Functional Testing for Pumping Systems

Functional Testing for Pumping Systems. 1

Constant Flow.. 3

Functional Testing Field Tips Constant Flow.. 3

Key Commissioning Test Requirements

Key Preparations and Cautions

Time Required to Test

Variable Flow.. 7

Functional Testing Field Tips Variable Flow.. 7

Key Commissioning Test Requirements

Key Preparations and Cautions

Time Required to Test

Testing Guidance and Sample Test Forms. 12

 

Functional Testing for Pumping Systems

This module of the Functional Testing Guide describes the benefits and the process of testing constant flow and variable flow pumping systems and integrating their operation into chilled water or hot water systems. Although the emphasis is on functional testing, this module also describes other related activities such as the verification checklists (also referred to as pre-functional tests) that are a precursor to functional testing.

       A constant flow water system typically includes both water distribution piping and pumps, as well as heat transfer elements (such as cooling and/or heating coils in air handling units, cooling towers, condenser bundles, and water-cooled process loads). Isolation valves, and occasionally 3-way control valves, as well as various temperature, pressure, and flow sensors are also typically included in a constant flow system.

       A variable flow water system typically includes water distribution piping and pumps, heat transfer elements, control valves, and various temperature, pressure, and flow sensors. A variable flow system also includes modulating valves that control, for example, cooling and/or heating coils in air handling units, terminal units, unit heaters, radiant baseboards, water-source heat pumps, and water-cooled process loads.

The information in this module provides practical advice useful to both new and experienced commissioning providers, as well as to building owners or operations and maintenance staff. The pumping systems module is organized into three main areas, as described below:

       The Functional Testing Benefits tables, for constant flow and variable flow water systems, describe benefits that a building owner or operator may experience as a result of testing. These tables can be used to help decide what level of testing to conduct.

       The Functional Testing Field Tips tables, for constant flow and variable flow water systems, provide guidance on issues that should be considered when planning or conducting testing.

       The Testing Guidance and Sample Test Forms table is a list of publicly available verification checklists and functional tests. These procedures can be adapted for use directly on your projects or can be used as a guideline for developing custom test procedures for integrated control functions. The tests are most often used in the new building commissioning process to verify installation and performance, but they can also be used in a retro-commissioning process to detect existing operational issues. The tests cover a range of examples of different approaches and levels of testing.

Refer to Functional Testing Basics for guidance related to all functional testing activities regardless of the component or system being tested. There are other sections of the Functional Test Guide that will also be helpful in integration of the pumping system with other systems. Additional integration guidance may be found by referencing the Chiller module and the Condenser module, in the context of how the pumping system should integrate with the chiller system and condenser system.

Constant Flow

Functional Testing Field Tips Constant Flow

Key Commissioning Test Requirements lists practical considerations for functional testing. Key Preparations and Cautions address potential problems that may occur during functional testing and ways to prevent them.

 

Key Commissioning Test Requirements

General

The performance of a constant flow water system is acceptable if it meets the design intent and specified operating sequence.

In some instances, witnessing the flushing and pressure testing of individual coils and/or distribution piping may be required.

Safeties, Interlocks, and Alarms

Verification that all safeties, interlocks, and alarms are programmed (or hard-wired, if applicable) and function correctly.

Sensors

Verification that sensor installation and calibration is sufficient to achieve the design control strategies. The DDC control system relies on input from various sensors (for example, temperature, pressure, and flow) in order to achieve the desired system operation. However, if sensors are not located correctly or the measured value from any sensor to the control algorithm is incorrect, the system will not respond as intended. Commissioning will ensure all sensors are located, installed, and calibrated correctly so that the DDC system will have accurate data from which to execute each control sequence.

Actuation and Sequencing

Verify proper stroke for control valves to ensure that they open and close completely (coil valves, isolation valves, etc.).

Control valve leakage testing reveals no detectable leakage when valve is commanded closed.

Verify proper distribution pump staging per the sequence of operations. Frequently, water and air temperature reset strategies are not coordinated; this can result in the unnecessary staging of distribution pumps ON. Optimizing various reset strategies, during both initial system set-up and commissioning will improve system control and minimize pumping energy.

Verify that 3-way control valves modulate correctly. This will help to ensure that simultaneous heating and cooling does not occur. For example, a leaky hot water valve on a pre-heat or heating coil will add unwanted heat to the air stream which can cause the chilled water valve to modulate open; this wastes heating and cooling energy.

Review TAB report, including flow, impeller size, and motor volt/amp measurements.

Setpoints and Reset Controls

1 The system operates and maintains chilled and hot water supply temperature setpoints and discharge air temperature setpoints in all modes including morning warm-up, occupied mode, and night low limit mode.

2 Control loops generate the proper setpoint based on the reset parameters. Reset parameters are optimized for the system.

3 Verify proper coordination between individual setpoints and reset strategies. Resetting the chilled water supply temperature warrants close attention. Without coordination between chilled water temperature reset and discharge air temperature reset, the air handler may be trying to make colder air than is possible with the chilled water supply temperature. This situation will result in distribution pumps operating at full flow even though there is no load on the system, wasting significant pumping energy.

Control Accuracy and Stability

Verify proper control sequence and integration over all components (such as setpoints, start-up/shut-down procedures, and time delays). This includes verification of proper stand-by pump operation in the case of a lead pump failure. Temperature control strategies impact water flow through the system and pump staging, which can cause system instability. Typically, testing entails verifying that the PID loop generates the proper control signal based on the setpoint. Testing should also verify the setpoints are optimized for the system or recommend modifications, if necessary.

Verify that condenser pumps and primary chilled and hot water pumps are started and proof of flow is established prior to the respective equipment being enabled.

Each air handling system does not exhibit any simultaneous heating and cooling (proper integration between heating coil, economizer control, and cooling coil control sequences).

Key Preparations and Cautions

Prefunctional Checklists and Start-up

Prefunctional checklists should be completed throughout construction during normal commissioning site visits as installation of the various components and systems are completed. Sensor and actuator calibration is typically considered to be part of the prefunctional checklist.

In addition to the prefunctional checklists, all component start-up procedures must be complete in order to conduct functional test procedures. Water-side TAB must also be complete prior to functional testing.

Valve leakage tests and tests that are targeted at verifying valve stroke, spring range, and sequencing should be conducted with the pumping system operating at its peak differential pressure. The differential pressure across the valve plug can have a significant impact on the close-off rating and shift the operating spring range of the valve. These tests should be performed prior to temporary system operation to ensure that equipment will not be damaged during functional testing.

Test Conditions, Considerations, and Cautions

The following points should be noted to avoid testing complications:

1 Ideally, functional performance testing of a constant flow water system should occur during the season in which the system is intended to operate (hot water in winter and chilled water in summer) to observe the entire system under normal operating conditions. If this is not possible due to the construction schedule, system operation and performance must be verified by either creating false loads on the equipment or through manipulation of setpoints to accommodate existing atmospheric conditions. For example, a load can be simulated by adjusting all setpoints to be 10F above or below current ambient conditions and allowing the system to respond accordingly.

2 Successful execution of the constant flow water system functional tests is dependent on the operation of ancillary equipment (air handling units, heat pumps, process loads, chillers, boilers, cooling towers). At a minimum, the prefunctional checklists should be completed on the components/systems served by the water system and should be capable of safe temporary operation.

3 If testing a condenser water system during cold weather conditions, be sure all freeze protection controls operate as intended to prevent operational problems.

4 Safety and interlock tests, as well as some test procedures and loop tuning efforts (for example, high/low limit cut-out setpoints, emergency shut-down procedures, and failure/back-up system operation) can place the system at risk if the sequences do not function as intended. Appropriate precautions and procedures should be in place to protect personnel and machinery, including plans for quickly aborting the test if necessary.

5 Rapid stroking of valves during a test process can cause water hammer problems in the piping systems. Consider stroking each valve in stages to prevent slamming valves open or closed, giving the system time to respond appropriately.

6 It is recommended that any reset strategies be disabled first and that only one control parameter be varied at a time so that basic system operation can be verified. Reestablish the resets for other control parameters progressively and verify system operation remains stable.

Instrumentation Required

Instrumentation requirements vary from test to test and typically include, but are not limited to, the following:

Temperature measurement devices (hand-held devices to calibrate existing sensors)

Differential pressure measurement devices (for testing installed flow meters or performing pump impeller tests)

Amperage and voltage measurement devices (to verify that measured values dont exceed nameplate)

Tachometer (for verifying pump speed)

Flow measurement devices (installed or hand-held devices to measure water flows)

Data loggers (to supplement existing sensors to verify system operation)

Time Required to Test

Overview

The time necessary to execute functional tests on an entire constant flow water system depends greatly on the size and complexity of the installation and specified control sequences. For example, the number of system components (such as cooling towers, condenser bundles, heat pumps, and water-cooled process loads), as well as the complexity of the sequence of operation (reset strategies, staging parameters, safeties/alarms) will significantly impact the time associated with testing the entire system. Therefore, time estimates have been separated out by component on a per unit basis, as well as on an overall system level. Component-level tests typically refer to discrete functions of each piece of equipment (for example, start/stop procedures, safeties, operational and failure interlocks, and alarms), whereas system-level tests focus on evaluating proper integration of each component to satisfy the desired control strategy (this includes staging, setpoints and reset strategies).

The time necessary to develop a specific functional test, or to adapt a generic test procedure to meet the specific needs of the current project, have not been included in the estimates above. A rough estimate is two to four hours for each component type.

The time associated with completing prefunctional checklists has not been included in the estimates above. These checks should be made throughout construction during normal commissioning site visits as installation of the various components and systems are completed. Sensor and actuator calibration, coil/piping flushing and valve stroke tests are typically considered to be part of completing the prefunctional checklists.

Component Level Testing

Component Level Testing Time Recommendations

One to two hours per distribution pump.

One hour or less per control valve (fully modulating and two-position), including individual stroke from full open to full close.

System Level Testing

Two to three hours to verify proper control strategies.

Two to four hours to verify proper distribution pump staging.

 

Variable Flow

Functional Testing Field Tips Variable Flow

Key Commissioning Test Requirements lists practical considerations for functional testing. Key Preparations and Cautions address potential problems that may occur during functional testing and ways to prevent them.

Key Commissioning Test Requirements

General

The performance of a variable flow water system being tested is acceptable if it meets the design intent and specified operating sequence.

In some instances, witnessing flushing and pressure testing individual coils and/or distribution piping may be required.

Safeties, Interlocks, and Alarms

Verification that all safeties, interlocks, and alarms are programmed (or hard-wired, if applicable) and function correctly.

Sensors

Verification that sensor installation and calibration is sufficient to achieve the design control strategies.

Actuation and Sequencing

1 Proper stroke for control valves to ensure that they open and close completely (coil valves, isolation valves, etc.)

2 Control valve leakage testing reveals no detectable leakage when valve is commanded closed.

3 Two-position control valves associated with the respective equipment open fully upon start-up and close fully upon shutdown. This is typical for water-source heat pumps and water-cooled process equipment.

4 Verify proper distribution pump staging and VFD control (if applicable) per the sequence of operations. Typically, distribution pumps in variable flow systems utilize a VFD to modulate pump speed in order to deliver water flow that matches system loads. VFD staging and modulation control is normally based on maintaining a constant differential pressure either across the distribution pumps themselves or out in the loop. The differential pressure setpoint is based on the pressure required to provide adequate flow through the worst case load (for example, the load with the highest overall pressure drop piping losses and device requirements) at full load. Often, the setpoint (either specified by the design engineer or estimated by the controls contractor, if not provided) is set artificially high, wasting pumping energy for the life of the building. The actual system pressure setpoint should be determined during the initial system set-up and commissioning to improve system control and minimize pumping energy.

5 Review TAB report, including flow, including flow, impeller size, and motor volt/amp measurements.

Setpoints and Reset Controls

1 The system operates and maintains chilled and hot water supply temperature setpoints and discharge air temperature setpoints in all modes including morning warm-up, occupied mode, and night low limit mode.

2 VFD control loops generate the proper setpoint based on the reset parameters (if applicable). Reset parameters are optimized for the system.

3 Verify differential pressure reset control strategy. Frequently, the discharge pressure setpoint is reset based on dynamic load requirements to reduce pump energy even further. Various indicators can be used to signify reduced load on the system, one example being valve position. In this control strategy, the system pressure setpoint is reset higher or lower in order to maintain one chilled water valve at a pre-set position (95% open, for example).

4 Verify proper coordination between individual setpoints and reset strategies. Resetting the chilled water supply temperature warrants close attention. Without coordination between chilled water temperature reset and discharge air temperature reset, the air handler may be trying to make colder air than is possible with the chilled water supply temperature. This situation will result in distribution pumps operating at full flow even though there is no load on the system, wasting significant pumping energy.

Control Accuracy and Stability

Verify proper control sequence and integration over all components (including proper sequencing of primary and secondary pumps, setpoints and reset strategies, start-up/shut-down procedures, and time delays). Temperature control strategies impact water flow through the system and pump staging, which can cause system instability. Typically, testing entails verifying that the control loop generates the proper signal based on the setpoint. Testing should also verify the setpoints are optimized for the system or recommend modifications, if necessary.

All control loops achieve stability (i.e. no hunting) within a reasonable amount of time (typically 2 to 5 minutes) after a significant load change (such as start-up, and automatic or manual recovery from shut down).

For variable primary-only chilled and hot water systems, verify the minimum VFD speed maintains minimum water flow rate required by the chiller and boiler manufacturers.

Key Preparations and Cautions

Prefunctional Checklists and Start-up

Prefunctional checklists should be completed throughout construction during normal commissioning site visits as installation of the various components and systems are completed. Sensor and actuator calibration is typically considered to be part of the prefunctional checklist.

In addition to the prefunctional checklists, all component start-up procedures must be complete in order to conduct functional test procedures. Both the air-side and water-side TAB must also be complete prior to functional testing.

Valve leakage tests and tests that are targeted at verifying valve stroke, spring range, and sequencing should be conducted with the pumping system operating at its peak differential pressure. The differential pressure across the valve plug can have a significant impact on the close-off rating and shift the operating spring range of the valve. These tests should be performed prior to temporary system operation to ensure that equipment will not be damaged during functional testing.

Test Conditions, Considerations, and Cautions

The following points should be noted to avoid testing complications:

1 Ideally, functional performance testing of a variable flow water system should occur during the season in which the system is intended to operate (hot water in winter and chilled water in summer) to observe the entire system under normal operating conditions. If this is not possible due to the construction schedule, system operation and performance must be verified by either creating false loads on the equipment or through manipulation of setpoints to accommodate existing atmospheric conditions. For example, a load can be simulated by adjusting all setpoints to be 10F higher or lower than the current ambient conditions and allowing the system to respond accordingly.

2 Successful execution of the variable flow water system functional performance tests is dependent upon the operation of ancillary equipment (for example, air handling units, terminal units, heat pumps, process loads, chillers, and boilers) At a minimum, the prefunctional checklist should be completed on the components/systems served by the water system and should be capable of safe temporary operation.

3 Integration of temperature setpoints must be coordinated between the boiler, chiller, and the equipment they serve. Uncoordinated setpoints can force the distribution pumps to operate at full flow even though there is basically no load on the system, wasting significant pumping energy.

4 Reset schedules can also conflict with each other. For example, resetting hot water supply temperature lower, or chilled water supply temperature higher, will tend to cause the respective coil valves to open. This could skew verification of the pump staging and modulation control strategy if the system changes unexpectedly while controlled functional tests are being performed. All resets should be overridden, except for those being tested, to prevent unwanted impact on the system during testing. Individual reset strategies should be disabled and only one control parameter varied at a time so that basic system operation can be verified. Reestablish the resets for other control parameters progressively and verify that system operation remains stable.

5 On large systems, heating and/or cooling coil valves may be arranged in a 2/3rd and 1/3rd configuration in which one valve (or set of valves) will satisfy 1/3rd of the load and the remaining valve(s) will handle the remaining 2/3rd of the load. The intent is to provide better control over the valve(s) to achieve better turndown characteristics during part load conditions. Proper tuning of a PID control loop may be difficult for a system that was designed to modulate all coil valves simultaneously to satisfy any load condition. Ensure valve control does not create instabilities in the water flow control loop or in the pump staging and discharge air temperature control loops, as well.

6 Safety and interlock tests, as well as some test procedures and loop tuning efforts (for example, high/low limit cut-out set points, emergency shut-down procedures, and failure/back-up system operation) could place the system at risk if the sequences do not function as intended. Appropriate precautions and procedures should be in place to protect personnel and machinery, including plans for quickly aborting the test if necessary.

7 Rapid stroking of valves during a test process can cause water hammer problems in the piping systems. Consider stroking each valve in stages to prevent slamming valves open or closed, giving the system time to respond appropriately. Rapid stroking may be an indication of control loop hunting.

Instrumentation Required

Instrumentation requirements vary from test to test and typically include, but are not limited to, the following:

Temperature measurement devices (hand-held devices to calibrate existing sensors)

Differential pressure measurement devices (to test installed flow meters or for performing pump impeller tests)

Amperage and voltage measurement devices (to verify that measured values dont exceed nameplate)

A tachometer (for verifying pump speed)

Flow measurement devices (installed or hand-held devices to measure water flows)

Data loggers (to supplement existing sensors to verify system operation)

Time Required to Test

Overview

The time necessary to execute functional tests on an entire variable flow water system depends greatly on the size and complexity of the installation and specified control sequences. For example, the number of system components (such as coils, unit heaters, radiant baseboards, heat pumps, and water-cooled process loads), as well as the complexity of the sequence of operation (reset strategies, VFD flow controls, staging parameters, safeties/alarms) will significantly impact the time associated with testing the entire system. Therefore, time estimates have been separated out by component on a per unit basis as well as on an overall system level. Component-level tests typically refer to discrete functions of each piece of equipment (for example, start/stop procedures, safeties, operational and failure interlocks, and alarms), whereas system-level tests focus on evaluating proper integration of each component to satisfy the desired control strategy (this includes staging, setpoints, and reset strategies).

The time necessary to develop a specific functional test, or to adapt a generic test procedure to meet the specific needs of the current project, have not been included in the estimates above. A rough estimate is two to four hours for each component type.

The time associated with completing prefunctional checklists has not been included in the estimates above. These checks should be made throughout construction during normal commissioning site visits as installation of the various components and systems are completed. Sensor and actuator calibration, coil/piping flushing and valve stroke tests are typically considered to be part of completing the prefunctional checklists.

Component Level Testing

One to two hours per distribution pump.

One hour or less is needed per control valve (fully modulating and two-position), including individual stroke from full open to full close. Sampling may be appropriate in certain situations (for example in a building that has 100 VAV boxes with reheat coils).

Individual components like cooling or heating coils can require many hours to capacity test. Several team members will be needed to set up and monitor all of the necessary operating points.

System Level Testing

Two to three hours is needed to verify proper reset strategies (for example, discharge air temperature, water temperature, and pressure).

Allow three to twelve hours to verify proper distribution pump staging to satisfy system setpoints.

 

Testing Guidance and Sample Test Forms

Pumping System Testing Guidance

This testing guidance describes the steps and potential issues that may arise during testing.  Since commissioning providers typically have their own style of forms, the Testing Guidance is not provided in a field-ready form.  Commissioning providers may use the Test Guidance to expand and improve upon their existing forms.  Example tests based on the Test Guidance documents are provided where available.

Test ID

Testing Guidance

(View Appendix D for Test Descriptions)

Source

(View Appendix E for Source Details)

Example tests

TG03

Pump Performance and Impeller Trim Analysis

STAC/PECI

Hot Water System Pump Test (Test ID 1009)

Chilled Water System Pump Test (Test ID 1010)

Condenser Water System Pump Test (Test ID 1011)

TG10

Valve Leak-By

STAC/PECI

 

TG16

Writing a Functional Test (general guidance)

STAC/PECI

Blank Test Form for Writing a Functional Test (Test ID 1015)

Example for Writing a Functional Test (Test ID 1020)

Pumping System Sample Test Forms

This table lists publicly-available sample tests from a variety of authors. Some of the tests are written for a specific building, while others are written for a general case.  This list of sample test forms also includes the Example Tests listed in the Testing Guidance table above.

Test ID

Test Forms

(View Appendix D for Test Descriptions)

Source

(View Appendix E for Source Details)

Pumping System Prefunctional Checklists

77

Pump Prefunctional Checklist

Multnomah/Kaplan

284

Pump Prefunctional Checklist

DOE/PECI

Pumping System Functional Test Procedures

272

Calibration and Leak-by Test Procedures

DOE/PECI

293

Boiler System Functional Test

DOE/PECI

362

Chilled Water System Verification Test Procedure

CoolTools/PG&E/Taylor

420

VFD Pump Application

DOE/PECI

1009

Hot Water System Pump Test  

PECI

1010

Chilled Water System Pump Test

PECI

1011

Condenser Water System Pump Test

PECI

1012

Data Collection Procedures for Hot Water Heating Pumps

PECI