UL-514B-BULLETINS-2005.pdf
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1、FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION Subject 514B September 9, 2005 SUMMARY OF TOPICS The following changes in requirements are being proposed: 1) New Marking And Current Test Requirements Applicable To Specifi c Types Of Flexible Conduit And Cable 2) New Construction And Ma
2、rking Requirements For Fittings For Use With Metal Clad (MC) Cable 3) Marking For Grounding Means STP BALLOTS DUE: October 9, 2005 ALL COMMENTS DUE: October 24, 2005 For your convenience in review, proposed additions to existing requirements are shown underlined and proposed deletions are shown line
3、d-out. 1) New Marking And Current Test Requirements Applicable To Specifi c Types Of Flexible Conduit And Cable BACKGROUND These proposals were submitted by CANENA THSC 23A, the working group responsible the harmonized Standard for Conduit, Tubing, and Cable Fittings, UL 514B. You are requested to r
4、eview the proposed new requirements and submit any comments through ULs Collaborative Standards Development System (CSDS). Comments will not be responded to; rather, they will be given to the working group for consideration. After the working group has reviewed any comments that are received, and ha
5、s determined whether or not adjustments need to be made to the proposals, the proposals will be advanced to ballot. RATIONALE GENERAL Proposal Submitter: NEMA Included in this topic are proposals to amend the application of the Current Test for applicable fl exible conduits and cables. Since these w
6、iring systems are not accepted as equipment grounding conductors in Canada, the proposals are restricted to Mexico and the US. The NEC, in section 250.118, recognizes each of these raceway or cable systems as equipment grounding conductors. Types AC and MC cables are not restricted in length or ampa
7、city with respect to the protection on circuits where they are used. Liquidtight Flexible Metal Conduit, (LFMC), Flexible Copyright Underwriters Laboratories Inc. Provided by IHS under license with ULLicensee=Army Northwestern Div./7838506130 Not for Resale, 08/30/2006 05:15:20 MDTNo reproduction or
8、 networking permitted without license from IHS -,-,- FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION Metal Tubing, and Flexible Metal Conduit (FMC) all are restricted to lengths of 1.8 m (6 ft.) and circuits having overcurrent protection devices rated at 20 amperes or less (except for
9、LFMC in trade sizes 3/4 (21) through 1-1/4 (35) which is 60A or less). The present application of the Current Test is uniform for all of these systems and does not refl ect the distinction between those systems with strict limits and those not so limited according to NEC section 250.118. Rationale f
10、or each proposal is separately provided but this general overview is important in understanding the distinctions underlying the different approach to application of the Current Test to AC and MC cables which are relatively unrestricted and the other systems having common restrictions as equipment gr
11、ounding conductors. Editorial Note From UL The following rationales for the proposed current test requirements are provided as they were submitted by NEMA and Steel City. The proposals were originally submitted as proposed new Clauses 8.13.6, 8.14.6, 8.16.9, 8.17.10, and 8.21.10, but did not include
12、 references to the new current test requirements in Clause 8.9, Current Test. To clearly specify all applicable current test requirements, UL proposes that the proposed requirements be included in existing Clause 8.9, Current Test, and that cross references to Clause 8.9 be added to Clauses 8.13, 8.
13、14, 8.16, 8.17, and 8.21. The proposal submitters agreed with this approach. UL also proposes to add Clause 8.9.1, General, and to renumber Clauses 8.9.1 8.9.6 to align the organizational structure of Clause 8.9 with the overall structure of the standard. The proposed changes to the text of the requ
14、irements in Clauses 8.9.1 8.9.6 are intended to ensure that all applicable existing and new current test requirements are applied. RATIONALE FITTINGS FOR FLEXIBLE METAL CONDUIT Proposal Submitter: NEMA See the General rationale for this topic. Note: The 2005 NEC will eliminate NEC 2002 250.118 (5) s
15、o this proposal does not address fi ttings for use with FMC of the “grounding type”. Although with conduit, the size of the grounding conductor is not known until the installation is complete, if unrestricted in length or minimum circuit protection, the appropriate current/time for the Current Test
16、would be determined as that of the largest current-carrying conductor that can be accommodated given the trade size of the conduit. The current test presently in the standard is solely based on the trade size of the male threaded portion of the fi tting. It is appropriate to reduce the test current/
17、time as proposed since when FMC is installed and relied upon as an equipment grounding conductor subject to the restrictions in length and circuit protection in 2002 NEC 250.118 (6) (see note above), neither the fi tting or the conduit will be subject to a fault current of the full magnitude expecte
18、d for the largest current-carrying conductor (according to table 21 column 3 which is based on UL467). The proposed test currents and times are consistent with those applied to FMC in UL1. RATIONALE FITTINGS FOR ARMORED CABLE Proposal Submitter: NEMA SEPTEMBER 9, 2005SUBJECT 514B-2- Copyright Underw
19、riters Laboratories Inc. Provided by IHS under license with ULLicensee=Army Northwestern Div./7838506130 Not for Resale, 08/30/2006 05:15:20 MDTNo reproduction or networking permitted without license from IHS -,-,- FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION See the General rationa
20、le for this topic. The design of each AC cable and its trade size provides specifi c identifi cation as to the size of the largest current-carrying conductor contained therein. The maximum throat diameter for a listed AC fi tting naturally limits the size of conductors that can pass through, and the
21、 maximum cable diameter is restricted by the cable securement feature of the fi tting. Because of these standard limits, the test current/time can justifi ably be based on the largest current-carrying conductor size in the largest 2-conductor cable for which the fi tting is intended and listed. The
22、present methodology employed in UL514B for determining the test current/time is based solely on the knockout size for which an AC connector is designed. Whenever possible, for fi ttings intended for use with AC cable, the most reliable method for determining the appropriate test current/time is to b
23、ase it on the maximum size current carrying conductor in the largest 2-conductor cable the fi tting can accept. Present marking requirements in UL 514B sufficiently provide the necessary identifi cation of cables to make this determination and to enable specifi ers and inspectors to review the fault
24、-current conditions for a given fi tting. RATIONALE FITTINGS FOR LIQUID-TIGHT FLEXIBLE METAL CONDUIT Proposal Submitter: NEMA NEC Section 250.118(6) distinguishes LFMC of the grounding type in trade sizes 3/8 (12) 1/2 (16), and 3/4 (21) 1-1/4 (35), from the larger trade sizes in their conditions for
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