Measure Guideline: Air Conditioner Diagnostics .

Measure Guideline:Air Conditioner Diagnostics,Maintenance, andReplacementD. Springer and B. Dakin PEAlliance for Residential Building Innovation (ARBI)March 2013

NOTICEThis report was prepared as an account of work sponsored by an agency of theUnited States government. Neither the United States government nor any agencythereof, nor any of their employees, subcontractors, or affiliated partners makes anywarranty, express or implied, or assumes any legal liability or responsibility for theaccuracy, completeness, or usefulness of any information, apparatus, product, orprocess disclosed, or represents that its use would not infringe privately owned rights.Reference herein to any specific commercial product, process, or service by tradename, trademark, manufacturer, or otherwise does not necessarily constitute or implyits endorsement, recommendation, or favoring by the United States government orany agency thereof. The views and opinions of authors expressed herein do notnecessarily state or reflect those of the United States government or any agencythereof.Available electronically at http://www.osti.gov/bridgeAvailable for a processing fee to U.S. Department of Energyand its contractors, in paper, from:U.S. Department of EnergyOffice of Scientific and Technical InformationP.O. Box 62Oak Ridge, TN 37831-0062phone: 865.576.8401fax: 865.576.5728email: mailto:reports@adonis.osti.govAvailable for sale to the public, in paper, from:U.S. Department of CommerceNational Technical Information Service5285 Port Royal RoadSpringfield, VA 22161phone: 800.553.6847fax: 703.605.6900email: orders@ntis.fedworld.govonline ordering: http://www.ntis.gov/ordering.htmPrinted on paper containing at least 50% wastepaper, including 20% postconsumer waste

Measure Guideline: Air Conditioner Diagnostics, Maintenance,and ReplacementPrepared for:The National Renewable Energy LaboratoryOn behalf of the U.S. Department of Energy’s Building America ProgramOffice of Energy Efficiency and Renewable Energy15013 Denver West ParkwayGolden, CO 80401NREL Contract No. DE-AC36-08GO28308Prepared by:David Springer and Bill Dakin, PE (Davis Energy Group)Alliance for Residential Building Innovation (ARBI)123 C StreetDavis, California 95616NREL Technical Monitor: Cheryn MetzgerPrepared under Subcontract No. KNDJ-0-40340-00March 2013iii

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ContentsContents . vList of Figures . viiList of Tables . viiDefinitions . viiiExecutive Summary . xAcknowledgements . xIntroduction . 11 Section 1: Planning and Decision Making Criteria. 3231.1 Defining the Problem .31.2 Maintenance Approaches .41.3 Energy Savings .51.4 The Consequences of No Action .51.5 Planning for Improvements and Risk Mitigation.6Section 2: Technical Description . 72.1 General Performance Interactions.72.2 Airflow Impacts .7Desired Airflow .7What Affects Airflow? .7Findings from the Field.9How Airflow Affects System Operation and Energy Use .11Airflow Measurement Methods .122.3 Refrigerant System Defects, Detection, and Correction .13What Can Go Wrong .13The Importance of Correct Refrigerant Charge .13The Effect of Non-Condensable Gases .14Fault Detection and Diagnosis .15Methods for Setting Refrigerant Charge .16Diagnostic Methods for Assessing Refrigerant Charge .16Evaporator Coil Fouling and Damage to Distributor Tubes .172.4 Repair or Replace? .17Condenser Replacement.17The Value of High Efficiency Systems .19Replacement of Other Components .19Section 3: Implementation . 213.1 The Preliminary Diagnostic (PD) Method .21Objectives and Scope .21Skills and Tools Required .22Measuring Airflow .22Before Starting Tests.23Preliminary Diagnostic Steps .233.2 The Comprehensive Diagnostic (CD) Method .27Objectives and Scope .27Skills and Tools Required .27Refrigerant Charge Test Overview .28Before Starting Tests.28Test Procedures .28Measurements (Enter all values into Table A-2) .29v

Cold and Hot Weather Testing .293.3 Calculations.30Temperature Split.30Condensing Temperature Over Ambient (COA) .30Superheat.30Subcooling .313.4 Diagnosis.31Evaluating the Measurements .31Using Diagnostic Flow Charts .32Removing and Replacing Refrigerant .34Equipment Replacement .35References . 38Appendix A: Test Forms and Checklists . 41Appendix B: Supporting Data and Calculations . 43B-1: Energy Savings for Replacement with High Efficiency Air Conditioners .43B-2: Replacement Blower Motor Energy Savings Estimates .45B-3: Verification of Temperature Split Method for Checking Refrigerant Charge.46Appendix C: Detailed Methods and Procedures . 48C-1: Air Conditioner Replacement Decision Tree.48C-2: Detailed Airflow Measurement Methods .49General Instructions .49Powered Flow Hood (Fan Flowmeter) .49Flow Grid .50Flow Capture Hood .50C-3: Detailed Condenser Coil Cleaning Instructions.51C-4: Refrigerant Procedures to Prevent Non-Condensables and Restrictions .52C-5: Vacuum Pump Maintenance .52C-6: Evacuation and Recovery Procedures.53C-7: Charging Procedures .56C-8: Proper Refrigerant Procedures to Avoid Non-condensables and Restrictions .56C-9: ASHRAE Recommendations for Proper Evacuation to Remove Non-condensable Airand Water Vapor .57C-10: Method to Detect Blocked Distributor Tubes .57Appendix D: Test Equipment Specifications and Calibration . 58D-1: Recommended Accuracy of Test Equipment .58D-2: Calibration Method for Digital Thermometer Sensors .58D-3: Refrigerant Gauge Calibration Procedure .58D-4: Other Devices .59vi

List of FiguresFigure 1. Primary system fault modes. . 3Figure 2. Examples of constricted ducts (Photo credit: R. Chitwood, reprinted with permission). 8Figure 3. Pressure loss as a function of velocity for commonly available filters. . 9Figure 4. Sources of pressure drop measured in 62 California homes (Source: Wilcox 2011,reprinted with permission). . 10Figure 5. Summary of airflow measurements from 62 California homes (Source: Wilcox, reprintedwith permission). . 10Figure 6. Impact of reduced airflow on cooling capacity (Source: Parker, reprinted withpermission). . 11Figure 7. Impact of reduced airflow on cooling system performance (Source: Parker, reprintedwith permission). . 12Figure 8. A powered flow hood in use. . 12Figure 9. Normalized EER versus charge and outside temperature (Source: P G &E, reprinted withpermission). . 14Figure 10. A digital manifold gauge. . 16Figure 11. Examples of condenser and evaporator coil fouling. . 17Figure 12. The Energy Conservatory TrueFlow flow grid. . 22Figure 13. Proper position of TXV sensing bulb. . 23Figure 14. Temperature and pressure test points. . 24Figure 15. Pressure loss diagnostic flow chart. . 24Figure 17. Refrigerant diagnostic flowchart: systems with fixed orifice expansion devices. . 33Figure 18. Refrigerant diagnostic flowchart: systems with thermostatic expansion devices. . 33Figure C-1. Air conditioner replacement decision tree. . 48Figure C-2. Pressure measurement locations. . 49Figure C-3. Removing of the top of the condensing unit for cleaning . 51Unless otherwise noted, all figures were created by the ARBI team.List of TablesTable 1. Estimated Energy Savings, Replacement Costs, and Simple Paybacks for 15 SEER vs. 13SEER Air Conditioner. . 19Table 2. Target Temperature Split (Return Dry Bulb – Supply Dry Bulb) . 26Source: California Energy Commission (CEC 2008). . 26Table 3. Recommended COA and EST Values to be Used in Diagnostics. . 32Table 4. Target Superheat. . 36Table 4 (continued). Target Superheat. . 37Table A-1. Preliminary Diagnostics Form. . 41Table A-2. Comprehensive Diagnostics Form (supplement to Table A-1). . 42Table B-1. Existing home assumptions by building vintage . 43Table B-2. Annual Energy Use Determined by BEopt. . 44Table B-3. Assumed Sizes of Replacement Air Conditioners. . 44Table B-4. Replacement Cost vs. SEER Rating. . 44Table B-5. Results of Comparative Tests of a PSC and ECM Motor. . 45Table B-6. Annual Cost Savings Calculation Example. . 46Table B-5. Laboratory Test Results Comparing Measured and Target Temperature Splits. . 47Unless otherwise noted, all tables were created by the ARBI team.vii

DefinitionsACCAAir Conditioning Contractors of AmericaAHRIAir Conditioning, Heating, and Refrigeration InstituteANSIAmerican National Standards InstituteARBIAlliance for Residential Building InnovationASHRAEAmerican Society for Heating, Refrigeration, and Air ConditioningEngineersBPIBuilding Performance InstituteCDComprehensive Diagnostic (a procedure as defined in this document)CECCalifornia Energy CommissionCFCChlorofluorocarbonCFMCubic feet per minuteCOACondensing Over Ambient”, or the difference between the condensingtemperature and the temperature of air entering the condensing coilDEGDavis Energy GroupECMElectronically commutated motorEEREnergy Efficiency Ratio, in Btuh per wattEPAEnvironmental Protection AgencyESTRefrigerant evaporation saturation temperatureFt2Square feetHERSHome Energy Rating SystemHFCHydrofluorocarbonHVACHeating, ventilation, and air conditioningkBtuhThousand British Thermal Units per hourkWKilowattkWhKilowatt-hourMERVMinimum efficiency reporting value (for air filters)NSOPNormal system operating pressure (for airflow measurement corrections)PDPreliminary Diagnostic (a procedure as defined in this document)PG&EPacific Gas and Electric CompanyPSCPermanent split capacitor (motor type)SCESouthern California EdisonSEERSeasonal energy efficiency ratioviii

SHRSensible heat ratioTDTemperature differenceTSOPTest system operating pressure (for airflow measurement corrections)TXVThermostatic expansion valveWWattw.cWater column (referring to inches of pressure)ix

Executive SummaryHeating and cooling energy use represents about 54% of all energy consumed in existingresidential buildings. Field studies have shown that more than half of installed air conditioning(AC) systems have significant

diagnostic tools for use in utility programs, a systematic method is needed to detect and identify major system faults by field technicians who do not have access to these tools. This guideline provides information on the impact of various defects and the potential energy