HVAC Commissioning

HVAC System Commissioning
Author:Chen Qian
0 Introductions
Commissioning is the process of ensuring systems are designed, installed, functionally tested, and operated in conformance with the design intent. Commissioning begins with planning and includes design, construction, start-up, acceptance, and training and can be applied throughout the life of the building. Furthermore, the commissioning process encompasses and coordinates the traditionally separate functions of systems documentation, equipment start-up, control system calibration, testing and balancing, and performance testing.
This definition refers to the building as a total system, which includes the structural elements, building envelope, life safety features, security systems, elevators, escalators, plumbing, electrical, controls, and the HVAC. The commissioning plan needs to consider interface requirements of individual building elements through integrated testing.
1 Phases of Commissioning
1.1 Program Phase
The HVAC commissioning process begins with the program phase. This process should begin as close to project inception as possible. Information gathered in this phase will be used to develop the system design and enable evaluation of system performance.
Objectives of the HVAC commissioning process during the program phase are to
(a) Document the owner's requirements as specified in the Owner's Program,
(b) Select the commissioning authority,
(c) Identify and assign responsibilities,
(d) Document the initial design intent, and
(e) Begin development of the Commissioning Plan.
1.2 Program-Phase Procedure
1.21 Owner's Program
The Owner's Program outlines the owner's overall vision for the facility and expectations of how it will be used and operated. The Owner's Program may include building utilization, user needs, occupancy requirements, type of building construction, system functions, and energy, and air quality and environmental performance criteria.
The commissioning authority and the design team are selected at this time. It may also be possible to select the construction firm at this time.
1.22 Design Intent
Design intent defines the benchmark by which the success of a project is judged.
When approved, the design intent document shall be used as the starting point for the development of the Basis of Design as defined in clause 4 and referred to in case of ambiguities or uncertainties about project design. Changes to the design intent occurring during the course of the project shall be documented, reviewed, and approved. The design intent document is to be included in the contract documents as a reference.
1.23 Commissioning Plan
The Commissioning Plan is a document, or group of documents, that defines the commissioning process at the various stages of project development. It is continually evolving and is expanded as the design and construction of the HVAC system progresses.
1.24 Basis of Design
The Basis of Design shall respond to, and be consistent with, performance criteria specified in the design intent document. The Basis of Design will include the heating, ventilating, and air-conditioning requirements for each occupancy, activity, and/or physical area of the proposed facility with specific reference to ASHRAE or other applicable standards, local building codes, and environmental quality objectives.
1.25 HVAC System Design Concepts
A written document is prepared defining design assumptions; building energy performance;
performance standards of the proposed HVAC system; the most appropriate conceptual approach; space requirements for equipment, intakes, and exhausts; zoning; and other HVAC system requirements that affect building use and aesthetics.
1.3 System Manual
The Systems Manual is to provide to the owner information needed to understand, operate, and maintain each system and inform others about each system.
At this time, the Systems Manual will contain a statement that conveys the required functional operation of the HVAC and related life-safety systems in all normal and emergency modes of operation. Information on space requirements for equipment, intake and exhaust location limitations, zoning criteria, and other HVAC system requirements affecting building use and aesthetics should be included if applicable.
2.1 Design Phase
The design phase of the HVAC commissioning process begins with the preparation of schematic design documents.
The objectives of the HVAC commissioning process during the design phase are to
(a) Document the design intent as it evolves;
(b) Continue development of the Commissioning Plan;
(c) Develop the commissioning specification;
(d) Prepare contract documents that clearly reveal, describe, and fulfill the design intent;
(e) Review and accept contract documents for compliance with design intent; and
(f) Coordinate other mechanical, electrical, fire safety, and life-safety service requirements with HVAC layout, equipment, and systems.
2.2 Design-Phase Procedures
2.21 Commissioning Plan
During the design phase, the approved preliminary Commissioning Plan is expanded to detail the activities of all participants involved in the commissioning process.
2.22 Commissioning Specification
The HVAC commissioning specification is part of the project specification. This is required to contractually implement the post-design phases of the process. The commissioning specification is a detailed description of the scope and objective of the commissioning process during the construction, acceptance, and post-acceptance phases of a project. It must specify the scope of work, roles, responsibilities, and requirements of each commissioning team member. It is needed by contractors to bid the services required.
The commissioning specification shall detail the acceptance phase procedures for verification and functional performance testing, as well as other required acceptance phase procedures.
3.1 Construction Phase
During the construction phase of the HVAC commissioning process, the HVAC system is installed, started, and put into operation.
The objectives of the HVAC commissioning process during the construction phase are to
(a) Review submittals;
(b) Finalize details of the Commissioning Plan;
(c) Conduct periodic commissioning team meetings;
(d) Observe construction, installation, start-up, operation, and testing and balancing; and
(e) Conduct O&M training.
During construction of the HVAC system, the O&M personnel should observe and monitor construction of the HVAC systems. They will develop a better understanding of the system's intended operation and performance and become familiar with the physical installation, particularly the location of equipment and devices, which may be hidden when construction is complete.
3.2 Construction-Phase Procedures
During the construction phase, the following activities shall be assigned:
(a) Preparing design changes,
(b) Reviewing submittals,
(c) Detailing the Commissioning Plan,
(d) Creating project-specific procedures and checklists,
(e) Making necessary observations and inspections,
(f) Updating documentation,
(g) Reporting progress and deficiencies to all parties involved, and
(h) Coordinating training of operations and maintenance personnel.
Observations of the progress of construction are important for updating the Commissioning Plan, particularly with respect to the scheduling of activities. In addition to construction requirements, observations should be conducted to ensure compliance with manufacturers' installation instructions. These observations should include, but not be limited to, the following HVAC subsystems and other interfacing building systems and activities:
(a) Air-handling and distribution and ventilation systems
(b) Heating systems
(c) Cooling systems
(d) Hydronic systems
(e) Piping
(f) Controls
(g) Building automation systems
(h) Life safety systems
(i) Energy supply systems
(j) Building envelope
(k) On-site equipment storage
(l) Indoor air quality methods and procedures
(m) Compliance with codes and standards
(n) Witness testing, including flushing, cleaning, pressure testing, and leakage testing
Controls testing and calibration should begin concurrent with, and be completed prior to, the completion of the testing, adjusting, and balancing work. Some verification procedures as indicated in clause 8 may occur here.
Testing, adjusting, and balancing work must be performed prior to acceptance procedures. Operational tests should also be conducted on equipment, duct, pipe, and control systems to verify that pressures, flow rates, and control functions meet design requirements.
3.3 Submittals
Submittals should include shop drawings, equipment submittals, and testing and balancing procedures
and forms. Submittals should also include test procedures, report forms, data sheets, and checklists that will be used in the functional performance testing.
Equipment submittals should include complete full and part-load performance data covering the entire operating range for each piece of equipment, especially heat exchange equipment such as boilers, furnaces, chillers, condensing units, heat exchangers, and coils. Data should include capacity, flow rates, velocity, pressure losses, power, rpm, electrical data, and all other pertinent data as necessary. After review of equipment submittals, the equipment operations and maintenance information (including parts lists, installation instructions, and special tool needs) should be submitted in accordance with specifications requirements.
Given the importance of the control systems to proper operation of the HVAC system, control submittals must be carefully reviewed to ensure they include all information needed by the operations and maintenance staff to keep the control systems adjusted and calibrated. Information should include the following:
(a) A fully labeled control piping or wiring schematic that shows point-to-point piping and wiring and includes all performance parameters such as set points, throttling ranges, actions, spans, proportional bands, and other control component adjustment or setting data. Locations of pneumatic test ports and electronic system terminal strips should be indicated on the schematic drawings.
(b) Sequence of operation (narrative description of control system functions) cross-referenced to the control schematics and elementary electrical ladder diagrams.
(c) Specification sheets for each control component, including calibration data.
(d) Flow charts or other documentation of application software specific to the project.
(e) Data to confirm interfaces to controlled equipment for compatibility and physical connection requirements.
3.4 Commissioning Plan
The Commissioning Plan shall be updated to define the on-site activities required for implementing
the commissioning specifications. This plan must be project-specific and reflect the actual equipment that will be installed. This Commissioning Plan should
(a) Detail the schedule of inspections during construction,
(b) Develop the schedule for verification and functional performance tests,
(c) Define the process for reporting and correcting any deficiencies identified, and
(d) Detail any training sessions for operations and maintenance personnel that are to take place during this phase.
3.5 Documentation
All commissioning activities that occur during the construction phase shall be documented, including, but not limited to. The documentation during the construction phase shall be updated to match the equipment supplied on the project.
4.1 Acceptance Phase
During the acceptance phase of the HVAC commissioning process, verification, functional performance tests, and other acceptance procedures will take place.
The objectives of the HVAC commissioning process in the acceptance phase are to
(a) Verify the accuracy of the final TAB report,
(b) Verify that the HVAC system complies with the contract documents,
(c) Establish an as-built record of the HVAC system performance,
(d) Complete the as-built records,
(e) Complete the commissioning report,
(f) Complete the Systems Manual, and
(g) Turn over the building to the owner.
4.2 Prerequisites to Acceptance Procedures
Before the acceptance procedures can start, the following shall be observed and documented:
(a) HVAC systems and associated subsystems have been completed, calibrated, and started up and are believed to be operating in accordance with contract documents.
(b) Automatic control systems have been completed and calibrated and are believed to be operating in accordance with contract documents.
(c) Testing, adjusting, and balancing procedures have been completed, and all TAB reports have been submitted and reviewed and discrepancies corrected and accepted.
4.3 Verification
Verification comprises a full range of checks and tests to determine that all components, equipment, systems, and interfaces between systems operate in accordance with contract documents.
4.31 Verification Procedures
4.311 Operating Tests and Checks.
Verification procedures include the following tests and checks.
(a) All verification procedures will be directed and witnessed and the results certified. The Commissioning Plan identifies responsibilities and details the procedures to be followed.
(b) The system equipment, e.g., chiller, boiler, HVAC unit, exhaust blowers, will be set into the operating mode to be tested, e.g., normal shutdown, normal auto position, normal manual position, unoccupied cycle, emergency power, and alarm conditions.
(c) Each operating cycle shall be tested after it has been running for a specified period of hours and
is operating in a steady-state condition.
(d) The position of each device and interlock that is identified on the checklist shall be inspected and verified. Each item shall be signed off as acceptable (yes) or failed (no).
(e) This test will be repeated for each operating cycle that applies to the HVAC system being tested.
(f) Operating checks shall include all safety cutouts, alarms, and interlocks with smoke control and life safety systems during all modes of operation of the HVAC system.
(g) If an operating deficiency is observed during a test, appropriate comments shall be added to the checklist data sheet.
(h) Verification of the interface of the monitoring and control system and the TAB criteria shall include the following steps:
1. Verify flow rates for air and water systems in all modes of operation of the HVAC system.
2. Verify operation of the terminal units in all modes of operation.
3. Verify minimum outdoor air intake in all modes of operation and at minimum and maximum total
airflow rates.
4. Verify building pressurization.
5. Verify total exhaust airflow and total outdoor air intake (OAI).
6. Verify operation of the IAQ monitoring system.
(i) Verification of the proper response of monitoring and control system controllers and sensors shall include the following steps:
1. For each controller or sensor, record the indicated monitoring and control system reading and the test instrument reading.
2. If the initial test indicates that the test reading is outside the control range of the installed device, the calibration of the installed device shall be checked and adjusted as required. The deficient device shall be retested and the results recorded on the checklist data sheet.
4.312 Verification of the Final TAB Report.
Verification procedures include the following tests and checks:
(a) The field verification of the final TAB report will be directed and witnessed and the results certified. The Commissioning Plan identifies responsibilities and details the procedures to be followed.
(b) A random sample of the report data shall be selected for verification. Report data are defined as the air velocity at a specific outlet, air or water flow rate, indicated differential pressure, electrical or sound measurement, or any other measurement that is applicable.
(c) The testing and balancing contractor shall be given sufficient advance notice of the date of field verification. However, the contractor shall not be informed in advance of the data points to be verified. The testing and balancing contractor must use the same instrument (by model and serial number) that was used when the original data were determined.
(d) Failure of an item is defined as follows:
1. For all readings other than sound, a deviation of more than 10%.
2. For sound pressure readings, a deviation of 3 decibels. Variations in background noise must be considered.
(e) A failure of more than 10% of the selected items shall result in the failure of acceptance of the final TAB report.
(f) Failure of the final TAB report shall require the testing and balancing contractor to complete the following work at no additional cost:
1. Any system failing the verification procedure must be re-balanced.
2. New total system TAB reports must be provided.
3. Field verification of the new TAB report must be performed.
4.32 Deficiencies.
If any deficiencies are identified in the HVAC systems or at the interface with other building systems during verification, the deficiencies must be documented and reported to the commissioning team.
4.33 Verification Report.
The final tabulated checklist data sheets shall be assembled in a verification report and submitted to the commissioning team for review.
4.4 Certificate of Readiness.
A Certificate of Readiness shall be issued stating that all equipment, systems, and controls are now complete and ready for functional performance testing to begin.
4.5 Functional Performance Testing
Functional performance testing should progress from tests of individual components of the central equipment and systems, including chillers, cooling towers, boilers, and pumping systems, to tests of the systems that distribute the HVAC services throughout the building.
For each test, the responsible party will install the measuring instruments and logging devices to record the test data for the required test period. The instrumentation shall meter and record all operating conditions to allow for complete evaluation of the test results.
Measurements will be required to allow for calculation of total capacity of the system for each mode of operation under test. These modes of operation include:
(a) Occupied/unoccupied
(b) Warm up/cool down
(c) Economizer cycle
(d) Emergency power supply
(e) Life safety/safety systems
1. Smoke control
2. Fire safety
3. Stair pressurization system
(f) Temporary upset of system operation
(g) Partial occupancy conditions
(h) Special cycles
If any test cannot be completed because of a deficiency outside the scope of the HVAC system, the deficiency shall be documented and reported to the owner. The deficiencies should be resolved and corrected by the appropriate parties and functional performance tests rescheduled.
If it is determined that the HVAC system is constructed in accordance with contract documents and that the performance deficiencies are not covered in the contract documents, a decision must be made as to whether any modifications required to bring the performance of the HVAC system up to the design intent will be implemented or if the functional performance testing will be accepted as submitted. If corrective work is performed, a determination must be made as to whether a portion of, or all, functional performance testing should be repeated and a revised report submitted.
Documentation developed during the acceptance phase consists of the following:
(a) Verification checklist data sheets.
(b) Verification report.
(c) Certificate of readiness.
(d) Functional performance test data records.
(e) System operation description and final design intent.
(f) Commissioning Report.
4.6 Final Acceptance
To conclude the acceptance phase, as-built documentation must be compiled, the Commissioning Report and Systems Manual must be completed and submitted, and recommendation for acceptance of the facility determined. It is possible that some acceptance procedures (such as off-season tests) may not have yet been completed, but this should not impede final acceptance.
5. Post-Acceptance Commissioning
Post-acceptance commissioning is the continued adjustment, optimization, and modification of the HVAC system to meet specified requirements. It may be utilized on any facility that has previously been commissioned consistent with this guideline. It includes updating documentation to reflect minor set point adjustments, system maintenance and calibration, major system modifications, and provision of ongoing training of operations and maintenance personnel.
The objective of post-acceptance commissioning is to maintain the performance of the HVAC system throughout the useful life of the facility in accordance with the current design intent.
5.1 Post-Acceptance Commissioning Requirements and Procedures
There are three identifiable levels of post-acceptance commissioning:
(a) ongoing commissioning activities,
(b) minor changes or modifications to HVAC systems and changes to occupancy and/or layout, and
(c) major modifications to facility layout and/or systems.
Major modifications require the same efforts, expanded to suit full system commissioning of any HVAC system or subsystem impacted by modifications. Overall system performance must be reestablished. When major modifications are carried out, commissioning procedures in accordance with clauses 5 through 8 should be undertaken, as applicable to the modification.
5.2 Documentation.
The final acceptance documentation will be an as-built record of the HVAC system's performance and operation. The Systems Manual will be updated to include any modifications that were made.