A.O.Smith Motor Master y APPLICATION University …downloads.dickmansupply.com/pdf/AOSmith/3200.pdf · A.O.Smith Motor Master y University INCLUDES: ... Systems using PSC compressor

A.O. SMITHA.O. SMITHA.O. SMITHA.O. SMITHA.O. SMITH

APPLICATION

A.O.SmithMotorMaster yUniversity

INCLUDES:

APPLICATION INFORMATION

TROUBLESHOOTING

OTHER MODULES INCLUDE:

PUMP MOTORS

HEATING, VENTILATING,

AIR CONDITIONING& REFRIGERATION

MOTORS

GENERAL PURPOSE MOTORS

SPECIAL PURPOSEMOTORS

HVAC&R Book 9/6/56 2:54 AM Page 1

ContentsHeating, Ventilating, Air Conditioning

& Refrigeration (HVAC&R):General Purpose & Special Purpose

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1HVAC&R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2The Refrigeration Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3Hermetic Compressors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4HVAC&R Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6Outdoor Sections—Residential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7Furnaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10Fan Coil Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13Room Air Conditioners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14PTACs (Packaged Terminal Air Conditioners) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15Air Curtains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15Evaporative Coolers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16Unit Heaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18Hot Water Circulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18Whole-House Ventilators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18Pedestal Fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19Fan Blade and Blower Wheel Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20Rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21General Purpose Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23Power Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23Special Purpose Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24Glass Washers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24Garage Door Opener/Commercial Door Opener/Gate Motor s . . . . . . . . . . . . . . . . . . . . .25Air Compressors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25Carbonator Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26Sump Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26Sewage/Effluent Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26Explosion Proof Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27Poultry Duty Fan Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27Transformer Cooling Fan Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27Motor Troubleshooting Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

© 2003 A.O. Smith Corporation

The information contained in this booklet is general in nature and is drawn from sources believed tobe reliable. It is intended for general information purposes only. The descriptions in this bookletmay not apply to a particular motor or a particular application. No warranties are intended to becreated by this information.

NOTICE:


IntroductionThis application guide is not intended to be a

repair manual for any of the equipmentdescribed. It is intended to provide generalknowledge to persons working in fields related toelectric motors and to provide service informationto qualified persons.

Motors are of little use by themselves. Theyare designed to be coupled to some other part andconvert electrical energy into mechanical energy.

The selection of a replacement motor for a spe-cific application would be a very involved processif it were necessary to start with the basics ofmagnetism, electricity, and motor constructioneach time a replacement was required. In orderto present replacement motor offerings in a logi-cal, orderly manner, the motors are grouped bytype, construction, and often, the application forwhich they are intended.

Motors in original applications are designed tobe operated under specific conditions. If theequipment or installation is modified, the motormay be overloaded. For example, if a furnacedesigned for use in a home with duct work isplaced in a shop and has little or no supply ductwork, it may be close to a free blow condition (nostatic pressure or resistance to air flow). Themotor may become overloaded.

A.O. Smith’s replacement motor selections areidentified by applications where possible. Thismakes it easier to narrow the choices in theselection process.

Heating, Ventilating,Air Conditioning, & Refrigeration Motors 1

Level 2 A.O.Smith


2 Heating, Ventilating, Air Conditioning, & Refrigeration Motors

Level 2 A.O.Smith

HEATING, VENTILATING, AIR CONDITIONING &REFRIGERATION (HVAC&R)

Heating and air conditioning applications oftenuse the same types of motors or share the samemotors if the systems are combined. Heating sys-tems using motors heat either air or water. Onceheated, the air or water is moved by a motor andblower or motor and pump.

All air conditioning systems using motors with-in the scope of this manual use essentially thesame principles. The components may look dif -ferent depending on the system capacity andconfiguration.

Heating ,Ventilating ,Air Condi-tioning &Refrigeration(HVAC&R)


Heating, Ventilating, Air Conditioning, & Refrigeration Motors 3

Level 2 A.O.Smith

THE REFRIGERATION CYCLEThe refrigeration cycle involves a number of

physics principles to convert energy from oneform to another, and to transfer that energy fromone point to another.

One of the principles in the change of state.Just as it takes energy to change ice at 32degrees fahrenheit to water at the same tempera-ture, energy transfer is required to change thestate of a refrigerant.

The diagram below describes the refrigerationcycle. Simply stated, electrical energy in the caseof an electrically driven compressor, compressesthe refrigerant gas and causes it to move throughthe system where it changes from a gas to a liq-uid and back. In addition to the changes in gasvolume, heat is added or taken away at differentpoints in the process.

TheRefrigerationCycle

▼

DISCHARGE LINE

SUCTION LINE

LIQUID LINE

RECEIVER

EXPANSIONVALVE

CAPILLARY TUBE

BLOWER/MOTOR

BULB

FAN/MOTOR

EVAPORATOR

CONDENSER

HIGH PRESSURE SIDE

LOW PRESSURE SIDE

REFRIGERATION DIAGRAM



A.O.Smith

Electrical energy is converted to mechanicalenergy by the compressor motor. The compressordraws a refrigerant gas from the evaporator, com-presses it and sends it to the condenser where itis liquefied. Refrigerant gas entering the con-denser is full of heat picked up from the previouscycle plus heat from the compression cycle. Inthe condenser, heat is removed from the refriger-ant and it returns to the liquid state. An expan-sion valve controls the flow of refrigerantbetween the condenser and evaporator. The tem-perature of the gas entering the evaporator islower than that of the air to be cooled. Heat isremoved from the air to be cooled. This heat isabsorbed into the liquid refrigerant causing achange of state back to a vapor. The cycle contin-ues until a thermostat senses that the desiredtemperature has been reached and shuts the sys-tem down.

HERMETIC COMPRESSORSThe motors and other components of the sys-

tem operate in a closed system and must be com-patible with each other. Compressors are desig-nated as hermetic or semi or accessible hermeticdepending on the type of construction. The wordhermetic means an airtight seal or sealed fromoutside elements. Typically, home refrigerator,room air conditioner, home air conditioner, andsmall commercially applied compressors are in awelded shell, leading to the hermetic designation.Larger commercial compressors use castings andother parts, similar to an automobile engine,which are bolted together and get the designationaccessible hermetic.

HermeticCompressor s

Hermetic Stator/Rotor



Level 2 A.O.Smith

The function of both types is essentially thesame. Due to the initial cost of the larger sys-tems, parts may be salvaged and used in rebuildor remanufacturer operations.

Hermetic motors are used in hermetic compres-sors. The sealed system contains a refrigerantgas and lubricating oil.

Hermetic motors are functionally the same asother types of motors except that the housing,bearings and shaft are provided by the compres-sor manufacturer. These motors are oftenreferred to as rotor/stator kits. Single phase ver-sions are often of the permanent split capacitor(PSC) type which does not require a startingswitch. Systems using PSC compressor motorsoften have “Dual Can” capacitors which are twoseparate capacitors in one housing. One capaci-tor is used for the compressor and one for the fanmotor.

A.O. Smith has a selection of hermeticrotor/stator kits for rebuild and remanufactureoperations.



Level 2 A.O.Smith

H VAC & RA p p l i c a t i o nB a s i c s

HVAC&R APPLICATION BASICSMany motors for heating, ventilation, air condi-

tioning and refrigeration applications aredesigned special purpose. Knowing the applica-tion makes it possible to begin the selectionprocess at a point where the possible replacementwill likely be found. An understanding of theapplication will help assure that the best possibleselection is made.

A heat pump performs the same functions as anair conditioning system, but contains a valvew h i ch changes the refrigerant flow and in effectchanges the evaporator into the condenser andvice versa. In heat pumps the coils are commonlycalled the indoor and outdoor sections. In the heatpump mode, heat is removed from the indoor coiland added to indoor air, and heat is added in theoutdoor coil. Heat is present in all substancesi n cluding air and water until absolute zero isr e a ched at which point all molecular activity stops.As an example, air at 30 degrees fahrenheit mayseem cold but it is warmer than air at 20 degreesfahrenheit because it contains heat.

Because they incorporate a change of state ofthe refrigerant, it is possible for heat pumps to bemore efficient than straight resistance heat. Thisefficiency is expressed as a measure of wattsinput to BTU output. A heat pump’s efficiencydecreases as the outside temperature decreases.Electric resistance strip heat is often incorporat-ed into heat pump systems and is activated whenthe heat pump cannot meet the demand for heat.

Some systems use water instead of air as theheat transfer medium in the outdoor section. Thewater may be a constant source in a drilled wellor a flowing source. Heat pumps are also used totransfer heat to swimming pools.

In systems using air as the heat transfer medi-um, fans driven by electric motors are used tomove air over the evaporator and condenser coils,facilitating heat transfer. Propeller fans are thenorm on the outside sections with blower wheelsused indoors.



Level 2 A.O.Smith

O u t d o o rS e c t i o n —R e s i d e n t i a l

OUTDOOR SECTIONS—RESIDENTIALEnclosed motors are widely used in new out-

door installations. The use of enclosed replace-ment motors has risen dramatically in recentyears. The service person may use one motor forboth enclosed and open applications, reducinginventory dollars. Even though a motor is totallyenclosed, it still needs to breathe and have aplace for moisture to drain. Replacement motorstypically have drain holes in both end frames. Aplug is required in the hole on the top of themotor as installed. If a motor has two plugs, theone on the bottom should be removed. If only oneplug is provided, it should be installed in the tophole.

If it is possible for rain or other moisture toaccumulate on the motor leads, the leads shouldbe placed to form a drip loop so the moisture willnot drain into the motor’s other components.

Almost all units being built today have 60degrees celsius (140 degrees fahrenheit) fanmotors on the hot side of the coil. The ambient oroutside air is pulled through the coil, picking upadditional heat before it passes over the motor. Ifthe ambient air is first drawn over the motor andthen pushed through the coil, the motor has alower operating temperature.

If a motor rated 40 degrees celsius (104 degreesfahrenheit) is installed on the hot side of the coil,nuisance tripping may occur, especially in highambient situations.

Motors used on residential systems are usuallysleeve bearing. Light commercial units whichlook just like the residential units may have ballbearing outdoor motors. The motor should defi-nitely be a special ball bearing design if a speedcontrol device is used.

FSE1036Totally Enclosed OutdoorSleeve Bearing Fan Motor

FE1036Totally Enclosed Outdoor Ball

Bearing Fan Motor



Level 2 A.O.Smith

Motor usage is heavily weighted to six pole(1075 RPM) designs, followed by eight pole (825RPM) then four pole (1625-1725 RPM) units.Two speed motors are used on some units toreduce operating speeds and costs when lowerambient temperatures do not require as much airflow over the coil.

Since the horsepower required for the fanvaries directly as the cube of the speed, a six polemotor cannot be used to replace an eight polemotor. Depending upon the static conditions, thesame fan blade may require almost three timesthe horsepower to run at 1100 RPM as it does at825 RPM.

Typical mountings are lug, belly band orextended motor thru bolts. Some motors usescrews in tapped holes in the main frame toattach mounting strips or cables.

Blocked coils reduce air flow to cool the motorand can cause an overload condition.

Fans may be statically balanced, but dynami-cally out of balance due to bent blades. This con-dition may lead to bearing failure.

The term split system refers to units with sepa-rate indoor and outdoor sections connected byrefrigerant line. Packaged units as the nameimplies, have all the components in one place.Room air conditioners, commercial rooftop units,PTACS (Packaged Terminal Air Conditioners)and mobile home packs are examples of packagedunits. Even though packs and commercial unitsare entirely outside and only ducted to the inside,they have a physical barrier between the insideand outside sections.

FS1037SClosed Except Lead EndOutdoor Sleeve Bearing

Fan Motor

Lug Mount Adapter Bracket



Level 2 A.O.Smith

Commercial systems whose components andconfigurations differ from basic home and com-mercial packaged and split systems may also usefractional horsepower motors in either indoor oroutdoor sections. Fan coil units with a motor andblower wheel(s) are used in systems wherechilled/heated water or refrigerant is pipedthrough a building instead of using a centralblower and duct work. Some chillers use thesame type outdoor fans and motors as rooftopand packaged units.

Motors used in commercial applications such ascondensers usually have ball bearing construc-tion because the loads are heavier. Sleeve bear-ing motors typically are quieter than ball bearingmotors and are favored in indoor air movingapplications.

Ball bearing motors may be used to replacesleeve bearing motors but not vice versa unlessyou are certain they will meet all applicationrequirements.

FC1106“Patented” Fan Canopy

Deluxe CommercialCondenser Fan Motor

FY310656 Frame, 3Ø Totally Enclosed

Ball Bearing CommercialCondenser Fan Motor

FB3056Base Mounted, 3Ø

Outdoor Ball BearingCondenser Fan Motor

BK1072Commercial Indoor

Blower Motor



Level 2 A.O.Smith

FURNACESFurnaces generally use motors for three func-

tions: move either heated or cooled air, movefuel, and provide air for combustion. A specificfurnace may use more than one motor. High effi-ciency furnaces capture more of the heat of com-bustion and use a motor and blower to providecombustion air and exhaust flue gases. Thesemotors are commonly called draft inducer motors.“C” frame and 3.3” are the most common motorsused in this application.

Natural gas and propane flow through controlvalves into the burner area of a furnace underpressure. Oil furnaces use a motor and pump tospray the oil into the burner area. NEMA stan-dard M and N flange motors are common in oilburner applications. Rotation, horsepower andflange type are key elements in motor replace-ment.

A furnace burns substances such as naturalgas, oil, propane, wood and coal. The heatexchanger separates the combustion process fromthe air in the space being heated. The motor andblower circulate air through the heat exchange ina continuous cycle until the desired temperatureis reached. In most cases, a thermostat and con-trol circuit is used to operate the cycle.

The thermostat controls the combustion cycle.The control circuit senses the plenum tempera-ture within the furnace and signals the blowermotor to start and stop. This same control circuitalso shuts off the combustion process if the blow-er motor fails to start.

Furnaces are designed as hi-boy or up-flow,counterflow or downflow, low-boy and horizontal,depending upon the space in which they areapplied. The motor/blower performs the samebasic function in all designs.

Furnaces

EL2002Reversible Switch Model Oil

Burner Motor



Level 2 A.O.Smith

A squirrel cage blower wheel powered by adirect drive PSC motor is the most common sys-tem now used in residential systems becausethey are efficient and compact. Six pole (1075RPM) multi speed motors are now the norm.Some eight pole (825 RPM) motors are also used.Belt driven blowers were common in the past andmany are still in use. Four pole (1725 RPM)motors are the most common. Some two speedmotors are used in conjunction with electronic aircleaners to provide continuous air movement toreduce drafts. Two speed belt driven motors mayhave one of two different types of internal switch-es. One type requires an external relay to switchfrom high to low and low to high speeds.

As mentioned above, three speed, direct drive,permanent split capacitor, 1075 RPM motors arethe most common. The speeds are available sothat the air flow may be tailored to the installa-tion. Different speeds are needed to move the airdepending upon the static pressure in a system.High speed may be used if the system has airconditioning since more work is required to movethe cold air which is heavier. Medium speedcould be used to move air in the heating mode.

The wire lead from any speed(s) not being usedshould be insulated separately and secured sothat it does not cause a short.

Furnace blower motors are available in both115 and 230 volt versions. The 115 volt versionsare a throwback to the days when most homesdid not have 230 volt systems. 230 volt versionsare more common today, especially on electric fur-naces.

FDL1036High Efficiency Indoor

Blower Motor

GF2034Belt Drive Blower Motor



Level 2 A.O.Smith

Electric furnaces are a combination of wirestrips and an air handler. The resistance of elec-tricity flowing through the wire strips createsheat. The strips heat air which is circulated bythe air handler. Electric furnaces use the sametype of air handlers and motors as other types offurnaces.

Some furnaces use variable speed motors runcontinuously. This feature prevents air frombecoming stratified and drafts are reduced. Also,with an electronic air cleaner, the air is constant-ly being circulated.

Furnace motors are normally of an open con-struction since they are in a relatively clean, dryand protected environment.

Multi speed direct drive blower motors are nor-mally designed to have at least 100 RPM differ-ence between speeds. It is not possible to knowexactly where a given motor will operate on oneof the lower speeds unless a loading point isdetermined. Multiple horsepower ratings andspeeds shown on stock motors are offered as aguide and are not exact. It is not possible todetermine speed on a bench with a strobe sincethe motor is not loaded and will operate close tothe same speed on all taps. These motors maytrip the overload on a bench test since they arenot loaded and will run faster than in an applica-tion, and do not have the necessary cooling airbeing drawn over them.

Most HVAC&R direct drive motors have non-NEMA standard mountings and shafts and haveframe suffixes of “Y” or “Z”. This does not meanthat stock replacements are not readily available.

In many cases, stock motor shafts will need tobe shortened for specific applications. Care mustbe taken to avoid bearing damage.

DL1036Standard Efficiency Indoor

Blower Motor

FM1036Fleximount Indoor

Blower Motor



Level 2 A.O.Smith

FAN COIL UNITSThese units are a combination of a fan, motor

and coil in one package. While a package con-taining these components in a residential, coolingonly system could technically be called a “fancoil”, usually the term refers to commercial andinstitutional applications where chilled or hotwater is sent through the coil.

A wide variety of product configurations isavailable. The motor and blower wheel principlesdiscussed under the furnace section also applyhere.

One common variety is the classroom typewhich uses a double shaft extension motor andtwo blower wheels whose length is large com-pared to the diameter. Using the small diameterwheels, the desired amount of air may be moved,but the unit does not protrude too far into theroom. The same type of motor and blower combi-nation is also found in hotel room units whichlook like PTACs.

Five inch diameter (42 frame) motors are verypopular, but some 48 frame motors are also used.Larger commercial direct drive units typicallyutilize ball bearing motors.

Fan CoilUnits

DBL64091050 RPM, 5 Speed Fan Coil

Motor, 42 Frame



Level 2 A.O.Smith

ROOM AIR CONDITIONERSLike PTACs, room units have all the compo-

nents in one package. Semi-enclosed motors arecommon, but many units use totally enclosedmotors because of the condensate water comingoff the coils. Belly band lug mount kits andresilient mount length adapters are often usedwith replacement motors.

Motors are single voltage and mostly 230V inunits above 9,000 BTU. Some units have a 277volt rating (sometimes marked 265 volt) which isa single phase power source from a three phasesystem. The largest percentage of motors are sixpole (1075 RPM) permanent split capacitordesigns. Some shaded pole motors will be foundin the lower BTU unit, but their use has beendeclining due to low efficiency.

Some 60 cycle units use four pole (1725 RPM)motors which are designed to operate at a slippeddown speed in the 1300-1425 RPM range. Theunit design requires speeds higher than 1075, butoperation at true four pole speeds is not requiredor desirable from a noise standpoint. These unitsrequire a direct OEM replacement.

Be aware that motors rated for both 60 and 50cycle will have RPMs listed as 1725/1425. The1425 RPM in this case is at 50 cycle operation, sothis motor is not an acceptable replacement for a60 cycle motor with the RPMs listed as 1425.

Room A i rC o n d i t i o n e r s

Lug Mount Bracket

End Frame Length Adapter Kit

SA1016Room Air/PTAC Motor



Level 2 A.O.Smith

PTACSPackaged terminal air conditioning units are

similar in construction to room air conditioners.All of the components are in one package. Theyare common in hotel/motel rooms, small officesand apartments. Strip electric heat is a commonoption. Heat pump versions are available. Manydifferent manufacturer’s units have the samedimensions so they may be used interchangeablyin a standard size wall sleeve.

Some PTAC designs use two single shaftmotors (one for the condenser side and one forthe blower wheel). Designs with one double shaftmotor are more common.

Typical blower motors require air over themotor for cooling. The blower motor used on twomotor PTACs is on the other side of the unitbulkhead from the blower wheel and does not getthe same air flow as a furnace blower motor. Anexact replacement should be used, or the unitshould be tested at the maximum ambient condi-tion to insure the motor will not overheat.

AIR CURTAINSAir curtains move a thin, high volume stream

of air from top to bottom in an open doorway tokeep the air on the opposite side from mixing.Double shaft motors with blower wheels are com-monly used.

PTACs

Air Curtains



Level 2 A.O.Smith

EVAPORATIVE COOLERSThese units which are also referred to as

swamp coolers are an alternative to air condition-ing in areas where the relative humidity is lowenough that the process is effective. They arecommon in the desert southwest and high desertareas such as Salt Lake City and Denver. Dryair moves over a media pad saturated with water.The moisture laden air is blown through the areato be cooled and exhausted through vents orslightly open windows. As the moisture evapo-rates inside the space, a cooling effect occurs.This is the same as the cooling effect on yourskin when water evaporates after stepping out ofthe shower.

Most motors used in home units mount in aresilient base and have the same ring to ringdimensions. Replacement motors are often soldwithout bases since the base doesn’t normallyfail. Single and two speed units are available.

The motors are connected to the blower wheelwith a drive belt. Proper belt tension is 1/2 to 3/4inch deflection at the center of the belt span.

The motor pulley must be of the type and sizerecommended by the cooler manufacturer. If anadjustable pulley is used, the pulley should be setby a technician with the necessary electrical testequipment. The adjustable pulley allows the load(blower) to run at a speed compatible with themotor.

E va p o ra t iv eC o o l e r s

V2054Evaporative Cooler Motor



Level 2 A.O.Smith

To set an adjustable pulley:1. Open pulley to maximum width and

tension belt.2. Read recommended motor amp rating at

the highest speed.3. Using an ammeter, measure the amps at

the highest speed.4. Stop motor, close pulley one-half turn and

retention belt.5. Repeat step 4 until the amp reading

meets but does not exceed the motor’srated amperage.

I M P O R TA N T : If the amperage exceeds themotor’s rating, the motor willoverheat and stop.

CAUTION: The motor will restart automati-cally after it cools and the over-load resets.

NOTE: Cooler installations not usingduct work will require a smallerdiameter pulley than the samecooler using duct work. The ductwork creates static pressure orresistance to air flow whichreduces the motor load and ampdraw.

An easy rule to follow is to check the motoramperage while running on high speed. It shouldnot exceed the nameplate amps.

Motors with all copper windings or a combina-tion of copper and aluminum windings are avail-able. With advances in connection methods andwinding insulation, there is little difference inthe reliability of either type.

Many motors are sold at retail with the home-owner doing the replacement.



Level 2 A.O.Smith

OBG2002

Unit Heater s

Hot WaterCirculator s

Whole-HouseVentilator s

UNIT HEATERSUnit heaters are the ductless furnaces that

hang from the ceilings of factories, warehousesand garages. The motor and propeller fan areusually visible. Enclosed motors are common dueto the often dusty environment.

Motors may be either belt drive or more com-monly, direct drive. The direct drive are usually42 or 48 frame designs using thru bolt/extendedstud or resilient ring mounts. Replacements areavailable with and without bases, and PSC typesoften have the capacitor mounted on the motor.

HOT WATER CIRCULATORSHeating systems that have hot water boilers

use a motor driven pump to circulate the water.

These motors have special shaft extensions andmounting brackets.

WHOLE - HOUSE VENTILATORSThe units normally mount in the ceiling,

pulling air in through open windows andexhausting it to the attic where it exits throughvents. Many older units used open drip proofmotors, but most new designs have totallyenclosed motors or some type of metal shield toreduce the fire hazard. Belt drive motors aregenerally four pole (1725 RPM), and direct driveare mostly six pole (1075 RPM).

UH1036Ball Bearing, Mounted

Capacitor, Unit Heater Motor



Level 2 A.O.Smith

Pedestal Fans

YA2020Yoke Mount

M i s c e l l a n e o u s

PEDESTAL FANSPedestal fan motors are used to circulate air

with a propeller type blade mounted directly onthe motor shaft.

Some motors are base mounted, but more com-mon is the yoke mount which is a bracket weldedor bolted to the motor frame. Extended motorthru bolts for mounting a fan guard are common.

MISCELLANEOUSMany applications using small (1/8 HP or less)

motors do not have replacement motors availablesince the unit cost is low. Examples include ceil-ing or “paddle” fans and window and box fans.

Other applications such as humidifiers, hoodexhaust fans, bathroom fans, refrigerators, smallroom air conditioners and furnace draft inducersmay use 3.3” diameter motors. Four pole shadedpole and two pole permanent split capacitormotor with thru bolt mountings are common.

AO1154, 3.3”

AO120, 3.3”



Level 2 A.O.Smith

Fan Bladeand Blo werWheel Basics

FAN BLADE AND BLOWER WHEEL BASICSThe horsepower needed to drive a propeller fan

or blower wheel varies directly with the cube ofthe speed if the static pressure or discharge areadoes not change.

The propeller fan needs more horsepower if thedischarge area is reduced (assuming speed doesnot change) and the blower wheel needs less.The reverse of these principles also apply.

The principles above have great importance forinstalled motors,and when selecting a replace-ment motor. As examples:

n Blocked or dirty coils on an outdoor unitreduce air flow and put more load on the fanmotor, possibly causing the thermal overloadto trip.

n If a 1075 RPM motor is used in place of an825 RPM motor, the loading is too high andthe motor will not operate.

n It may be impossible to determine if areplacement furnace motor is properly loadedif the access panel(s) is not in place - staticconditions have changed.

ROTATIONThe selection of a replacement motor obviously

requires one that turns in the proper direction forthe application. Many single phase replacementmotors are dual rotation. Some product groupshave motors that are identical except for rotationand other groups or specific motors have the rota-tion which matches the original OEM offering.



Level 2 A.O.Smith

RotationRotation on some double shaft motors may

effectively be changed by rotating the motor180˚. The rotation of any three phase motor isreversed by switching any two of the three lineleads.

There are several ways to identify the rotationof a motor in the application.

1. Look at the motor nameplate, connectiondiagram and physical connection.

2. If the motor has not failed completely and isstill operable, observe the rotation and markthe end frame or main frame.

3. Look for a rotation arrow on a propeller fanand blower wheel or housing.

4. Determine which way the air must flow inthe unit and then look at the propeller orwheel and housing.

Diagram A Diagram B

LEADINGEDGE

LEADINGEDGE

LEADINGEDGE

AIR OUT

SIDE VIEW MOTOR

WEDGEACTION

FORWARD CURVED BLOWER WHEEL

SIDE VIEW

TOPVIEW

CUPPED SIDE OF BLADE



Level 2 A.O.Smith

The propeller fan moves air by the wedgeaction of the blades. If the blades are cupped, airwill move away from the cupped side. If theblades are flat (normally they are not) as inDiagram C, air will move in either directiondepending upon motor rotation.

The lower edge of the fan blade, as related tothe wedge action, is the leading edge just as thethinnest part of a wedge goes in first to split alog.

Blower wheels are centrifugal fans. As withany centrifugal action, the speed is greatest atthe outermost portion of the device, in this case,the wheel’s outside diameter. The fins may beslanted in the direction of the air flow, but this isnot always the case. If the motor and wheel arenot together, it will be necessary to determine onwhich side the motor mounts.

If the motor applied to the blower wheel inDiagram B ran in the opposite direction, airwould move in the same direction as shown butnot efficiently.

Replacement motors often have rotation letterssuch as CWLE (clockwise, looking at the leadend) or CCWLE. The letters CWPE (clockwise,looking at the pulley or shaft extension end) arealso used on some motors.

Drawing a simple sketch of the motor, fan andunit often helps in the orientation process.


General Purpose Motors 23

Level 2 A.O.Smith

G e n e r al Purpose MotorsGeneral purpose motors as their designation indicates

may be used in a variety of applications. The designer of apiece of equipment can tailor the load so that a generalpurpose motor may be applied. The system consisting ofthe motor and the driven load often has a rating whichindicates the standard and maximum amount of work itcan do. The ratings may or may not include an overload orsafety factor. As an example, a hydraulic pump systemused to power a lift has a limit to the amount of pressure itcan develop and transfer to other system components. Ifthe lift is rated for 10,000 pounds, and the load is 20,000pounds, a relief valve must open or the weakest link in thesystem will fail. The replacement motor should be equiva-lent to the original design. A weaker motor would notallow the system to operate as designed. And, a strongermotor may create an unsafe condition. In the case of atable saw, the load varies depending upon the type of woodbeing cut, and the speed of the cut. A 1/2 horsepower motormay be suitable to start and run the saw and cut pine, butit may be okay to apply a 1-1/2 horsepower motor to thesame saw in order to cut oak.

The important point here is to select a replacementmotor equivalent to the original unless you have enoughknowledge of the application to be certain that a stronger,weaker or different type of replacement motor is acceptableand safe.

POWER TOOLSGeneral Purpose NEMA 48 and 56 frame, 2 pole and 4

pole motors are common on contractor and home type toolssuch as drill presses, jointer planners and table saws.Motors should have manual overloads or no overload.There are no exceptions to this rule - EVER! If a motorhad an automatic overload and tripped, it could start unex-pectedly after cooling and cause injury.

The information and procedures described in the replace-ment module of this series will assist in determining thatyou are dealing with a general purpose motor. Catalog list-ings of general purpose motors are organized by physicaland electrical characteristics to aid in the selection process.

Pow erTools

EB31043Ø Enclosed

Industrial Duty

RB1074Capacitor Start Resilient Base


24 Special Purpose Motors

Level 2 A.O.Smith

Special Pur p o s eM o t o r s

Following are some examples of special purposemotor applications. Keep in mind that the origi-nal equipment was tested to insure that themotor would operate safely and properly underthe conditions for which it was designed.Modification or misapplication may be unsafeand detrimental to the motor or equipment.

There are literally thousands of applicationsusing general purpose type motors with mechani-cal and electrical variations. Each of these varia-tions must be evaluated to determine if a stockmotor will work, possibly with modifications, or ifa replacement must be obtained from the OEM.

GLASS WASHERSSump pump motors are often used on glass

washers used in bars. This use is not condonedby motor manufacturers. A motor designated forglass washer duty should be used and wiringmust be done in accordance with all applicablecodes and include a ground fault device.

GlassWasher s


Special Purpose Motors 25

Level 2 A.O.Smith

GARAGE DOOR OPENER MOTORSCOMMERCIAL DOOR OPENER MOTORSGATE MOTORS

In general, these motors are excellent exam-ples of good design and application and providetestimony to the reliability of today’s motor pro-duction processes. If a motor does have adefect that will lead to failure, that failure ismost likely to occur early in the warranty peri-od at which time the entire unit is replaced. Ifa motor fails at some later time, it is usuallyless expensive to replace the entire unit.

Commercial units utilize reversing switchesand are usually serviced by door firms who gettheir motors from the original equipment man-ufacturers.

AIR COMPRESSORSMotors used in air compressor applications

may be belt drive or direct drive. On directdrive units, the compressor housing usuallyprovides support for the shaft extension endbearing. As such, these are partial motors andreplacements are not available in a stock motorline. Belt drive compressors use a more con-ventional motor with a base and single shaftextension. Horsepower, service factor andRPMs are the keys to identifying a replacementmotor. The horsepower and CFM (cubic feetper minute of air) characteristics of compres-sors are often advertised. Commercial/industri-al compressors use NEMA frame motors withidentifiable service factors. Hobby compressorsoften have motors with the service factormarked as special. Special means less thanone.

Also, keep in mind that there is a range ofperformance within the same horsepower rat-ing, depending upon motor type and manufac-turer. Check the replacement motor amps afterinstallation to verify selection.

AirCompressor s

GarageDoor OpenerMotors/CommercialDoor OpenerMotors/Gate Motor s

CP1502M


26 Special Purpose Motors

Level 2 A.O.Smith

Some electric compressor horsepower ratingshave been determined by comparing the CFM toa compressor using a gasoline engine. Since thegasoline engines are not as efficient as electricmotors, a compressor may be called five horse-power even though the motor does not actuallydevelop five horsepower. Amps are important inthe final motor selection since they determine therequired circuit capacity to which the compressorwill be connected. A replacement motor with theequivalent horsepower and service factor may notbe acceptable due to the efficiency of the originalmotor. Some motors are capacitor start and run,with more than one run capacitor. A replacementcapacitor start only motor may have runningamps which are too high.

CARBONATOR PUMPThese motors are used in beverage dispensing

systems. The shaft extension is special anddesigned to mate to the pump. Carbonator pumpmotors are also used in hydraulic pump applica-tions. Even though the mounting is special, it isuniform among motor manufacturers.

SUMP PUMPMotors used on sump pumps may be of the

pedestal type and mounted on the end of a sup-port column (1-1/2”ID or 1-3/4”OD), or theimmersible type. Most smaller immersible typesare not repairable. Key factors in selecting apedestal type replacement are horsepower, ser-vice factor, enclosure, protector/overload and hubdimensions.

SEWAGE/EFFLUENT PUMPSMotors used in these applications are sealed in

a housing and may or may not be repaired orreplaced by a qualified service person. The elec-trical designs are generally similar to stock typemotors, but their mounting is special. The origi-nal equipment manufacturer should be contactedregarding replacement.

CarbonatorPump

Sump Pump

Sewage/EffluentPumps

CB2024A

SP2030A


Special Purpose Motors 27

Level 2 A.O.Smith

EXPLOSION PROOF APPLICATIONSMotors used in hazardous environments such

as flour mills and gas pumping applicationsrequire special construction features so that ashort or spark in the motor will not ignite flam-mable liquids, vapors or dust that may be pre-sent. The design, manufacturing and applicationof these motors is subject to Underwriter’sLaboratory rules and many other local andnational codes.

Many OEM gasoline pump motors have specialmounting flanges and on/off switches and are notreplaceable by stock type motors.

Due to the liability potential, recommendationsshould not be made as to the application of thesemotors. The person making the purchase shouldhave the training and qualifications to know theexact motor required.

POULTRY DUTY FAN MOTORSCommercial poultry house fans use both alu-

minum and steel propeller blades, direct or beltdriven, mainly by base mounted motors. Thedesigns are usually totally enclosed, air over(TEAO), meaning they rely on the blade’s airmovement for cooling air.

It is essential to the chicken’s survival that hot,stale air is exhausted.

TRANSFORMER COOLING FAN MOTORSThese are very specialized direct drive pro-

peller fan motors used to cool large electric utilitytransformers. They are sometimes referred to as“fin fan” motors. The design is very robust,employing ball bearings and stainless steelshafts. Replacement motors are normallysecured through the original equipment channel.

ExplosionProofApplications

Poultry DutyFan Motor s

TransformerCooling FanMotor s

XP1070


28 Motor Troubleshooting Guide

Level 2 A.O.Smith

M o t o rTro u b l e s h o o t i n g

G u i d eSome procedures require special tools and spe-

cific product knowledge which is beyond thescope of this module.

These tips and suggestions are offered for per-sons with proper qualifications and necessarytest equipment, and as information of generalinterest to persons in the replacement motordistribution channel.

There is not a single listing of motor trou-bleshooting procedures to be followed in a givenorder. The procedures will also differ for new andexisting installations and motors that are beingbench checked. As with anything dealing withelectricity, personal safety is the prime concern.

BENCH CHECKFirst, consider what symptom lead to the

motor’s removal from service. Examples: “It wasnoisy,” “it wouldn’t start when the power wasapplied,” “it tripped the breaker,” “it runs for sev-eral minutes then shuts off,” “it just hums whenpower is applied,” “smoke came out when it wasturned on.”

WARNING!This is not a guide forthe do-it-yourselfer.

Bench Chec k


Motor Troubleshooting Guide 29

Level 2 A.O.Smith

Knowing why a motor failed may be importantin selecting the proper replacement motor, andinsuring a good service life.

Try to determine the age of the installation andif the motor is the original. If the motor is areplacement, how long has it been in service?Does it appear to have been properly installed?What is the duty cycle or service period?

Having some indication of the problem oftenindicates items to check first. A bench check isusually a confirmation of a suspected problem.The type of motor and its construction willdictate which items may be checked withoutdisassembly.

The following tips and suggestions are by nomeans complete, but offer some of the basicsrelating to a motor and its application. Othermodules cover some subjects in more detail, andspecific knowledge from other sources may beneeded.

n To the degree possible, check the same areasin the application as would be done in abench test.

n Is there any evidence of water damage?n Does the shaft turn freely?n On sleeve bearing motors, check end play

(.01-.06” normal). Lack of end play couldcause motor to bind when hot.



Level 2 A.O.Smith

n On belt driven loads with sleeve bearingmotors, check to see that the motor is orient-ed properly in relation to the bearing’s oilwick window.

n Excess heat is the enemy of a motor. If themotor has been operating properly, has any-thing changed? Is the voltage too high or toolow? Is the ambient too high for the motor?Are internal or external fans clean andintact? Has foreign material gotten into themotor? Is normal air flow around the motorblocked, causing recirculation?

n Is there any evidence of physical damage oroverheating?

n In applications such as direct drive furnaceblowers, the motor needs system air for cool-ing. There is not a general rule of thumb, butuse of a replacement motor significantlystronger than the original may result in over-heating. Speed will be up and the systemmay not provide enough air for cooling.Select a close replacement and check ampsafter installation.

n Check windings for continuity.n Check for continuity between motor leads or

terminal board and frame as indication ofshort to ground.

n Check capacitor if capacitor start and/or run.n Check the overload if accessible.n If a single phase motor with a mechanical

start switch starts but does not come up tospeed, check the switch for proper operation.If this same type motor just hums and doesnot start, check the switch and start winding.


Motor Troubleshooting Guide 31

Level 2 A.O.Smith

n If motor appears to run okay it may be okay.Or, it may have an internal problem such asloose or plugged cooling fan. It is possible fora winding coil to be shorted onto itself with-out indicating an open condition. The motorwould be weak and probably overheat underload. If the motor has a terminal board, con-nections could be loose causing intermittentoperation.

n Check for phase imbalance on three phasesystems.

n Checking a motor in its application is theonly practical method for most people todetermine performance under load. If themotor is defective, the application providesmany clues to help determine the cause . Didthe motor fail due to a defect or old age. Or,was its failure hastened by the application orenvironment? The application is the onlyplace an attempt may be made to check volt-age.

n On permanently installed equipment, thevoltage may vary depending upon the totalsystem load. It can also vary with the totalload on the power company grid.

n Mobile equipment such as rental units areoften abused through the use of inadequateextension cords or undersized generators.

n Was the motor misapplied or has the applica-tion load change? Dirty or blocked coils mayoverload a condenser motor. Reduced staticpressure may overload a motor driving ablower wheel.

n Is the belt driven load free to turn, and inproper operating condition?



Level 2 A.O.Smith

n Most motor applications have service manu-als whose procedures, especially those involv-ing safety, should be followed. Within thescope of this discussion, the assumption mustbe made that the procedures have been fol-lowed to the point where the motor is sus-pected, and proper voltage (nameplate as con-nected +10%) is available to the motor.

n In addition to the electrical hazard, anapplied motor could be very hot if a start wasattempted during other test procedures.

n Always ground motor and secure so startingtorque will not cause it to move in bench test.

n Always use the proper tools (not a hammer)to remove fans and pulleys from a motor thatis to be reinstalled. Likewise, never poundanything onto a motor shaft. A ball bearingcan easily become brinelled or work hardenedleading to eventual failure.

n In a new installation of new equipment thatdoes not start, follow the established proce-dures to the point where a motor check is rec-ommended. The procedure is basically thesame for a replacement motor on an existingapplication except the case where the motorburned out as soon as the power was applied.In this case, the motor was probably hookedup wrong.

n On a replacement motor there is slight possi-bility that the wrong nameplate was applied.Does the connection information physicallymatch the motor? Are other motors with thesame part number but different date codesthe same? Specific resistance values from themanufacturer may be required for positiveconfirmation.


NOTES:

The information contained in this booklet is general in nature and is drawn from sources believed tobe reliable. It is intended for general information purposes only. The descriptions in this bookletmay not apply to a particular motor or a particular application. No warranties are intended to becreated by this information.

NOTICE:


531 NORTH FOURTH STREETTIPP CITY, OH 45371

(937) 667-2431FAX: (937) 667-5873

www.aosmithmotors.com

© 2003 A.O. Smith Corporation 1/03 Bulletin #3200


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