UL 250 CRD-2014 UL Standard for Safety Household Refrigerators and Freezers - Section Paragraph Reference Supplement SC Subject Alternative Path for Electronic Controls (Edition 1.pdf

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1、UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULUNDERWRITERS LABORATORIES INC. CERTIFICATION REQUIREMENT DECISIONThis Certification Requirement Decision is prepared and published by Underwriters Laboratories Inc.(UL). It is normative for the a

2、pplicable UL Product Certification Program(s); however, it is currently notpart of the UL Standard(s) referenced below.Product Category (CCN): SHMR, SHZZStandard Number: UL 250Standard Title: Standard for Household Refrigerators and FreezersEdition Date: November 1, 1993Edition Number: 10Section / P

3、aragraph Reference: Supplement SCSubject: Alternative Path for Electronic ControlsDECISION:IEC. This material is reproduced from IEC 60335-1 with permission of the American National Standards Institute (ANSI) on behalfof the International Electrotechnical Commission. All rights reserved.SUPPLEMENT S

4、C ALTERNATIVE PATH FOR ELECTRONIC CONTROLS REQUIREMENTSINTRODUCTIONSC1 ScopeSC1.1 Throughout the Supplement, when reference is made to requirements in “this Standard,” thereference is to requirements in the main body of the Standard and not to other requirements of theSupplement.SC1.2 These requirem

5、ents provide an alternative path for investigation of electronic controls used inappliances covered by this standard.SC1.3 In the context of this Supplement, an electronic control is a circuit incorporating at least oneelectronic component and that causes the intended output of the appliance energy

6、source(s) (e.g. heaters,moving parts, humidity, radiation) to vary.SC1.4 In the context of this Supplement a motor speed drive would be considered an electronic control.SC1.5 Circuits that transmit or receive signals (analog or digital), transform or convert electricity to supplyother circuits (e.g.

7、 power supply) or simply switch an electrical load (e.g. electronic relay) are not controlsbut are subject to the requirements of this Supplement when they are integrated (physically or functionally)with a control.SC1.6 A self-regulating PTC heater is not considered a control from the perspective of

8、 this Supplement.When a thermistor is used as a sensor or as part of a thermal management function of a control, it isinvestigated as part of the control.SC1.7 The functional safety requirements for smart or remotely enabled are specified in Supplement SB.SC1.8 Thermal motor protectors in direct con

9、tact with motor windings and intended for direct control ofthe motor supply are outside the scope of this Supplement even if they incorporate one or more electroniccomponents.UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULException No.1: Elec

10、tronic circuits that provide thermal motor protection but only have a thermal sensorin direct contact with motor windings are within the scope.Exception No. 2: Electromechanical thermal motor protectors in direct contact with the motor windingswhere the protector is connected to electronic circuits

11、that provide the motor load control are within thescope.SC1.9 Electronic circuits that provide control functions intended to prevent special hazards such as anexplosion or whose failure could directly cause a hazard in the appliance are outside the scope of thisSupplement.SC2 GeneralSC2.1 The requir

12、ements of this Supplement are intended to apply to the electronic control and how thecontrol is integrated in the appliance. The overall appliance construction, performance testing and markingrequirements are applicable as specified in this Standard except as cited in the following requirements.SC3

13、GlossarySC3.1 CAPACITOR, CLASSXAcapacitor suitable for use in situations where failure of the capacitoror RC unit would not lead to an increased risk of electric shock but could result in an increased risk of fire.Examples would be capacitors connected phase to phase or phase to neutral.SC3.2 CAPACI

14、TOR, CLASSYAcapacitor suitable for use in situations where failure of the capacitormay lead to an increased risk of electric shock. Examples would be capacitors connected across theprimary and secondary circuits where electrical isolation is required to prevent an electric shock orbetween hazardous

15、live parts and accessible parts.SC3.3 DANGEROUS MALFUNCTION Unintended operation of the appliance that may impair safety.Operating Control functions whose failure would result in a Dangerous Malfunction would be consideredSafety Critical Functions. See clause SC3.10.Note 1 Electronic circuits execut

16、e varying functions that are integrated within a control or appliance. Some of these functions areevoked during the normal operation of the product to either optimize performance or reduce overstressing of components whileothers are designated to address abnormal operation of the product due to load

17、 failures. Dangerous malfunction addresses thecorrectness of those functions that operate during normal operation of the appliance. A failure of the function to operate correctlycould lead to a hazardous condition.Note 2 Control functions whose failure might result in a Dangerous Malfunction would i

18、nclude:a) An operating control function necessary to comply with the Temperature Test, Section 8.6 of this Standard.b) A function to prevent the unexpected operation of the appliance from a stand-by mode where the operation wouldresult in an increased risk of electric shock, fire or injury to person

19、s.c) An electronic disconnection circuit whose failure may increase the risk of fire, electric shock or injury to persons.Example 1: An example would be the unattended energization of a heating appliance. The user might haveplaced flammable materials near the appliance based on the assumption the ap

20、pliance would remain off.Example 2: An example would be the unexpected energization of an appliance with hazardous rotating parts.d) Interlocks necessary for the safe operation of the appliance.STANDARD NUMBER: UL 250 -2-UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION

21、WITHOUT PERMISSION FROM ULe) Scald protection provided by the operating control of an electric water heater.f) A zero-cross switching function to allow the use of low capacity switching devices to control higher loads.SC3.4 ELECTRONIC DISCONNECTION The de-energizing of the functional load of the app

22、liance byan electronic device of a circuit with no air gap.SC3.5 HAZARD OF ITSELF The risk of fire or electric shock emanating from the electronic control only.SC3.6 INTENTIONALLY WEAK PART A part intended to rupture under conditions of abnormaloperation to prevent the occurrence of a condition whic

23、h could impair compliance with this standard.SC3.7 LOW-POWER CIRCUIT A circuit or parts of circuits farther from the supply source than alow-power point.SC3.8 LOW-POWER POINT A point closest to the supply source in an electronic circuit where themaximum available power to an external load at the end

24、 of 5 seconds does not exceed 15 watts.SC3.9 PROTECTIVE ELECTRONIC CIRCUIT (PEC) An electronic circuit that prevents a hazardoussituation under abnormal operating conditions. The function of a Protective Electronic Circuit would beconsidered a Safety Critical Function. See clause SC3.10.SC3.10 SAFET

25、Y CRITICAL FUNCTION Control, protection and monitoring functions which are beingrelied upon to reduce the risk of fire, electric shock or injury to persons.CONSTRUCTIONSC4 ComponentsSC4.1 Temperature sensing, thermistor devicesSC4.1.1 A temperature sensing device, such as a positive temperature coef

26、ficient (PTC) thermistor and anegative temperature coefficient (NTC) thermistor, that performs a Class B control function shall complywith Annex J of the Standard for Automatic Electrical Controls for Household and Similar Use, Part 1:General Requirements, UL 60730-1, or the Standard for Thermistor-

27、Type Devices, UL 1434. Theminimum rated number of cycles shall be as specified in this standard. See 8.20 for defrost heatercontrols.SC4.2 Printed wiring boardsSC4.2.1 Printed wiring boards shall comply with the Standard for Printed Wiring Boards, UL 796, and shallhave a flammability rating and othe

28、r characteristics as specified in this Standard.Exception: A printed circuit board solely in a Low-Power Circuit need not comply with UL 796.SC4.2.2 Any printed wiring board that complies with the requirements for Direct Support in the Standardfor Printed Wiring Boards, UL 796, is considered to prov

29、ide an insulating base with a ComparativeTracking Index (CTI) of minimum 100.SC5 EnclosureSC5.1 The enclosure of an electronic control shall comply with the appliance enclosure requirementsspecified in this Standard.STANDARD NUMBER: UL 250 -3-UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPROD

30、UCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULSC6 Field ConnectionsSC6.1 Provision for connection of external data or communication networks (wired or wireless) shallcomply with the requirements of the Standard for Information Technology Equipment Safety Part 1:General Requirements, UL 60950-1.SC6

31、.2 Electronic controls that respond to external communication signals or data shall comply with therequirements of this Supplement.Exception: A communication device that is not integral with the electronic control (e.g. wholly located ona separate circuit board) and complying with the Standard for I

32、nformation Technology Equipment Safety Part 1: General Requirements, UL 60950-1, is considered to fulfill this requirement.SC6.3 Connections from the appliance intended to power remote devices shall be powered by sourcescomplying with the requirements of one of the following:a) The Standard for Clas

33、s 2 Power Units, UL 1310, orb) The Standard for Low Voltage Transformers Part 1: General Requirements, UL 5085-1;and The Standard for Low Voltage Transformers Part 3: Class 2 and Class 3 Transformers,UL 5085-3 as a Class 2 transformer.c) The Standard for Information Technology Equipment Safety Part

34、1: GeneralRequirements, UL 60950-1, as a Safety Extra Low Voltage and Limited Power Source.SC7 Electrical SpacingSC7.1 Electrical spacing between uninsulated live parts of an electronic control and between theuninsulated live parts of an electronic control and accessible metal parts of the rest of t

35、he appliance shallcomply with the electrical spacing requirements specified in this Standard.Exception No. 1: Electrical spacing (through air or over insulating surfaces) may instead comply with therequirements for Creepage Distances, Clearances and Distances Through Solid Insulation of theStandard

36、for Safety of Household and Similar Electrical Appliances, Part 1: General Requirements, UL60335-1 (Clause 29). The anticipated Pollution Degree is 3 and the Overvoltage Category is II.Exception No. 2: Electrical spacing (through air or over insulating surfaces) may instead comply with therequiremen

37、ts in the Standard for Insulation Coordination Including Clearances and Creepage Distancesfor Electrical Equipment, UL 840. The anticipated Pollution Degree is 3 and the Overvoltage Category isII.SC7.2 The conductors of different circuits shall be separated in accordance with the requirementsspecifi

38、ed in this Standard.SC8 Electrical InsulationSC8.1 Materials employed as electrical insulation shall comply with the requirements specified in thisStandard.SC9 Control FunctionsSC9.1 GeneralSTANDARD NUMBER: UL 250 -4-UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITH

39、OUT PERMISSION FROM ULSC9.1.1 Electronic circuits or parts of circuits shall be analyzed to determine if the function of the controlis necessary for compliance with this Standard.SC9.1.2 In the evaluation of electronic circuits, the contacts of relays, contactors, or other devices thatcycle during t

40、he Normal Temperature Test shall be short-circuited.SC9.2 Protective electronic circuits/controlsSC9.2.1 A control or circuit whose function must be relied upon for compliance with an abnormal operationtest of this Standard shall be considered a Protective Electronic Circuit.SC9.2.2 A control or cir

41、cuit that activates and must be relied upon during any of the component and otherfaults specified in Clause SC15 shall be considered a Protective Electronic Circuit.SC9.2.3 An electronic circuit is not considered a Protective Electronic Circuit if, during the abnormaloperation tests in this Standard

42、 and with the function of the circuit defeated, other independent andreliable protective means is sufficient for compliance with the requirements of this Standard.SC9.2.4 A circuit intended to provide motor overload protection as specified in this Standard shall beconsidered a Protective Electronic

43、Circuit.SC9.2.5 Protective Electronic Circuits include but are not limited to the following:a) Temperature limiting controlsb) Motor overload protector, overheating protectionc) Pressure limiting deviced) Door switches that perform an interlock function.SC9.3 Operating controls or circuits that perf

44、orm safety critical functionsReserved for future use.SC10 Evaluation of the Different Types of Control CircuitsSC10.1 All types of circuitsSC10.1.1 An electronic control shall have the parameters as specified in this Standard. These include butare not limited to:a) Endurance cycles,b) Maximum set-po

45、int,c) Manual or automatic resetSC10.1.2 An electrical component shall not be connected across the contacts of an electronic control thatoperates during an Abnormal Operation Test of this Standard or otherwise serves a safety function (e.g.interlock).STANDARD NUMBER: UL 250 -5-UL COPYRIGHTED MATERIA

46、L NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULException: Electrical components may be connected across the contacts provided that any singlecomponent fault does not result in a loss of protective function.SC10.1.3 All control circuits shall be evaluated to determ

47、ine the effects of electronic circuit faults.SC10.1.4 When the applicable faults specified in clause SC15.11 are imposed one at a time they shallnot result in:a) The control being a Hazard of Itself, orb) The loss of a control function of a Protective Electronic Circuit, orc) The loss of any Safety

48、Critical Function of an operating control.SC10.1.5 The risk of electrically generated fire from the faults of clause SC15.11 is considered to bemitigated in Low-Power Circuits.SC11 Protective Electronic CircuitsSC11.1 Appliances incorporating a Protective Electronic Circuit that relies upon a progra

49、mmablecomponent for one or more of its safety functions shall incorporate measures to control the fault/errorconditions that would impair the safety functions.SC11.2 The evaluation of the programmable component shall be in accordance with Annex R of theStandard for Safety of Household and Similar Electrical Appliances, Part 1: General Requirements,UL60335-1, Edition 5.SC11.3 Appliances incorporating a Protective Electronic Circuit that relies upon a programmablecomponent for one or more of its safety functions shall be subjected to the test of the