Overload Relays & Thermal Unit . - Granite City Electric

Product Descriptionsolder pot are combined in a one piece, nontamperable unit. Melting alloythermal overload relays must be reset by a deliberate hand operation afterthey trip. A reset button is usually mounted on the cover of enclosed starters.Thermal units are rated in amperes and are selected on the basis of motorfull load current, not horsepower.Heater CoilNon-Compensated Bimetallic85%-115%Trip AdjustmentBimetalStripContactBimetallic thermal overload relays employ a U-shape bimetal stripassociated with a current carrying heater coil.When an overload occurs, theheat will cause the bi-metal to deflect and operate a control circuit contact.Different heaters give different trip points. In addition, most relays areadjustable over a range of 85% to 115% of the nominal heater rating.Bimetallic overload relays are used where the controller is remote or difficultto reach. Three wire control is recommended when automatic restarting of amotor could be hazardous to personnel.Bimetallic Overload Relay with SideCover RemovedAutomatic ResetThese relays are field convertible from hand reset to automatic reset andvice-versa. On automatic reset after tripping the relay, contacts willautomatically reclose when the relay has cooled down. This is an advantagewhen the relays are inaccessible. However, automatic reset overload relaysshould not normally be used with 2-wire control. With this arrangement, themotor will restart when the overload relay contacts reclose after an overloadrelay trip, and unless the cause of the overload has been removed, theoverload relay will trip again. This cycle will repeat and eventually the motorwill burn out due to the accumulated heat from the repeated inrush andoverload current. More important is the possibility of danger to personnel.The unexpected restarting of a machine may find the operator ormaintenance man in a hazardous situation as he attempts to find out why hismachine has stopped.600Motor Damage AreaPercent Full Load Current500400Motor Heating Curve300200100Ambient Temperature Compensated BimetallicTime Required To Trip01234567Minutes89101112Graph shows motor heating curve and overload relay trip curve.Overload relay will always trip at a safe value.Overload Relay Trip CurveAmbient-compensated bimetallic overload relays are designed for oneparticular situation; that is, when the motor is at a constant ambienttemperature and the controller is located separately in a varying ambienttemperature. In this case, if a standard thermal overload relay were used, itwould not trip at the same level of motor current if the controller temperaturechanged. The standard thermal overload relay is always affected by thesurrounding temperature. To compensate for temperature variations, anambient-compensated overload relay is used. Its trip point is not affected bytemperature, and it performs consistently at the same value of current.Thermal Overload Relay Trip CharacteristicsMelting alloy and bimetallic overload relays are designed to approximate theheat actually generated in the motor. As the motor temperature increases, sodoes the temperature of the thermal unit. The motor and relay heating curves(left) show this relationship. From this graph we can see that no matter howhigh the current drawn, the overload relay will provide protection yet will nottrip unnecessarily.Solid State Overload RelayThere are some substantial advantages to using the solid state electronicdevice. The device does not require thermal units. The customer does nothave to exercise skill at the selection procedure nor is there a need to stock55/98 1998 Square D All Rights Reserved

Product Descriptionthermal units for repair or replacement. Not having to install thermal units can save from 20-30% of theinstallation time for a starter or separate overload relay, as compared to the traditional NEMA devices.The solid state device, when operated within its operating temperature range, does not require ambientcompensation. Only the level of current being drawn by the motor affects the trip of the device.Solid state devices are typically available as part of a starter or as a separate component. This adds tothe flexibility of their application and mounting. Some solid state devices are designed to retrofit meltingalloy or bi-metal devices from the same manufacturer. This flexibility provides the user a migration pathto the new technology. Product selection and application are not dramatically different from thetraditional melting alloy or bi-metal devices. The mounting and “look” are also similar to the traditionaldevices. Backward compatibility can also be useful if the decision is made to standardize on the newtechnology and the user wishes to upgrade the existing installed base.The most important feature offered by a solid state overload relay is phase loss protection. While aphase loss causes a significant current increase in the remaining phases of the motor circuit, there is amajor increase in rotor current that can cause motor damage.The time it takes for a melting alloy device to trip is determined only by the level of current in theremaining phases. The majority of the motors installed (world-wide) are run at about 70% of their fullload capability. In these situations, the phase loss condition may result in a level of current in theremaining phases just slightly above the actual FLA of the motor and, therefore, only slightly above therating of the thermal unit. Therefore, it could take a substantial amount of time for the melting alloy devicein this application to respond to phase loss.The bi-metal device offers a limited form of phase loss protection by means of a differential trippingmechanism where the device will trip somewhat faster when an overload is detected on only two of thephases. This device contrasts with a solid state overload relay with phase loss protection that would tripin less than three seconds and alert the user of a potential distribution system problem in advance ofmotor failure. Consequently, the problem does not have an opportunity to affect other equipment on thesystem.The solid state device also provides phase unbalance protection where the device will trip if the currenton any phase is 25% greater than the average of all three phases. Phase unbalances are typicallycaused by an unbalanced up-stream single phase load that can disturb phase voltages. Such acondition can similarly lead to excessive rotor currents and motor damage.6 1998 Square D All Rights Reserved5/98

Thermal Overload Relays – NEMA RatedMelting AlloyNEMA-rated Thermal Overload Relays feature: Exclusive One-Piece Thermal Unit Trip Free Reset Mechanism on Types F, G & S Inverse Time Delay Trip Replaceable Contact Units on Types F, G & S Alarm Contact AvailableSlow trip (Class 30) and quick trip (Class 10) melting alloy thermal units are available for all Size 1, 2, 5and 6, and some Size 3 and 4 applications. Thermal units are not included.For Separate Mounting – Melting Alloy – 600 Volts Maximum, AC or DCaSizeMaximum FullLoad Current(Amperes)Open Typefor Separate Panel MountingFor Terminal Block Channel Mounting OrderOpen Type Relay and Bracket Kit BelowLeft Hand TypeTypeRight Hand TypeSingle Pole Construction (One N.C. Contact) — 1 Thermal Unit RequiredType O1RGO11R.Three Pole Construction (One Common N.C. Contact on Type S Only) — 3 Thermal Units Use 3 Type GO11R Relays Listed Above.a Maximum power circuit rating for separate mounting overload relays, Types C, F, G, T and U, is 600 volts AC or DC; Type S is 600 volts AC only.Maximum control circuit contact rating for Types C, F, G, T, U and SDO18 is 600 volts AC and 250 volts DC; the remaining Type S versions are 600volts AC only.Replacement Melting Alloy Overload Relays for Square D Class 8536 StartersLocate Class 8536 Starter in this ColumnOrder Class 9065 Overload Relay from this ColumnTypeNumber of ThermalUnits RequiredNEMA SizeTypeSeriesNumber 3-5SDO4SDO513q1PSCA2SDO101SDO7SDO813qType 5SDO15SDO16SDO173235SGA3‡SDO1816SHA&B3SEO53q For 4-pole starters used on two phase systems order 2 thermal units plus one Class 9998 Type SO31 jumper strap kit for every two starters. Each kitincludes two jumper straps.u Type S Size 5 starters use three Type SDO18 overload relays per starter.Special Features for Melting Alloy TypesFormSubstitute 1-N.O. isolated alarm contact and 1-N.C. contact per relay. (Type S starters only)pY342pSubstitute 2-N.C. contacts for standard N.C. contact per relay. (Type S starters only)Y344pModify Type U relay to accept Type FB quick trip or SB slow trip thermal units. (Accepts Type C standard trip)Y21kModify Type SDO12 relays to accept Type FB quick trip or SB slow trip thermal units, and Type F, and Type SDO15 relays to accept TypeFB quick trip thermal units. (Rejects Type CC standard trip units)Y81kk This form cannot be field modified.p Field modification possible. Order 9999 S04 (for Form Y342) or 9999 S05 (for Form Y344).75/98 1998 Square D All Rights Reserved

Thermal Overload Relays – NEMA RatedBimetallicBimetallic thermal overload relays feature automatic reset or hand reset and a trip-free mechanism.There are ambient temperature-compensated versions. Note that thermal units are not included in theshown prices.For Separate Mounting – Bimetallic – 600 Volts Maximum AC or DCaDescriptionSizeMaximum Full LoadCurrent (Amperes)Open Type forSeparate Panel MountingNumber of ThermalUnits Required2560100180DAGAHAJA1Single Pole Construction (One N.C. Contact)Class 9065Type SEO6B2Three Pole ConstructionNon-Compensated00, 0, 1234Non-CompensatedThree Pole Construction (One Common SPDT Contact on Type S)Non-CompensatedAmbient 6BSEO9B3For additional selections see International Control Products.a Maximum control circuit contact rating for Type S versions is 600 volts AC only.Replacement Overload Relay forSquare D Class 8536 Bimetallic Overload Relay on an Existing StarterOrder Class 9065 Overload Relayfrom this ColumnLocate Class 8536 Starter in this ColumnNEMASizeTypeSeriesNumber ofPolesFormTypeNumber ofThermal 2SEO6BSEO6B23333q B indicates ambient temperature-compensated bimetallic overload relay.B1 indicates single phase non-ambient temperature compensated bimetallic overload relay.B2 indicates polyphase non-ambient temperature compensated bimetallic overload relay.k Form B5 and Form Y59 use 1 overload relay block per phase. B5 indicates single phase bimetallic overload relay. Y59 indicates single phase ambienttemperature compensated bimetallic overload relay.p B2Y500 indicates bimetallic overload relay with current transformer sensing. BY500 indicates ambient temperature compensated bimetallic overloadrelay with current transformer sensing. This part number does not include the current transformer assembly (Current Transformer part number31102-084-50).8 1998 Square D All Rights Reserved5/98

Thermal Overload Relays – NEMA RatedSolid State Overload Relay, Motor Logic Base UnitBase Unit relays feature: 3 to 1 adjustment range for trip current; phase loss and unbalance protection;direct replacement for Type S melting alloy; and LED power indication. They are ambient insensitive andself–powered. Electrical remote reset is also available.Base Unit: For Separate Mounting Solid State Overload Relay600 Volts AC MaximumFull LoadCurrent Range (Amperes)Open TypeSize (3-Pole)Trip Class 10Trip Class 220SS320SS420SS520c Size 00C , 0, and 1 are supplied without lugs. Lower amperage loads can be protected by looping of power wires.f Size 5 is a complete drop-in replacement for Square D NEMA Type “S” melting alloy, bimetallic, and Y500 overload relays only.Base Unit: Replacement SSOLR for Retrofit of Square D Type S StarterSolid State Overload Relay – 600 Volts AC MaximumOrder Class 9065 Overload from these columnsLocate 8536 Starterin this columnNEMA SizeFull Load CurrentRange (Amperes)Open TypeTrip Class 10Trip Class R320SR420SR520SR620SR720p 00C , 0 and 1 are supplied without lugs. Lug - Extender Kits are available for Size 00C , 0 and 1.a Size 5, 6 and 7 Replacement Overloads are overload relays only for existing NEMA Type “S” starters with Motor Logic. External CTs and additionalcomponents are not included.Additional Standard Features Self-poweredRepeat trip accuracy: /- 2%Normally closed trip contactVisible trip indicationTrip free operationAmbient insensitivityHarmonic immunityThermal memoryTrip test function3 Second trip on phase imbalance 25% (see Page 13)Optional Features Auxiliary contactsElectrical remote resetLug-Lug kits for separate mountingDIN rail adapter bracketLug-Extender kit for retrofit (00C, 0, 1)95/98 1998 Square D All Rights Reserved

Thermal Overload Relays – NEMA RatedSolid State Overload Relay, Motor Logic Feature Base UnitFeature Unit relays include all of the features found on the Base Unit relays plus: switch selectable tripclass; Class II ground fault detection; and direct replacement for Type S melting alloy. These relays willalso accept the Analog Output Module or Seriplex communication module. Electrical remote reset isalso available.Feature Unit: For Separate Mounting Solid State Overload Relay600 Volts AC MaximumSize(3 Pole)Full Load Current Range(Amperes)Open Type00Bc00Cc0c1c2345f1.5 – 4.53–96 – 189 – 2715 – 4530 – 9045 – 13590 – 270SFB20SFC20SF020SF120SF220SF320SF420SF520Trip Class 10/20c Size 00B, 00C, 0, and 1 are supplied without lugs. Lower amperage loads can be protected by looping of power wires.f Size 5 is a complete drop-in replacement for Square D NEMA Type “S” melting alloy, bimetallic, and Y500 overload relays only.Feature Unit: Replacement SSOLR for Retrofit of Square D Type S StarterSolid State Overload Relay – 600 Volts AC MaximumOrder Class 9065 Overload from this columnLocate 8536 Starterin this columnNEMA SizeFull Load Current a6a7a1.5 – 4.53–96 – 189 – 2715 – 4530 – 9045 – 13590 – 270180 – 540270 – 810Open TypeTrip Class ST720p Size 00B, 00C, 0, and 1 are supplied without lugs. Lower amperage loads can be protected by looping of power wires.a Size 5, 6 and 7 Replacement Overloads are only for existing NEMA Type “S” starters with Motor Logic . External CTs and additional componentsare not included.Additional Standard Features Self-poweredRepeat trip accuracy: /- 2%Normally closed trip contactVisible trip indicationTrip free operationAmbient insensitivityHarmonic immunityThermal memoryTrip test functionGround fault detection3 Second trip on phase imbalance 25% (see Page 13)Optional Features Auxiliary contactsElectrical remote resetLug-Lug kits for separate mountingDIN rail adapter bracketLug-Extender kit for retrofit (00B, 00C, 0, 1)4-20 mADC, analog output moduleSeriplex communication module10 1998 Square D All Rights Reserved5/98

Thermal Overload Relays – NEMA RatedApplication DataGeneralOverload relays are intended to protect motors,controllers, and branch-circuit conductors againstexcessive heating due to prolonged motorovercurrents up to and including locked rotorcurrents. Protection of the motor and the otherbranch-circuit components from higher currents,due to short circuits or grounds, is a function of thebranch-circuit fuses, circuit breakers, or motorshort-circuit protectors.Nameplate Versus NEC Full-load CurrentThe 1996 NEC in Tables 430-147, 430-148, 430149 and 430-150 lists full-load currents accordingto motor horsepower and voltage. According toArticle 430-6, these full-load currents should beused, rather than the motor nameplate full-loadcurrent, to determine the ampacity of conductors,ampere ratings of switches, or branch-circuitovercurrent devices, etc. It is specifically stated inArticle 430-6, however, that “separate motorrunning overcurrent (overload) protection shall bebased on the motor nameplate current rating.”Service FactorNEMA standards for motors list service factors of1.15 to 1.25 for general-purpose ac motors from1/2 to 200 horsepower. Other motors, such astotally-enclosed, fan-cooled, and motors over 200horsepower have a standard 1.0 service factor.Because of the way in which the standards areestablished, there is no simple way of determiningthe service factor without looking at the motornameplate. For this reason all of the thermal unitselection tables in this catalog are designed for1.15 to 1.25 service factor motors, except thetables for Class 8198 High Voltage Starters.These tables are designed for 1.0 service factor. Itis important to know when a motor has a servicefactor of 1.0, because failure to recognize this factwill result in an over-sized thermal unit selectionand reduced motor protection.Motor Branch Circuit DesignMinimum safety provisions for the control ofmotors are set forth in the National ElectricalCode. Although these minimum provisions mustbe met, they are no substitutes for an intelligentselection of protective devices made on the basisof the motor circuit being designed. The coderecognizes this fact in Article 430, Section D,“Where maximum branch-circuit protective deviceratings are shown in the manufacturer’s overloadrelay table for use with a motor controller or areotherwise marked on the equipment, they shallnot be exceeded even if higher values are allowed(by the code).”Square D furnishes an instruction sheet withevery starter. Each instruction sheet includesthermal unit selections and either fuse or circuitbreaker selections, or both as applicable.The capability of industrial systems to deliver highshort circuit currents has been increasing steadilyover the years. This fact has caused muchconcern about the capability of motor controllersto withstand high current faults, without creatinghazards for personnel and destruction ofequipment. NEMA standards require thatcontactors be able to interrupt currents up to 10times full load current. Therefore, it is acceptablefor the overload relay to respond before the shortcircuit protector up to this level. At currents above10 times motor full load current the short circuitprotective device must respond first to minimizeequipment damage. A fully coordinated system isachieved when the overload relays operate inresponse to motor overloads before the fuses orcircuit breaker, and the fuses or circuit breakeropen the circuit before the overload relays trip orburn out on short-circuit currents.Proper coordination requires a thoroughknowledge of the time versus current limits of allof the branch circuit components as well as thetime versus current trip characteristics of theoverload relay and short circuit protective device.Overload RelaysThermal overload relays sense motor current byconverting this current to heat in a resistanceelement. The heat generated is used to open anormally closed contact in series with a startercoil causing the motor to be disconnected fromthe line.In spite of being relatively simple and inexpensive,thermal overload relays are very effective inproviding motor running overcurrent protection.This is possible because the most vulnerable partof most motors is the winding insulation and thisinsulation is very susceptible to damage byexcessively high temperature.Being a thermal model of a motor, the thermaloverload relay will produce a shorter trip time at ahigher current similar to the way a motor will reachits temperature limit in a shorter time at a highercurrent. Similarly, in a high ambient temperature,a thermal overload relay will trip at a lower currentor vice versa allowing the motor to be used to itsmaximum capacity in its particular ambienttemperature (if the motor and the overload are inthe same ambient).115/98 1998 Square D All Rights Reserved

Thermal Overload Relays – NEMA RatedApplication DataOnce tripped, the thermal overload relay will notreset until it has cooled, automatically allowing themotor to cool before it can be re-started.Cutaway View of StandardTrip Melting AlloyThermal UnitSquare D manufactures two basic types ofthermal overload relays, the melting alloy and thebimetallic. In some types, the bimetallic isavailable in both non-compensated and ambienttemperature-compensated versions. In bothmelting alloy and bimetallic, single element andthree element overloads are available.Motor Logic Solid State overload relays use anelectronic method of detection, which respondsdirectly to the motor current. When tripped theoverload relay may be reset either manually orremotely using the Remote Reset Module. TheSolid State overload relay provides overloadprotection only for three phase motors rated up to600 volts AC.Class 9065 Type SEO5Three-Pole ConstructionThe Solid State overload relay provides protectionfor phase loss and phase unbal

have to exercise skill at the selection procedure nor is there a need to stock Bimetallic Overload Relay with Side Cover Removed Overload Relay Trip Curve Motor Damage Area Motor Heating Curve Time Required To Trip 0123456789101112 Minutes 100 200 300 400 500 600 Percent Full Load Current Graph shows motor heating curve and overload relay trip .