Most of us think of data centers when we think “mission critical,” but the category goes into financial and health sectors as well. These five phases of commissioning can provide some additional peace of mind about performance, no matter which type of critical mission is at stake.

Mission critical (MC) refers to any part of a system (equipment, process, procedure, software, etc.) whose failure will result in death or serious injury to people, loss or severe damage to equipment, environmental harm, or the failure of business operations that are critical to the organization’s operation.

Types of MC projects include hospitals, data centers, and banks/financial industries. The types of systems and their components that combined in MC systems (MCS) are emergency distribution/UPS backup, heating and cooling plant, and critical communication infrastructure.

Today’s MC applications require commissioning authorities (CAs) to follow five basic steps of the commissioning process:
  • Level 1: Design/Submittal Review

  • Level 2: Factory Witness Testing

  • Level 3: Installation Observations, Equipment Startups, and Pre-Functional Sign-off

  • Level 4: Independent Electrical and Mechanical Sub-System and System Functional Testing

  • Level 5: Integrated Systems Testing
Many times, you will hear of business data centers being the main topic in an MC environment; however, MC commissioning inclusively takes in all systems and their supporting infrastructure as noted above. The commissioning of such facilities needs to be as complete and critical as the building that encloses these systems. Unplanned/unexpected downtime of these systems is considered unacceptable.

Due to the importance of the types of installations, the mechanical and electrical infrastructure is designed with redundancy to ensure no single point of failure can produce a system outage. Mechanical, heating, and cooling system performances are a necessity due to the nature of the environments they are servicing. The electrical systems of critical system environments must be capable of redundant backup in the event of loss of normal power. For these reasons, it is critical that the mechanical and electrical systems, working together, remain reliable and operating as designed. Therefore, commissioning is essential to ensure the systems are fully functional before the building is occupied and placed into service. A critical failure after these systems go online cannot occur due to the serious nature of what these systems support.


MCS commissioning is often challenging, especially when an existing functioning facility expands or upgrades, as these existing systems must remain operational 24/7 to support current operational occupied conditions. The CA is often required to provide staff during hours that the owner can provide a “shut-down,” e.g., weekends or evenings.

Today, energy conservation measures focused on reducing MCS operating costs challenge the design team and the facility team with the introduction of new, untested technology. To assist in the design challenges, CAs need to be brought into the project scope early in the design process.

It is essential that the electrical CA communicate with the mechanical CA during this design phase to address how their respective systems will work together. Within the design phase, both mechanical and electrical CAs will perform reviews prior to construction and share those reviews to better understand the complexity of sequences required to meet the performance intent of the systems. Early commissioning input provides an external third-party perspective on the design to ensure control and monitoring systems are installed to properly support collection of testing data that will be needed during the acceptance phase.

In addition, to support this work by the CAs, a commissioning specification and execution plan must be developed as a strategic road map to test the systems and bring them online to meet the owner’s needs. This plan must be detailed and specific to execute the plan in a step-by-step system integrated format during the startup and testing phase of the project, and it must include the proper roles and responsibilities for all parties involved from the owner to the general contractor and the subcontractors.


MC mechanical and electrical systems are designed for continuous service availability and uninterrupted service of the critical systems in the event of a failure. The designer must take these requirements into account in order to ensure the system will perform under varying operating conditions and failure scenarios.

A key role of the CA in the design phase is to provide insight to the design and future operation of the systems with owner comments on the design, reviewing for system performance, points of possible failure, and input into improving the operation and maintainability of the facility. CAs typically have a viewpoint much different from traditional designers. Commissioning design reviews include insights in construction coordination, system installations, systems and O&M activities, which provide a valuable asset to the owner and the building’s maintenance staff after construction is complete.

During the design process, the CA will:
  • Assist in the development and review of the owner’s project requirements (OPR)

  • Review the basis of design (BofD)

  • Perform design and specification reviews

  • Develop commissioning specifications

  • Prepare a commissioning plan

  • Schedule a controls integration meeting

  • Perform master project scheduling
Although it is already a LEED®-required document, the owner, design team, and CA should develop and implement an OPR. This is the foundation of any project, not just MC projects, and a critical set of documents that outlines and provides the vision and goals of the owner’s project. The CA reviews and provides input to this document along with the design team’s BofD. It also allows the CA a more complete understanding of the owner’s intent and final project deliverables that they are requiring and paying for. It allows the CA and design team a guideline to follow to ensure the owner’s needs are met.

Both of these documents are developed in the schematic phase, prior to equipment pre-purchase phase, and updated throughout the design and construction phases. This is to maintain current knowledge and understanding of the changes in the project that were approved by the owner.

In order to become familiar with and gain a complete understanding of the project, the CA provides three design reviews. These take place at the 100% design development phase, 60% mid-construction documents, and 90% construction documents. These design reviews are shared with the entire team for clarification where needed and become part of the final commissioning report.

Some items of importance for a MC design review are:
  • Inclusion of the commissioning specification/execution plan, formatted to coincide with the design team’s specifications within the design project documents. The commissioning specification/execution plan outlines the tasks and responsibilities of each participant in the project.

  • Prior to the closing out of the design phase and prior to distribution of the 100% contract documents, the CA facilitates a controls integration meeting with the design team. The owner can attend; however, more importantly, the owner’s facility engineer should attend this meeting when the sequences of operation and system performance requirements are discussed and finalized. This meeting provides the CA the format to discuss the testing phase for each system and the expectations of how the systems will be tested. This meeting provides the required information for the CA to draft the functional performance test (FPT) documentation. Within this discussion, and per the design requirements, the mechanical systems must be capable of maintaining space temperature and humidity for the type of occupancy, as well as redundancy in equipment and heating and cooling media sources. The electrical systems must be reliable, redundant, and flexible to adapt to changing load conditions. The electrical system must have the dedicated capacity and reliability for multiple load scenarios (load-shedding protocols must included a list of priority systems that absolutely cannot go down and others that can be brought down with little effect to the main system critical components).

  • UPS and generator backup are both critical and essential.

  • The operational protocols of both the mechanical and electrical systems must be clear, detailed, reliable, and prioritized along with educating the facility operators.
Within the pre-construction phase, it is important for the owner, CA, and the construction management team to sit down and integrate the five levels of commissioning within the master project schedule. Although the CA keeps a current schedule called the commissioning test plan and schedule, the input from the CA to the master project schedule is critical to the project. Why? All the steps that must occur from a commissioning standpoint are sequenced by other steps to be taken by the contractor/trades. These need to be discussed and understood prior to construction to ensure all parties are on the same page and all installation and performance expectations are met.


Factory witness testing provides the opportunity for all involved parties to witness how the main critical systems are assembled at the factory. Seeing a system in the factory offers the ability to review internal components not easily seen when fully assembled, to gain insight on how that system operates as well as the opportunity to meet the equipment manufacturing personnel, and to receive factory information not readily available in the field.


Construction in MC facilities is far more complex than other types of construction. As the installations of the systems progress, the CA must visit the site during phases of the installation of the systems to familiarize themselves with the construction status and progress. The duct, piping, and electrical systems must be reviewed and walked down, and the CA must be aware of any deviations in the design that could affect system performance, maintenance, or other conflictions that would create a substantial loss in construction progress.

The CA needs to utilize all available information to document the installation status and progress. These documents will include field reports, installation checklists, pre-functional documentation, and photographs to be compiled and later included in the final commissioning report. A deficiencies list from these installation site visits is shared with the team for corrective measures to be executed prior to the actual testing of the systems.

The CA, once approved submittals are available for systems, must develop commissioning integrated test documentation. These customized FPTs are for the specific application of equipment and break out the list of operational sequences into a step-by-step testing and operating format. These documents must follow the step-by-step process of testing the systems and must include integrated test protocols to ensure all mechanical and electrical systems operate as one integrated system, not just individual services and components.

Drafts of these test documents need to be distributed to the design, construction, and operational teams to be reviewed for clarification and questions. This is the last opportunity for all parties to have input and make corrections to the operational programming of systems. These clarifications and operational corrections will be included in the final functional test documents. These final functional test documents will be distributed to all parties for the final dry run testing by the trades prior to final commissioning FPT demonstrations.

During startup of critical systems (e.g., boilers, chillers, generators), at a minimum the CA needs to be present to observe the startup and testing process which aids in knowledge of how the final integrated operation will occur. All equipment startup documents will be included in the final commissioning report. Any air and water balancing needs to achieve the design requirements. All unsolvable balancing deficiencies must be brought to the attention of all parties to ensure a timely resolution is implemented.

During the construction phase, the CA will:
  • Schedule a commissioning kickoff meeting

  • Schedule regular commissioning meeting

  • Assist in developing a training plan

  • Attend construction and scheduling meetings to keep the commissioning test plan and schedule in sync with the overall master schedule

  • Review submittals and RFIs

  • Attend factory witness testing and document results

  • Create the pre-functional and finalize FPT procedures

  • Finalize the integrated testing script narratives

  • Perform site visits to observe component and system installations

  • Update corrective and pending issues logs

  • Witness startup of equipment

  • Witness NETA certified electrical testing


Commissioning demonstrations should be witnessed by members of the design team, construction team, CAs, and owner’s O&M teams. It is an opportunity for a final review and additional training review for the MC site operators and facility staff. As these systems are critical to maintaining the MC operations, personnel need to be fully familiar with the system design and operational intent of the OPR and BofD. During testing, long-term trending of critical MCS data points need to be compiled and analyzed to evaluate actual operational performance. Actual performance will require analysis to fine tune controls and to ensure optimized performance. During the warranty period, usually one year after substantial completion, performance of all systems need to be continually reviewed to ensure the system is operating under all seasonal conditions.

During FPT demonstrations, all deficiencies found are to be documented by the CA and then distributed to all parties to ensure corrections can be implemented in a timely manner. All these deficiencies must be resolved or repaired before the commencement of integrated testing. Once corrections are implemented, the systems affected require an additional review to ensure that when tested as a fully integrated system, they are operating as planned and no additional deficiencies are noted.

A crucial part of the training of site facility personnel is the ability for the key staff members to witness both the equipment startups and FPT acceptance.

During the acceptance phase, the CA will:
  • Coordinate, witness, and document FPT performed by the installing contractors and coordinate retesting as necessary until satisfactory performance is achieved. The FPT shall include operating the system and components through each of the written sequences of operation, and other significant modes and sequences, including startup, shutdown, unoccupied mode, manual mode, staging, miscellaneous alarms, power failure, security alarm when impacted, and interlocks with other systems or equipment.

  • Confirm air and water systems balancing by spot testing and or by reviewing completed reports and by selected site observation.

  • Coordinate and witness tests on respective HVAC equipment during both the heating and cooling season. However, some overwriting of control values to simulate conditions needs to be allowed. FPTs need to incorporate the use of control system trend logs and read-outs in order to provide a high level of confidence in proper system function.


The intent of integrated testing is to simulate the real-life conditions that the MC environment could be subjected to during its daily operation. In MC language, this phase is Level 5. Unlike the Level 4 discussed in acceptance, the integrated testing phase must verify the functions of every piece of critical equipment, since it functions as part of the entire interrelated system. A BofD incorporates redundant reliability and system-level redundancy and takes into consideration failure modes, since testing each scenario of failure is a necessity prior to the completion of the project

During integrated test demonstration, the use of resistive load banks is required to reproduce a full building design load (electrical and cooling demand). During this phase of demonstration, simulated multiple scenarios of failures such as power outages, loss of utility service, equipment failures, loss of communication, and human error will be demonstrated.


MCS commissioning is the higher end of commissioning where, unlike simplistic system commissioning, larger skill set demands are placed on the CA with high-end life safety commissioning experience. This commissioning scenario is not for the beginners and must be facilitated by a CA through the five levels of commissioning.ES