This checklist identifies Key Commissioning Test Requirements and Key Preparations and Cautions for testing chiller systems. When writing a test, use this checklist to help ensure that these key areas have been covered. The buttons following the checklist items link to supporting information within the Functional Testing Guide and the Control System Design Guide.
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Control System Design Guide |
Key Commissioning Test Requirements
- ___ 1. During design review, the following items should be addressed to avoid issues during functional testing:
- a) Sensor selection is sufficient to achieve the design control strategies.
- b) The refrigerant evacuation system, if provided, will keep the chiller room at negative pressure relative to adjacent areas.
- c) Individual HVAC system setpoints and reset schedules and the chilled water reset strategies are properly coordinated to ensure adequate system control and operation.
- d) Coordination between chilled water temperature and coil design should be checked. It is possible that the air temperature coming off the coil may not meet setpoint due to design limitations of the coil itself.
- a) Sensor selection is sufficient to achieve the design control strategies.
- ___ 2. The following are considered “prefunctional” checks that should be completed and verified prior to performing a functional test (note that this is not a comprehensive list of all prefunctional checks):
- a) In the design sequence of operations, all reset control strategy setpoints are coordinated with each other in order to avoid operational problems.
- b) All safeties, interlocks, and alarms are programmed (or hard-wired, if applicable) and functioning correctly.
- c) Isolation valves are installed and operating correctly.
- a) In the design sequence of operations, all reset control strategy setpoints are coordinated with each other in order to avoid operational problems.
- ___ 3. Sensor installation and calibration is sufficient to achieve the design control strategies.
- ___ 4. Chiller meets the specified performance requirements for temperature or part-load operation, as well as specified efficiency requirements.
- ___ 5. Chillers and primary CHW pumps stage up and down appropriately, per the sequence of operations.
- ___ 6. Time delay between chiller start/stop commands follows the design sequence of operations.
- ___ 7. Proper reset parameters are verified per the design sequence of operations The sequence may be revised to optimize system operation relative to atmospheric conditions and system load.
- ___ 8. Individual HVAC system setpoints and reset schedules and the chilled water reset strategies are properly coordinated to ensure adequate system control and operation.
- ___ 9. The chilled water supply temperature reset does not adversely impact supply air dehumidification.
- ___ 10. The proper control sequence and integration of all components is verified (including set points and reset strategies, start-up / shut down procedures, and time delays).
- ___ 11. PID loops generate the proper set points (e.g. CHW temperature) based on the reset parameters.
- ___ 12. All PID control loops achieve stability (i.e. no hunting) within a reasonable amount of time (typically no more than 5 minutes) after a significant load change, such as start-up, and automatic or manual recovery from shut down.
- ___ 13. Proper operation of a refrigerant monitoring system (if applicable) has been verified.
Key Preparations and Cautions
- 1. Successful execution of the chiller functional performance tests is dependent on the operation of ancillary equipment (for example, air handling units, heat pumps, process loads, cooling towers, and distribution pumps). At minimum, the prefunctional checklists should be completed on the components/systems served by the chiller and should be capable of safe temporary operation.
- 2. Safety and interlock tests, as well as some test procedures and loop tuning efforts (for example, high or low refrigerant cut-out setpoints, 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.
- 3. If testing the chiller during cold weather conditions, be aware of the potential impact on cooling towers and condenser water temperature if conditions are near freezing.
- 4. If the chiller is tested during off-peak months, ensure that the spaces served by the respective air distribution systems (air handling and terminal units) do not exceed safe temperatures. Many times systems will be tested while construction is still being completed within the spaces being served. Decreasing space temperatures well below ambient conditions may cause discomfort or create unsafe working conditions. Cold space conditions may also adversely impact various construction processes, like drying paint or sheetrock, curing concrete, or the application of adhesives.
- 5. All resets, except the one being tested, should be overridden to prevent unwanted system interaction during testing. Once the specific reset control strategy has been verified, the remaining resets should be reinstated. System operation should then be monitored to ensure all control processes remains stable.
- 6. If the chilled water temperature reset strategy is tested when there is minimal to no cooling load, be sure to test the high end of the reset (warmest chilled water supply temperature) first in order to minimize test time. It is easier and faster to take heat away from the loop rather than try and add to it when there is very little load on the system.
- 7. Enough load on the plant must exist in order to verify full chiller staging. This may require waiting to perform this test until peak cooling-season conditions occur.
Page last updated: September 11, 2006