1、Subject 508 (in reply, refer to Subject 508) 12 Laboratory Drive Research Triangle Park, NC 27709 August 16, 2001 TO: Standards Technical Panel (STP) for Industrial Control Equipment, STP 508, Industry Advisory Conference of UL for Industrial Control Equipment, Subscribers to ULs Standards Service f
2、or Industrial Control Equipment SUBJECT: Report of the Meeting of the Industry Advisory Conference of UL for Industrial Control Equipment; Request for Comments on the Proposed Requirements for the Seventeenth Edition of the Standard for Industrial Control Equipment, UL 508; PROPOSED EFFECTIVE DATES
3、The following topics were discussed at the meeting: 1. Standards Technical Panels (STPs) - ULs Enhanced Standards Development Process 2. Manual Motor Controllers Suitable for Tap Conductor Protection in Group Installations 3. Backfeeding of Self-Protected Combination Motor Controllers 4. Short Circu
4、it Tests - A. Bus Bar Accessories for Use With Industrial Control Equipment, B. Assemblies of Indostrial Control Equipment 5. Equipment Rated 601 - 1500 Volts 6. Insulating Materials 7. Spacings 8. Insulating Barriers 9. Float and Pressure Operated Switches -A. Float Switches, B. Short Circuit Test
5、and Three Phase Motor Ratings, C. Ratings for Pressure Operated Switches IO. Miscellaneous Apparatus - A. Resistors, B. Power Supplies II. Field Wiring Terminals 12. Marking Locations 13. New Descriptive Report Format - Discussion Regarding the Elimination of Figures, Illustrations, etc. 14. NEMA Ra
6、tings on Equipment SUBJECT 508 -2- AUGUST 16,2001 15. Proposed First Edition of UL 60947-1 General Rules and UL 60947-4-1 Contactors and Starters 16. Reorganization of Industrial Control Equipment Product Categories 17. Proposed New Standard for General-Purpose Branch-Circuit Motor Controllers 18. S
7、chedule for Next Meeting COMMENTS DUE: October 12,2001 A meeting of the Industry Advisory Conference of UL for Industrial Control Equipment was held on April 9 b) the ampacity of the tap conductor, on the line side of the manual motor controller, is not less than 1/10 of the ampere rating of the bra
8、nch circuit protection for the motor group; and c) when listed and specifically marked for this purpose. SUBJECT 508 -5- AUGUST 16,2001 In support of the panel action, UL is proposing requirements for inclusion in UL 508 to evaluate a manual motor controller for this purpose. This proposal includes
9、additional performance tests consistent with the substantiation presented to the code making panel and marking requirements for manual motor controllers suitable for use as tap conductor protection within motor groups. The proposed marking, ”Suitable for Tap Conductor Protection in Group Installatio
10、ns” is also included in the NEC text of the revision to Section 430-53(d). As these devices will be limited by the NEC proposal for use on the load side of the branch circuit protection only, the current UL 508 general industrial spacings are sufficient for this use. The proposed performance test pr
11、ogram includes evaluation of the integral overcurrent protection to interrupt short circuits and faults to ground. In order to demonstrate the interrupting ability of the device and to minimize impedance in the test circuit, the interrupting tests will be performed without an additional branch circu
12、it protective device on the line side. In addition, the device will be required to comply with performance requirements for motor disconnect switches. As these devices do not have a means for remote control of their contacts, there are also provisions in the proposal to conduct short circuit testing
13、 of motor controllers that will be installed on the load side of these devices. Per the aforementioned NEC revisions, UL also plans to revise the guide information with the following text for Manual Motor Controllers (NLRV) to facilitate identification of these devices in the field: Tap Conductor Pr
14、otection - Manual motor controllers that have been additionally investigated for use as tap conductor protection within a motor group are marked ”Suitable as Tap Conductor Protection in Group Installations”. These devices are intended to be installed on the load side of motor branch circuit protecti
15、on for a motor group in accordance with Section 430-53(d)(3) of the National Electrical Code. Industry suggested that these proposals be revised to address the use of replaceable and non- replaceable current elements. UL has revised and included additional proposals to address this concern. UL has a
16、lso included additional proposals to address manual motor controllers intended for use as tap conductor protection based upon the discussions at the meeting. Revisions to Table 67.1, Marking locations for industrial control equipment, resulting from the proposed requirements are located in Item 12,
17、Marking Locations of this meeting report. IMPACT As these proposals represent an additional level of performance that is optional for manual motor controllers, no review or retest of currently Listed or Recognized components will be necessary. Therefore, UL proposes that these revisions become effec
18、tive upon publication. 3. BACKFEEDING OF SELF-PROTECTED COMBINATION MOTOR CONTROLLERS RATIONALE and DISCUSSION Back-feeding is a common practice with certain types of components, such as a circuit breaker, to overcome wiring problems for a specific installation. Manufacturers have asked what evaluat
19、ion would be required to permit a self-protected combination motor controller to be back-fed, that is, have the source of supply connected to the terminals normally used for connection of the load. SUBJECT 508 -6- AUGUST 16,2001 Back-feeding is not feasible for most combination motor controllers as
20、this would place discrete components such as the motor controller, and motor overload relay, on the line side of the motor branch circuit protection and disconnecting means. In the case of a self-protected combination motor controller, this construction is possible when all of the combination motor
21、control functions are contained in a common housing. In general, when a self-protected combination motor controller is mounted on a horizontal DIN rail, the line side terminals for connection to the supply are on the top and the load side terminals for connection of the motor load are on the bottom.
22、 UL proposes to add requirements to UL 508 to specifically address this optional installation method. These proposals would require self-protected combination motor controllers intended for back-fed installation to comply with the line side terminal spacing requirements on both the line and load sid
23、es of the device and also undergo additional performance requirements with the line and load connections reversed. The additional performance requirements are intended to demonstrate that the device can safely operate in this mode without having to repeat the entire test program. As most combination
24、 motor controllers are not able to be back-fed, UL is proposing that only those self-protected combination motor controllers that comply with the additional requirements be marked to indicate their suitability for back-feed ing . The performance requirements selected to evaluate back-fed self-protec
25、ted combination motor controllers are similar to those for back-fed circuit breakers evaluated to UL 489, Standard for Molded-Case Circuit Breakers, Molded-Case Switches and Circuit Breaker Enclosures. An industry representative suggested that use of the term ”backfeed” as part of a product marking
26、may be misunderstood by installers. It was also suggested by industry that perhaps the term ”reverse-fed” rather than ”back-fed” would be more appropriate and recommended that UL review the Standard for Ground-Fault Circuit-Interrupters, UL 943 to look for similar marking requirements that may be le
27、ss ambiguous. UL has reviewed UL 943 and found no reference to terms relating to ”back-fed” or ”reverse-fed”. Also, UL 489 was reviewed and there are several references to ”back-fed”, but no definition of the term. UL has revised 88.9 to require identification of the alternate wiring connections onl
28、y. UL has also modified the proposed text for inclusion in the guide information for NKJH to the following: ”Unless otherwise marked, self-protected combination motor controllers are not intended to be installed with the line and load connections reversed.” IMPACT As the proposed requirements repres
29、ent an additional installation method for self-protected combination motor controllers, no review or retest of currently Listed products will be necessary. Therefore, UL proposes that these revisions become effective upon publication. 4. SHORT CIRCUIT TESTS -A. BUS BAR ACCESSORIES FOR USE WITH INDUS
30、TRIAL CONTROL EQUIPMENT RATIONALE and DISCUSSION UL has Listed and Recognized bus bars as accessory parts for use with industrial control equipment. Some of these bus bar accessories have their own mounting means. For example, motor controllers are connected via specially designed supports with stab
31、s that engage the bus bars or are provided with terminal assemblies for attachment of a short length of conductor. UL has evaluated these assemblies SUBJECT 508 -7- AUGUST 16,2001 for compliance with applicable requirements from UL 845, Standard for Motor Control Centers, including the spacing requi
32、rements, separate withstand short circuit testing of bus bars, as well as short circuit tests of bus bars with attachment of connectors or stabs, and branch circuit protective devices. Other accessory bus bars are intended for use with specific motor controllers and are provided with open spade conn
33、ectors or pins that are arranged to fit into existing field wiring terminals of the motor controller. These bus bars are supported only by the connections to the motor controller. UL has evaluated these assemblies for compliance with requirements from UL 508, including spacing requirements and have
34、conducted short circuit tests with manual controllers with integral overcurrent protection connected to the load side of the bus bar. These bus bars are covered in the category for Manual Motor Controllers. Manufacturers have asked UL whether the spacing requirements in Table 76.3 apply to bus bars
35、used on the line side of Listed self-protected combination motor controllers. UL is proposing to revise UL 508 to specify that the spacing requirements for devices intended for installation on the line side of branch circuit protection to comply with the spacing requirements in Table 76.3. Additiona
36、lly, UL is proposing revisions to the short circuit test to specify the test procedures used for evaluating bus bar accessories. Table 53.1, footnote c, has also been revised to include maximum damage criteria for bus bars following the short circuit test specified in proposed 50.1.8. See Topic 2, M
37、anual Motor Controllers Suitable for Tap Conductor Protection in Group Installations, for revised Table 53.1. Industry expressed concern in regards to whether the devices would be used in group installation or in the feeder circuit. UL indicated that based upon discussions, the proposals would be re
38、vised and the resulting revisions reflected in this meeting report. IMPACT As these proposals contain additional construction and performance requirements for bus bar assemblies, a review and retest of Listed and Recognized products will be necessary. UL proposes that the requirements become effecti
39、ve 24 months after publication. 4. SHORT CIRCUIT TESTS - B. ASSEMBLIES OF INDUSTRIAL CONTROL EQUIPMENT RATIONALE and DISCUSSION Manufacturers have submitted products that include various pieces of industrial control equipment together with one or more overcurrent protective devices in a common enclo
40、sure. The current requirements in UL 508 do not require short circuit ratings for equipment intended for non-motor loads. However, when combined with one or more overcurrent protective devices, additional evaluation of the assembly is necessary to determine damage that would be incurred to the enclo
41、sure due to fault current. If more than one circuit is involved, the evaluation will establish a single short circuit rating for the assembly. UL had proposed revisions to UL 508 that would have required the short circuit test to be conducted to establish short circuit current ratings for assemblies
42、 containing overcurrent protection. Industry indicated that the proposal to require short circuit tests was too restrictive. They suggested incorporating concepts from UL 508A, Standard for Industrial Control Panels as an alternate means to establish short circuit ratings without conducting addition
43、al tests. Therefore, UL has withdrawn proposed paragraph 50.1 .I O. SUBJECT 508 -8- AUGUST 16,2001 5. EQUIPMENT RATED 601 - 1500 VOLTS RATIONALE The current requirements for industrial control equipment rated 601- 1500 volts are contained in Part XVIII of UL 508. However, requirements in other parts
44、 of UL 508, such as for the dielectric voltage withstand test and short circuit test, do not specifically reference when Part XVIII applies. UL is proposing to revise UL 508 to delete Part XVIII and to include the requirements for 601- 1500V equipment in the applicable parts of UL 508. Proposed revi
45、sions that pertain to Part XVIII requirements for insulating materials are included under agenda item 6, Insulating Materials. IMPACT As the proposed revisions clarify existing requirements for equipment rated 601- 1500 volts, no review or retest of currently Listed or Recognized components will be
46、necessary. Therefore, UL proposes that these requirements become effective upon publication. 6. INSULATING MATERIALS RATIONALE and DISCUSSION Since the inclusion of Table 15.1 in UL 508 which gives specific requirements for evaluating insulating materials for compliance with the direct support requi
47、rements in UL746C, Polymeric Materials - Use in Electrical Equipment Evaluations, revisions have been made to UL 746C. Additionally, when the table was added, previous references to UL 746C were eliminated. This inadvertently caused direct support requirements in Part XVIII of UL 508 for equipment r
48、ated 601 - 1500V to refer to CTI values instead of to UL 746C which specifies inclined plane tracking test for insulating materials used at voltages greater than 600V. UL 746C has been revised to allow a glow-wire test as an alternate test method to the abnormal overload test. The test method for Gl
49、ow-Wire End-Product Test in UL 746C indicates that it is based upon the Glow-Wire End-Product Test in IEC 695-2-1/1. The glow wire temperature specified in UL 746C for non-household products is 750C. While previous requirements in UL 746C implied that better CTI performance may be required depending on the equipment environment, revisions have now specified CTI Performance Level Category (PLC) levels for various applications. These revisions assign CTI PLC level 4 to devices for indoor use where contamination is controlled. This corresponds to definition of pollution degree 2. A CTI PLC of
