Vol ume 2 Issue II

P.O. Box 410 • Schofield, WI 54476715.359.3121 • Fax 715.000.0000 • www.greenheck.com

Based on the output results ofthis data, Greenheck engineersare able to select the bearingsthat best meet each individualapplication.

The lightest duty fans normallyonly require the performance ofball bearings with stamped steelhousing. The main designcharacteristic that definesstamped bearings is the rubbersleeve around the bearing insert,which snaps into the stampedhousing. These are well suitedfor applications with very lightloads and lower speeds. The useof these bearings is limited tofan products with 3⁄4 inch andsmaller diameter shafts, andone horsepower and smallermotors.

Air handling qua l i t yWhen the operating level of theball bearings with stamped steelhousing is exceeded, airhandling quality ball, sphericalor tapered roller pillow block orflange-mount bearings areprimarily specified.

These bearings have beenengineered specifically for airhandling applications andfeature special construction and

Bearings are one of the mostcritical components in theoperation of a fan. Typically,noise and vibration levels arerequired to be kept at a levelbelow that of most applications.Additionally, fan bearingsoperate at higher speeds andcarry lighter loads. It is becauseof these special designrequirements that carefulconsideration must be given tothe selection of the appropriatebearing for each application.

B earing sel ec t i onMost manufacturers use sometype of bearing selectionprogram that calculatesequivalent bearing loads andbearing life. Some of the mainselection criteria include shaftdiameter and weight; lubricantviscosity; motor horsepower;fan sheave pitch diameter,weight and location on theshaft; fan speed; fan wheelweight; bearing and wheellocations on the shaft; thrustloads; and the direction of beltpull. Most often the selectionprogram used is one developedby a bearing manufacturer.Greenheck engineers use Dodgebearing selection software.

J uly 2000A pub l i cat i on for the engineering com m un i t y

P.O. Box 410 • Schofield, WI 54476715.359.6171 • Fax 715.355.2399 • www.greenheck.com

Bearings and bearing applications

tighter quality control. In orderfor a bearing to be of “airhandling quality,” it must meetthe following specifications:

1. Reduced swivel torque -Proper alignment of the bearingto the shaft is essential inpreventing vibration, noise anddamage to the bearingcomponents. To allow a bearingto self align under light loading,it must have a low swiveltorque. A low swivel torqueenables the outer race of thebearing to pivot or swivelwithin the cast pillow block,allowing the bearing to align tothe shaft much easier. It shouldbe noted that this feature isspecial only to air handling ballbearings and tapered rollerbearings. Spherical designsinherently allow for easy self-alignment. The race has a radiusthat allows the rollers to pivotwithin the race.

Bearings and bearing

applications . . . . . . . . . . . . . .1

Wind-driven rain testing on

louvers . . . . . . . . . . . . . .4

Energy Recovery Ventilators

- Stand Alone vs. Bolt-On

System . . . . . . . . . . . . . .6

I N S I D E TH IS I S S U E

Copyright © 2000 Greenheck Fan Corp.

Bearings and bearing applications, continued from page 1

within the ball bearingapplication range. Inour fan and ventilationline, Dodge D-Lok ballbearings are used onGreenheck’s extendedpressure upblastcentrifugal CUBEexhaust fans (ModelCube-XP).

The balance of the fan andventilator products that exceedthe limitations of the stampedsteel bearings use the ballbearing with the set screwlocking method. This includesfans with a shaft diameter ofone inch and larger, and a motorof 1 1⁄2 horsepower and larger. Inapplications with lower speedsthe D-Lok mechanism isavailable, however, the D-Lokadvantages are negligible andnot cost justified.

offsetting its rotating axis.Secondly, the shaft and bearingrace come into surface-to-surface contact upon tightening.This increase in contact surfacearea not only improves theholding strength of the bearingto the shaft, but it alsoeliminates problems with burrson the shaft caused by thetightening of set screws.

Greenheck uses Dodge D-Lokball bearings for all centrifugal,vane axial and industrial units

2. Noise and vibrationtesting - All “air handlingquality” bearings are100% vibration tested.These stringent teststandards are designed todiscover microscopicmanufacturing defectsthat may either causehigher noise levels orlead to premature failure of thebearing.

3. Bore Size Test - All “airhandling quality” bearings are100% inspected to insure thatthe inner race diameter is withintolerance. A bore size largerthan tolerance would allow thebearing to shift which couldcause misalignment.

The benefits of “air handlingquality” bearings to the life ofventilation equipment are beingseen throughout the HVACindustry. More and moremanufacturers are providing airhandling quality bearings astheir standard.

Ball bear i n g s

The Dodge D-Lok pillow blockbearing incorporates a “heavy-clamp-style” locking collar as analternative to the typical setscrew locking system. Thisdesign allows the bearing raceto be tightened concentricallyabout the shaft. This type oflocking mechanism gives twodistinct advantages over the setscrew method. First it maintainsone common center axis of theshaft and bearing, whereastightening of the set screwforces the shaft off to one side,

2 En g i n eering Update J uly 2000

Ball bearing with D-Lok

Roller bearing with set screw Ball bearing with set screw

Most manufacturers use some type ofbearing selection program that calculatesequivalent bearing loads and bearing life

based on various input data.

Determining the right bearing for theright application enables your system to

work at maximum efficiencies.

Above: Stamped steel bearingRight: Stamped steel bearing with

rubber isolation within housing

Bearings and bearing applications, continued from page 2

In such a case, a flange-mountbearing can be used. Thebearing components areessentially the same as thepillow block version, but thehousing allows for facemounting around the shaftinstead of pedestal mountingunder the shaft.

S um m ar yOutlined in this article are manyof the different standard bearingoptions and typical applicationsfor which they are used. Thisinformation is merely a

guideline to helpcommunicate a betteroverall understanding ofbearings and goodbearing application.

Don’t let your airhandling equipmentsuffer a short life spanbecause of prematurebearing failure.

Applications are oftentimes unique, and your selectionwill be based upon the bearingoptions best suited to your jobspecifications.

Greenheck engineers have over40 years of experience inbearing selection and workclosely with our vendors toensure customers receive thehighest quality products.Determine what bearing lifeyour application requires, (seethe April issue of EngineeringUpdate) and let Greenheck’sexperienced engineering teamspecify the right bearing for thejob.

free labyrinth seal and a largergrease cavity. Higher speeds canthen be attained and the rollersbecome the limiting factorinstead of the seal.

Split pillow block housingsincorporate a tapered adaptersleeve-mount locking system.Because of the geometry of thesleeve-mount design, a largerbearing is required for the sameshaft size as would be used in asolid pillow block design.

Consequently,the capacity ofthe rollers

increases, thusrequiring ahigher minimalradial load for proper operationof the rollers.

In some applications wherecontaminants need to be keptout of the bearing, special sealsother than the labyrinth-type areused in the split pillow blockhousing. In these cases, the sealmay be a speed-limiting factorand must be accounted for inthe selection of the bearing.

In certain products, such assome vane axial belt drive fans,the installation of a pillow blockbearing can be difficult simplybecause of physical spaceconstraints within the belt tube.

When the application load andspeed exceed the capacity of ballbearings, roller pillow blockbearings are typically specified.Like ball bearings, rollerbearings can carry acombination of radial and thrustloads; however, roller bearings,in order to operate properly,require a radial load at leastequal to the thrust load.Insufficient radial loadingallows the rollers to skid withinthe race, which couldcause premature failureof the bearingcomponents. Taperedroller bearings whichare similar to thespherical rollers, arecommonly specified forvertical applicationswhere high thrust loadsare encountered.

Currently, roller bearings areavailable with either thestandard set screw-lockingmethod, or the Dodge Imperialpatented adapter-mountingsystem (spherical roller bearingsonly).

B earing housingsThus far all of the bearingoptions we have discussed havebeen of either stamped or castpillow block housingconstruction. Once theapplication exceeds the speedlimit for the contact seal andgrease sump design of thesehousing designs, a split pillowblock bearing is typicallyspecified. The split pillow blockdesign incorporates a friction-

En g i n eering Update J uly 2000 3

Flange mount bearing

Split housing

Wind-driven rain testing for louvers

only one or two. To evaluateeach manufacturer’sperformance claims,understanding the differencesbetween these test standards isimportant.

The table below comparesAMCA, HEVAC, and DadeCounty test standards.

Water Pe n e t rat i onI n te rpre tat i onThe AMCA 500-L Wind-DrivenRain standard is similar to theHEVAC standard. Both of thesestandards require forced air like

louver performance. Thisprompted manufacturers todesign a new type of louver,commonly referred to as a`wind-driven rain’ louver. Thefollowing describes therequirements of the three mostcommonly used test standards: 1. AMCA Standard 500-L (wind-

driven rain or waterpenetration)

2. HEVAC3. Dade County testing protocol.

Manufacturers are not requiredto test in accordance with allstandards-- they may test to

Different regions of the worldrequire special considerationsfor building construction andcomponent design. Oneconsideration is a climate withsevere wind and rain, such ashurricanes. Typical louvers inthe industry were not originallydesigned or tested to handlesuch extreme conditions. Inresponse to engineers,architects, and building ownersrequesting higher levels ofprotection, variousorganizations have developedtest standards to addressconcerns of severe weather on

4 En g i n eering Update J uly 2000

39 in. x 39 in. core dim.48 in. x 48 in. 39 in. x 39 in.

Sample size or Largest sizeoutside dim. outside dim.

48 in. x 48 in. outside dim.

Water Application External Spray Wetted wall and External Spray External Spray

Method simulated rainfall

3 in./hr. 4 in./hr.

Water Rate or and 3 in./hr. 8.8 in./hr.

8 in./hr. optional 1.25 gpm on wetted wall

External Air Movement 29 mph with 35, 70, 90, and 110 mph0 29 mph

(wind driven) 50 mph optional extended range: 140 mph

Internal Air Movement 0, 94.4, 196.9, 295.3, 0, 94.4, 196.9, 295.3,Max. of 1250 fpm None

(drawn through) 393.7, 492.1, 590.6, 393.7, 492.1, 590.6,

689.0 fpm 689.0 fpm

Duration 30 min. per 15 min. per 30 min. per 15 min.; 35, 70, and 90 mph

test velocity test velocity test velocity 5 min.: 110 and 140 mph

Rated on effectiveness vs. Rated on effectiveness vs. Met the following watercore area at all 8 open hole at all 8 penetration requirements:velocity points Beginning point of velocity points

Water carry-over limit 35 mph: nonewater penetration at

Effectiveness ratings: Effectiveness ratings: 70 mph: none0.01 oz. of water

A = 99 to 100% A = 99 to 100% 90 mph: 0.05% of waterper ft.2 of free area

B = 95 to 98.99% B = 95 to 98.99% applied

C = 80 to 94.99% C = 80 to 94.99% 110 mph: 0.05% of water

applied

140 mph: 0.05% of water

applied

AMCA 500-LHEVAC Dade County

Wind-Driven Rain Water Penetration

Wind-driven rain testing, continued from page 4

models certified to thetraditional AMCA 500-L WaterPenetration tests. Greenheckrain-resistant models EVH-602and EVH-801 are qualified tothe HEVAC standard and arecurrently at AMCA for 500-LWind-Driven Rain certification.Dade County test specimens areunder construction for testing inthe Fall of 2000. With our widevariety of certified products,you can specify Greenheck withconfidence.

means and rates. Dade Countyrequires that air be forced intothe face of the louver at 35, 70,90, and 110 mph (there is also anextended range of 140 mph) .Each velocity (35, 70, 90, and 110mph) is not required to be tested(i.e. a manufacturer can test alouver per Dade County at only35 mph). For Dade County,velocity tests require differentdurations: 15 min. at 35, 70, and90 mph, and 5 min. at 110 and140 mph. The water carry-over(the amount of water that passesthrough the louver) must bezero for the 35 and 70 mph testsand 0.05% of the total waterapplied for the higher velocities.

(The information here onlytakes into consideration thewater penetration portion of thestandards.)

Greenheck has the most louver

Dade County, but also requireair to be drawn through thelouver (see figures 1, 2, and 3).Drawing air through the louversimulates the air intake into thebuilding.

AMCA and HEVAC introducewater at a rate of 3 in. per hourof rainfall. AMCA allowsextended qualifications for 50mph forced air and 8 in. perhour of rainfall (only for the 39in. x 39 in.). Whereas DadeCounty has up to five testvelocities, AMCA and HEVAChave eight, each of which mustbe tested and given an`Effectiveness Rating’. TheEffectiveness Rating is simply acomparison of the amount ofrain through an opening in awall and the amount of rainthrough a louver mounted inthat opening. The EffectivenessRatings have letter designationsof A, B, C, or D and have arange of effectiveness assignedto them. For instance, a louverpreventing 93% of the waterthat penetrated through theopen hole test would be givenan Effectiveness Rating of `C.’Since an Effectiveness Rating isgiven at each of the eightvelocities, one louver couldtheoretically have all fourEffectiveness Ratings.

Dade County requires testing ofthe largest louver size themanufacturer wants to offer; theother two standards requiretesting of a set size with largersizes automatically qualifying.Each standard introduces waterinto airflow, but by different

En g i n eering Update J uly 2000 5

Forced Air

Water Nozzles

LouverWind Simulation Fan

Forced Air

Water Nozzles

Wind Simulation FanLouver

Drawn Air

Figure 1:

Dade County testsetup.

Figure 2:

AMCA 500-LWind-Driven rainand HEVAC testsetup.

Louver

Drawn Air

WaterDropandWettedWallManifolds

Figure 3: AMCA 500-L Water Penetration

Energy Recovery Ventilators - Stand Alone vs. Bolt-on systems

that has to be exhaustedanyway. The bolt-on ERV is nottied into the exhaust systemallowing the conditioned air toescape into the atmosphere. Inmany commercial buildings, theexhaust air code required isroughly half of the outdoor airvolume. This means comparedto the bolt-on unit, the standalone ERV can recover energyfrom twice as much air leavingthe building. The net impact isnearly double the effectivenessfor the stand alone system.

To illustrate this point, let’scompare a stand alone unit to a

that incorporates the standalone ERV is superior to thebolt-on system. Thefundamental reasons for thiscan be found by taking a look atmore than just the outdoor airrequirements. If we considerboth the outdoor air andexhaust air requirements ofcommercial buildings, theadvantages of the stand alonesystem become apparent.

O ve rall System EfficiencyThe stand alone ERV systemprovides the most efficientmethod of ventilating a buildingbecause it steals energy from air

Many HVAC system designershave realized the benefits ofusing Energy RecoveryVentilators (ERVs) incommercial and institutionalbuildings. However, as withmany newly adoptedtechnologies, questions of howbest to apply this product arebeing raised. One applicationissue in particular is whether toapply an ERV as a stand aloneunit on its own curb, or as abolt-on accessory to a rooftopair conditioning unit.

What is the difference betweenthe two systems? Although bothsystems require an exhaust airstream as an energy source topre-condition outdoor air, theprimary difference between thetwo systems is where theexhaust air is taken from. Thedrawings below illustrate thisdifference and help visualizehow the ERVs tie into theHVAC ventilation system. Thefollowing describes thedifferences in the two systems.

Some system designers mayshow a preference for the bolt-on ERV. This may be becausethey perceive that theinstallation cost will be lower, orthey prefer having a single pointof responsibility for theERV/rooftop unit.

Note: The above points that favorthe bolt-on units are usuallypromoted by air conditioningequipment sales people attemptingto lump the ERVs with the airconditioning equipment.

In most cases, a system design

6 En g i n eering Update J uly 2000

Supply Air

Packaged RooftopAir Conditioner

Outdoor Air

Exhaust Air

Exhaust Air

Exhaust Fan

Exhaust AirRelief Air

Bolt onERV

Return Air

Return Air Supply Air

Packaged RooftopAir ConditionerOutdoorAir

Exhaust Air

Pre-ConditionedOutdoor AirExhaust Air

Stand Alone ERV

Stand Alone ERV SystemA stand alone ERV system is capable of exhausting air from spaces that need to be exhaustedanyway. (i.e., restrooms, offices, breakrooms,e tc.) An exhaust fan is eliminated by the ERV

Bolt-On ERV SystemA bolt-on ERV system draws its exhaust air from the return duct only. An exhaust fan isstill required for spaces such as restrooms, offices, and breakrooms.

ERVs- Stand Alone vs. Bolt-on systems, continued from page 6

installation is far easier on astand alone system. Exhaustand outdoor air duct runsprovide recommendedlocations for airflowmeasurement. Determiningexhaust and outdoor airvolumes in the bolt-onconfiguration is practicallyimpossible.

• Exhaust fans and outdoor airfans are simultaneouslyenergized so the buildingoperates as it was designed.Separate controls, interlocks,and field coordination tomaintain a balanced buildingare eliminated.

Note: In some traditional systemswithout energy recovery, exhaustfans were energized by occupancysensors (i.e., motion detectors orlight switches) in an effort to saveenergy. These systems prohibited asteady building balance and werecounter-productive to properventilation and indoor environmentcontrol.

• Often, the system designerchooses to balance the airflow by increasing theexhaust air volume fromareas such as restrooms andconference rooms. This resultsin fresher, better ventilatedspaces and improved comfortfor occupants.

I n s ta l l at i on Co s tThe installation cost of a standalone ERV system is typicallyless than the installation cost ofa bolt-on ERV system.

• With the stand alone ERV, the

Ve n t i l at i on Con t rolCombining outdoor air andexhaust air ventilation functionsinto a single unit help drive animportant practice in goodHVAC design – buildingventilation balance. In layman’sterms: What goes in must comeout. Traditionally, the outdoorair needs and the exhaust airneeds were calculated inseparate thought processes. Thedesigner would specify theminimum outdoor air andexhaust air volumes required bycode, but would stop short ofcomparing the totals to checkthe ventilation balance.Frequently, this led to overpressurized buildings wheredoorways were transformedinto wind tunnels. In somecases, buildings becamenegatively pressurized andinfiltration made indoor climatecontrol difficult.

Stand alone ERV systemsinherently remind the HVACengineer to perform thebuilding balance check becausethe outdoor air and exhaust airvolumes are located on the sameequipment schedule.Additionally, the outdoor airand exhaust air fans areinterlocked within the ERVcontrol center. This translatesinto the following benefits of astand alone ERV compared to abolt-on.

• The ventilation design is morelikely to meet the engineer’sintentions, typically a slightlypositive building pressure.

• System balancing after

bolt-on system based upon thefollowing:

• A commercial buildingrequires 3,000 cfm of outdoorair based on ASHRAEStandard 62.

• Based on codes, the minimumexhaust is 1,500 cfm fromareas such as restrooms andconference rooms.

• The building is to have aslight positive pressure andspecifies total exhaust/reliefair of 2,700 cfm (10%positive).

• Outdoor air design point is95db/78wb and room air isspecified at 75db/50% rh.

Stand Alone System: Becausewe can exhaust the restroomsand conference rooms with theERV, we can recover energyfrom the total 2,700 cfm ofexhaust/relief air. The resultingeffectiveness at 3,000 cfmoutdoor air and 2,700 cfmexhaust air is 75%. This pre-conditions the outdoor air from95db/78wb to 80db/67wb. Theair conditioning load is reducedby more than 11 tons.

Bolt-on System: Because wecannot recover air from therestrooms and conferencerooms, there is only 1,200 cfm ofrelief air left to recover energyfrom. The resulting effectivenessat 3,000 cfm outdoor air and1,200 cfm exhaust air is only40%. Outdoor air is only pre-conditioned to 87db/72.5wband the load is only reduced by6 tons.

En g i n eering Update J uly 2000 7

supply fan and wheel. The exhaustfan continues to operate.

S um m ar yIn summary, the stand aloneERV system has manyadvantages over the bolt-onsystem. When considering thetotal ventilation system, thestand alone ERV offers higherefficiencies, provides a morereliable means of controllingventilation, minimizesinstallation costs and enablesenergy recovery and economizertechnologies to be combined formaximum energy savings.

E con omizer Operat i onAnother issue that is pertinentin a large portion of the U.S. ishow to incorporate ERVs andeconomizers into the samesystem. Since the bolt-on ERV ismounted on the rooftop unit atthe outdoor air intake, aneconomizer is not able to beincorporated into a bolt-on ERVsystem. This sacrifices the freecooling savings that many statesrequire in their energystandards. See illustration aboveright.

Since stand alone ERVs aremounted on separate curbs anddo not occupy the outdoor airintake of the rooftop airconditioning unit, theeconomizer section may still beeasily used in conjunction withthe ERV.

Note: Greenheck ERV controlcenters have separate contactors forexhaust fan, supply fan and wheelmotors. During economizeroperation, the ERV receives aneconomizer “make” signal from therooftop unit and shuts down the

ERV is performing thefunction of an exhaust faneliminating the need topurchase one.

• The exhaust ductwork is thesame whether an exhaust fanor ERV is used.

• No additional roof or wallpenetrations are needed forstand alone ERVs. The samepenetrations that are neededfor the ERV were needed forthe exhaust fans as well. (Insome cases, the ERV takes theplace of several exhaust fansand penetrations arereduced.)

• The stand alone system ismore efficient. This may allowgreater down sizing of airconditioning equipment,lowering equipment cost.

• Ducting outdoor air from theERV to the air conditioningunit is minimal. In most cases,the outdoor air is simplyducted to a return air trunknear the ERV. Additional ductwork is usually less than 20feet.

8 En g i n eering Update J uly 2000

GreenheckP.O. Box 410 Schofield, WI 54476

ERVs- Stand Alone vs. Bolt-on systems, continued from page 7

Return Air Supply Air

Packaged RooftopAir Conditioner

Economizer Hood(Replaces Bolt-on ERV)

Outdoor Air

PRSR - STDUS POSTAGE

PAIDPERMIT No 32

Wausau WIAddress Service Requested