ron
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First, I believe that a cord or cable is not permitted to extend from a piece of IT equipment installed on top of a raised computer room floor, to below a computer room floor per 400.8(2), unless a leniency from 645 is used.
I believe that the cord from a piece of IT equipment that extends below a raised floor, must be DP rated per 645.5(D)(5) [considering that 645.4 is complied with NEC 70-2005]. The later seems to agree with an interpretation by Holt.
http://www.ecmweb.com/mag/electric_code_quandaries_10/
I was having a discussion with a coworker about this topic and he disagrees. The deal was that I would submit a Technical Document Interpretation question to NFPA, and have a clear answer. Unfortunately for me, either I cannot ask a clear question, or I am wrong in my initial statements because the NFPA rep seems to agree with my coworker.
My question: NFPA70-2005 Section 645.5(D)
Server racks installed in a datacenter. The datacenter is compliant with Section 645.4. The plug strip installed in the equipment rack is UL listed as IT equipment. Since the cord extending from the plug strip to the receptacle is part of the IT listed assembly, it is not technically part of the premises wiring, If that cord extends below the raised floor, must it be rated as DP?
NFPA rep response: I am pleased to answer your question with regard to cords under raised floors in an Article 645 application. Cord-and-Plug connected equipment would follow the requirements of 645.5 (B). Cables would follow the requirements of 645.5 (D). DP is a type of flexible cable and not a type of flexible cord. Cords are limited by their length in an under-floor application. Cables are limited by their construction type in an under-floor application. Since receptacles associated with information technology equipment and branch-circuit receptacles are permitted under the floor, the cords and cord and plug connections are permitted under floor as restricted by 645.5 (B).
My followup question: The following is related to your distinction between cords and cables in your response. Article 400.8(2) appears to restrict cords and cables from being installed below a raised floor, when the cord is run through a hole in the raised floor. Considering the restriction in 400.8, in order to run a cord from a power strip mounted in a server rack to a receptacle mounted below the raised floor, there would have to be a special permission given in 645.5(D).
If the installation is compliant with 645.4, 645.5(B) permits a 15 foot cord, but makes no indication that the cord can be installed below a raised floor. So from your separate definition of cord and cable types, it appears that a cord is not permitted below a raised floor at all? I'm not sure that this is the intent. Could you confirm?
The logic that I considered when struggling through the code implications of this question included the following:
A cord was a special type of cable (a factory assembly of two or more conductors having an overall covering). The cord is listed with the IT equipment.
645.5(D) identifies wiring method leniencies permitted by 645 below the raised floor if the installation is compliant with 645.4.
645.5(D)(2) identifies the acceptable wiring methods for the branch circuit below the raised floor serving the receptacle.
645.5(D)(5)a.b or c. identifies special cables permitted below the raised floor, typically communication or control type cables but also special interconnecting cable manufactured before 1994.
645.5(D)(5) identifies that if the cable is not 645.5(D)(2) [branch circuit serving the receptacle] or 645.5(D)(5)a. b. or c. [communication or control type cables], then it must be Type DP. Since a cord from a new model power strip is not identified in 645.5(D)(2) or 645.5(D)(5)a. b. or c., then it seems that it must be Type DP.
Could you help me clarify the logic that may be different than the intent of the NFPA 70 document?
NFPA rep followup response: Section 400.8(2) does not restrict cords through penetrations below a raised floor in an Information Technology Equipment Room. Penetrations as per NFPA 75-2003 Standard for the Protection of Information Technology Equipment through a raised floor are called ?openings? and not ?holes.? Also, a raised floor is not a structural floor. It is a platform with removable panels where equipment is installed, with the intervening space between it and the main building floor used to house the interconnecting cables and at times is used as a means for supplying conditioned air to the information technology equipment and the room.
Thank you for sharing your logic concerning your question regarding cords and type DP Cable. I appreciate your research and logic to arrive at your conclusion. Typically, a cord would be used to connect the listed information technology equipment to the branch-circuit wiring as described in your original e-mail. Typically, it is desirable to keep the amount of plastic and other combustible material under a raised floor at a minimum. Generally keeping interconnecting cable length at a minimum is not an option, since longer cables to interconnect IT equipment in the area are needed. Cables having higher fire resistance such as cable type DP and others passing the fire resistance tests indicated in the Fine Print Note after 645.5(D)(5) are used.
Also, please consult NFPA 75-2003 Standard for the Protection of Information Technology Equipment for requirements for automatic detection systems for this raised floor application. Typically, the detection system selection process should evaluate the ambient environmental conditions in determining the appropriate device, location, and sensitivity. In high airflow environments, air-sampling detection devices should be considered.
If there is still a concern about the flame resistance of the cord from a listed piece of IT equipment, the product manufacturer could be consulted about the type of outer covering of the cord used. Specifically, the cord?s performance in either the ANSI/UL 1581-2001 ?Vertical Tray Flame Test? or the CSA C22.2 No.0.3-M-2001 ?Vertical Flame Test? of the Test Methods for Electrical Wire and Cables should be evaluated.
Also, if there is a great concern for the cord(s) and it?s products of combustion, the branch-circuit wiring could be extended above the raised floor through a wiring method as permitted in 645.5(D)(2) which include some non-metallic wiring methods.
I'm glad that the NFPA rep has gone back and forth with me, but the responses do not agree with me and are not clear enough for me to understand the logic. I don't understand how a definition in a different standard (like NFPA 75) can be used to interpret words in NFPA 70. Any comments are appreciated.
[ December 26, 2005, 09:55 AM: Message edited by: ron ]
I believe that the cord from a piece of IT equipment that extends below a raised floor, must be DP rated per 645.5(D)(5) [considering that 645.4 is complied with NEC 70-2005]. The later seems to agree with an interpretation by Holt.
http://www.ecmweb.com/mag/electric_code_quandaries_10/
I was having a discussion with a coworker about this topic and he disagrees. The deal was that I would submit a Technical Document Interpretation question to NFPA, and have a clear answer. Unfortunately for me, either I cannot ask a clear question, or I am wrong in my initial statements because the NFPA rep seems to agree with my coworker.
My question: NFPA70-2005 Section 645.5(D)
Server racks installed in a datacenter. The datacenter is compliant with Section 645.4. The plug strip installed in the equipment rack is UL listed as IT equipment. Since the cord extending from the plug strip to the receptacle is part of the IT listed assembly, it is not technically part of the premises wiring, If that cord extends below the raised floor, must it be rated as DP?
NFPA rep response: I am pleased to answer your question with regard to cords under raised floors in an Article 645 application. Cord-and-Plug connected equipment would follow the requirements of 645.5 (B). Cables would follow the requirements of 645.5 (D). DP is a type of flexible cable and not a type of flexible cord. Cords are limited by their length in an under-floor application. Cables are limited by their construction type in an under-floor application. Since receptacles associated with information technology equipment and branch-circuit receptacles are permitted under the floor, the cords and cord and plug connections are permitted under floor as restricted by 645.5 (B).
My followup question: The following is related to your distinction between cords and cables in your response. Article 400.8(2) appears to restrict cords and cables from being installed below a raised floor, when the cord is run through a hole in the raised floor. Considering the restriction in 400.8, in order to run a cord from a power strip mounted in a server rack to a receptacle mounted below the raised floor, there would have to be a special permission given in 645.5(D).
If the installation is compliant with 645.4, 645.5(B) permits a 15 foot cord, but makes no indication that the cord can be installed below a raised floor. So from your separate definition of cord and cable types, it appears that a cord is not permitted below a raised floor at all? I'm not sure that this is the intent. Could you confirm?
The logic that I considered when struggling through the code implications of this question included the following:
A cord was a special type of cable (a factory assembly of two or more conductors having an overall covering). The cord is listed with the IT equipment.
645.5(D) identifies wiring method leniencies permitted by 645 below the raised floor if the installation is compliant with 645.4.
645.5(D)(2) identifies the acceptable wiring methods for the branch circuit below the raised floor serving the receptacle.
645.5(D)(5)a.b or c. identifies special cables permitted below the raised floor, typically communication or control type cables but also special interconnecting cable manufactured before 1994.
645.5(D)(5) identifies that if the cable is not 645.5(D)(2) [branch circuit serving the receptacle] or 645.5(D)(5)a. b. or c. [communication or control type cables], then it must be Type DP. Since a cord from a new model power strip is not identified in 645.5(D)(2) or 645.5(D)(5)a. b. or c., then it seems that it must be Type DP.
Could you help me clarify the logic that may be different than the intent of the NFPA 70 document?
NFPA rep followup response: Section 400.8(2) does not restrict cords through penetrations below a raised floor in an Information Technology Equipment Room. Penetrations as per NFPA 75-2003 Standard for the Protection of Information Technology Equipment through a raised floor are called ?openings? and not ?holes.? Also, a raised floor is not a structural floor. It is a platform with removable panels where equipment is installed, with the intervening space between it and the main building floor used to house the interconnecting cables and at times is used as a means for supplying conditioned air to the information technology equipment and the room.
Thank you for sharing your logic concerning your question regarding cords and type DP Cable. I appreciate your research and logic to arrive at your conclusion. Typically, a cord would be used to connect the listed information technology equipment to the branch-circuit wiring as described in your original e-mail. Typically, it is desirable to keep the amount of plastic and other combustible material under a raised floor at a minimum. Generally keeping interconnecting cable length at a minimum is not an option, since longer cables to interconnect IT equipment in the area are needed. Cables having higher fire resistance such as cable type DP and others passing the fire resistance tests indicated in the Fine Print Note after 645.5(D)(5) are used.
Also, please consult NFPA 75-2003 Standard for the Protection of Information Technology Equipment for requirements for automatic detection systems for this raised floor application. Typically, the detection system selection process should evaluate the ambient environmental conditions in determining the appropriate device, location, and sensitivity. In high airflow environments, air-sampling detection devices should be considered.
If there is still a concern about the flame resistance of the cord from a listed piece of IT equipment, the product manufacturer could be consulted about the type of outer covering of the cord used. Specifically, the cord?s performance in either the ANSI/UL 1581-2001 ?Vertical Tray Flame Test? or the CSA C22.2 No.0.3-M-2001 ?Vertical Flame Test? of the Test Methods for Electrical Wire and Cables should be evaluated.
Also, if there is a great concern for the cord(s) and it?s products of combustion, the branch-circuit wiring could be extended above the raised floor through a wiring method as permitted in 645.5(D)(2) which include some non-metallic wiring methods.
I'm glad that the NFPA rep has gone back and forth with me, but the responses do not agree with me and are not clear enough for me to understand the logic. I don't understand how a definition in a different standard (like NFPA 75) can be used to interpret words in NFPA 70. Any comments are appreciated.
[ December 26, 2005, 09:55 AM: Message edited by: ron ]
