Design Guide for Integration of Fixed-Mount Circuit Breakers

Transcription

1 Design Guide Design Guide for Integration of Fixed-Mount Circuit Breakers WL Low Voltage Power Circuit Breakers

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3 Contents Introduction... 3 Mounting... 3 Mounting Surface... 3 Mounting Hardware... 4 Compartment Design... 5 Minimum Compartment Size... 5 Electrical Clearances... 6 Bus Bar Connections Rear Horizontal Bus Terminals Rear Vertical Bus Terminals Front-accessible Bus Terminals Front Bus Terminal Lug Kits Bus Bracing Phase Barriers Door Cut-Outs Flush Mounted Semi-Flush Mounted Control Wiring Space Additional Resources... 30

4 Design Guide for Integration of Fixed-Mount WL Low Voltage Power Circuit Breakers Introduction When designing electrical power distribution equipment, there are many important questions that must be answered. Improperly installed fixed-mount power circuit breakers can reduce the performance characteristics or the overall life span of the product. The following guidelines are offered as recommended practices for installing fixed-mounted Siemens type WL low-voltage power circuit breakers, covering topics such as mounting requirements, compartment size, minimum ventilation, electrical clearances, bus bar connections, and bus bracing. In addition to these recommended practices, applicable industry standards and regional code requirements should be considered. This Guide will highlight some of these issues and recommend corresponding solutions applying the Siemens type WL family of low voltage power circuit breakers. Mounting Mounting Surface WL Circuit Breakers should be mounted to a surface capable of supporting the weight of the circuit breaker and which is flat to within 3/64 inch. The approximate weights of the circuit breaker are listed in Table 1. Table 1: Weights Frame Size No. of Poles Interrupting Class Frame Rating (A) I 3 S, H, L II 3 S, L C S, H, L III 3 L H, L Approximate Weight (lbs) 3 WL Low Voltage Power Circuit Breakers Design Guide

5 3/64 The mounting surface may be tilted up to 30 in any direction, or combination thereof. Mounting Hardware The feet of the circuit breaker include four captive nuts, sized as shown in Table 2. Mounting hardware kits may be purchased from Siemens. Table 2 Frame Size Nut Size Hardware Kit Contents Recommended Torque I M8 WLMETRC M8 bolt (4) 15 lb-ft II M8 lockwasher (4) M8 flat washer (4) III M10 WLMETRC3 M10 bolt (4) M10 lockwasher (4) M10 flat washer (4) 30 lb-ft WL Low Voltage Power Circuit Breakers Design Guide 4

6 Compartment Design The following recommendations provide guidelines for minimum sizing of and clearances within the circuit breaker compartment. Other arrangements may be feasible, but must be validated by design testing in accordance with ANSI C37.50 or UL 489, as applicable. Minimum Compartment Size Minimum circuit breaker compartment sizes should be met in order to provide adequate interrupting and circuit breaker cooling space. Table 3 describes the recommended minimum circuit breaker compartment sizes. All fixed-mount WL circuit breakers are considered 100% rated when applied in accordance with Table 3. Note that WL circuit breakers rated below 3000 amperes do not require any ventilation openings within the circuit breaker compartment. For the greatest overall effectiveness of the ventilation (when necessary), the openings should be situated above and below the circuit breaker terminals. Table 3: Minimum Circuit Breaker Compartment Size Recommendations Frame Size No. of Poles Interrupting Class Frame Rating (A) Width (in.) Height (in.) Depth (in.) Cubicle Ventilation Top (in 2 ) I 3 S, H, L II 3 S, L, C S, H, L III 3 L C H, L Bottom (in 2 ) 5 WL Low Voltage Power Circuit Breakers Design Guide

7 Electrical Clearances In order to prevent flashover from phase-to-phase or phase-to-ground during circuit breaker operations, it is recommended that the specified minimum clearances be maintained at all times. Tables 4-8 describe various minimum recommended clearances for different construction considerations. Table 4 describes the minimum clearances to phase conductors or grounded metal components for an open circuit breaker compartment with no internal barriers. Maintaining these clearances will provide adequate arcing space above the circuit breaker to prevent a phase-to-phase or phase-to-ground arc flash event. Table 4: Minimum Clearances to Phase Conductors or Grounded Metal Components Frame Size No. of Poles Interrupting Class A1 (in.) B1 (in.) C1 (in.) System Voltage 480 V 600 V 480 V 600 V 480 V 600 V I 3 S H L II 3 S L S, H, L III 3 L H, L D A1 B1 C1 cubicle door / deadfront cover minimum distance from the top of the arc chute to the nearest grounded metal barrier or live parts above the circuit breaker minimum horizontal space above the arc chutes free of obstruction minimum distance to phase or neutral conductors located behind the circuit breaker WL Low Voltage Power Circuit Breakers Design Guide 6

8 Table 5 describes the minimum clearances to grounded metal components for an open circuit breaker compartment with grounded metallic internal barriers either behind the circuit breaker, above the circuit breaker, or both. Maintaining these clearances will provide adequate arcing space above the circuit breaker to prevent a phase-to-phase or phase-to-ground arc flash event. Table 5: Minimum Clearances to Grounded Metal Components Frame Size No. of Poles Interrupting Class A2 (in.) B2 (in.) C2 (in.) System Voltage 480 V 600 V 480 V 600 V 480 V 600 V I 3 S H L II 3 S L S, H, L III 3 L H, L D A2 B2 C2 cubicle door / deadfront cover minimum distance from the top of the arc chute to the nearest grounded metal barrier or live parts above the circuit breaker minimum horizontal space above the arc chutes free of obstruction minimum distance to an insulator or grounded metal barrier separating the circuit breaker from phase or neutral conductors 7 WL Low Voltage Power Circuit Breakers Design Guide

9 Table 6 describes the minimum clearances to phase conductors or insulated components for an open circuit breaker compartment with no internal barriers. Maintaining these clearances will provide adequate arcing space above the circuit breaker to prevent a phase-to-phase or phase-to-ground arc flash event. Table 6: Minimum Clearances to Insulated Materials Frame Size No. of Poles Interrupting Class A3 (in.) B3 (in.) C3 (in.) System Voltage 480 V 600 V 480 V 600 V 480 V 600 V I 3 S H L II 3 S L C S, H, L III 3 L C H, L D A3 B3 C3 cubicle door / deadfront cover minimum distance from the top of the arc chute to the nearest grounded metal barrier or live parts above the circuit breaker minimum horizontal space above the arc chutes free of obstruction minimum distance to phase or neutral conductors located behind the circuit breaker WL Low Voltage Power Circuit Breakers Design Guide 8

10 Table 7 describes the minimum clearances to insulated components for an open circuit breaker compartment with grounded metallic internal barriers either behind the circuit breaker, above the circuit breaker, or both. Maintaining these clearances will provide adequate arcing space above the circuit breaker to prevent a phase-to-phase or phase-to-ground arc flash event. Table 7: Minimum Clearances to Insulated Materials Frame Size No. of Poles Interrupting Class A4 (in.) B4 (in.) C4 (in.) System Voltage 480 V 600 V 480 V 600 V 480 V 600 V I 3 S H L II 3 S L C S, H, L III 3 L C H, L D A4 B4 C4 cubicle door / deadfront cover minimum distance from the top of the arc chute to an insulating barrier or insulated parts above the circuit breaker minimum horizontal space above the arc chutes free of obstruction minimum distance to an insulator or grounded metal barrier separating the circuit breaker from phase or neutral conductors 9 WL Low Voltage Power Circuit Breakers Design Guide

11 Table 8 describes the minimum clearances to an L -shaped insulation barrier isolating the arcing space above the circuit breaker from the rest of the circuit breaker compartment. Maintaining these clearances will provide adequate arcing space above the circuit breaker to prevent a phase-to-phase or phase-to-ground arc flash event. Table 8: Minimum Clearances to Insulated Materials Frame Size No. of Poles Interrupting Class A5 (in.) B5 (in.) System Voltage 480 V 600 V 480 V 600 V I 3 S H L II 3 S L C S, H, L III 3 L C H, L D A5 B5 cubicle door / deadfront cover minimum distance from the top of the arc chute to an insulating barrier above the circuit breaker minimum horizontal space above the arc chutes free of obstruction WL Low Voltage Power Circuit Breakers Design Guide 10

12 Bus Bar Connections Siemens offers several means of connecting the primary conductors to the circuit breakers: Rear horizontal bus terminals (standard) Rear vertical bus terminals (optional accessory kit) Front-accessible bus terminals (optional accessory kit) Table 9: Bus Bar Connection Options Frame Size No. of Poles Interrupting Class Frame Rating (A) Rear Horizontal Optional Connectors Rear Vertical I 3 S, H, L Standard Standard II 3 S, L, C Standard 3000 Standard 4 S, H, L Standard 3200 Standard III 3 L Standard C Standard 4 H, L Standard Front- Accessible Types of Conductors An appropriate number of conductors should be applied to each terminal to carry the load protected by the circuit breaker. The minimum number of conductors may differ based on bus geometry, applied coatings, presence (or absence) of nearby heat sources, air flow across the conductors, and other factors. Many industry standards provide a rule-of-thumb of a current density of 1000 amperes per square-inch of copper, or no more than 700 amperes per square-inch of aluminum. The following Table includes some conductor recommendations. 11 WL Low Voltage Power Circuit Breakers Design Guide

13 Table 10: Recommended Conductor Sizing Continuous Current (A) Conductor Quantity Size 800 Cu 1 1/4 x 3 Al 1 1/4 x Cu 2 1/4 x 3 Al 2 1/4 x Cu 2 1/4 x 3 Al 2 1/4 x Cu 2 1/4 x 4 Al 2 1/4 x Cu 2 1/4 x 5 Al 4 1/4 x / 3200 Cu 3 1/4 x Cu 4 1/4 x Cu 6 1/4 x 5 5 1/4 x 6 WL Low Voltage Power Circuit Breakers Design Guide 12

14 Rear Horizontal Bus Terminals Fixed-mount WL circuit breakers are supplied with silver-plated copper terminal pads. These pads are designed to accept bus bar assemblies, supported independently from the circuit breaker.! WARNING Hazardous energy. Improper support may cause serious injury or equipment damage. During short circuit events, the following connection methods may cause excessive strain on the conductors, which could result in rupturing of the circuit breaker housing, and therefore must be avoided: 1. Cable terminations directly to the circuit breaker terminal pads. 2. Flexible conductors connected directly to the circuit breaker terminal pads. 3. Unbraced/unsupported bus bar conductors connected directly to the circuit breaker terminal pads. Cable lugs and flexible conductors should not be connected directly to the circuit breaker terminals. These types of connectors (cable lugs and flexible conductors) may be connected to bus bars connected to the circuit breaker terminals beyond the first short-circuit brace. The mounting holes on the circuit breaker terminals are ø 19/32 in. It is recommended to use ½-13 SAE grade 5 hardware, torque to 50 lb-ft. A best practice for bus bar design is to include adjustment slots, to allow for minor alignment corrections before securing the circuit breaker terminals to the power distribution equipment s bus structure.! WARNING Hazardous energy. Improper support may cause serious injury or equipment damage. Bus bracing must be installed in a manner that does not apply excessive mechanical stress to the circuit breaker terminals or accessory connector kits. In order to facilitate even current distribution and minimize the potential for excessive heating when using multiple conductors per phase, it is advisable to mount bus bars to both the top and bottom surface of the circuit breaker terminals as shown below. 13 WL Low Voltage Power Circuit Breakers Design Guide

15 Frame Size I Frame Size II Frame Size III WL Low Voltage Power Circuit Breakers Design Guide 14

16 Rear Vertical Bus Terminals An alternative method to connect the primary conductors is via the rear vertical bus accessory kits. These silver-plated copper accessories rotate the standard horizontal conductors of the circuit breaker 90 degrees to a vertical orientation. These connectors are designed to accept bus bar assemblies, supported independently from the circuit breaker. Table 11: Rear Vertical Bus Terminal Kits Frame Size No. of Poles Interrupting Class Frame Rating (A) Catalog Number I 3 S, H, L WLH1R12CONUL II 3 S, L WLL2R16CONUL 2000 WLL2R20CONUL WLL2R30CONUL C WLC2R30CONUL 4 S, H, L WL4L2R16CONUL 2000 WL4L2R20CONUL * 3200 WL4L2R32CONUL * III 3 L, C WLC3R50CONUL 4 H, L WL4L3R50CONUL * * Supplied as standard for these circuit breaker ratings. WARNING Hazardous energy. Improper support may cause serious injury or equipment damage.! During short circuit events, the following connection methods may cause excessive strain on the conductors, which could result in rupturing of the circuit breaker housing, and therefore must be avoided: 1. Cable terminations directly to the circuit breaker terminal pads. 2. Flexible conductors connected directly to the circuit breaker terminal pads. 3. Unbraced/unsupported bus bar conductors connected directly to the circuit breaker terminal pads. Cable lugs and flexible conductors must not be connected directly to the rear vertical bus terminal connectors. These types of connectors (cable lugs and flexible conductors) may be connected to bus bars connected to the rear vertical bus terminal connectors beyond the first short-circuit brace. The mounting holes on the circuit breaker terminals are ø 19/32 in. It is recommended to use ½-13 SAE grade 5 hardware, torque to 50 lb-ft. 15 WL Low Voltage Power Circuit Breakers Design Guide

17 A best practice for bus bar design is to include adjustment slots, to allow for minor alignment corrections before securing the circuit breaker terminals to the bus structure of the power distribution equipment.! WARNING Hazardous energy. Improper support may cause serious injury or equipment damage. Bus bracing must be installed in a manner that does not apply excessive mechanical stress to the circuit breaker terminals or accessory connector kits. In order to facilitate even current distribution and minimize the potential for excessive heating when using multiple conductors per phase, it is advisable to mount bus bars to both the top and bottom surface of the circuit breaker terminals as shown below. Frame Size I WL Low Voltage Power Circuit Breakers Design Guide 16

18 Frame Size II 3-Pole Interrupting Class Frame Rating (A) N, S, H, L C Dimension "A" 4-Pole 17 WL Low Voltage Power Circuit Breakers Design Guide

19 Frame Size III Fill any unused slots with spacers before torquing bus hardware to keep from bending conductors. 3-Pole 4-Pole WL Low Voltage Power Circuit Breakers Design Guide 18

20 Front-Accessible Bus Terminals Another option for connecting primary conductors is via the front-accessible bus accessory kits. These silver-plated copper accessories provide connection points above/below the circuit breaker, easing the installation or removal of the circuit breaker when only the front side of the circuit breaker is accessible. These connectors are designed to accept bus bar assemblies, cable lugs, or flexible bus conductors. Table 12: Front-Accessible Bus Connector Kits Frame Size No. of Poles Interrupting Class Frame Rating (A) Catalog Number I 3 S, H, L WLH1F12CONUL II 3 S, L WLL2F16CONUL 2000 WLL2F20CONUL 2500 WLL2F25CONUL 3000 WLL2F30CONUL III 3 L WLL3F50CONUL The mounting holes on the circuit breaker terminals are ø 19/32 in. It is recommended to use ½-13 SAE grade 5 hardware, torque to 50 lb-ft. Cable lugs and flexible conductors may be connected directly to the front-accessible connectors. Frame Size I 19 WL Low Voltage Power Circuit Breakers Design Guide

21 Frame Size II (800A 2500A) Frame Rating (A) Dimension "A" Frame Size II (3000A) WL Low Voltage Power Circuit Breakers Design Guide 20

22 Frame Size III Front Bus Terminal Lug Kits The following wire connector kits are designed to allow cable conductors to be connected to the front connector accessory kits for WL circuit breakers rated 2000 A and below, and for available fault current levels of 65 ka and below. These wire connectors have been tested in accordance with UL 486A 486B for flexible stranded cables. Table 13: Lug Kits Catalog number Maximum continuous current (A) Maximum number of conductors Conductor wire size WLS2P12CONUL kcmil (Cu / Al) WLS2P20CONUL kcmil (Cu / Al) Tightening torque for conductors 325 lb-in. 375 lb-in. 21 WL Low Voltage Power Circuit Breakers Design Guide

23 Bus Bracing The bus terminals (standard or accessory kits) are not intended to support the equipment bus structure, nor are they intended to provide short circuit bracing. The following table provides recommendations for supporting the primary bus conductors. The distances vary based on the short-circuit rating of the apparatus. Longer distances and other means of support may be validated through short-time withstand testing of the equipment s bus structure. All phases may be braced together to prevent separation during short-circuit conditions. Line and load conductors may be braced separately, or braced against each other. Table 14: Minimum Bus Bracing Recommendations Short-time or short-circuit rating (ka) Distance to first brace (in.)! WARNING Hazardous energy. Improper support may cause serious injury or equipment damage. Bus bracing must be installed in a manner that does not apply excessive mechanical stress to the circuit breaker terminals or accessory connector kits. WL Low Voltage Power Circuit Breakers Design Guide 22

24 Phase Barriers In service entrance applications, it is often necessary to include a sectionalizing barrier separating line and load bus from each other. In many other applications, it is desirable to include phase-to-phase and/or phase-to-ground isolation barriers. The following circuit breaker types (see Table 14) include 5/32 in. wide groves in the rear face of the circuit breaker to facilitate addition of line/load and phase-to-phase barriers. Table 15: Integral Phase Barrier Provisions Frame Size No. of Poles Interrupting Class Interrupting Class Frame Rating (A) I 3 S, H, L S, H, L II 3 S, L, C S, L C C S, H, L S, H, L III 3 L L C C H, L H, L Integral Barrier Provisions Vertical Horizontal 23 WL Low Voltage Power Circuit Breakers Design Guide

25 To assist in the securing of the barriers, mounting holes have been provided, as illustrated below. These mounting holes are intended to be used with #10-16 thread-forming screws, with a maximum installed length of 5/8 in. The following drawings provide dimension specifics for each of the different circuit breaker models. Frame Size I WL Low Voltage Power Circuit Breakers Design Guide 24

26 Frame Size II 3-Pole 4-Pole 25 WL Low Voltage Power Circuit Breakers Design Guide

27 Frame Size III 3-Pole 4-Pole WL Low Voltage Power Circuit Breakers Design Guide 26

28 Door Cut-Outs WL circuit breakers are suitable to be mounted such that the front escutcheon is either flush with the face of the circuit breaker compartment door (or dead-front cover), or with the front escutcheon protruding through the panel. Flush Mounted The following figures may be used when the circuit breaker is mounted such that the front escutcheon is intended to be flush with the front of the equipment. Frame Size I (mechanism only visible) Frame Size II and III (mechanism only visible) 27 WL Low Voltage Power Circuit Breakers Design Guide

29 Frame Size I (mechanism + ETU visible) Frame Size II and III (mechanism + ETU visible) WL Low Voltage Power Circuit Breakers Design Guide 28

30 Semi-Flush Mounted One of the following figures may be used when the circuit breaker is mounted such that the front escutcheon is intended to protrude through the front of the equipment. Frame Size I Frame Size II and III Frame Size II and III (with door sealing frame WLDSF) 29 WL Low Voltage Power Circuit Breakers Design Guide

31 Control Wiring Space Control wiring should not be routed above the arc chutes of the circuit breaker. Wiring in this space may become damaged and may cause undesirable arcing or a flashover during opening operations of the circuit breaker. Additional Resources The WL circuit breaker website has a complete set of tools for engineering solutions utilizing this family of low voltage power circuit breakers. Selection and configuration guides Online configurator Application guides Instructional videos 2-D dimensional drawings 3-D models WL Low Voltage Power Circuit Breakers Design Guide 30

32 Siemens Industry, Inc Triangle Parkway Norcross, GA Subject to change without prior notice Order No.: CBBR-FXMDG-0316 All rights reserved Printed in USA 2016 Siemens Industry, Inc. Subject to changes and errors. The information given in this document only contains general descriptions and/or performance features which may not always specifically reflect those described, or which may undergo modification in the course of further development of the products. The requested performance features are binding only when they are expressly agreed upon in the concluded contract.