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  • Why High Temperature Wire is Not Required on Connector Strip Pigtails 

    If you run into a situation where the local Contractor or inspector will not accept the connector strips manufactured by ETC without changes to their construction based on  concerns about the temperature rating of the 12/3 Type SO tails installed on the connector strips due to their proximity to stage lighting fixtures.

    I would like to offer the following information and comment, perhaps to give additional new information that might cause them to reconsider their position on this matter.

    1.  Both the connector strips and the stage lighting fixtures are listed under the same standard: UL1573.

    • The Scope of UL1573 is defined by UL as follows:
    • Stage and Studio Luminaires and Connector Strips
    • 1.1.1.    1 Scope
    • 1.1 These requirements cover stage and studio luminaires rated 600 volts or less for use in theaters, studios, and similar locations in accordance with Articles 520 and 530 of the National Electrical Code, NFPA 70.
    • 1.2 These requirements cover borderlights, spotlights, floodlights, footlights, professional photographic lights, portable strip lights, and the like, that use incandescent, fluorescent, high-intensity discharge, xenon, and other high-pressure electric discharge lamps, as well as connector strips, drop boxes, and the like, when rigged similarly to borderlights. These requirements do not cover stage and studio luminaires using carbon arc lamps.
    • 1.3 These requirements do not cover miscellaneous special purpose lights, amateur movie lights, or lighting intended for residential use.

    UL1573 contemplates the use of listed luminaries and connector strips in the same environment, and does not contain a pigtail length limit or a requirement for high temperature cable on pigtails.

     

    2.    NEC Article 520 defines the allowable types of portable cable for use in Theaters and Similar Locations.  As defined in section 520.68 (A) (1), this requirement calls for Extra Hard Usage cords or cables. The typical temperature rating of these cords is 90 degrees C, sometimes 105 degrees C.


    3.    Section 520.68 (A) (3) defines the allowable cable construction for high temperature applications. The section  allows the use of a "special assembly" of high temperature conductors in a glass fiber sleeve where one end is permanently attached to the equipment.  Section 520.68 (A) (3) states:
        "Portable stage equipment requiring flexible supply conductors with a higher temperature rating where one end is permanently attached to the equipment shall be permitted to employ alternate, suitable conductors as determined by a qualified testing laboratory and recognized test standards"
        UL has determined that such a high temperature special assembly is required on certain UL Listed Stage luminaries, but not on connector strips.

    4.    NEC Section 520.46 defines the requirements for connector strips. There is no pigtail length limit or high temperature wire requirement.

    5.    Section 520.42 defines the conductor insulation requirements for connector strips. This section contemplates elevated ambient temperatures and requires interior conductors to be rated at 125 degrees C, with their ampacity based on 60 degree conductors. However, this section states:
        "All drops from connector strips shall be 90 degree C wire sized to the ampacity of 60 degree C cords and cables with no more than 150mm (6 in) of conductor extending into the connector strip."
        It is this statement that makes it allowable to use a type SO cable on pigtails, and one reason that UL does not require a high temperature cable in this application. A "drop" is a "pigtail".

    6.    It is important to remember that a theatre is a Special Occupancy in the NEC. This acknowledges that special equipment, listings, and methods of operation are applicable in theatres.  One of the well-known methods of operation in a theatre is to tie back portable cords or pigtails (usually with black sash cord on a temporary basis), so that they cannot come into contact with heat-producing fixtures that might operate at temperatures above the ultimate insulation temperature of the cord.

    If there is a situation where  the Contractor or Consultant wishes to shorten the connector strip pigtails in order to prevent them from coming into contact with fixtures.

    Even if this were required by the NEC or UL (which it definitely is not), this would not solve the problem that the consultant or inspector believes exists. That is because the NEC allows the use of extension cables and "twofers" (Y-adaptors defined in section 520.69) that are constructed from 90 degree C cable. These would certainly be used in the event of short pigtails, just as they are used in connector strips with flush-mounted outlets in order to get the power to the precise location of the fixture. Thus, the same "problem" would simply be transferred from pigtails to portable cords.

    In speaking with a member of the Code Making Panel 15 ( who are responsible for the contents of NEC Article 520) they stated;
    "I am often presented with proposals that seek to make the Code more stringent. This happens in nearly every Code cycle. CMP 15 then asks the question:
    'Is there a record of loss of property or injury to support making the requirements more stringent?'
    In the case of high-temperature cable or length limits on connector strip pigtails, I can assure you that no such loss experience exists. Connector strip pigtails simply don't fail very often due to contact with fixtures, because is well understood in the context of the Theater Special Occupancy that they should never come in contact with fixtures. Operational methods to prevent this contact are also well known.  This construction of connector strips and pigtails is used in virtually every theatre in the county. Furthermore, I can assure you that this question of temperature rating of pigtails has been asked and answered in the context of the NEC and proposals to the Code. The public record is there for all to examine in past NFPA documents.  It explains exactly how Section 520.42 came into being.  For anyone anxious to modify a proven, listed, NEC-compliant connector strip to a "better" design, I might encourage them to first review the NFPA ROP and ROC documents to understand the history of the current Code requirements."  I'd be happy to provide precise references to the applicable Code Cycle."