A building is a total system containing many parts, including:
- Structural systems
- Building envelope
- Life safety systems (sprinkler, fire and smoke control)
- Security systems
- People moving systems (elevators and escalators)
- Plumbing systems
- Electrical systems
- HVAC systems
- Building Automation System (BAS)
Many of these systems are interconnected and interact with other systems (such as electrical, plumbing, and HVAC) and include subsystems (such as the BAS). The high cost of energy and the current concerns about indoor air quality and environmental pollution reinforces the need to ensure the building systems operate in conformity with the requirements of the design specifications.
Commissioning is defined as the planned, systematic, and documented process of inspecting and testing that a building's various systems performance meets the needs and specifications of the owner and his representative (architect, engineer, project manager.
The objectives of commissioning include:
- To advance the building from the stage of static completion to a working order that meets the specified requirements
- To assure the owner gets what was paid for
- To turn over to the owner a fully and properly functioning building ready for occupancy
- To fully recover the capital investment over the life of the building through management, efficiency, and user satisfaction.
Commissioning is the logical step-by-step procedure whereby someone (representing the owners' interest) witnesses appropriate tests of all components and systems to validate performance as designed and specified and that they are ready for active service. ASHRAE defines the commissioning of an installation as:
ASHRAE refers to the building as a total system including the parts listed above, and further repeats the definition substituting building system for installation and system for buildings.
The commissioning authority, preferably a third-party, should be a qualified person, company, or agency that implements the overall commissioning process in cooperation with the commissioning team. The commissioning authority should be an experienced professional, preferably with a PE so that interaction with the design team is at a professional level.
The owner can appoint the commissioning authority to be someone on staff, a third party (individual or firm) or other qualified entity. The size and makeup of the team responsible for conducting the commissioning depends on the size and complexity of the project. The commissioning role should not be confused with that of the construction manager.
There are four major phases in the commissioning process:
Ideally, the commissioning process starts at the beginning of a project and is a continuing process that performs a number of functions. The extent and degree to which these functions are performed will again depend on the size and complexity of the project.
- Pre-design phase - Set the commissioning parameters and responsibilities, identify the team members, documents the basis to develop the building design criteria including building use, occupancy, design assumptions, building construction, loads and interior zoning, cost factors, and subsequent design compromises.
- Design phase - Develop commissioning requirements for each building system, including the intended operation, and performance; develop the commissioning plan, including documentation, verification and maintenance requirements.
- Construction phase - Prior to installation, verify items to be installed are in accordance with the specifications, review and document shop drawings, installation and maintenance manuals. Oversee pressure and leak testing, flushing, chemical or other such cleaning, and fluid flow adjustments. Perform pre-start inspections upon completion of systems construction. Oversee test and balance work that commences after the prestart inspection. After any test and balance work is completed, begin performing the functional testing of equipment, subsystems, interacting systems, and components.
- Acceptance phase - The reiterative procedures include verifying and documenting:
- Equipment and subsystem capacity and seasonal performance tests, correlating the results to the design criteria
- Environmental Testing
- Deferred functional performance tests
- Itemized list of corrective measures
- Intersystem functional tests
- Fine tuning including reassessment of design values and control setpoints to achieve the required performance
- Submission and receipt of the "as built" drawings
- Prepare acceptance documentation
- Operator Training- The Operator participation in helping or watching the initial startup, testing and adjusting of each system should be an important part of the training strategy with instruction coming from various qualified sources, such as:
- The appropriate team member should instruct the operators on the intended operation and limitations of each system during full- and part-load conditions, indoor air quality control, energy conservation and emergency procedures.
- Each major equipment manufacturer and system supplier should instruct on their installed equipment including a review of the O&M manuals, recommended maintenance and calibration procedures, schedule, spare parts inventory, and parts availability.
- The test and balance contractor should provide training in the testing and ongoing adjustment and rebalancing procedures necessary to maintain and verify proper performance.
- Final Acceptance
- Post-Acceptance Phases - continuing periodic retesting of major systems and subsystems, particularly after any alterations and changes. Identify procedures for scheduling preventive maintenance, and handling and documenting of complaints. Continuing complaints may indicate the need for recommissioning of affected systems.
An overriding factor of importance is that the specification documents describe how each system is designed and defines the acceptable tolerances. Inspection during construction is part of good engineering practice and should not be overlooked or minimized.
This diagram indicates some of the acceptance phase checklist items of one step in commissioning a fan - the static prefunctional inspection. In addition functional tests are conducted to confirm the fan operates as required in combination with other components of the overall HVAC system, such as:
- Safety shutdowns in response to smoke detector and freeze alarms; test alarms for manual or automatic reset as appropriate.
- Proper control from building automation system (BAS)
- Automatic regulation by appropriate control inputs
- Interlocking of the fan with other equipment and checking that other fan operation does not cause the fan to freewheel backwards, which could trip a Variable Speed Drive on startup.
The O&M staff should be part of the commissioning process during the inspection and tests, including a thorough walk-around and inspection followed by an explanation of the system operation.
Building Commissioning Cost
Commissioning can be very expensive and the cost varies with size, complexity and number of systems to be tested. References indicate the cost can range from 1.5 to 6 percent of the mechanical cost, 2 to 3 percent of the electrical cost, and 1 to 3 percent of the total building cost.
This cost is justified by even the partial loss of efficiency in building operation, which could cost much more than the commissioning cost. In addition, excessive callbacks and warranty claims and expense can also cost the designer, contractor, manufacturer and owner a lot of time and money, not to mention the aggravation. Projects where the environmental and life safety aspects are critical obviously deserve a full commissioning investment. Certainly, not all commercial buildings fall into this category.
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