Independent Performance Verification of SEMCO’s Total Energy … › admin › UploadedFiles › Images › GTRI... · 2018-10-24 · ASHRAE Standard 84-1978 Method of Testing Air-to-Air

Part 1 - Test Facility & Procedure

Independent PerformanceVerification of SEMCO’s Total

Energy Recovery Wheels

Completed byChris Downing, P.E.

ContentsPurpose ...................................................................................................1Introduction ...........................................................................................1The Products ..........................................................................................2The Standards ........................................................................................3SEMCO Test Facility ............................................................................4Controlling Test Conditions .................................................................8Data Acquisition ....................................................................................8Temperature, Humidity, And Tracer Gas - Grids .................................9Test Procedures and Results ................................................................12ASHRAE 84-1991 Requirements ........................................................12Desiccant Wheel Carryover vs. Cross-contamination ......................14ARI Standard 1060-97 Rating Points .............................................. 14Exception to ARI 1060-97: Purge Section Utilized ....................... 15Final Test Results ............................................................................... 16How to Contact SEMCO Incorporated .......................................... 16

© SEMCO Incorporated 1999. All rights reserved.

The information in this technical bulletin is furnished for informationaluse only, is subject to change without notice, and should not be con-strued as a commitment by SEMCO Incorporated. SEMCO Incorpo-rated assumes no responsibility for any errors that may appear in thistechnical guide.

No part of this publication may be reproduced, stored in a retrievalsystem or transmitted, in any form or by any means, electronic, me-chanical, recording, or otherwise, without the prior written permissionof SEMCO Incorporated.

i • Independent Performance Verification of SEMCO’s Total Energy Recovery Wheels & Test Facility

Independent Performance Verification of SEMCO’s Total Energy Recovery Wheels & Test Facility • 1

Purpose

This report summarizes the results of a performance testing programconducted in accordance with ASHRAE Standard 84-1991 entitledMethod of Testing Air-to-Air Heat Exchangers as well as the ARI Standard1060-97 entitled Rating Air-to Air Energy Recovery VentilationEquipment.

The primary purpose of this report is to provide independentverification of performance, in accordance with both the ASHRAE andARI standards, for all SEMCO total energy recovery wheel products.The report also provides independent verification of compliance forthe SEMCO test facility with all guidelines as set forth in the ASHRAEStandard 84-1991.

This report was prepared in conjunction with the Georgia TechResearch Institute (GTRI) which observed the collection of performancedata for each of the SEMCO wheels tested. GTRI also conducted all ofthe SF6 tracer gas tests and analysis as called for by both the ASHRAE84-1991 and ARI 1060-97 standards.

This report is organized in four parts. Part 1 describes the SEMCOtest facility and the methods and procedures used to collect theperformance data. Part 2a presents the results for the TE Series of SEMCOEXCLU-SIEVE™ total energy recovery wheels. Part 2b presents the resultsfor the FV Series of SEMCO total energy recovery wheels. Part 2cpresents the results for the TEC Series of SEMCO total energy recoverywheels.

Introduction

In 1986 SEMCO constructed its first test facility in accordance withASHRAE Standard 84-1978 Method of Testing Air-to-Air Heat Exchangers.In the same year, Messrs.. Ron Howell, Ph.D., and Harry Sauer, Ph.D.,completed a certification program for the EXCLU-SIEVE™ TE seriestotal energy wheel product. The program also verified that the testfacility met all requirements of the ASHRAE Standard 84-1978. At thattime Dr. Howell and Dr. Sauer were both members of the ASHRAE84 standard project committee. This certification program wasupdated in 1994 to reflect improvements made in humiditymeasurement as recommended by Dr. Howell and Dr. Sauer (see theappendices section for a report summary).

Designing, building and operating a test facility in accordance withthe ASHRAE Standard 84-1991 requires a significant investment. Fewsuch facilities exist. Manufacturers of air-to-air energy recoveryequipment must invest in a test facility built to ASHRAE standardssince it is essential for providing accurate performance ratings of currentproducts over the wide range of conditions encountered in actualapplications, and for the development of future products and productenhancements. Without such a facility, obtaining meaningfulperformance ratings is not possible.

2 • Independent Performance Verification of SEMCO’s Total Energy Recovery Wheels & Test Facility

The Products

SEMCO began production of The EXCLU-SIEVE™ TE seriesproduct in 1986. Since then it has been supplied as a component inSEMCO’s EP energy recovery systems or as a cassette in large fieldbuilt systems. The TE series total energy recovery wheel utilizes a 3Åmolecular sieve desiccant to avoid contaminant carry-over from theexhaust air stream. It is the product addressed by Dr. Howell’scertification letter dated August 23, 1994 (see Part 2a of this report).

The FV series total energy recovery wheel utilizes the same 3Åmolecular sieve desiccant used for the EXCLU-SIEVE™ TE seriesproduct, but the recovery media is less deep and has smaller flute spacing.This product is utilized in SEMCO’s FV and FV-T lines of packagedenergy recovery systems.

The TEC series total energy wheel is a second tier product designedfor our OEM partners. It uses a composite desiccant and, as a result,does not have the selective transfer capability offered by the otherSEMCO products. It also features a different depth and flute spacingthan either of the TE or FV products.

As a service to its customers, SEMCO has maintained acommitment to provide current and credible independent certificationof recovery performance for all of its products. Over the years, designengineers and owners of major research facilities, medical centers,manufacturing facilities and landmark office towers have been ableto take full advantage of the reduction in chiller and boiler capacityas a result of this certified performance data.

Verification of performance is frequently becoming a requirementby designers, as it should be, given the significant benefits provided bya well performing product when compared to the sizable riskassociated with accepting a poor performing product.


The Standards

The ASHRAE Standard 84-1991 is very comprehensive. It requiresperformance data over a wide range of operating conditions, i.e., facevelocities and airflow ratios. Using a tracer gas, it quantifies theperformance of the purge at various pressure differentials. Finally, itcalls for the adjustment of measured performance to compensate forany measured carry-over. The ASHRAE Standard 84-1991 defines bothhow the testing facility must be built, instrumented and operated aswell as how the resulting data must be presented. The test proceduresand test facility requirements set forth in the ASHRAE Standard 84-1991 provide the background for the ARI rating standard.

Under the auspices of ARI, the manufacturers of air-to-air energyrecovery ventilation equipment established a product section. Theengineering committee of the product section updated the Standard1060-97 for the purpose of rating equipment. The ASHRAE Standard84-1991 provides the method of testing for the ARI Standard but notthe rating points. The ARI Standard rates an energy recovery deviceat two flow conditions, “rated flow” and “75% of rated flow”, with therated flow (i.e. face velocity) condition being specified by themanufacturer of the equipment being tested.

Details of the SEMCO test facility and the requirements of theASHRAE 84-1991 standard are described in Section SEMCO Test Facility.The performance data required by the ASHRAE standard, includingsensible and total performance curves for a wide range of face velocitiesand airflow ratios is presented in Section Test Procedures and Results.


Over the past two years SEMCO has made significant enhancements toits air-to-air heat exchanger testing facility. Technology upgrades weremade to much of the instrumentation, data acquisition hardware andsoftware, and humidity and pressure measurement devices. Theseenhancements improved the accuracy of the data collected whilereducing the time required to collect and analyze the data.

Figure 1 is a schematic of the SEMCO energy recovery test facility.This diagram lists the major components of the test facility used tocomplete the energy recovery testing discussed in this report. Thetest facility was designed to meet or exceed all requirements ofASHRAE Standard 84-1991. For this reason, Figure 1 looks verysimilar to the sample diagram shown as Figure 4 in the ASHRAEstandard. Enhancements to the ASHRAE schematic made bySEMCO include separate preconditioners for the outdoor and returnair streams (return air heating, cooling and humidification control isshown as optional by the ASHRAE schematic), improved accuracyof much of the instrumentation and the integration of a dataacquisition system to allow for real time sampling and mass/energybalance confirmation.

Table 1 compares the accuracy of the instrumentation requiredby the ASHRAE standard with that used in the SEMCO test facility.As shown, the required accuracy is met or exceeded in all instances.This is especially true for pressure and tracer gas measurements wherethe level of accuracy is improved by 60% and 90% respectively.

Table 2 provides a simplified error analysis based on the accuracyratings listed in Table 1. As shown, sensible effectiveness is measuredwithin +/-1.4% based upon the accuracy of instrumentation includedin the SEMCO test facility. The latent effectiveness and totaleffectiveness are measured within +/-5.0% and +/-3.5% respectively.

This analysis emphasizes the importance of utilizing temperatureand humidity instrumentation that has the highest possible level ofaccuracy to obtain latent and total effectiveness data that is meaningful.For example, if the humidity measurement accuracy is reduced to alevel of +/-1 degree Fahrenheit in dew point, the latent effectivenesserror will exceed +/-10%.

As important as measurement accuracy is the need for collectingreal time data and maintaining steady state conditions within a verynarrow range. For example, the ASHRAE standard calls for the grainlevel of the incoming air streams not to exceed +/-2.8 grains (.0004 lb/lb). If this minor change occurs in only one of the incoming air streamsduring the sampling of four separate locations, the latent effectivenesswould be impacted by 5.7% (i.e. 2.8/49 grains).

As previously stated, the maximum error in the measured totalenthalpy performance data based on the manufacturer’s ratedinstrument accuracy was determined to be approximately +/- 3.5%. Aseparate analysis based on the agreement and repeatability of the varioussensors in the SEMCO test facility documented an accuracy for theSEMCO test facility of better than approximately +/- 3% for totalenthalpy performance.

SEMCO Test Facility


Figure 1: Schematic of the SEMCO test facility designed in accordance with the ASHRAE Standard84-1991.


Table 1. SEMCO Test Facility Instrumentation Accuracy Compared with ASHRAEStandard 84-1991 Criteria.

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View of the SEMCO test facility.Data acquisition shown in the fore-ground.


Table 2. Simplified Error Analysis Resulting from Instrumental AccuracyRatings Listed in Table 1.

Note that airflow inaccuracy with nozzles has an insignificant impact on sensible, latent and total performance error.

* Based on instrument accuracy specified by ASHRAE Standard 84-1991 shown in Table 1.

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The SEMCO test facility features two air stream loops each controlledby one conditioner (see Figure 1). Conditioner #1 maintains the returnair temperature and humidity. Conditioner #2 does the same for theoutdoor air.

Each conditioning system includes a fan, a cooling coil, a heatingcoil, and a humidifier. The fan capacity is modulated with a variablefrequency drive. The cooling coil provides saturated air while an electricreheat coil with multiple stages and SCR control supplies the necessaryreheat to achieve precise testing conditions. The steam humidifier iscapacity controlled as well.

Each conditioning unit is independently controlled to maintain thedesired setpoint by the SEMCO digital control and data acquisitionsystem. For example, during the cooling season test, the desiredconditions are maintained by first humidifying the air stream to ahumidity level that is slightly above the dewpoint condition desired.Next this humidified air stream is overcooled as it passes through thecooling coil. Finally, the overcooled air is drawn through the post-heatingcoil. In this manner, very stable conditions are maintained for the outdoorand return air streams.

Controlling Test Conditions

Data Acquisition

To obtain accurate, repeatable test results, data must be collected,processed and reported for each sampling instrument in the test facilityin real time. This is accomplished in the SEMCO test facility with aKeithley data acquisition system running Testpoint™ software. Thissoftware provides a graphical interface of the SEMCO test facility asshown in Figure 2. The screen provides real time conditions throughoutthe test facility. The software simultaneously computes and displayseffectiveness values and tracks the energy (temperature), moisture andmass (flow) balances to alert the lab technician when a steady statecondition is achieved.

Each reported data point is an average of 10 actual data points (madepossible with the Testpoint™ software) which further increases theaccuracy of the test procedure. For each condition recorded,approximately 10 recorded data points (or 100 actual data points) areaveraged to provide the basis for the ASHRAE and ARI performancecharts.


As called for in the ASHRAE Standard 84-1991, all measurements oftemperature, humidity and tracer gas concentrations, which are used tocalculate performance parameters, were pulled from a sampling grid.The grid is designed to dissect the sampling chamber into 16 equalareas.

Temperature is measured with precision RTD’s which run in separateshielded cables and are grounded individually on the Keithly dataacquisition boards. Dunmore style relative humidity sensors, individuallycalibrated and checked against a General Eastern chilled mirrorinstrument, are also run in shielded cables and grounded to the Keithlyboard.

Sulfurhexaflouride (SF6) was used as the tracer gas to determine theamount of carry-over. GTRI recommended SF6 as the tracer gas for itallowed for a 10 times higher accuracy of measurement than proposedby the ASHRAE and ARI standards. The Bruel and Kjaer Model 1302utilized by GTRI measured SF6 at a level of accuracy that results in anerror of only +/-.01% vs. the .1% allowed. Based on past experience,GTRI determined that this increased level of accuracy would be necessaryto quantify any carry-over within the SEMCO wheel and to assure thatthe certified performance was not enhanced by leakage from the returnto the supply air stream.

Temperature, Humidity, And Tracer Gas -Grids

Sampling grids and mixing screensas typically set up in the SEMCOtest facility.


Figure 2: Sample of Data Acquisition Screen for Actual Test Point.


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Table 3. Key Performance Parameters Measured and Displayed By The DataAcquisition System.


The test results documented in this report were obtained using proceduresand facilities that were designed and operated in accordance with theASHRAE Standard 84-1991.

Test data was also obtained as called for by the ARI Standard 1060-97. The data is presented in accordance with the subject standard withone exception. All testing was completed with a purge section, not justone point as called for by the ARI rating procedure. SEMCO does notrecommend the application of energy recovery wheels without a purgesection. Thus, all SEMCO wheels are sold and applied with a purgesection.

Test Procedures and Results

ASHRAE 84-1991 Requirements

The ASHRAE standard requires that the sensible and total effectivenessdata be presented over a wide range of operating conditions (defined asmaximum flow rate through 25% of the maximum flow rate) and in aseries of curves for flow ratios that vary from 1-to-1 through 0.5-to-1.Performance test data for each of the SEMCO total energy wheels ispresented in this format.

The standard requires that “... the effectiveness values be correctedby calculation of the effect of carry-over and leakage, when applicable.”SEMCO used a purge section in all tests and maintained a positivepressure between the supply air and return air streams. The resultantcarry-over was measured by GTRI and was determined to benonexistent or insignificant. Therefore, a correction to the measuredperformance to reflect carry-over and/or leakage was not necessary.

The ASHRAE standard also requires that “... the air frictionpressure drop data be reported as a pressure-velocity curve in termsof standard air over the range of expected operating conditions.” Testdata for each of the SEMCO total energy wheels has been providedin this format.

Finally, the ASHRAE standard requires tracer gas carry-over testingto be completed “... over the range of expected operating conditions.”A sample carry-over test condition is provided for the worst case condition(i.e. minimal purge driving force) for each wheel tested and is locatedunder the pressure loss data at the end of this section. Table 4 showsthe resulting purge volume and carry-over that results at differentoperating purge pressures and optimized purge angles (adjusted basedon the operating pressures to provide for effective purging).

In conclusion, this report includes all of the data required by theASHRAE Standard 84-1991, without exception, for each of the SEMCOtotal energy wheel products.


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Table 4. Carry-over and purge volumetesting at various pressure differentialsbetween the supply air stream (SA),return air stream (RA), and outdoor airstream (OA).

Notes:1. Completed at 600 ft/min face velocity and 20 rpm. Purge angle limited to 10degrees then adjusted as pressure increased.2. Testing completed as required by ASHRAE 84-1991 standard.3. Testing conducted with the SEMCO TE series wheel at 20 rpm.4. Testing reflects the proper utilization of a purge section where the angle ischanged to compensate with changing pressure differential so that the properamount of purge air is provided to limit Carry-over within the wheel media.


The ARI 1060-97 standard requires that the measured sensible, latentand total effectiveness data be presented at two airflow conditions; at100 percent and at 75 percent of the rated flow condition with the ratedflow condition being specified by the equipment manufacturer. Flowconditions are to be reported in increments of 50 cfm and theeffectiveness values are to be “expressed in terms of percent, in multiplesof one percent.”

Standard rating conditions are to be reported for both heating andcooling conditions, with the dry bulb and wet bulb conditions specifiedbeing similar to that called for by the ASHRAE 84-1991 standard.Pressure loss though the heat exchanger is called for at the conditionstested and is reported in “in. of water in multiples of 0.05 in. of water.”

ARI Standard 1060-97 Rating Points

Desiccant Wheel Carry-over vs. Cross-contamination

The ASHRAE standard 84-1991 tracer gas test (sometimes referred toas carry-over percentage) is a measure of the amount of exhaust airtransported into the supply air either through leakage or, in the case of arecovery wheel, purge inefficiency. This measurement is used to correctthe measured recovery effectiveness so that it is not artificially inflated.

The ASHRAE tracer gas test procedure uses sulfurhexaflouride (SF6),a large, nonpolar molecule which is inert and can be measured accu-rately at very low levels. This procedure was not designed to indicatethe degree of exhaust air contaminant carry-over that can occur due tocosorption by the desiccant or diffusion through a permeable substrate.Research has shown that this type of carry-over can be orders of magni-tude greater than that from other sources (up to 60%) depending on theheat exchanger design, the desiccant used and the tracer gas utilized.

Since the sole purpose for utilizing energy exchangers is to deliver“fresh air” for dilution ventilation, it is important that these devices befurther tested using a number of different tracer gasses, representing thevarious families of chemical compounds typically encountered in in-door environments.

For example, a heat exchanger might show less than 1% carry-overwhen challenged with SF6 in accordance with ASHRAE guidelines, butmay actually Carry-over 50% of certain common chemical contaminants.The net effect being that the energy exchanger would need to delivermore than two times the air provided by a similar device that did notcarry over contaminants to provide the same dilution effect and reachthe same level of indoor air quality.

In certain applications such as those involving toilet exhaust or smok-ing, no significant carry-over would be considered acceptable. As aresult, knowing the “total” Carry-over percentage, including leakage, purgeinefficiency and desiccant cosorption or diffusion through the substrateis very important in the design of energy recovery devices that willprovide for acceptable indoor air quality.


Exception to ARI 1060-97: Purge Section UtilizedAll data reported on the “ARI Standard 1060-97 Rating Sheet”contained in Part 2 of this report were obtained utilizing a purgesection. The ARI Standard 1060-97 calls for testing to be conductedwithout a purge for the four rating points, then recommends a fifthrating point with a purge completed at the heating condition and at100% of the rated airflow. Given that SEMCO does not recommendthe application of energy recovery wheels without a purge sectionand does not offer product without a purge section, providingperformance data as called for by the current ARI 1060 standard wouldnot provide information useful to design engineers selecting andevaluating SEMCO equipment.

As part of its testing program, SEMCO did collect performancedata without a purge section (see Table 3 for a sample point). Theimprovement in measured recovery performance that resulted from theelimination from the purge was small. The Carry-over percentage,however, increased from 0 to approximately 3 to 7% for the wheelstested.

The testing pressure differential between the “leaving supply air”(SA) and the “entering exhaust air” (RA) was increased from the 0 in.wg.+1- .05 in.wg. called for by the ARI 1060 standard to approximately .25in.wg.. This small change was made to ensure that any leakage goesfrom the supply air stream to the exhaust air stream to eliminate thepossibility of enhancement of the reported performance as a result ofCarry-over or leakage. As currently written, the zero pressure differentialbetween the supply air and return air streams and elimination of a purgesection (in the ARI standard) relies heavily on the accuracy of the tracergas testing equipment and methodology to correct and adjust themeasured recovery performance due to the Carry-over that exists at theseconditions. As shown by Table 3 this correction can be significant. Theinstrumentation required to measure the accepted tracer gas materials isextremely costly and also requires frequent calibration to ensure theaccuracy required by both the ASHRAE and ARI standards.

The potential for increased error in the final performance calculationsas a result of the inaccuracy of the tracer gas testing (whether a wheeldevice without a purge or a stationary device which allows leakage betweenair streams) at the specified 0 in. w.g. pressure differential is significant.This inaccuracy is simply eliminated by testing at a slight positive pressurebetween the supply air and return air streams and using an effective

In addition to effectiveness data and pressure loss data, the ARIstandard calls for results of a tracer gas test completed at the airflowconditions tested but at ambient conditions with no psychrometricchanges between the four air streams (as per ASHRAE 84-1991). Fortotal energy wheel tested with a purge section, the ARI standard requiresthat the manufacturer report the wheel speed, the purge angle used andthe purge volume (as defined by the ASHRAE Standard 84-1991). Allof this information is provided for each SEMCO wheel type along withthe corresponding ASHRAE Standard 84-1991 test data.


Final Test Results

The test results for the various energy recovery wheel product seriesare presented under separate cover in Part 2a, 2b and 2c of this report.

Figures 3a-c, 4a-c and 5a-c show the performance data required bythe ASHRAE and ARI test standards. Figures 3i show both total andsensible effectiveness curves at various supply to return airflow ratios forthe TE, FV and TEC series wheels respectively, as required by theASHRAE Standard 84-1991. Figures 4i show the pressure loss data. Tables5i list the results of the tracer gas carry-over tests as called for by theASHRAE Standard.

For each wheel product series, the results of the ARI 1060 standardare presented in tabular formats called for by the standard. A purgesection was used for all data reported.

In 1991 Dr. Ron Howell and Dr. Harry Sauer conducted the firstperformance certification program for the TE Series of total energyrecovery wheels. A copy of their original report is included in Part 2a.The newly collected data shown in Figures 3a1, 3a2 and 4a agree verywell with the results of the first certification program.

purge (for wheel type devices). As importantly, this condition reflectsthe way the product is typically applied and also provides a moreconservative performance rating.

For these and other reasons, SEMCO recommended to the ARIengineering committee during the drafting of the standard that theproposed 0 in. w.g pressure differential be increased from 0 (+1- .05) toat least a positive .1 to .25, and more preferably to also include data atthe 2.5 in. wg required by the previous version of the ARI Standard1060. These recommendations were not incorporated into the finalstandard despite SEMCO’s objections.

SEMCO continues to work with the ARI Air-to-Air Energy RecoveryVentilation Product Section to revise the Standard 1060 so that moremeaningful results reflecting real applications be presented.

How to Contact SEMCO Incorporated

You can contact SEMCO Incorporated by phone, fax, e-mail or throughour web site at www.semcoinc.com.

SEMCO IncorporatedDWP Service1800 East Pointe DriveColumbia Missouri 65201-3508

1-888-4SEMCOINC (1-888-472-6264)573-443-1483Fax: 573-886-5408e-mail: [email protected]

SEMCO embraces a policy of continuous development and improvement, the right is reserved to supply products which may differ from those illustrated and described in this

publication. Certified dimensions will be supplied upon request on receipt of order.

© SEMCO LLC 2015 All Rights Reserved. The SEMCO logo is a registered Trademark of SEMCO LLC.

WE BRINGAIR TO LIFE

WE BRING AIR TO LIFE

SEMCO® is a global leader in air

management. We specialize in the

design and manufacture of a wide

range of air climate and air movement

solutions. Our collective experience

is unrivalled.

Our constant aim is to provide systems that

precisely deliver the best indoor air quality

and performance, as well as maximize

energy efficiency.

SEMCO® A Fläkt Woods CompanyCorporate Headquarters1800 East Pointe Drive

Columbia, Missouri 65201-3508 USA

573 443 1481

[email protected]

To learn more about SEMCO offerings and to contact your nearest representative please visit www.semcohvac.com

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Independent Performance Verification of SEMCO’s Total Energy … › admin › UploadedFiles › Images › GTRI... · 2018-10-24 · ASHRAE Standard 84-1978 Method of Testing Air-to-Air