There is a fairly specific order of testing associated with the functional testing process. Generally, testing should proceed from the support system level, to the component level, to the subsystem level, to the system level. In most cases, tests at the support system level and component level can occur concurrently. For example, the electrical contractor can verify the power distribution equipment associated with an air handling unit while the mechanical contractor is testing the coils and terminal equipment, and the control contractor is verifying sensor wiring and calibration. Simultaneous testing is also possible at the subsystem level as long as the various subsystems are not interdependent for the process under test.
For a typical air handling system, the general order of testing might be as follows:
1 Verify, start-up, and test the supporting utility systems such as the power distribution system, chilled water system, and steam system.
2 While the supporting utility systems are being tested, verify connections and calibration for the various control elements and safety interlocks associated with the system.
3 Verify, start-up and test the individual components directly served by the supporting utility systems like the cooling and heating coils and terminal equipment.
4 Test the integrity of any safety systems to the extent possible without operating the fan. These tests give the test team a measure of confidence that the system will be protected when the fan and its drive are started up. For example, a meter might be connected across the contacts on the system’s discharge static pressure limit switch and the set point changed so that it is above the ambient pressure to verify that the contacts change state and that the switch must be manually reset. As another example, the permissive interlock circuit should be verified to ensure that the outdoor air dampers are open on a 100% outdoor air unit prior to start-up. The functionality of the dampers and the limit switches and their settings should be verified prior to actually allowing the interlock to start the fans.
5 Verify, start-up, and test the supply fan, return fan and exhaust fans. Note that there may be a specific order in which the fans should be started to minimize over or under pressurization or maintain necessary flow relationships. One hundred percent outdoor air systems may require the simultaneous start-up of the supply and exhaust fans or temporary limits on the capacity capabilities of the fans to prevent pressurization problems when they first start.
6 Immediately complete testing the safety systems so that they will protect the system for the remainder of the test sequence.
7 Test control functions associated with individual system components like the mixed air low limit controller the discharge static pressure control.
8 Test integrated control functions where multiple components must function together. The discharge temperature control sequence is a common example because maintaining set point will require the stable, repeatable interaction of a cooling coil, heating coil, and economizer sequenced using one loop or as cascading control loops.
9 Test the system for totally integrated operation. Functions such of these involve the interaction of multiple independent components that control process variables that impact the inputs to the control loops associated with other process variables. Instability in one loop can quickly cascade into instability in other loops, and these instabilities may exist only under specific operating conditions. These tests include power failure response with restart and recovery, or testing the interactions of the building static pressure control system with the economizer cycle and the fan capacity control system. A system that was stable in all tested operating modes during a fall start-up may become unstable during colder weather when the effects of economizer damper non-linearity become more pronounced. These instabilities can have far reaching impacts on the performance of the building as can be seen from the example in the Integrated Operation and Control Module.
Documentation is an important part of any commissioning process. Having the documents listed below on hand for the functional testing process will be helpful for creating and performing the tests.
These documents will provide valuable information regarding the characteristics of the equipment installed on the project. If the commissioning provider has been involved in the shop drawing review process, then this information should already be available to them in their project files. If not, then copies should be obtained from the appropriate contractor(s) prior to developing functional tests.
Ideally, the machinery characteristics depicted on the shop drawings will be identical to the specified characteristics in the contract documents. However, substitutions made by the contractor during the buy-out process often result in machinery being provided that is similar to what was specified, but not identical. In a perfect world, the design team will have reviewed these differences. But occasionally equipment is approved or installed without approval and does not meet the specified performance requirements; thus, any effort to functionally test the equipment to prove that it meets the specified levels of performance will be unproductive. Pointing out a problem of this sort after the equipment has been purchased and installed will result in some heated discussions. Issues of this type must be resolved prior to functional testing since efforts aimed at proving unachievable performance will need to be repeated once the deficiency is corrected.
The bottom line is that it is highly desirable for the commissioning provider to be included in the shop drawing review process. When shop drawings are approved, a design shifts from concepts that exist as lines on paper and words in specifications to three-dimensional, bolted-in-place reality. And, while there may be some costs associated with modifications during the shop drawing review process, these costs will be far less than those associated with modifying it after it has been fabricated or installed. For example, a commissioning provider reviewing an air handling unit shop drawing might notice that there is no access section provided between the preheat and cooling coil, which makes cleaning coils and installing temperature control elements between the coils virtually impossible. Once the lines and words become physical walls, ducts, pipes and machinery, it may be nearly impossible to resolve the problem in a satisfactory, cost effective manner.
The benefits of time spent by the commissioning provider in reviewing shop drawings and submittals include:
1 The commissioning provider becomes familiar with the machinery that they will be testing.
2 The commissioning provider identifies commissioning and operations and maintenance issues for correction at a point in time where the costs associated with correction will be minimal.
3 An independent “second set of eyes” reviews the proposed equipment selections in light of the project’s design intent and specification requirements.
While the commissioning provider is not directly responsible for ensuring that the specified machinery and levels of performance are furnished and installed, they have a vested interest in this process since a successful test is unlikely unless the machinery is capable of the intended performance.
In most cases, installation inspection report forms are generated by the commissioning provider and are a part of the project documentation package associated with the commissioning process.
Documentation of verification checks can be accomplished by a variety of methods including:
· Collecting a signed certification letter or other verification from the responsible party.
· Having the responsible party sign the functional test procedure.
· Informal verification by the executor of the functional test.
Having this information readily available during the functional testing process can provide a handy reference if problems are encountered or questions arise regarding the systems readiness for testing.
Performance sheets are often generated by the commissioning provider but can also be standard forms provided by the manufacturer. The general intent is to provide a convenient place to document key system performance parameters during the start-up process. Examples of the information documented include motor voltages and amperage, component pressure drop, system temperatures and other physical parameters related to the system. Many times, the functional testing process will involve documenting these parameters as a system responds to a test process and then comparing them to the base case documented at start-up in the equipment performance sheets.
The equipment installation and operation and maintenance manuals are essential for reference while developing and performing a functional test. Often these manuals contain specific information and requirements that should either be verified prior to start-up or verified by functional testing. This information is also an important part of the documentation package generated by the commissioning process and will be a key component of any systems manual developed by the commissioning team.
Unless otherwise directed, the equipment suppliers will furnish the equipment installation and O&M manuals with their product when it is shipped. There are several potential problems with this approach.
· Often the information provided in this manner becomes part of the colorful paper that is seen blowing around the construction site when the field staff, intent on moving the machinery from the shipping trailer into the building, set the documentation aside and then forget to recover it after they complete the equipment setting operation.
· To develop good installation checklists, start-up plans, and functional testing plans, it is essential that the commissioning provider and construction team have access to this information prior to the arrival of the machinery.
Requesting that the suppliers provide the manuals immediately upon approval of the shop drawings can usually circumvent these problems. In most instances, obtaining the information at this point in the process is not a problem but may require some persistence on the part of the commissioning provider and contractors since it is not the normal sequence of events. Many manufacturers will be happy to provide the information earlier in the process because it allows them to satisfy one of their contractual obligations at a point in time when they are focused on the project rather than responding to a request for information that was provided but subsequently lost when the equipment arrived on site. Furnishing the information directly to the commissioning provider and contractor ensures that the information is going to the people who are directly responsible for including it in the construction documentation package.
In most instances, the balancing contractor will need to have substantially completed their balancing efforts prior to the final phases of functional testing of the air handling system. Assuming they have used proper techniques, the information they have gained in their efforts will be a good indicator of the system’s baseline performance and readiness for final testing. Reviewing the balance information prior to the final steps in the functional testing process because can provide insights into how the system is going to respond to tests. In some cases, the information in the balance report may result in a decision to delay final testing until a deficiency documented by the balancing process is corrected.
Having a good operating sequence is a critical component for developing a good functional test plan and a good system narrative for the projects system’s manual. If such a narrative does not exist, it is often in the commissioning provider’s best interest to work with or push the design team towards developing one. If the details of the operating sequence are not anticipated and addressed by the design process, then “mother nature” will bring them up for resolution in the field. As a result, the problems will be addressed reactively, rather than being addressed proactively by parties with a detailed understanding of the design intent.
Most people recognize the need to document the results of the functional tests as they move through the testing process. What is sometimes overlooked is to document the “as found” and “as left” conditions; the system state immediately prior to and after the test process.
The “as found” information can be critical to recovering from a problem encountered in a test because it usually represents a stable system state that can be achieved by the current system configuration, even if it is not the final state required by the design intent. If problems are uncovered by the functional test, returning the system to the as found state will allow the loads it serves to be maintained while a solution to the issue is developed. Documenting “as found” conditions typically involves noting flow rates, pressures, temperatures, and other system operating parameters as well as the set points, tuning parameters, valve and damper positions, and other inputs that create them. As a general rule, if you move something, or change a setting, note the original position or value before making the change.
Documenting the “as left” information serves several purposes. It formally records the operating state that the system was left in after testing. For a successful test sequence, this record documents successfully achieving design intent. If you are returning the system to the state it was in prior to the test, this documentation provides a good crosscheck against the “as found” information to verify that parameters are returned to the previous state. For additional discussion of “as left” conditions, refer to Section 14 - Returning to Normal.