1、UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULUNDERWRITERS LABORATORIES CERTIFICATION REQUIREMENT DECISIONThis Certification Requirement Decision is prepared and published by Underwriters Laboratories (UL). Itis normative for the applicable
2、UL Product Certification Program(s); however, it is currently not part ofthe UL Standard(s) referenced below.Product Category (CCN): SHZZStandard Number: UL 250Edition Date: November 1, 1993Edition Number: 10Section / Paragraph Reference: VariousDECISION:Revise the standard to allow double insulatio
3、n in lieu of grounding for thermoelectric refrigerators asfollows:1.4 The equipment is air-cooled employing hermetic refrigerant motor-compressors, or is of the absorptiontype employing electricity as the heat source, or is of the thermoelectric type. These requirements applyto.New Par. 2.30A THERMO
4、ELECTRIC REFRIGERATOR A refrigerator which is cooled by the PeltierEffect. Direct Current is applied to a semiconductor which creates a temperature gradient that can transferheat from one surface to another.4.9.1.1 A refrigerator intended for cord connection to an ac power supply shall be equipped w
5、ith a flexiblecord having an equipment grounding conductor terminating in a grounding-type attachment plug thatcomplies with the American National Standards designated in Table 4.4Exception No. 1: A refrigerator intended for connection.Exception No. 2: An equipment grounding conductor and grounding-
6、type attachment plug are not requiredon d Double-Insulated thermoelectric refrigerators.4.9.1.1.1 A double insulated thermoelectric refrigerator shall be equipped with a flexible cord terminatingin a polarized plug with the large blade connected to the grounded conductor of the refrigerator. If thep
7、ower cord is detachable, the connection shall not be reversible.4.9.4.1 A refrigerator shall have provision for grounding.Exception: An equipment grounding conductor is not required for cord-connected thermoelectricrefrigerators rated nominal 120 V and less than 12 amperes, provided all line voltage
8、 components andwiring are protected by a system of Double Insulation in accordance with the Standard for DoubleInsulation Systems for Use in Electrical Equipment, UL 1097, and General Requirements for DoubleInsulated Equipment, CSA Standard C22.2 No. 0.1. See also par. 4.9.5.1.4.9.4.7 On a grounded
9、cord-connected refrigerator, the grounding conductor of the power supply cord.New Par. 4.9.4.8 An appliance marked as being provided with Double Insulation shall not be provided witha means for grounding. See 11.1.27.New Par. 11.1.27 A double insulated appliance shall be permanently marked with the
10、statement “DOUBLEINSULATION”, “DOUBLE INSULATED”, or the double insulation symbol a square within a square.UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULNew Par. 11.2.7 An appliance provided with a 2-blade, polarized attachment plug shall be
11、 provided withthe following instructions or the equivalent: “To reduce the risk of electric shock, this appliance has apolarized plug (one blade is wider than the other). This plug will fit in a polarized outlet only one way. Ifthe plug does not fit fully in the outlet, reverse the plug. If it still
12、 does not fit, contact a qualified electricianto install the proper outlet. Do not change the plug in any way.”RATIONALE FOR DECISION:The standard did not specifically anticipate this design and the US and Canadian National ElectricalCodes permit protection by a system of double insulation in lieu o
13、f equipment grounding (NEC 250.114and CEC 10-408(3), respectively).Copyright 2007 Underwriters Laboratories Inc.UL, in performing its functions in accordance with its objectives, does not guarantee or warrant thecorrectness of Certification Requirement Decisions it may issue or that they will be rec
14、ognized or adoptedby anyone. Certification Requirement Decisions are the opinion of Underwriters Laboratories Inc. inpractically applying the requirements of the standard. They do not represent formal interpretations of thestandard under American National Standards Institute (ANSI) processes. UL sha
15、ll not be responsible toanyone for the use of or reliance upon Certification Requirement Decisions by anyone. UL shall not incurany obligation or liability for damages, including consequential damages, arising out of or in connectionwith the use or reliance upon Certification Requirement Decisions. The electronic version of theCertification Requirement Decision is the current version and previously printed copies may be outdated.This document is published as a service to ULs certification customersSTANDARD NUMBER: UL 250 -2-
