TESTING OF BELIMO PRESSURE INDEPENDENT CHARACTERIZED CONTROL VALVES

Transcription

1 TESTING OF BELIMO PRESSURE INDEPENDENT CHARACTERIZED CONTROL VALVES November, 25 Submitted by: Iowa Energy Center Address: DMACC, 26 S. Ankeny Blvd. Ankeny, IA 521 Phone: Fax: Web Site:

2 Conditions Iowa State University, the Iowa Energy Center, and the National Building Controls Information Program (NBCIP) logos may not be used in any advertising or publicity, or otherwise to indicate Iowa State University s, the Iowa Energy Center s or NBCIP s endorsement of or affiliation with any Belimo product or service. ii

3 Executive Summary The objective of the testing described in this report was to evaluate the performance of Belimo pressure independent characterized control valves () against conventional globe control valves for terminal reheat and chilled water cooling coil applications in a commercial office building. Testing compared the to Siemens Powermite MT series globe valves. Testing was performed at the Iowa Energy Center Energy Resource Station (ERS). A brief description of the testing and findings are provided below. Terminal Reheat Open Loop Test: The purpose of this test was to measure the water flow rate through the test valves as a function of the valve position (i.e., % open) and the differential pressure across the valve. Open-loop tests were conducted on a Belimo and a correctly sized Siemens Powermite MT globe valve. Consistent with the manufacturer s literature, for a differential pressure range of 5 to 3 psi (34.5 to 26.8 kpa), the flow rate through the Belimo was essentially independent of differential pressure for a fixed valve position. As expected, the flow rate through the Siemens valve increased as the differential pressure increased for a fixed valve position; however, the flow rate though the Siemens valve with the valve fully open was 13 to 15% higher than expected based on the manufacturer s literature. Testing also revealed that the Belimo valve has an equal percentage characteristic curve, while the Siemens valve has a nearly linear characteristic curve. Terminal Reheat Closed Loop Test Effect of Valve Sizing on Valve Performance: The purpose of this test was to evaluate the control performance of the in comparison to a correctly sized and two oversized conventional globe valves. The three Siemens valves included a correctly sized valve (Powermite MT with C v = 1.6), an oversized valve (Powermite MT with C v = 2.5), and a very oversized valve (Powermite MT with C v = 4.). Control performance was evaluated in terms of the temperature control, actuator travel, actuator starts and stops, actuator reversals, and the cumulative change in the water flow rate. Actuator travel, actuator reversals, and the cumulative change in the water flow rate were consistently and significantly less for the Belimo valve in comparison to the Siemens valves. The Belimo valve also tended to have fewer starts and stops, although there were three cases out of seven where the Belimo valve had a slightly higher number of starts and stops. These results confirm what can be visually observed from plots of the feedback signals of the valves, flow rates through the valves, and temperature responses associated with the valves. Specifically, the Belimo valve control was more stable than the Siemens valve control for the tests conducted and the tuning parameters utilized. The temperature control of the Belimo and Siemens valves was similar, with the exception occurring for operation at low flow rates. The Belimo valve provided stable control under all test conditions (even for the test designated CL 2.4 in which the inlet pressure to the Belimo valve was much more oscillatory than the inlet pressure to the Siemens valve) and was capable of producing stable flow rates below.2 GPM (.13 L/s). By contrast, the Siemens valve had difficulty providing stable flow at low flow rates and instead would tend to open and close periodically with resultant flow rates that fluctuated between and.25 GPM (.16 L/s). As a result, the temperature being controlled tended to fluctuate as well. iii

4 The impact of valve sizing on control performance was made especially apparent by considering the cumulative change in the water flow rate. This parameter, which represents the sum of the change in the water flow rate from the current sampling time to the previous sampling time, increased significantly as the flow coefficient of the Siemens valve increased and the valve authority decreased. Terminal Reheat Closed Loop Test System Performance Test: The purpose of this test was to compare energy use, control stability, start-up time and other relevant performance characteristics of Belimo s to correctly sized Siemens Powermite MT globe valves under normal system operating conditions. Based on 19 days of test data, the temperature control of the two valves was comparable, although the Siemens valves were more aggressive and resulted in temperatures that fluctuated around the room setpoint temperature to a greater extent than was seen for the Belimo valves. The difference in the control performance was quantified using the cumulative change in the flow rate. For the perimeter rooms, this parameter was generally two to five times greater for the Siemens valves than for the Belimo valves, indicating superior control on the part of the Belimo valves. There was not a significant difference seen in energy use of the terminal reheat coils controlled by the different brands of valves. The heating water loop pump energy was directly affected by the system differential pressure setpoint. In CL 3.1 and CL 3.2, a higher setpoint was used on the system equipped with Belimo valves and higher energy use resulted. In CL 3.3, the setpoint was the same for the two systems and the energy use was also the same. At low loads, the system equipped with Belimo s had heating water temperature drops across the reheat coils of the perimeter rooms that were 5 to 9ºF (2.8 to 5ºC) higher than the system with Siemens globe valves with the same system differential setpoint was used for the two heating water loops. The higher temperature drops associated with the Belimo system were accompanied by lower heating water flow rates, although the differences in the flow rates between the Belimo and Siemens systems were small when compared to the design flow rate of the systems. Finally, there was no difference observed in the system startup time between the Belimo and Siemens systems. This finding and the lack of any pumping energy difference may be due in part to the small number of zones served by the ERS test systems and the fact that the ERS systems have a reverse return piping arrangement. AHU Chilled Water Open Loop Test: The purpose of this test was to quantify the water flow rate through the AHU chilled water cooling coil test valves as a function of the valve position (i.e., % open) and the differential pressure across the valve. This test mimicked the Terminal Reheat Open Loop Test. Open-loop tests were conducted on a Belimo PT and a correctly sized Siemens Powermite MT globe valve. Consistent with the manufacturer s literature, for a differential pressure range of 7 to 15 psi (48.3 to 13.4 kpa), the flow rate through the Belimo was nearly independent of differential pressure for a fixed valve position. As expected, the flow rate through the Siemens valve increased as the differential pressure increased for a fixed valve position; however, the flow rate though the Siemens valve iv

5 with the valve fully open was 21% lower than expected based on the manufacturer s literature. Testing also revealed that, like the smaller valves used for the terminal reheat application, the Belimo valve has an equal percentage characteristic curve, while the Siemens valve has a nearly linear characteristic curve. AHU Chilled Water Closed Loop Test Control Performance: The purpose of this test was to evaluate the control performance of the Belimo in comparison to a correctly sized conventional globe valve for an AHU chilled water cooling coil application. Testing was conducted on a Belimo PT and a correctly sized Siemens Powermite MT globe valve. Control performance was evaluated in terms of the temperature control, actuator travel, actuator starts and stops, actuator reversals, and the cumulative change in the water flow rate as disturbances were introduced via changes to the supply air temperature setpoint and primary chilled water pump speed. The test was performed twice, first with the Belimo installed in AHU-A and the Siemens valve in AHU-B for CL 5.1, and then with the Siemens valve installed in AHU-A and the Belimo in AHU-B for CL 5.2. In both CL 5.1 and CL 5.2, the Belimo exhibited stable control over the entire test and was capable of providing stable flow as low as.99 GPM (.62 L/s), whereas the Siemens valve exhibited unstable control at flow rates below 4 GPM (.252 L/s). The inability of the Siemens valve to provide stable flow at low loads resulted in significantly higher values of certain control performance parameters compared to the Belimo valve. For instance, the Siemens valve made three to six times more reversals than the Belimo valve, and the cumulative change in water flow rate associated with the Siemens valve was four or more times that for the Belimo. The temperature control of the Belimo and Siemens valves was similar, with the exception occurring for operation at low flow rates, where unstable flow rates associated with the Siemens valve led to unstable supply air temperatures. In addition, although the Belimo demonstrated more stable control than the Siemens valve and produced slightly higher temperature rises across the cooling coil at low load conditions, any pumping energy savings resulting from the improved control performance was not distinguishable in this test. Overall Findings: The tests described above were performed to verify performance characteristics of the Belimo in comparison to conventional globe valves. A summary of those characteristics and findings from the tests are provided in the table on the following pages. v

6 Performance Characteristic Ability to maintain perfect valve authority Decreased start-up time (i.e., time required to bring the temperature in all rooms up to the occupied heating setpoint from night setback conditions) resulting from the prevention of overflow and underflow to individual terminal reheat coils Reduction in pumping costs Findings The provided stable control under all operating conditions, even in circumstances where the inlet pressure was very unstable due to unstable control of the heating water loop pump (see Figure 3-14 and accompanying results, particularly the stable water flow rate in Figure 3-15a), and even at very low flow rates (see Figures 3-5a and 3-16a for the terminal reheat application, and Figure 6-8a for the chilled water cooling coil application). In contrast, the conventional globe valve was unable to provide stable flow at low flow rates and instead cycled between closed and slightly open at low flow rates (see Figures 3-5b and 3-16b for the terminal reheat application, and Figure 6-8b for the chilled water cooling coil application), with resultant temperature responses that also cycled (see Figures 3-6b, 3-17b and Figure 6-9b). For the globe valves, the control performance deteriorated as the valve size increased and the valve authority decreased. There was no difference observed in the start-up time between the system equipped with for the terminal reheat valves and the system equipped with conventional globe valves. This may be due in part to the small test system and the fact that the test system is a reverse return system. Plots of the room temperatures for the two systems are provided in Figure 4-3 and the corresponding heating water flow rates to the rooms are shown in Figure 4-4. Terminal Reheat Application: When the heating water loop pumps were controlled to maintain equivalent differential pressure setpoints between the supply and return mains, the pumping energy use of the system equipped with s was approximately equal to that of the system equipped with conventional globe valves. Although a reduction in water flow rate was seen at low loads in the system with s, the reduction was small and did not produce measurable pumping energy savings. This may be due in part to the small test system and the fact that the test system is a reverse return system. A comparison of the system heating water flow rate and heating water loop pumping power is shown in Figure 4-6. Chilled Water Cooling Coil Application: Although the Belimo demonstrated more stable control than the Siemens valve and produced slightly higher temperature rises across the cooling coil at low load conditions, any pumping energy savings resulting from the improved control performance was indistinguishable. A comparison of the pumping energy use is shown in Figure vi

7 Increased water-side temperature differential across the terminal reheat coil and AHU chilled water cooling coil, and resulting effect on boiler and chiller efficiency Automatic, dynamic system balancing, particularly at low loads Terminal Reheat Application: At low loads, the system equipped with s had heating water temperature drops across the reheat coils of the perimeter rooms that were 5 to 9ºF (2.8 to 5ºC) higher than the system with globe valves. It was not possible to measure any improvement in the boiler efficiency because the system performance of the s and globe valves was evaluated simultaneously and the heating water loops on the two systems was served by a common boiler. Chilled Water Cooling Coil Application: At low loads, the AHU equipped with the generally had a slightly higher chilled water temperature rise across the cooling coil on average than the AHU equipped with the globe valve. The temperature rise across each coil is plotted in Figure 6-15 for CL 5.1 and CL 5.2. The difference in the temperature rise is approximately 1 to 2ºF (.56 to 1.11ºC) at low loads (the second half of the test). It was not possible to measure any improvement in the chiller efficiency because the performance of the and globe valve was evaluated simultaneously and the chilled water loops on the two AHUs was served by a common chiller. This characteristic actually produces the three previous characteristics (i.e., decreased start-up time, reduced pumping costs, and increased water-side temperature differential), although the start-up time phenomenon is associated with high loads, whereas the pumping cost savings and increased temperature differential are expected to be more pronounced at low loads. The increased temperature differential was observed in this testing, but the other two characteristics were not. vii

8 Table of Contents Table of Contents...viii List of Figures... x List of Tables... xiv 1 Introduction Objective Scope Test Facility Terminal Reheat Open Loop Test Test Valves Test Set-Up Test Conditions and Procedure Instrumentation Results Conclusions Terminal Reheat Closed Loop Test Effect of Valve Sizing on Valve Performance Test Units Test Set-Up Room Temperature Control with Fixed Inlet Pressure to Control Valve Discharge Air Temperature Control with Fixed Inlet Pressure to Control Valve Room Temperature Control with Variable Inlet Pressure to Control Valve Test Conditions and Procedure Instrumentation Results Conclusions Terminal Reheat Closed Loop Test System Performance Test Test Units Test Set-Up Test Conditions and Procedure Instrumentation Results Conclusions Air-Handling Unit Chilled Water Open Loop Test Test Units Test Set-Up Test Conditions and Procedure viii

9 5.4 Instrumentation Results Conclusions Air-Handling Unit Chilled Water Closed Loop Test Control Performance Test Units Test Set-Up Test Conditions and Procedure Instrumentation Results Conclusions A. Appendix A: Test Suite 2 Results A.1. Plotted Results for CL A.2. Plotted Results for CL A.3. Plotted Results for CL A.4. Plotted Results for CL A.5. Plotted Results for CL A.6. Plotted Results for CL A.7. Plotted Results for CL B. Appendix B: Test Suite 3 Results B.1. Tabulated Results for CL B.2. Tabulated Results for CL B.3. Tabulated Results for CL C. Appendix C: Test Suite 5 Results C.1. Plotted Results for CL C.2. Plotted Results for CL ix

10 List of Figures Figure 1-1: Schematic of the side-by-side test rooms of the Energy Resource Station... 3 Figure 2-1: Schematic of heating water Loop-A and instrumentation setup for Test Suite Figure 2-2: Flow rate through the Belimo as a function of differential pressure and commanded signal to the valve... 8 Figure 2-3: Relationship between the commanded and scaled feedback signals for the Belimo... 9 Figure 2-4: Flow rate through the Siemens Powermite MT globe valve as a function of differential pressure and commanded signal to the valve Figure 2-5: Relationship between the commanded and scaled feedback signals for the Siemens Powermite MT globe valve. The unscaled feedback signal ranges from.2 to 13.98% closed. The scaled feedback signal ranges from to 1% open Figure 2-6: Flow rate through the Belimo and Siemens Powermite MT globe valve as a function of the scaled valve feedback signal at a differential pressure of 5 psi (34.5 kpa) Figure 3-1: Schematic of heating water Loop-A and Loop-B and instrumentation setup for Test Suite Figure 3-2: Typical control sequence at the ERS for a pressure- independent VAV box with hydronic reheat Figure 3-3: Room airflow setpoint and room temperature setpoint schedules for CL 2.1, CL 2.2 and CL Figure 3-4: Valve position feedback signal for CL Figure 3-5: Heating water flow rate for CL Figure 3-6: Room temperature control for CL Figure 3-7: Room airflow control for CL Figure 3-8: Inlet pressure to control valves for CL Figure 3-9: Entering air temperature to reheat coil for CL Figure 3-1: Accumulated room temperature error for CL Figure 3-11: Accumulated actuator travel for CL Figure 3-12: Accumulated starts and stops for CL Figure 3-13: Accumulated reversals for CL Figure 3-14: Inlet pressure to control valves for CL Figure 3-15: Valve position feedback signal for CL Figure 3-16: Heating water flow rate for CL Figure 3-17: Discharge air temperature control for CL Figure 3-18: Accumulated discharge air temperature error for CL Figure 3-19: Accumulated actuator travel for CL Figure 3-2: Accumulated starts and stops for CL Figure 3-21: Accumulated reversals for CL Figure 4-1: Schematic of heating water Loop-A and Loop-B and instrumentation setup for Test Suite Figure 4-2: Pumping performance for January 18, 25 (CL 3.1) Figure 4-3: Room temperature control for January 18, 25 (CL 3.1) x

11 Figure 4-4: Heating water flow rate for January 18, 25 (CL 3.1) Figure 4-5: Cumulative change in heating water flow rate for January 18, 25 (CL 3.1) Figure 4-6: Pumping performance for February 6, 25 (CL 3.3) Figure 5-1: Schematic of chilled water loop and instrumentation setup for Test Suite Figure 5-2: Flow rate through the Belimo as a function of differential pressure and commanded signal to the valve... 5 Figure 5-3: Flow rate through the Siemens Powermite MT globe valve as a function of differential pressure and commanded signal to the valve Figure 5-4: Flow rate through the Belimo and Siemens Powermite MT globe valve as a function of the scaled valve feedback signal at a differential pressure of 7 psi (48.3 kpa) Figure 6-1: Schematic of chilled water system and instrumentation setup for Test Suite Figure 6-2: Supply air temperature setpoint and primary chilled water pump speed profiles for CL 5.1 and CL Figure 6-3: Chilled water cooling coil entering air temperatures for CL Figure 6-4: Airflow rates across the chilled water cooling coils for CL Figure 6-5: Chilled water cooling coil entering water temperatures for CL Figure 6-6: Chilled water cooling coil valve control signal for CL Figure 6-7: Chilled water cooling coil valve feedback signal for CL Figure 6-8: Chilled water flow rate for CL Figure 6-9: Supply air temperature control for CL Figure 6-1: Accumulated supply air temperature error for CL Figure 6-11: Accumulated actuator travel for CL Figure 6-12: Accumulated starts and stops for CL Figure 6-13: Accumulated reversals for CL Figure 6-14: Cumulative change in chilled water flow rate for CL Figure 6-15: Temperature rise across the chilled water cooling coil for CL 5.1 and CL Figure 6-16: Averaged chilled water flow rate for CL 5.1 and CL Figure 6-17: Secondary chilled water pump power for CL 5.1 and CL Figure A-1: Valve control signal for CL Figure A-2: Valve position feedback signal for CL Figure A-3: Heating water flow rate for CL Figure A-4: Room temperature control for CL Figure A-5: Room airflow control for CL Figure A-6: Inlet pressure to valve for CL Figure A-7: Differential pressure across valve for CL Figure A-8: Accumulated room temperature error for CL Figure A-9: Accumulated actuator travel for CL Figure A-1: Accumulated starts and stops for CL Figure A-11: Accumulated reversals for CL Figure A-12: Valve control signal for CL Figure A-13: Valve position feedback signal for CL Figure A-14: Heating water flow rate for CL Figure A-15: Room temperature control for CL Figure A-16: Room airflow control for CL Figure A-17: Inlet pressure to valve for CL xi

12 Figure A-18: Differential pressure across valve for CL Figure A-19: Accumulated room temperature error for CL Figure A-2: Accumulated actuator travel for CL Figure A-21: Accumulated starts and stops for CL Figure A-22: Accumulated reversals for CL Figure A-23: Valve control signal for CL Figure A-24: Valve position feedback signal for CL Figure A-25: Heating water flow rate for CL Figure A-26: Room temperature control for CL Figure A-27: Room airflow control for CL Figure A-28: Inlet pressure to valve for CL Figure A-29: Differential pressure across valve for CL Figure A-3: Accumulated room temperature error for CL Figure A-31: Accumulated actuator travel for CL Figure A-32: Accumulated starts and stops for CL Figure A-33: Accumulated reversals for CL Figure A-34: Valve control signal for CL Figure A-35: Valve position feedback signal for CL Figure A-36: Heating water flow rate for CL Figure A-37: Discharge air temperature control for CL Figure A-38: Inlet pressure to valve for CL Figure A-39: Differential pressure across valve for CL Figure A-4: Accumulated room temperature error for CL Figure A-41: Accumulated actuator travel for CL Figure A-42: Accumulated starts and stops for CL Figure A-43: Accumulated reversals for CL Figure A-44: Valve control signal for CL Figure A-45: Valve position feedback signal for CL Figure A-46: Heating water flow rate for CL Figure A-47: Discharge air temperature control for CL Figure A-48: Inlet pressure to valve for CL Figure A-49: Differential pressure across valve for CL Figure A-5: Accumulated room temperature error for CL Figure A-51: Accumulated actuator travel for CL Figure A-52: Accumulated starts and stops for CL Figure A-53: Accumulated reversals for CL Figure A-54: Valve control signal for CL Figure A-55: Valve position feedback signal for CL Figure A-56: Heating water flow rate for CL Figure A-57: Room temperature control for CL Figure A-58: Room airflow control for CL Figure A-59: Inlet pressure to valve for CL Figure A-6: Differential pressure across valve for CL Figure A-61: Accumulated room temperature error for CL Figure A-62: Accumulated actuator travel for CL Figure A-63: Accumulated starts and stops for CL xii

13 Figure A-64: Accumulated reversals for CL Figure A-65: Valve control signal for CL Figure A-66: Valve position feedback signal for CL Figure A-67: Heating water flow rate for CL Figure A-68: Room temperature control for CL Figure A-69: Room airflow control for CL Figure A-7: Inlet pressure to valve for CL Figure A-71: Differential pressure across valve for CL Figure A-72: Accumulated room temperature error for CL Figure A-73: Accumulated actuator travel for CL Figure A-74: Accumulated starts and stops for CL Figure A-75: Accumulated reversals for CL Figure C-1: Valve control signal for CL Figure C-2: Valve position feedback signal for CL Figure C-3: Chilled water flow rate for CL Figure C-4: Supply air temperature control for CL Figure C-5: Sum of room airflow rates for CL Figure C-6: Temperature rise across cooling coil for CL Figure C-7: Inlet pressure to valve for CL Figure C-8: Differential pressure across valve for CL Figure C-9: Accumulated supply air temperature error for CL Figure C-1: Accumulated actuator travel for CL Figure C-11: Accumulated starts and stops for CL Figure C-12: Accumulated reversals for CL Figure C-13: Cumulative change in flow rate for CL Figure C-14: Secondary pump power for CL Figure C-15: Valve control signal for CL Figure C-16: Valve position feedback signal for CL Figure C-17: Chilled water flow rate for CL Figure C-18: Supply air temperature control for CL Figure C-19: Sum of room airflow rates for CL Figure C-2: Temperature rise across cooling coil for CL Figure C-21: Inlet pressure to valve for CL Figure C-22: Differential pressure across valve for CL Figure C-23: Accumulated supply air temperature error for CL Figure C-24: Accumulated actuator travel for CL Figure C-25: Accumulated starts and stops for CL Figure C-26: Accumulated reversals for CL Figure C-27: Cumulative change in flow rate for CL Figure C-28: Secondary pump power for CL xiii

14 List of Tables Table 1-1: Summary of tests performed for the VAV terminal reheat application... 2 Table 1-2: Summary of tests performed for the AHU chilled water cooling coil application Table 2-1: Specifications for valves used for Test Suite Table 3-1: Valve specifications for Test Suite Table 3-2: Test set-up for room air temperature control with constant inlet pressure to control valve and variable heating water loop pump speed Table 3-3: Test set-up for discharge air temperature control with constant inlet pressure Table 3-4: to control valve and variable heating water loop pump speed Test set-up for room air temperature control with variable inlet pressure to control valve and constant heating water loop pump speed Table 3-5: Summary of control performance parameters for Test Suite Table 4-1: Valve specifications for Test Suite Table 4-2: Test set-up for Test Suite Table 4-3: Daily average energy use and temperature control characterization for the occupied period of Test Suite Table 4-4: Daily average heating water flow control characterization for Test Suite Table 4-5: Summary of system balancing performance at low loads for CL 3.3. The A test rooms are served by Belimo and the B test rooms by Siemens globe valves Table 5-1: Specifications for valves used for Test Suite 4 and Test Suite Table 6-1: Summary of control performance parameters for Test Suite Table B-1: Daily reheat energy use, cumulative temperature error, and cumulative change in water flow rate for test rooms East-A and East-B for CL Table B-2: Daily reheat energy use, cumulative temperature error, and cumulative change in water flow rate for test rooms Interior-A and Interior-B for CL Table B-3: Daily reheat energy use, cumulative temperature error, and cumulative change in water flow rate for test rooms South-A and South-B for CL Table B-4: Daily reheat energy use, cumulative temperature error, and cumulative change in water flow rate for test rooms West-A and West-B for CL Table B-5: Daily reheat energy use, cumulative temperature error, and cumulative change in water flow rate for test rooms East-A and East-B for CL Table B-6: Daily reheat energy use, cumulative temperature error, and cumulative change in water flow rate for test rooms Interior-A and Interior-B for CL Table B-7: Daily reheat energy use, cumulative temperature error, and cumulative change in water flow rate for test rooms South-A and South-B for CL Table B-8: Daily reheat energy use, cumulative temperature error, and cumulative change in water flow rate for test rooms West-A and West-B for CL Table B-9: Daily reheat energy use, cumulative temperature error, and cumulative change in water flow rate for test rooms East-A and East-B for CL Table B-1: Daily reheat energy use, cumulative temperature error, and cumulative change in water flow rate for test rooms Interior-A and Interior-B for CL Table B-11: Daily reheat energy use, cumulative temperature error, and cumulative change in water flow rate for test rooms South-A and South-B for CL xiv

15 Table B-12: Daily reheat energy use, cumulative temperature error, and cumulative change in water flow rate for test rooms West-A and West-B for CL xv

16 1 Introduction 1.1 Objective The objective of the testing described in this report was to evaluate the performance of Belimo pressure independent characterized control valves () against conventional globe control valves for terminal reheat and air-handling unit (AHU) chilled water cooling coil applications in a commercial office building. Specifically, testing was performed to verify the performance of the with respect to the following characteristics: Ability to maintain perfect valve authority; Decreased start-up time (i.e., time required to bring the temperature in all rooms up to the occupied heating setpoint from night setback conditions) resulting from the prevention of overflow and underflow to individual terminal reheat coils; Reduction in pumping costs; Increased water-side temperature differential across the terminal reheat coil and AHU chilled water cooling coil, and resulting effect on boiler efficiency; and Automatic, dynamic system balancing, particularly at low loads. 1.2 Scope This report describes the results of a series of tests undertaken to evaluate the performance of the Belimo in comparison to a conventional globe valve. Tests were performed for a variable-air-volume (VAV) terminal reheat application and an AHU chilled water cooling coil application. The tests consisted of the following: 1. Terminal Reheat Open Loop Test: The purpose of this test was to quantify the water flow rate through the terminal reheat test valves as a function of valve position (i.e., % open) and the differential pressure across the valves. 2. Terminal Reheat Closed Loop Test Effect of Valve Sizing on Valve Performance: The purpose of this test was to evaluate the control performance of the in comparison to a correctly sized and two oversized conventional globe valves for a terminal reheat application. 3. Terminal Reheat Closed Loop Test System Performance Test: The purpose of this test was to compare energy use, control stability, start-up time and other relevant performance characteristics as the test valves were utilized under normal system operating conditions for a terminal reheat application. 4. AHU Chilled Water Open Loop Test: The purpose of this test was to quantify the water flow rate through the AHU chilled water cooling coil test valves as a function of valve position (i.e., % open) and the differential pressure across the valves. 5. AHU Chilled Water Closed Loop Test Control Performance: The purpose of this test was to evaluate the control performance of the in comparison to a correctly sized conventional globe valve for an AHU chilled water cooling coil application. Summaries of the tests are provided for reference in Table 1-1 and Table

17 Table 1-1: Summary of tests performed for the VAV terminal reheat application. Test Description Test Number System A Test Room Configuration System B Test Room Configuration Open-loop test to determine flow rate through test valve as a function of the differential pressure across the valve and the degree to which the valve is open. Tests performed in South A Test Room. OL 1.2 Closed-loop room air temperature control with constant inlet pressure to control valve and variable heating water loop pump speed. Tests performed in South A and South B Test Rooms. OL 1.1 Belimo Not used CL 2.1 CL 2.2 CL 2.3 Correctly sized globe valve: Siemens Powermite MT (C v = 1.6) Belimo Belimo Belimo Correctly sized globe valve: Closed-loop discharge air temperature CL 2.4 Siemens Powermite control with constant inlet pressure to MT (C v = 1.6) control valve and variable heating water loop pump speed. Tests performed in South A and South B Test Rooms. CL 2.5 Belimo Closed-loop room air temperature control CL 2.6 with variable inlet pressure to control valve and constant heating water loop pump speed. Tests performed in South A and South B Test Rooms. CL 2.7 Correctly sized globe valve: Siemens Powermite MT (C v = 1.6) Very oversized globe valve: Siemens Powermite MT (C v = 4.) Not used Correctly sized globe valve: Siemens Powermite MT (C v = 1.6) Oversized globe valve: Siemens Powermite MT (C v = 2.5) Very oversized globe valve: Siemens Powermite MT (C v = 4.) Belimo Correctly sized globe valve: Siemens Powermite MT (C v = 1.6) Belimo Belimo Closed-loop system comparison under normal operation with installed in one system and correctly sized globe valves installed in second system. Tests performed using all test rooms for System A and System B. CL 3.1 Perimeter Rooms: Belimo Interior Room: Belimo Perimeter Rooms: Siemens Powermite MT Interior Room: Siemens Powermite MT Same as CL 3.1, except s are installed in System B and globe valves are installed in System A. Tests performed using all test rooms for System A and System B. CL 3.2 Perimeter Rooms: Siemens Powermite MT Interior Room: Siemens Powermite MT Perimeter Rooms: Belimo Interior Room: Belimo Same as CL 3.1, except the differential pressure setpoint (used to control the heating water loop pump) between the supply and return lines for the heating water loop is the same for both systems, whereas in CL 3.1 and CL 3.2 it was not. Tests performed using all test rooms for System A and System B. CL 3.3 Perimeter Rooms: Siemens Powermite MT Interior Room: Siemens Powermite MT Perimeter Rooms: Belimo Interior Room: Belimo

18 Table 1-2: Summary of tests performed for the AHU chilled water cooling coil application. Test Description Open-loop test to determine flow rate through test valve as a function of the differential pressure across the valve and the degree to which the valve is open. Tests performed using AHU-A chilled water cooling coil. Test Number AHU-A Chilled Water Cooling Coil Set-up AHU-B Chilled Water Cooling Coil Set-up OL 4.1 Belimo PT Not used OL 4.2 Closed-loop supply air temperature control with a variable inlet pressure to CL 5.1 control valve. Tests performed using chilled water cooling coils for AHU-A and AHU-B. CL 5.2 Correctly sized globe valve: Siemens Powermite MT (C v = 1.) Belimo PT Correctly sized globe valve: Siemens Powermite MT (C v = 1.) Not used Correctly sized globe valve: Siemens Powermite MT (C v = 1.) Belimo PT 1.3 Test Facility Testing was performed at the Iowa Energy Center, Energy Resource Station (ERS). A schematic of the facility is shown in Figure 1-1. The facility consists of four matched pairs ( A and B ) of test rooms facing east, south, west and in the interior. Side A of each test room pair is isolated from side B and is served by a separate heating, ventilating and air-conditioning system. The Figure 1-1: Schematic of the side-by-side test rooms of the Energy Resource Station. 3

19 paired rooms are identical in their construction and heating and cooling loads. This design enables side-by-side comparisons of the systems and/or the algorithms that control them. Additional information on the ERS, including an online virtual tour of the facility, can be viewed at the following web site: 4

20 2 Terminal Reheat Open Loop Test The purpose of this suite of tests, which is designated Test Suite 1, was to evaluate the pressure independent feature of the Belimo. The test consisted of measuring the water flow rate through the test valve as a function of valve position and pressure drop across the valve for a VAV terminal reheat application. 2.1 Test Valves Testing compared the performance of one Belimo and one correctly sized Siemens Powermite MT series globe valve and actuator assembly. The selection of the valves was based on the design flow rate of the terminal reheat coil of an exterior room in the ERS. This design flow rate is 3 GPM (.19 L/s). The globe valve was sized to produce a pressure drop of 4 psi (27.6 kpa) with the valve wide open. Detailed specifications for the valve and actuator assemblies are provided in Table 2-1. Table 2-1: Specifications for valves used for Test Suite 1. Valve Designation Belimo Siemens Powermite MT Manufacturer Belimo Siemens Model Powermite MT Type Globe (Stroke 7/32") Line Size 1/2 " 1/2 " Cv N/A 1.6 Design Flow Rate 3 GPM (.19 L/s) N/A Close-Off Pressure 2 PSI (1379 kpa) 16 PSI (113 kpa) Manufacturer Belimo Siemens LR24-MFT US+NO+P- Model 128 SQS65U Fail-in-Place, DA/RA Type (adjustable) Fail-in-Place, RA Actuator 35 in-lb f (4 N-m) min. Force torque 9 lb f (4 N) Run-Time 1 seconds 3 second Input Signal - 1 VDC - 1 VDC Feedback Output - 1 VDC - 1 VDC Power 24VAC±2%, 24VDC±1% 24VAC, +2%, -15% The valves are normally open and the actuators do not have spring return. 2.2 Test Set-Up The test valve was installed on the return side of the reheat coil in the South-A test room as shown in Figure 2-1. An Endress Hauser model Cerabar M PMC 41 single-point pressure 5

21 Interior A Test Room T H C T A Existing valve CLOSED LEGEND - Pressure Independent Characterized Control Valve F CGCV - Conventional Globe Control Valve A - Actuator (Analog) F - Flow Meter East A Test Room T H C T A Existing valve CLOSED T P DP - Temperature Sensor - Pressure Sensor - Differential Pressure Sensor F VFD - Variable Frequency Drive C - Controller H C South A Test Room T T A Test valve: - Belimo - CGCV F P1 DP H C West A Test Room T T A Existing valve CLOSED F C VFD Heating Water Boiler Figure 2-1: Schematic of heating water Loop-A and instrumentation setup for Test Suite 1. transducer ( 1 psig [ kpa] calibrated span; accuracy of ±.2 % of calibrated span) was used to measure the valve inlet pressure. An Endress Hauser model Deltabar S PMD 235 differential pressure transducer ( 43 psig [ kpa] calibrated span; accuracy of ±.1 % of calibrated span) was used to measure the pressure drop across the valve. The water flow rate was measured using a Badger Meter model Magnetoflow TM electromagnetic flow meter (.1 33 fps [ m/s]; accuracy of ±.25% of flow rate). The reheat coil in South-A (and all other perimeter test rooms) is a single-row plate fin type coil with a design water flow rate of 3 GPM (.19 L/s) and a design water pressure drop through the coil of 1.4 ft. of water (4.19 kpa). Two pumps were used to achieve the desired pressure drop across the test valve for each test condition. The Loop-A heating water pump is normally used to circulate water to the VAV 6

22 terminal reheat coils. A second pump, designated the booster pump, was installed to enable higher pressures to be achieved. The speed of each pump was controlled via a variable frequency drive. To minimize pressure disturbances during testing, the reheat coil valves for the remaining three test rooms on Loop-A (East-A, West-A and Interior-A) were overridden to remain closed for the duration of the test. 2.3 Test Conditions and Procedure The first test was performed on the Belimo on November 24, 24. The valve was tested at all combinations of the following conditions: Commanded Signal to Valve: 1, 15, 2, 25, 3, 35, 4, 6, 8, 1, and 4% open (2% open corresponds to a commanded signal to the valve of 2 VDC for a to 1 VDC output range) Differential Pressure Across Valve: 5, 1, 15, 2, and 3 psi (34.5, 69, 13.4, 137.9, and 26.9 kpa); achieved by adjusting the speeds of the circulating and booster pumps for Loop-A The initial test point was a commanded signal of 1% open and a differential pressure across the valve of 5 psi (34.5 kpa). The commanded signal was then increased to the next test condition (i.e., 15% open) while the differential pressure was held constant. Conditions were typically allowed to stabilize for three to five minutes between test points. Testing continued in this way until the commanded signal was 1% open. The final test point at a given differential pressure was a commanded signal of 4% open. This point was recorded to enable the test valve hysteresis to be evaluated. The procedure was then repeated at differential pressures of 1, 15, 2, and 3 psi (69, 13.4, 137.9, and 26.9 kpa). After completing the test of the Belimo, the Siemens Powermite MT globe valve was installed in its place and the test procedure repeated on November 28-29, 24. The two tests were designated as follows: OL1.1 Belimo OL1.2 Siemens Powermite MT 2.4 Instrumentation The following list of measurement and control points were monitored and recorded during the test: 1. Inlet pressure to test valve (psig); note that throughout this report, inlet pressures are measured relative to atmospheric pressure 2. Differential pressure across the test valve (psi) 3. Water flow rate (gallons per minute) 4. Commanded signal to test valve (% open) 5. Valve position feedback (% open) 6. Heating water pump speed (% of maximum or Hz) 7. Reheat coil entering water temperature ( F) 8. Reheat coil leaving water temperature (i.e., temperature at the valve, F) 7

23 Each of these eight points was recorded at 1 second intervals using a National Instruments data acquisition system. 2.5 Results The water flow rate through the Belimo as a function of the differential pressure across the valve and the commanded (or input) signal to the valve is shown in Figure 2-2. The commanded signal has units of % open ; for example, 35% open corresponds to a commanded signal of 3.5 VDC. The data points in Figure 2-2 and subsequent figures in this chapter are one minute averages obtained from the 1 second data. The curves in Figure 2-2 indicate that the flow rate through the Belimo is nearly independent of the differential pressure across the valve for a given commanded signal to the valve. At the design condition (i.e., commanded signal of 1% open), the flow rate varies from 3.12 GPM at 5 psi to 3.19 GPM at 3 psi (.197 L/s at 34.5 kpa to.21 L/s at 26.9 kpa). The maximum flow rate over this pressure range is 3.21 GPM at 15 psi (.23 L/s at 13.4 kpa). In general, the flow rate varies by less than.11 GPM (.7 L/s) over the range of pressures tested for a given commanded signal. The only exception occurs at a commanded signal of 4% open, where the variation in flow rate is slightly greater. Figure 2-2 contains two curves corresponding to a commanded signal of 4% open. The first curve corresponds to data obtained with the commanded signal increasing from 35% open to Differential Pressure Across Valve (kpa) Heating Water Flow Rate (GPM) Heating Water Flow Rate (L/s) 1% open 15% open 2% open 25% open 3% open 35% open 4% open 6% open 8% open 1% open 4% open.5.4 hysteresis data Differential Pressure Across Valve (psi) Figure 2-2: Flow rate through the Belimo as a function of differential pressure and commanded signal to the valve. 8

24 4% open and the second curve (labeled hysteresis data) corresponds to data obtained with the commanded signal decreasing from 1% open to 4% open. The flow rates are significantly different for the two curves (.28 to.43 GPM [.18 to.27 L/s] for the first curve and.45 to.65 GPM [.28 to.41 L/s] for the second curve). Based on the feedback signal from the actuator, a commanded signal results in consistent positioning of the valve (i.e., the position feedback corresponding to a commanded signal of 35% open is 43.8% open, independent of the differential pressure across the valve). The relationship between the commanded signal and the feedback signal is shown in Figure 2-3. The feedback signal has been scaled to range from to 1% open. The unscaled feedback ranges from approximately 4.9 to 73% open. Note in Figure 2-3 that there are five data points corresponding to five differential pressures for each commanded signal. The only exception is a commanded signal of 4% open, which has ten data points. Because they overlap one another, multiple data points appear to be a single point in Figure 2-3. The data in Figure 2-3 indicates that the hysteresis observed in the data in Figure 2-2 is not due to inconsistent positioning of the control valve. With this assumption, the most likely source of the hysteresis is the pressure regulator device in the, which must respond to pressure changes that occur as the valve is opened and closed. Although some hysteresis is observed, it could be argued that it is unimportant because a feedback application will simply reposition the valve as necessary to achieve the desired process condition. 1 Scaled Valve Feedback Signal (% Open) Valve Commanded Signal (% Open) Figure 2-3: Relationship between the commanded and scaled feedback signals for the Belimo. 9

25 The performance of the valve is consistent with Belimo literature on the. Although some slight pressure dependencies can be observed in the data (the flow rate increases slightly at higher differential pressures), the variations are less than 6.5% of the design flow of 3 GPM (.19 L/s). The water flow rate through the Siemens Powermite MT globe valve as a function of the differential pressure across the valve and the commanded signal to the valve is shown in Figure 2-4. The commanded signal again has units of % open and 35% open corresponds to a commanded signal of 3.5 VDC. Figure 2-4 consists of data obtained with the balancing valve 42% closed (solid lines) as well as data obtained with the balancing valve fully open (dashed lines). Because the balancing valve is located upstream of locations where the inlet pressure and differential pressure measurements are made, the balancing valve will not affect the flow rate through the control valve at a specific differential pressure and valve position. Partially closing the balancing valve will, however, limit the ability of the pumps to achieve high differential pressures when the valve is fully open or nearly fully open. Specifically, the pumps were unable to provide enough head to produce the higher pressure drops when the Siemens valve was 8% open (2 and 3 psi [137.9 and 26.9 kpa] could not be achieved) and 1% open (15, 2 and 3 psi [13.4, and 26.9 kpa] could not be achieved) and the balancing valve was 42% closed. As a consequence, these curves are incomplete. The missing data points were obtained through retesting with the balancing valve 1% open. Additional data points were also collected with the balancing valve 1% open (dashed curves in Figure 2-4) to demonstrate that the balancing valve does not influence the flow rate at a specific differential pressure and commanded signal to the valve. This assertion is borne out by the data. The curves in Figure 2-4 indicate that the flow rate through the Siemens valve increases as the differential pressure across the valve increases for a fixed commanded signal to the valve. This is consistent with Siemens literature on the Powermite MT series valve. The flow rates measured when the valve was fully open are 13 to 15% higher than expected based on Siemens literature. For example, for a differential pressure of 5 psi (34.5 kpa), a flow rate of 4.14 GPM (.261 L/s) was measured and for a differential pressure of 1 psi (69 kpa), a flow rate of 5.76 GPM (.363 L/s) was measured. The Siemens literature indicates the flow rates should be approximately 3.6 GPM at 5 psi and 5.1 GPM at 1 psi (.227 L/s at 34.5 kpa and.322 L/s at 69 kpa). Based on the measured flow rates, the Siemens valve has a flow coefficient (C v ) of approximately 1.82, whereas the manufacturer stated flow coefficient is 1.6. It was noted in Section 2.1 that the globe valve was sized to produce a 4 psi (27.6 kpa) pressure drop across the valve when it is fully open. This sizing practice is common in the field and the calculated flow coefficient based on this criteria is C v = 1.5. The Siemens Powermite MT , with a flow coefficient of 1.6, was closest to the desired value of C v = 1.5. ASHRAE sizing criteria, which states that the control valve pressure drop should be at least 25 to 5 percent of the system loop pressure drop, suggests a valve with a flow coefficient of C v = 1.14 is appropriate for this application. Thus, based on actual performance, the correctly sized conventional globe valve was 21 to 6% oversized depending on which of these two criteria are used for selection. 1