1、NEMA Standards PublicationNational Electrical Manufacturers AssociationNEMA 250-2014Enclosures for Electrical Equipment (1000 Volts Maximum)NEMA 250-2014 Enclosures for Electrical Equipment (1000 Volts Maximum) Published by National Electrical Manufacturers Association 1300 N. 17th Street, Suite 900
2、 Rosslyn, VA 22209 www.nema.org 2014 National Electrical Manufacturers Association. All rights, including translation into other languages, reserved under the Universal Copyright Convention, the Berne Convention for the Protection of Literary and Artistic Works, and the International and Pan America
3、n copyright conventions. 2014 National Electrical Manufacturers Association NOTICE AND DISCLAIMER The information in this publication was considered technically sound by a consensus among persons engaged in its development at the time it was approved. Consensus does not necessarily mean there was un
4、animous agreement among every person participating in the development process. The National Electrical Manufacturers Association (NEMA) standards and guideline publications, of which the document herein is one, are developed through a voluntary standards development process. This process brings toge
5、ther volunteers and/or seeks out the views of persons who have an interest in the topic covered by this publication. Although NEMA administers the process and establishes rules to promote fairness in the development of consensus, it does not write the documents, nor does it independently test, evalu
6、ate, or verify the accuracy or completeness of any information or the soundness of any judgments contained in its standards and guideline publications. NEMA disclaims liability for any personal injury, property, or other damages of any nature, whether special, indirect, consequential, or compensator
7、y, directly or indirectly resulting from the publication, use of, application, or reliance on this document. NEMA disclaims and makes no guaranty or warranty, express or implied, as to the accuracy or completeness of any information published herein, and disclaims and makes no warranty that the info
8、rmation in this document will fulfill any particular purpose(s) or need(s). NEMA does not undertake to guarantee the performance of any individual manufacturers or sellers products or services by virtue of this standard or guide. In publishing and making this document available, NEMA is not undertak
9、ing to render professional or other services for or on behalf of any person or entity, nor is NEMA undertaking to perform any duty owed by any person or entity to someone else. Anyone using this document should rely on his or her own independent judgment or, as appropriate, seek the advice of a comp
10、etent professional in determining the exercise of reasonable care in any given circumstance. Information and other standards on the topic covered by this publication may be available from other sources, which the user may wish to consult for additional views or information not covered by this public
11、ation. NEMA has no power, nor does it undertake to police or enforce compliance with the contents of this document. NEMA does not certify, test, or inspect products, designs, or installations for safety or health purposes. Any certification or other statement of compliance with any health- or safety
12、-related information in this document shall not be attributable to NEMA and is solely the responsibility of the certifier or maker of the statement. 250-2014 Page i 2014 National Electrical Manufacturers Association TABLE OF CONTENTS 1 GENERAL . 1 1.1 Scope . 1 1.2 References 1 1.3 Definitions 3 2 E
13、NCLOSURE TYPES, FEATURES, AND APPLICATIONS 5 2.1 General 5 2.2 Specific Types . 5 3 CONSTRUCTION 9 3.1 General 9 3.2 Units of Measurement . 9 3.3 MaterialsGeneral 9 3.4 MaterialsPolymeric . 9 3.5 Corrosion ProtectionGeneral . 9 3.5.1 Indoor Corrosion Protection . 10 3.5.2 Outdoor Corrosion Protectio
14、n . 10 3.5.3 Annealed Coating . 10 3.5.4 Bends and Forms on Zinc Coatings . 11 3.5.5 Hot Dipped Galvanized Damage 11 3.5.6 Cast Iron . 11 3.5.7 Corrosion Protection for Type 3X, 3RX, 3SX, 4X and 6P Enclosures . 11 3.6 Openings . 11 3.6.1 Equipment Openings 11 3.6.2 Ventilation . 11 3.6.3 Drainage Op
15、enings 12 3.7 Mounting 12 3.8 Conduit Connection . 12 3.9 Hubs and Fittings . 12 3.10 Knockouts 12 3.11 External Operating Mechanisms . 13 3.12 Access to Interior . 13 3.13 Closing Hardware 13 3.14 Gaskets 13 3.15 Observation Windows 14 4 MARKING 15 4.1 Type Designations . 15 4.2 Supplemental Markin
16、gs . 15 4.3 Location of Markings . 15 4.4 Enclosure Orientation 15 4.5 Conduit Hubs and Closure Plates . 15 4.6 Equipment Openings . 16 4.7 Drainage Openings 16 5 DESIGN TESTS . 17 5.1 General 17 5.2 Test For Protection Against Access to Hazardous Parts 23 5.2.1 Non-ventilated Enclosures Test Method
17、 23 5.2.2 Ventilated Enclosures Test Method . 23 5.2.3 Evaluation . 23 5.3 Test for Protection Against Ingress of Water (Dripping and Light Splashing) . 23 5.3.1 Method A 24 5.3.2 Method B 24 5.3.3 Evaluation . 24 5.4 Test for Protection Against Ingress of Water (Rain) 24 250-2014 Page ii 2014 Natio
18、nal Electrical Manufacturers Association 5.4.1 Method 24 5.4.2 Evaluation . 25 5.5 Test for Protection against Ingress of Solid Foreign Objects (Settling Airborne Dust, Lint, Fibers, And Flyings) . 28 5.5.1 Outdoor Dust Test 28 5.5.2 Indoor Dust Tests . 29 5.6 External Icing Test . 31 5.6.1 Test Met
19、hod 31 5.6.2 Evaluation . 31 5.7 Test for Protection Against Ingress of Water (Hosedown) 32 5.7.1 Test Method 32 5.7.2 Evaluation . 32 5.8 Indoor Corrosion Protection (Rust-Resistance Test (24-Hour Salt Spray Test) 32 5.8.1 Test Equipment 32 5.8.2 Salt Solution . 32 5.8.3 Air Supply . 33 5.8.4 Tempe
20、rature . 33 5.8.5 Test Procedure . 33 5.8.6 Evaluation . 33 5.9 Outdoor Corrosion Protection 33 5.9.1 600-Hour Salt Spray Test . 33 5.9.2 Evaluation . 33 5.9.3 1200-Hour Moist Carbon DioxideSulfur DioxideAir Test . 33 5.10 Corrosion ProtectionType 3X, 3RX, 3SX, 4X Or 6P Enclosures . 33 5.10.1 Evalua
21、tion . 34 5.11 Test for Protection Against Ingress of Water (Temporary Submersion) . 34 5.11.1 Test Method 34 5.11.2 Evaluation . 34 5.12 Test for Protection Against Ingress of Water (Prolonged Submersion) 34 5.12.1 Alternate Tests . 34 5.13 Oil Exclusion Test 35 5.13.1 Test Method 35 5.13.2 Evaluat
22、ion . 35 5.14 Gasket Tests . 35 5.14.1 Aging Test 35 5.14.2 Evaluation . 35 5.14.3 Oil immersion test . 36 Annex A Comparison Between NEMA Enclosure Type Numbers and ANSI/IEC Enclosure Classification Designations . 37 A.1 GENERAL 37 Annex B Descriptions, Applications, Features, and Test Criteria of
23、Enclosures for Hazardous (Classified) Locations . 37 B.1 GENERAL 37 B.2 SPECIFIC TYPES . 37 B.2.1 Enclosure Features . 38 B.2.2 Enclosure Test Criteria . 39 Tables 2-1 Comparison of Specific Applications of Enclosures for Indoor Nonhazardous (Unclassified) Locations 5 2-2 Comparison of Specific Appl
24、ications of Enclosures for Indoor and Outdoor Nonhazardous (unclassified) Locations . 6 3-1 Knockout Dimensions 13 250-2014 Page iii 2014 National Electrical Manufacturers Association 5-1A Degrees of Protection Against Access to Hazardous Parts 18 5-1B Degrees of Protection Against Solid Foreign Obj
25、ects . 19 5-1C Degrees of Protection Against Water 21 5-1D Additional Protection 22 5-2 Tightening Torque . 24 Figures 5-1 Rain-test Spray-head Piping . 26 5-2 Rain-test Spray Head 27 250-2014 Page iv 2014 National Electrical Manufacturers Association FOREWORD This standards publication covers the c
26、lassification and description of enclosures for electrical equipment. Enclosures for rotating apparatus have not been included. The primary purpose of this publication is to permit a potential user to determine: 1) The type of enclosure appropriate for the application. 2) The features the enclosure
27、is expected to have. 3) The tests applied to the enclosure to demonstrate its conformance to the description. These standards are used by the electrical industry to provide guidelines for the manufacture and proper application of enclosures and to promote the benefits of repetitive manufacturing and
28、 widespread enclosure availability. Each type of enclosure is described in general and functional terms where practicable, and omits reference to structural details and specific applications except where they are essential to the identification of the enclosure type. For such structural details and
29、specific applications, see the appropriate NEMA product standards publication. Individual product standards publications incorporating enclosure construction unique to the product design may reflect the type of designations contained herein provided the design tests for such construction equal or ex
30、ceed the requirements of this standards publication. User needs have been considered throughout the development of this publication. Proposed or recommended revisions should be submitted to: Senior Technical Director, Operations National Electrical Manufacturers Association 1300 N. 17th Street, Suit
31、e 900 Rosslyn, VA 22209 NEMA 250-2014 revises and supersedes NEMA 250-2008. This standards publication was developed by the NEMA Enclosure Section of the National Electrical Manufacturers Association. Section approval of the standard does not necessarily imply that all section members voted for its
32、approval or participated in its development. At the time it was approved, the Enclosure Section was composed of the following members: Adalet Cleveland, OH Allied Moulded Products, Inc. Bryan, OH Boltswitch, Inc. Crystal Lake, IL Cooper B-Line Sherman, TX Eaton Corporation Moon Township, PA Emerson/
33、EGS Electrical Group Rosemont, IL GE Energy, Industrial Solutions Plainville, CT Hoffman Enclosures Inc. Anoka, MN Hubbell Incorporated Shelton, CT Killark Electric Mfg. Company St. Louis, MO Rittal Corporation Urbana, OH Siemens Industry Inc. Norcross, GA Schneider Electric USA, Inc. Lexington, KY
34、Stahlin Enclosures Belding, MI Thomas and, 2) enclosures for indoor or outdoor locations, Types 3, 3X, 3R, 3RX, 3S, 3SX, 4, 4X, 6, and 6P. b. Hazardous (classified) locations: 1) Enclosures for indoor locations, Types 7 and 9; 2) Enclosures for indoor or outdoor locations, Type 8; and, 3) Enclosures
35、 for mining applications, Type 10. Requirements for enclosures for non-hazardous (unclassified) locations are contained in the body of the standard. Requirements for enclosures for hazardous (classified) locations are contained in Annex A of the standard. This standard covers the requirements to pro
36、vide protection to the enclosed equipment against specific environmental conditions. This standard supplements requirements for enclosures that are contained in the individual product standards. This standard does not cover the requirements for protection of the enclosed equipment against conditions
37、 such as condensation, icing, corrosion, or contamination, which may occur within the enclosure or which may enter via conduit or unsealed openings. A product that contains features, characteristics, components, materials, or systems new or different from those in use when the standard was developed
38、, and that involves a risk of fire, electric shock, or injury to persons shall be evaluated using the appropriate additional component and end-product requirements as determined necessary to maintain the level of safety for the user of the product as originally anticipated by the intent of this stan
39、dard. 1.2 REFERENCES The following documents contain provisions, which through reference in this text constitute provisions of this standards publication. By reference herein these publications are adopted, in whole or in part as indicated in this publication. American National Standards Institute (
40、ANSI) 11 West 42nd Street New York, NY 10036 American Society of Mechanical Engineers (ASME) 345 East 47th Street New York, NY 10017-2392 ANSI/ASME B1.20.1 Pipe Threads, General Purpose (In) 250-2014 Page 2 2014 National Electrical Manufacturers Association ANSI/ASME B94.11M Twist Drills ASTM Intern
41、ational 100 Barr Harbor Drive West Conshohocken, PA 19428 ASTM A 653/A 653M Standard Specification for Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed) by the Hot-Dip Process ASTM B117 Standard Practice for Operating Salt Spray (Fog) Apparatus ASTM B555 Standard Guide f
42、or Measurement of Electrodeposited Metallic Coating Thickness by the Dropping Test ASTM D471 Rubber Property-Effect of Liquids ASTM D5964 Standard Practice for Rubber IRM 902 and IRM 903 Replacement Oils for ASTM No. 2 and ASTM No. 3 Oils. International Electrotechnical Commission (IEC) 3, rue de Va
43、remb P.O. Box 131 1211 Geneva 20 Switzerland ANSI/IEC 60529 Degrees of protection provided by enclosures (IP Code) The Instrumentation, Systems, and Automation Society (ISA) 67 Alexander Drive Research Triangle Park, NC 27709 USA ANSI/ISA 12.12.01 Nonincendive Electrical Equipment for use in Class I
44、 and II, Division 2, and Class III, Divisions 1 and 2 Hazardous (Classified) Locations. National Fire Protection Association (NFPA) 1 Batterymarch Park PO Box 9101 Quincy, MA 02269 ANSI/NFPA 70 National Electrical Code ANSI/NFPA 496 Purged and Pressurized Enclosures for Electrical Equipment ANSI/NFP
45、A 497 Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas. ANSI/NFPA 499 Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas
46、 Superintendent of Documents US Government Printing Office Washington, DC 20402 30 CFR Part 18 Electric Motor-Driven Mine Equipment and Accessories Underwriters Laboratories Inc. (UL) 333 Pfingsten Road Northbrook, IL 60062 ANSI/UL 50 Enclosures for Electrical Equipment Non-Environmental Considerati
47、ons 250-2014 Page 3 2014 National Electrical Manufacturers Association ANSI/UL 50E Enclosures for Electrical Equipment Environmental Considerations ANSI/UL 94 Tests for Flammability of Plastics Materials for Parts in Devices and Appliances ANSI/UL 157 Gaskets and Seals ANSI/UL 514B Conduit, Tubing,
48、Cable Fittings ANSI/UL 746C Polymeric Materials Use in Electrical Equipment Evaluations ANSI/UL 1203 Explosion-Proof and Dust-Ignition-Proof Electrical Equipment for Use in Hazardous (Classified) Locations ANSI/UL 1332 Organic Coatings for Steel Enclosures for Outdoor-Use Electrical Equipment ANSI/U
49、L 1439 Tests for Sharpness of Edges on Equipment 1.3 DEFINITIONS The following definitions are applicable in this standard. accessible edge: Any peripheral surface that is subject to contact by persons installing, using, or maintaining the product. cover: An unhinged portion of an enclosure that covers an opening. degree of protection: The extent of protection provided by an enclosure against access to hazardous parts, against ingress of foreign solid objects and/or against ingress of water and verified by stand
