane Coburn and Associates
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1. Codes EPO or No A Consideration of NEC Articles 645 10 and 685 BY KEITH LANE P E RCDD NTS SPECIALIST LC LEED AP Director VP Engineering SASCO Seattle ost people in the electrical design and construction indus try are inclined to associate a data center or critical environ ment with an emergency power off EPO But what every designer doesn t know is that an EPO is not always required in a data center Article 645 in the 2005 edition of the Nation al Electrical Code discusses the requirements for information technology equipment It is important to note that NEC chapters 1 through 4 are required for the design of electrical dis tribution systems Chapters 5 6 and 7 are for special conditions that apply to special occu pancies and equipment occupancies such as hospitals garages bulk fuel storage and classified areas and yes IT equipment These spaces typically require a significant number of additional requirements in order to be code compliant If the electrical distribution system designer follows the requirements of chapter 1 through The first item is a huge issue for the typical data center and other critical environments During its life the typical data center will see many changes in its IT equipment With the continual evolution of servers routers and mass storage devices and the changing power and HVAC densities due to the propagation of the blade server in data centers cable changes are inevita2. E will chair a scoping committee studying ways to achieve building designs as close as is feasible to net zero energy use defined as a building which on an annual basis uses no more energy than is provided by the building s on site renewable energy sources This study will provide the basis for the development of Advanced Energy Design Guides to go 50 and beyond minimum standards for energy use The scoping study recently was completed and identified measures that achieve significant energy savings Some of the measures identified are e Improved daylighting and electrical illumination systems e Reduction of parasitic power requirements in air and water distribution systems e Separate treatment of ventilation and internal thermal loads e Improved delivery of conditioning to where it is needed e Improved part load performance of HVAC components e Water loop heat pump systems Speaker will address topics such as net zero energy building ideas case studies integrated design daylighting HVAC and ventilation distribution systems and architectural perspec tives as a bridge to engineering Consulting Specifying Engineer JANUARY 2007 O PUSH HERE THEN putt oon a IT managers often see EPO devices as a single point of failure forced on them with the requirements of 300 11 The electrical system designer can utilize nonmetallic raceways i e PVC within the raised floor area because
3. as it is done in a normal building In a critical environment the tripping of a main breaker may just turn on the backup generators change the position of a static transfer switch or just kick in the batteries on a UPS system The fire personnel do not have the time to study complex one line diagrams in order to disable the electrical system in an emer gency situation Additionally Article 645 is proposed to diminish the spread of smoke and fire Article 645 is intended to reduce the spread of fire and smoke by requir ing fire resistant walls and separate independent HVAC systems for IT rooms and data centers as well as smoke detec tion under the raised floor As stated above the major advan tage when complying with Article 645 is that listed IT equipment cables are not required to be secured as required in other sections of the NEC Each branch circuit conductor for data processing equipment must have an ampacity not less than 125 of the total connected load NEC 645 5 In addition to hard wiring IT equip ment you can connect data process ing equipment to a branch circuit by either a flexible cord or a cord set assembly as long as the flexible cord is no longer than 15 ft with an attach ment plug and the cord set assembly floor must be accessible 2 You must also install the branch circuits for receptacles or hard wired equipment in one of the following types of raceway rigid metal conduit rigid nonmetallic co
4. many of the requirements of the standard exist according to Roger Hedrick who co authored the book The manual is targeted toward builders and subcontractors but will also be useful for code officials researchers and interested homeowners The manual has been developed as a document that will accompany Standard 62 2 and provide guidance for applying its requirements to the design and construction of residential buildings David Grimsrud chair of the Standard 62 2 committee said It serves as a guide to clarifying issues for users To order visit the ASHRAE org Bookstore at www ashrae org 20 Consulting Specifying Engineer e JANUARY 2007 room which is typically not occupied 3 Ventilation in the underfloor area must be for the IT equipment room only except as provided in 645 4 2 The ven tilation system shall be arranged with appropriate smoke detection devices so air circulation will cease after the detec tion of fire or products of combustion 4 Openings in raised floors must pro tect the cables against abrasions and minimize the debris underneath the raised floor 5 Cables other than indicated in no 2 above must be listed for use Type DP data processing cable except for a interconnecting cables enclosed in a raceway b interconnecting cables list ed with equipment manufactured prior to July 1 1994 and installed with that equipment c cable type designation Type TC CL2 CL3 PLT
5. this space is not subject to physical damage or required to comply with the environmental airspace requirements of 300 22 C The use of nonmetallic race ways in an air handling space is not pro hibited because the air does not move within the rest of the building If there is a fire inside the data center the toxic fumes emitted by nonmetallic wiring methods will only affect the data center New User s Manual for Standard 62 2 SHRAE published a manual to aid users in designing and constructing homes and apartments that comply with its residential ventilation and indoor air quality stan dard The manual was co developed by the Indoor Air Quality Association The User s Manual is the first for ASHRAE Standard 62 2 2004 Ventilation and Accept able Indoor Air Quality in Low Rise Residential Buildings which provides the minimum requirements necessary to achieve acceptable indoor air quality for dwellings The 62 2 User s Manual will provide HVAC engineers and IAQ consultants with practi cal information to ensure that ventilation positively affects the indoor environment Robert G Baker IAQA president and ASHRAE member said IAQA was pleased to be a co spon sor of this dynamic publication The manual explains how to comply with all the requirements of the standard provides examples illustrating specific methods of complying with sections of the standard and includes background material explaining why
6. C NPLF FPL OFC OFN CM and CATV Conductors with Before designing a data center that conforms with 645 dete mine the risks and advantages that this NEC article provides and consult the local AHJ green or green with one or more yel low stripes insulated 4 AWG and larger and marked for use in cable trays or CT use are permitted for equipment grounding bonding of the raised floor parts and d abandoned cables Remove these unless they are in metal raceways Before designing a data center that conforms with NEC Article 645 deter mine the risks and advantages that the section of the NEC provides and evalu ate your electrical design with the local AHJ After this analysis you may deter mine that Article 645 is not appropriate for your project A wrong choice in design could dra matically affect the operation of the critical environment If an emergency power off is installed it is incumbent upon the data center operation staff to only allow trained personnel into the critical environment lese
7. ble and regular This continuing change of the location of IT equipment would be sig nificantly more restrictive if the IT power and communication cables and associated boxes connectors and plugs had to be tied down to comply with other section of the NEC The typical data center raised floor also acts as a means of distributing air from the comput er room air conditioning CRAC units through perforated tiles and across the racks of servers on top of the raised floor Because the raised floor is used to distribute air this area is a ple num In typical air plenums the data cables need to be plenum rated Article 645 if all parts are adhered to allows NEC Article 645 of has a number of special pro visions that the electrical system designer should consider before deciding to install an EPO for non plenum rated cable In addition to the requirement of an EPO the raised floor must be served from a dedicated mechanical system 4 only the EPO is not a required part of the electrical distribution system The electrical engineer or system designer must be aware of the special provisions that Article 645 allows in reference to the installation of power and communication cables under the raised floor before deciding to omit the EPO for the electri cal distribution system There are many advantages to complying with Article 645 but the two main advantages are the following 1 Listed IT equipment power cables com munication ca
8. bles and interconnecting cables and associated boxes connectors plugs and receptacles are not required to be secured as required in the NEC articles 1 through 4 2 Non plenum rated cables are allowed under the raised floor This is required so the air does not exchange with the rest of the building If there is a fire inside of the data center the toxic fumes pro duced by nonmetallic wiring methods will only affect the data center room and equipment because the data center is not occupied by people on a regular basis Additionally venti lation in the underfloor area must be for the data center only and be provided with smoke detection so that air circulation will stop when fire or combustion is detected Most data center maintenance personnel are not big fans of the EPO stations required by this section of the NEC for critical IT envi ronments These devices can be a single point of failure We have all heard the stories of an inadvertent disconnect by untrained person nel or the stacks of boxes pilled up along the entrance that trip the critical service offline Consulting Specifying Engineer JANUARY 2007 VFD Induced Shaft Current Kills AC Motors Protect your motors against shaft current bearing damage Improve system reliability Patents Pending AEGIS ser SHAFT GROUNDING RING The World s Most Effective Shaft Grounding Brush m Extends motor life dramatically improves system reliability m Pro
9. nduit intermediate Human error is often the source of unintended shutdown EPO devices are often the culprits metal conduit electrical metallic tub ing electrical nonmetallic tubing metal wireway nonmetallic wireway surface metal raceway with metal cover non metallic surface raceway flexible metal conduit liquidtight flexible metal con duit liquidtight flexible nonmetallic conduit Type MI cable Type MC cable or Type AC cable These supply conduc tors shall be installed in accordance ASHRAE Details Energy Saving Measures A n update on measures that have shown to yield significant energy reductions will be presented at ASHRAE s 2007 Winter Meeting in Dallas in a seminar Achieving 50 and Beyond Approach to Net Zero Energy Use in Buildings Part 1 It takes place from 7 45 a m to 9 15 a m on Jan 29 and is followed by Part 2 from 10 45 a m to 12 15 p m Achieving that goal will require more than simply substituting or adopting new technolo gies and systems It will acquire changes in design practice in which the design team converts energy strategies into building plans sections details and construction The guidance is being developed by ASHRAE in cooperation with the American Institute of Architects the Illuminating Engineering Society of North America and the U S Green Building Council through a series of Advanced Energy Design Guides for the commercial building sector John Mitchell P
10. ors and ceilings with protected openings After reading all of this you still may be wondering why the NEC would provide for a means of so easily discon necting power in a critical environment After all there is so much design and money spent to improve reliability and availability of the systems Any down time can be very expensive You have to remember that the main intent of the NEC is to protect people and property not to ensure the most uptime for your facility The main intent of the special requirements detailed in Article 645 for data centers is to protect fire person nel from being injured or electrocuted When emergency responders enter a data center or other critical environ ment they need to have a fast and sim Additionally where run on the sur face of the floor it must be protected against physical damage The electrical contractor can install receptacles and run power cables com munications cables connecting cables and interconnecting cables under raised floors But you can do this only if the construction meets these conditions 1 The raised floor must be of suitable construction and the area under the When an electrical system designer chooses to abide by Article 645 there is an exception for not requiring EPO paragraph 645 10 provides an exception that qualifies under Article 685 ple method of ensuring that the elec trical system is dead Without the EPO the fireman may trip the main breaker
11. red to be secured as with other NEC sections common in nuclear power plants paper mills and other hazardous facilities Because power and HVAC systems are the major means of support of all data centers and critical environments very careful deliberation should be given to whether or not to comply with the additional requirements of Article 645 The prerequisites for these relaxed NEC codes are found in NEC 2005 Article 645 4 which states that the article shall apply provided than several conditions are met Again this is an optional code article Depending on your system appli Standards cation the electrical distri bution system engineer can elect to abide by the require ments or not In addition to the above require ments for a disconnecting means other particular requirements of Article 645 include 1 Equipment that can be installed in the room must be listed as IT equipment 2 A separate HVAC system is provided that is dedicated to the IT equipment and is separated from the other areas of occupancy Any HVAC system that serves other occupancies shall be per mitted to also serve the information technology room if fire and smoke dampers are provided at the point of penetration of the room boundary 3 The room is occupied only by those personnel required for maintenance and fictional operation of the critical environment 4 The room is separated from other occupancies by fire resistant rated walls flo
12. ven in thousands of applications Outperforms and outlasts conventional brushes Maintenance free Contamination proof unaffected by dirt grease or contaminants Standard sizes for motors with 0 311 shafts or greater For a free technical paper on shaft grounding technologies call TEL 1 866 738 1857 sales est aegis com www est aegis com Electro Static Technology An ITW Company Input 223 at csemag com quickResponse Codes If an electrical engi neer or system design er chooses to abide by Article 645 there is an exception for not requiring EPO Para graph 645 10 provides an exception to instal lations that qualify under the provisions of Article 685 Integrated Electrical Systems NEC Article 685 is uti lized when an orderly shutdown is necessary to ensure safe opera tion Conditions of main tenance and supervision are required to ensure that only qualified per sonnel service the equip ment In addition effec tive safeguards acceptable to the AHJ are required The NEC indicates that for some industrial processes the sudden loss of power to critical equipment provides for an unac ceptable level of risk In these cases an orderly shutdown is required to prevent severe damage to equipment and to mitigate risk to personnel The NEC fur ther states that orderly shutdown is The major advantage to com plying with 645 is that listed IT equipment cables are not requi
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