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1、FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION Subject 508A July 28, 2006 SUMMARY OF TOPICS The following changes in requirements are being proposed: 1. For Preliminary Review Only: Short Circuit Rating Industrial Control Panel Enclosures 2. For Preliminary Review Only: Redefi ned Spa
2、cing Requirements For Terminal Blocks Used In Industrial Control Panels. 3. For Preliminary Review Only: Withdrawal of requirement 1.6.5 4. For Preliminary Review Only: Type 2 Protection SCCR 5. For Preliminary Review Only: Clarifi cation Of Interrupting Rating Versus Short Circuit Current Rating 6.
3、 For Preliminary Review Only: Update List Of Default Values 7. For Preliminary Review Only: Addition Of UL 248-8 Fuses Class J Intermediate Sizes To Table SB4.2 8. For Preliminary Review Only: Short Circuit Current Ratings 9. For Preliminary Review Only: Bus Bar Arrangement and Identifi cation of Hi
4、gh Leg 10. For Preliminary Review Only: Ground Detectors for Ungrounded Secondary Circuits 11. For Preliminary Review Only: Identifi cation of Grounded Circuit Conductor 12. For Preliminary Review Only: Motor Disconnect Switch Location in Variable Speed Drive Circuit 13. For Preliminary Review Only:
5、 Number of Service Disconnects 14. For Preliminary Review Only: System Bonding Jumper and Grounding Electrode Conductor Terminal 15. For Preliminary Review Only: Wire Bending Space at Input Field Wiring Terminals 16. For Preliminary Review Only: Surge Control Devices for Use on Specifi c Electrical
6、System COMMENTS DUE: September 11, 2006 FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION For your convenience in review, proposed additions to existing requirements are shown underlined and proposed deletions are shown lined-out. 1. For Preliminary Review Only: Short Circuit Rating Indu
7、strial Control Panel Enclosures RATIONALE Proposal submitted by Gordon Davis The NEC requires short circuit markings for control panels. One of the major criterion for passing a short circuit test is that the door or cover of an enclosure does not open or otherwise expose live parts. Because of the
8、design of custom panels, it is not practical to test each panel. This proposal will allow minimum assurance that enclosure integrity will not be compromised to a point of hazard during short circuit conditions. It is also designed to be cost effect to industry, while adding to the safety of the cons
9、umer. PROPOSALS (NEW) 64.3 An enclosure complying with SB4.5 may be marked, Short circuit rating _ Amps RMS _ volts _ horsepower. (NEW) 64.4 An enclosure complying with Table SB4.1 may be marked in accordance with the short circuit rating found in the table. Table SB4.1 Assumed maximum short circuit
10、 current rating for unmarked components Table SB4.1 effective April 25, 2006 ComponentShort circuit current rating, kA Bus bars10 Circuit breaker (including GFCI type)5 Current metersa Current shunt10 Enclosure5 Fuseholder10 Industrial control equipment: a. Auxiliary devices (overload relay)5 b. Swi
11、tches (other than mercury tube type)5 c. Mercury tube switches Rated over 60 amperes or over 250 volts5 Rated 250 volts or less, 60 amperes or less, and over 2 kVA3.5 Rated 250 volts or less and 2 kVA or less1 Motor controller, rated in horsepower (kW) a. 0 50 (0 37.3)5c b. 51 200 (38 149)10c c. 201
12、 400 (150 298)18c d. 401 600 (299 447)30c JULY 28, 2006SUBJECT 508A-2- Table SB4.1 Continued on Next Page FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION Table SB4.1 Continued ComponentShort circuit current rating, kA e. 601 900 (448 671)42c f. 901 1500 (672 1193)85c Meter socket base1
13、0 Miniature or miscellaneous fuse10b Receptacle (GFCI type)2 Receptacle (other than GFCI type)10 Supplementary protector0.2 Switch unit5 Terminal block or power distribution block10 a A short circuit current rating is not required when connected via a current transformer or current shunt. A directly
14、 connected current meter shall have a marked short circuit current rating. b The use of a miniature fuse is limited to 125-volt circuits. c Standard fault current rating for motor controller rated within specifi ed horsepower range. (NEW) SB4.5 Enclosures with short circuit ratings greater than tabl
15、e SB4.1 SB4.5.1 Enclosures marked with short circuit ratings greater than Table SB4.1 shall comply with SB4.5.2 SB4.5.4. SB4.5.2 An enclosure shall be short circuited with a Type D Combination Motor Controller per the short circuit test found in UL 508. The instantaneous trip circuit breaker shall n
16、ot be a current limiting type. The overload protective device shall not use a current transformer. The magnetic or solid state controllers and the overcurrent protective devices shall be appropriately sized and protected. SB4.5.3 The criterion for passing is that the door or cover shall not open or
17、otherwise expose live parts as determined by the use of an articulated fi nger. SB4.5.4 The hinges, latches or locks that comply with the passing criterion may be used on additional enclosures of equivalent construction, including minimum volume, at the same rating without additional test. 2. For Pr
18、eliminary Review Only: Redefi ned Spacing Requirements For Terminal Blocks Used In Industrial Control Panels. RATIONALE Proposal submitted by Dan Nachtigall, Rockwell Automation Terminal blocks currently used within power circuits (feeder or branch) in industrial control panels comply with the spaci
19、ngs per Use Group C in UL 1059, the Standards for Terminal Blocks. These spacings are equivalent to those defi ned in Table 10.1, Column A of UL 508A. The new spacing requirements per Table 10.2 of UL 508A for terminal blocks used in feeder circuits would restrict the use of these terminal blocks, a
20、nd limit the availability of suitable terminal blocks to those evaluated for service equipment use per Use Group A in UL 1059 for non-service equipment applications. To redefi ne the spacing requirements for terminal blocks used in power circuits, the following addition to UL 508A shall be made as s
21、hown below. JULY 28, 2006SUBJECT 508A-3- -,-,- FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION PROPOSAL (NEW) 10.9 Terminal blocks used within power circuits shall comply with the spacings specifi ed in Column A of Table 10.1. 3. For Preliminary Review Only: Withdrawal of requirement 1
22、.6.5 RATIONALE Proposal submitted by Chuck Goetz, UL Manufacturers have noted a need to build control panels that include some components for remote control of dispensing equipment, are located in a non-hazardous location, and contain a large number of additional circuits supplying other equipment i
23、nstalled in ordinary locations. Additionally, the current scope of UL 1238 does not permit assembly of equipment other than that used specifi cally for dispensing equipment. Further defi nition of applications where the use of UL 1238, the Standard for Control Equipment for use with Flammable Liquid
24、 Dispensing Devices, is appropriate from those where UL 508A is able to be used need to be developed. Until revisions to UL 1238 are made to address these applications, UL is proposing that requirement 1.6.5 of UL 508A be deleted. PROPOSAL (DELETED) 1.6.5 Equipment intended to control the operation
25、of pumps dispensing gasoline or other fl ammable liquids is covered by the Standard for Control Equipment for Use with Flammable Liquid Dispensing Devices, UL 1238. 1.6.5 added September 1, 2005 4. For Preliminary Review Only: Type 2 Protection SCCR RATIONALE Proposal submitted by Todd Lottmann, Coo
26、per Bussmann The testing procedures of UL 508E follow that of UL 508, high fault current test. It is stated in UL 508E in paragraph 5.1, for the purpose of Type “2” coordination, the motor controller, with or without thermal overload relay, shall comply with the applicable requirements in the Standa
27、rd for Industrial Control Equipment, UL 508. Both tests perform the “O” and “CO” shots. The only difference is the level of acceptable damage to the components. The UL 508E acceptable damage level is very minimum compared to UL 508. Therefore since the level of safety of the equipment and personnel
28、will be greatly increased, the following new text should be added to SB4.2.2(c). PROPOSAL SB4.2.2 The short circuit current rating of a component shall be established by one of the following methods: a) The short circuit current rating marked on the component or on instructions provided with the com
29、ponent; JULY 28, 2006SUBJECT 508A-4- FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION b) The short circuit current rating determined by the voltage rating of the component and the assumed short circuit current from Table SB4.1; or c) The short circuit current rating for a load controlle
30、r, motor overload relay, or combination motor controller that has been investigated in accordance with the performance requirements, including short circuit test requirements for standard fault currents or high fault currents specifi ed in the Standard for Industrial Control Equipment, UL 508, and T
31、ype 2 Coordination Short Circuit Tests of Electromechanical Motor Controllers in accordance with UL 508E and described in the manufacturers Procedure. SB4.2.2 effective April 25, 2006 5. For Preliminary Review Only: Clarifi cation Of Interrupting Rating Versus Short Circuit Current Rating RATIONALE
32、Proposal submitted by Todd Lottmann, Cooper Bussmann Changing SCCR to interrupting rating fi xes an improper reference and clarifi es the requirement as the interrupting ratings of branch circuit overcurrent protectives is used. The new text will clarify how to deal with overcurrent protective devic
33、es which are not marked with an interrupting rating. PROPOSALS SB4.3.2 For branch circuits supplied by a Listed circuit breaker marked current limiting in the feeder circuit, the short circuit current rating on the line side of the circuit breaker shall be one of the following: a) The short circuit
34、current rating of the feeder circuit breaker when all of the components in the branch circuit have a short circuit current rating not less than the published peak let-through current of the circuit breaker, see Figure SB4.1, and the short circuit current interrupting rating of all branch circuit pro
35、tective devices on the load side are not less than the short circuit current rating of the feeder circuit breaker.; For branch circuit devices not marked with an interrupting rating, the values in Table SB4.1 shall be used. b) The smallest short circuit current rating of any branch circuit protectiv
36、e device on the load side of the feeder circuit breaker, when the conditions of SB4.3.2(a) exist except the short circuit current interrupting rating of the branch circuit protective devices on the load side are less than the short circuit current rating of the feeder circuit breaker. For branch cir
37、cuit overcurrent protective devices not marked with an interrupting rating, the values in Table SB4.1 shall be used. c) The smallest short circuit current rating of any branch circuit on the load side of the feeder circuit breaker, when the conditions of SB4.3.2(a) or SB4.3.2(b) are not met. Revised
38、 SB4.3.2 effective April 25, 2006 SB4.3.3 For branch circuits supplied by a Class CC, G, J, L, RK1, RK5, or T fuse in the feeder circuit, the short circuit current rating on the line side of the fuse shall be one of the following: a) The short circuit current rating of the feeder fuse when all of th
39、e components in the branch circuit have a short circuit current rating not less than the peak let-through current corresponding to the specifi c fuse class employed from Table SB4.2 based on the current rating of the fuse and the available short circuit current on the line side of the fuse, and the
40、short circuit current interrupting rating of all branch circuit protective devices on the load side are not JULY 28, 2006SUBJECT 508A-5- FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION less than the short circuit current rating of the feeder fuse.; For branch circuit overcurrent protec
41、tive devices not marked with an interrupting rating, the values in Table SB4.1 shall be used; b) The smallest short circuit current rating of any branch circuit protective device on the load side of the feeder fuse, when the conditions of SB4.3.3(a) exist except the short circuit current interruptin
42、g rating of the branch circuit protective devices on the load side are less than the short circuit current rating of the feeder fuse. For branch circuit overcurrent protective devices not marked with an interrupting rating, the values in Table SB4.1 shall be used; c) The smallest short circuit curre
43、nt rating of any branch circuit on the load side of the feeder fuse, when the conditions of SB4.3.3(a) or SB4.3.3(b) are not met. Revised SB4.3.3 effective April 25, 2006 6. For Preliminary Review Only: Update List Of Default Values RATIONALE Proposal submitted by Todd Lottmann, Cooper Bussmann This
44、 change will aid the user in determining the rating of an unmarked combination motor controller. PROPOSAL Table SB4.1 Assumed maximum short circuit current rating for unmarked components Table SB4.1 effective April 25, 2006 ComponentShort circuit current rating, kA Bus bars10 Circuit breaker (includ
45、ing GFCI type)5 Current metersa Current shunt10 Fuseholder10 Industrial control equipment: a. Auxiliary devices (overload relay)5 b. Switches (other than mercury tube type)5 c. Mercury tube switches Rated over 60 amperes or over 250 volts5 Rated 250 volts or less, 60 amperes or less, and over 2 kVA3
46、.5 Rated 250 volts or less and 2 kVA or less1 Motor controller and combination motor controller, rated in horsepower (kW) a. 0 50 (0 37.3)5c b. 51 200 (38 149)10c c. 201 400 (150 298)18c d. 401 600 (299 447)30c e. 601 900 (448 671)42c f. 901 1500 (672 1193)85c Meter socket base10 Miniature or miscel
47、laneous fuse10b Receptacle (GFCI type)2 JULY 28, 2006SUBJECT 508A-6- Table SB4.1 Continued on Next Page FOR INTERNAL UL OR CSDS USE ONLY NOT FOR OUTSIDE DISTRIBUTION Table SB4.1 Continued ComponentShort circuit current rating, kA Receptacle (other than GFCI type)10 Supplementary protector0.2 Switch
48、unit5 Terminal block or power distribution block10 a A short circuit current rating is not required when connected via a current transformer or current shunt. A directly connected current meter shall have a marked short circuit current rating. b The use of a miniature fuse is limited to 125-volt cir
49、cuits. c Standard fault current rating for motor controller rated within specifi ed horsepower range. 7. For Preliminary Review Only: Addition Of UL 248-8 Fuses Class J Intermediate Sizes To Table SB4.2 RATIONALE Proposal submitted by Todd Lottmann, Cooper Bussmann Since the values are tested and listed as part of the UL 248-8 standard, this would offer fl exibility and increase the level of protection of the customers equipment. This should be allowed as either pa