Process versus technical commissioning
While processing commissioning handles all the paperwork and background research, technical commissioning ensures each building systems works as specified.
Commissioning has become an accepted and necessary part of the construction process especially in the mechanical contracting field. The word commissioning is used in everyday discussions by owners and engineers without a real understanding of the processes involved, however.
ASHRAE has defined commissioning as: “Commissioning is the process of ensuring that systems are designed, installed, functionally tested, and capable of being operated and maintained to perform in conformity with the design intent.”
This definition goes a long way toward defining the intent of the commission process. Two methods of commissioning have evolved: process commissioning and technical commissioning.
Process commissioning is a method of commissioning that concentrates on ensuring that documentation has been completed to show various aspects of the construction process have been tested and acknowledged to be working by the installing contractor. The process commissioning agent will assemble design review reports from the engineer that shows how the engineer addressed the owner’s project requirements. This type of commissioning collects all the field tests performed by the various mechanical contracting trades that show all equipment, pipe, duct, controls, and accessories were installed as specified.
Similar startup reports completed by the contractors show all equipment was started and run in accordance with the manufacturer’s requirements are also collected. Checkout and test and balance (TAB) contractor’s reports are reviewed for accuracy.
O&M manuals and training information are reviewed for conformance to the specification requirements. Random room sampling may be done to verify that systems are controlling properly. It is not necessary for the process commissioning agent to have detailed technical knowledge of the project.
Process commissioning relies on the technical expertise of others to verify system operation. The process commissioner’s area of expertise is the commissioning process itself. A final report with all the appropriate data will be assembled and presented to the owner as proof that the specifications were followed. The commissioning agent will state, “Here is the report to prove that the project was commissioned. Our process commissioning has been completed.”
Technical commissioning the system, and an intimate understanding of system controls and of the TAB process.
Because the technical commissioning agent is working for the owner to ensure that the project is designed and constructed to operate in accordance with the owner’s requirements, this is a professional service and should be contracted directly with the owner. The technical commissioning agent provides the biggest benefit to the owner by being involved in the initial stage of the design process. Design decisions that affect cost and operation are made during the early design stages; previous experience of the technical commissioning agent is invaluable in helping keep design decisions on task.
The technical commissioner also ensures that the proper contract language, forms, commissioning plan , and outline of commissioning-related work are placed in the contract documents. This is done to help the contractors understand their responsibilities in the technical commissioning process and also to place the responsibility for the proper implementation of the commissioning process onto the mechanical contracting firms.
During the construction phase of the project, the differences between the process and technical commissioning become more apparent. While the process commissioner reviews the construction commissioning forms completed by the contractors, the technical commissioning agent is involved in periodic site inspections to actually observe and review the installation and startup methods to ensure that the contractor’s reports are being completed in the proper manner and systems are operating properly.
The technical commissioning process becomes more labor-intensive in the final phases of the construction process. While the process commissioner may review the final TAB report, the technical commissioning agent will monitor and observe the setup procedures that are used by the TAB contractor. The process used to set up the initial air handler and terminal units are observed to ensure the TAB contractor actually understands the implementation of proper TAB procedures. When the final TAB report is completed, the technical commissioner will verify all readings to ensure the system is balanced properly.
The process commissioner may review the control testing and setup procedures. The technical commissioning agent will perform a point-to-point checkout on 100% of all loops to verify that each sensor and loop is communicating with the proper devices, and will verify that control components are installed, operating, and calibrated properly.
Once the control and TAB testing is complete and systems are physically observed and verified for proper operation, functional performance tests are conducted on 100% of the systems with the control contractor to conclusively prove the systems operate in the automatic mode and maintain system setpoints within design and prove the system loops are stable. Where the process commissioner will randomly sample a small percentage of spaces, the technical commissioner will physically test 100% of all loops to verify that each loop controls and is stable. This is accomplished by physically changing a setpoint and trending the control response over time. This trend graph of actual measured conditions over time compared with setpoints is visible proof that the systems work as intended.
For example a space thermostat may be adjusted from 75 to 72 F, the trend graph will show how the room temperature responds to this change and will either prove or disprove that the room thermostat loop controls the space temperature to the owner’s project requirements. The project is not complete until all loops are proven to be working as intended. All data are assembled and given to the owner as the final commissioning report .
When completed, the commissioning firm will provide the owner with a final report and state, “Here is our report. We have personally tested every single loop and observed the operation of every single component. We have graphs to show that each loop performs as required. We guarantee your building will work as intended because we were the people that performed the final testing.”
The bottom line--and most important aspect to the owner--is that a technical commissioning agent performed all appropriate tests, and that the building operates according to the owner’s project requirements.