Already a subscriber? 
MADCAD.com Free Trial
Sign up for a 3 day free trial to explore the MADCAD.com interface, PLUS access the
2009 International Building Code to see how it all works.
If you like to setup a quick demo, let us know at support@madcad.com
or +1 800.798.9296 and we will be happy to schedule a webinar for you.
Security check
Please login to your personal account to use this feature.
Please login to your authorized staff account to use this feature.
Are you sure you want to empty the cart?
ASHRAE Standard 120-2022 -- Method of Testing to Determine Flow Resistance of HVAC Ducts and Fittings (ANSI Approved), 2022
- ANSI/ASHRAE Standard 120-2022 [Go to Page]
- CONTENTS
- FOREWORD
- 1. PURPOSE
- 2. SCOPE [Go to Page]
- 2.1 This standard may be used to determine the change in total pressure resulting from airflow in HVAC ducts and fittings.
- 2.2 The test results can be used to determine duct flow losses in pressure loss per unit length. Fitting losses are reported as local loss coefficients.
- 2.3 This standard does not cover interpretation of test data.
- 3. DEFINITIONS, SYMBOLS, AND SUBSCRIPTS [Go to Page]
- 3.1 Definitions
- 3.2 Symbols and Subscripts. Table 1 displays symbols and subscripts used throughout this standard, along with their units and description.
- 4. COMPLIANCE REQUIREMENTS [Go to Page]
- 4.1 A duct or fitting test complies with this standard if the requirements of Section 6, “Instrumentation,” and Section 7, “Flow Measuring Systems and Test Setups,” have been met.
- 4.2 A person or persons determining compliance shall state in writing that the test procedures and general test requirements of Section 8, “Observations and Conduct of Test,” have been met.
- 4.3 A person or persons determining compliance shall state in writing that the calculation requirements of Section 9, “Calculations,” and Section 10, “Test Results and Report,” have been met.
- 5. APPLICABILITY [Go to Page]
- 5.1 Type of Ducts. This standard specifies test conditions for rigid and flexible ducts of rectangular, round, flat oval, or other shapes constructed to contain airflow. Elastic materials that change size greater than 5% of any linear dimension with ...
- 5.2 Type of Fittings. This standard specifies test conditions for fittings designed for use with the ducts described in Section 5.1.
- 5.3 Sizes. This standard covers test conditions for ducts with an internal hydraulic diameter 50 mm or larger.
- 5.4 Test Air Velocities. This standard specifies test conditions for velocities in the range from 6 m/s to 36 m/s.
- 5.5 Measured Pressure Differential. The minimum pressure loss for a fitting shall be 75 Pa.
- 6. INSTRUMENTATION [Go to Page]
- 6.1 Accuracy and Precision. Measurements from the instruments shall be traceable to primary or secondary standards calibrated by the National Institute of Standards and Technology (NIST) or to the Bureau International des Poids et Mesures (BIPM) if a...
- 6.2 Pressure
- 6.3 Static Pressure Wall Taps. The static pressure at a point in a smooth wall duct shall be sensed with a wall pressure tap of the proportions shown in Figure 1. Disk-type wall taps made in accordance with Figure 2, or static taps on a pitot-static ...
- 6.4 Pitot-Static Tubes. Static pressure for flexible and corrugated ducts shall be sensed with a pitot- static tube of the proportions shown in Figure 3. A pitot-static tube without the total pressure opening at the tip of the tube is permissible. Th...
- 6.5 Temperature
- 6.6 Flow Rate. Nozzles and orifices meeting the specifications in this standard are considered reference flow measuring devices. Referenced nozzles and orifices do not require calibration. Other flow measuring devices are acceptable for use only afte...
- 7. FLOW MEASURING SYSTEMS AND TEST SETUPS [Go to Page]
- 7.1 Flow Measuring Systems. Flow measuring systems using nozzles or orifices required by this standard are illustrated in Figures 7 and 8.
- 7.2 Test Setups. Approved test setups are illustrated in Figures 9 through 18. These figures specify the test setup arrangement, including the pressure measuring stations for each category of test fitting and duct. Two types of test systems are shown:
- 7.3 Selection Guide. The appropriate combination of test setup and airflow measuring system are shown by Table 2. Examples of the various combinations of test specimen setups and flow measuring systems are shown in Informative Appendix D.
- 7.4 Chambers and Plenums
- 7.5 Test Ducts
- 7.6 System Leakage. All joints in the test system shall be sealed. Measured leakage between the flow measuring station(s) and the test specimen shall not exceed 0.5% of the minimum test flow rate at the maximum pressure expected during the test. A su...
- 7.7 Fan and Flow Control. A fan to move air through the test system and a means of varying the flow rate shall be provided for the test system. Fans used to obtain the desired test flow rate shall be selected to produce sufficient pressure at the des...
- 7.8 Flexible Duct. A flexible duct setup guide is given in Informative Appendix C.
- 8. OBSERVATIONS AND CONDUCT OF TEST [Go to Page]
- 8.1 General Test Requirements
- 8.2 Data to Be Recorded
- 8.3 Test Procedures
- 9. CALCULATIONS [Go to Page]
- 9.1 Calibration Correction. Calibration corrections shall be applied to individual readings before averaging or other calculations. Calibration corrections need not be made if the correction is smaller than one-half the maximum allowable error as spe...
- 9.2 Density and Viscosity of Air
- 9.3 Flow Rate at the Measurement Station
- 9.4 Flow Rate at the Test Specimen. The flow rate at the test specimen Qx shall be calculated by Equation 26:
- 9.5 Test Velocity. The test velocity shall be determined using Equation 27:
- 9.6 Test Reynolds Number. The Reynolds number at the test specimen shall be calculated using Equation 28:
- 9.7 Test Velocity Pressure. The velocity pressure at any plane x in the test system shall be calculated using Equation 29:
- 9.8 Pressure Loss of the Test Specimen at Test Conditions. The total pressure loss of a test duct or fitting shall be the pressure measurement differential as shown on the test setups (Figures 9 through 18) corrected for the duct pressure losses betw...
- 9.9 Test Specimen Pressure Loss Calculations
- 10. TEST RESULTS AND REPORT [Go to Page]
- 10.1 Report. The report of a laboratory test of a duct or fitting shall include the purpose, scope, results, test data, and descriptions of the test specimen, test setup, and instruments as outlined in Section 8. The laboratory shall be identified by...
- 10.2 Data
- 11. REFERENCES
- INFORMATIVE APPENDIX A: TIME–WEIGHTED AVERAGE
- INFORMATIVE APPENDIX B: LEAKAGE MEASUREMENT [Go to Page]
- B1. Pressure Lines
- B2. Leakage Test Setup and Measurement [Go to Page]
- B2.1 Method A. One system configuration for leak checking the test setup, including the nozzle board, is shown in Figure B-2. For this test setup, seal the terminal end of the test setup as shown by Figure B-2, and provide a connection for a positive...
- B2.2 Method B. An alternative approach for leak testing the test setup, including the nozzle board, under positive pressure is shown in Figure B-5. For this test setup, seal the terminal end of the test setup as shown in Figure B-5. Keep one nozzle i...
- INFORMATIVE APPENDIX C: FLEXIBLE DUCT TEST SETUP GUIDE [Go to Page]
- C1. STRAIGHT DUCT
- C2. BENDS
- INFORMATIVE APPENDIX D: EXAMPLE TEST SYSTEMS [Go to Page]
