Commissioning critical facilities
Critical facilities, such as hospitals, laboratories, and data centers have demanding operational requirements that merit much more rigorous commissioning efforts than most other buildings.
Critical facilities, such as hospitals, laboratories, and data centers have demanding operational requirements that merit much more rigorous commissioning (Cx) efforts than most other buildings. Not only does this drive up Cx costs, but also the Cx benefits. In the broader view of building Cx, there are two main components: the process used to commission the facility and the personnel executing the Cx tasks. The quality of both of these components must be on par with the sophistication of the systems and operations and maintenance requirements of critical facilities.
The basic outline of the Cx process is generally agreed upon within the industry, such as embodied in ASHRAE Guideline 0-2005 , “The Commissioning Process,” including the involvement of the commissioning authority (CxA) beginning in the pre-design phase, to capture the owner’s project requirements, through the end of first 12 months of occupancy to enable four seasons of tuning. Sticking to this cradle-of-design to cradle-of-operations definition for critical facilities is imperative.
At the start, the building owner must determine the goals of the project leading to a building’s construction or renovation, and contract an independent third-party Cx team with sufficient knowledge, experience, and resources to conduct the Cx. The owner and Cx team’s leader (the CxA) must then work together to ensure that the Cx process is sufficiently detailed to achieve these objectives.
The Cx team’s experience, integrity, and ability to communicate with the project team are critical to the success of the project because the Cx team will be directing members of the project team to participate in the Cx process. Cx roles and responsibilities will be apportioned to the members of the project team, including:
Design team personnel
Regardless of the parties performing Cx, the experience and expertise of the individuals used must be sufficient to ensure the tests are written and executed to prove performance of the systems.
Depth and rigor
The primary factor that determines the Cx approach and delineates Cx for critical facilities from conventional buildings is the depth and rigor of the Cx process. All Cx activities should be considered, from those in the pre-design phase to those that are part of the occupancy and operations phase. To begin, determine the level of assurance necessary for your facility and then establish the level of effort to provide that assurance through the Cx process. This includes not only evaluating the depth of review and verification testing activities, but also which systems should be included. Depth and rigor of implementation are reflected in three primary areas:
Systems to be commissioned
Scope for testing components
Scope for testing systems alone and integrated.
Regarding the systems, there are systems that “must” be commissioned and others that “can” be optionally commissioned. Systems that must be commissioned are those that are critical facility operations, including electrical distribution and environmental control (HVAC) within the critical spaces. Life-safety systems, including fire detection, suppression, and alarm systems, also are critical, and so are building automation systems. The “can” systems are the ancillary systems, such as task lighting.
Regarding the components, each component within a system has a specific purpose and operation to fulfill that purpose. The extent to which that component is tested to ensure it operates correctly needs to be established based upon its impact on system performance. For example, if a space temperature needs to be controlled within 1 F, the appropriate sensor should be tested against that criterion, in its installed configuration, within the actual operating temperature range.
Regarding systems and integrated systems, they are designed to operate according to a specified sequence of operation. The sequence is a combined group of operational criteria to be maintained and system responses to data inputs to achieve those criteria. The testing of a critical system must test all the designed sequences, in all component configurations, in a real-world environment. If a chiller plant has three chillers and is designed to operate with all three in a lead/lag redundant configuration, the load-test needs to stage up to three chillers and all the way back down to one chiller. Also, this needs to be done with all three lead-chiller configurations. Furthermore, the coordination of pump start/stop, isolation valve open/close, and chiller start/stop/status needs to be tested to ensure it works in all configurations. These may seem redundant or over the top, but these scenarios will very likely occur in real life, and it’s impossible to tell if the systems will respond adequately unless they are tested.
Speaking of real life, systems operate in simultaneously, so integrated systems testing should duplicate real life operation of the facility as closely as possible. This will require simulating data center operations to check integrated HVAC and electrical performance. To mock-up data center operations, smaller suitcase load banks (30-kVa) can be spread evenly over the raised floor area to mimic the computer load. This enables integrated systems testing to ensure computer room air-conditioning units are providing uniform heat removal and staging properly. Infrared scan can be performed to identify hot spots. It is also important to research to local utility’s substation breaker reclosure scheme in order to develop real life “pull the plug” power outage testing scenarios. Often overlooked is a short time outage when a substation breaker recloses after clearing a fault.
As defined ASHRAE Guideline 0 the Cx process consists of multiple phases, each having prescribed tasks. The major tasks within each phase are listed below, with examples of the types of issues requiring significant definition and detail.
Pre-design phase: The pre-design phase lays the foundation for the Cx of the project. It is in this phase that the owner’s project requirements (OPR) is developed and the Cx scope and plan are determined. It is in this phase that the “depth and rigor” of the testing must be determined. Key steps in this phase include:
Develop the OPR
Determine the scope and budget of the Cx process
Develop the initial commissioning plan (CP).
The purpose of Cx is to ensure the delivered facility meets the OPR. For data centers, the OPR will include the required the Tier level, user requirements, environmental and safety requirements, redundancy levels, system expectations, operating efficiencies, and other owner expectations for the facility.
The CxA must work with the owner to identify the depth of testing, which will be the basis for the Cx scope. The CxA will develop a CP based on the Cx scope and OPR. The plan will identify all steps in the process, detailing the performance, documentation, and acceptance criteria. A CP for critical facilities will necessarily be much more detailed than that of a normal project. Clearly and thoroughly defining the requirements and the process from the project outset is necessary to achieve this end result.
Design phase: The design phase is where the design team creates construction documents in accordance with the OPR. During this phase, the CxA must ensure the systems and facility proposed will meet the OPR. It is also key to ensure the Cx requirements are detailed in the construction documents and in the CP. Major steps in this phase include:
Review Basis of Design (BOD)
Ensure Cx requirements are detailed in specifications
Define operator training requirements
CxA reviews design documents and resolves issues.
The CxA must review design documents from the BOD through the issuance of construction documents. The reviews need to focus on the documents ability to meet all aspects of the OPR with sufficient detail to ensure the contractors can fully understand the system requirements. It is essential that the documents do not leave the contractor to interpret any part of the system sequence, which often results in “this is how we always do it” or “this is how we did it on my last project” reasoning that leads to deficiencies.
The CxA and design team should meet to ensure that any issues identified are understood by the designers and resolved in a manner that satisfies the owner. In particular, design operating sequences need careful attention. The system sequences must be fully developed to ensure every operating condition is clearly defined, including normal operations, staging up/down, failure, and emergency sequences.
The specifications should detail the requirements of the contractors and define the Cx process, including testing plans and acceptance criteria. Critical facilities will require considerably more verification testing than other types of projects. The training requirements must be included in the appropriate equipment sections to ensure that sufficient training is provided to allow the owner’s O&M staff to operate the facility as intended.
Construction phase: This is the phase most people associate with Cx, however, if the steps in the previous phases have not been correctly implemented, this phase will be difficult to complete successfully. Key steps in this phase include:
Detailed test procedure development /execution
Installation verification and startup testing
The CxA will review the submittals to ensure the equipment will meet the OPR and can be properly commissioned. Key items to focus on in submittal review are part-load conditions due to concurrent operation of redundant equipment, and ensuring the operating sequences are detailed in control systems documents.
The approved submittals and O&M manuals will be used to develop the installation, startup, and functional testing procedures. The sequences in critical facilities are not standard. Generic or canned test procedures will not test all required sequences nor detail the expected results. The test procedures must detail all sequences and required results for the specific systems installed.
Verification of the HVAC systems balancing will need to be performed on 100% of the critical systems prior to functional testing. Functional testing of mechanical systems that cannot deliver or receive design flow will not provide accurate test results.
Because there so many complex interlocks and redundancies on systems in critical facilities, the CxA executing or witnessing tests must have the experience to identify possible failures or system shortcomings that are not obvious to the untrained eye. Simply observing tests and checking boxes that they occurred does not provide quality service.
Due to the complexity of critical facility operation, the O&M staff must be properly trained to understand the operation of all equipment, systems and sequences. For the sustainability of the site, the O&M staff must understand and be comfortable with all of the systems in all their conditions, from routine to fire, power, and other types of emergencies.
Operations and occupancy phase: The Cx team should assist in coordinating contractor callbacks and perform any deferred systems testing. Additionally, the Cx Team should work with the Owner’s Operations and Maintenance (O&M) staff to identify systems not operating efficiently, including causes and solutions to return the systems to efficient operation. Key steps in this phase include:
Warranty site visit
Enhanced O&M staff training
While performing the deferred testing and warranty site visit, the CxA should go over the operation of the facility with the O&M staff, identifying any issues the group may have with system/component operation. The CxA should provide additional training to the staff as necessary to provide the staff with the knowledge and comfort level in the system operation.
Who does what?
The second critical factor in the Cx approach is identifying the qualifications of the personnel required to facilitate the depth and rigor of the process. With all of the tasks associated with the process, how do you determine “Who does what?” The CxA and owner need to determine who will perform this testing and to what level, based upon the level of assurance necessary. Possible conflict of interest issues need to be evaluated when determining roles and responsibilities. The criticality of the systems to be commissioned will be a primary factor in deciding who is best suited to perform the Cx tasks.
For critical facilities, each entity should perform the work best suited to their strengths. Design engineers are very good at producing a set of construction documents to provide reality to the owner’s facility needs. Contractors are very good at providing labor and materials and constructing a facility in the most logical and economical manner to fit a schedule. CxA are very good at evaluating and testing systems to provide assurance the systems fulfill the requirements of the facility.
A knowledgeable third party CxA provides an independent point of view in the installation and operation of the systems. Knowledge in the design combined with experience operating the equipment and systems provides a unique set of skills that the CxA must possess. The perceived disadvantage of the independent CxA is that there is significant extra cost associated with this option. As we will explain later, this is not the case.
When selecting a Cx team, experience and diversity are a must. The requirements of the Cx team must be specific to ensure that the tests are written and witnessed by personnel with sufficient experience to verify that the systems will meet the OPR. Ensure that personnel have the appropriate level of experience required by each task in each process. This does not mean that a professional engineer with 20 years of experience needs to take a pitot tube duct traverse to ensure a restroom exhaust fan is delivering design flow. However, that level of expertise is required to verify all the required operating scenarios are included in the control sequences for the chiller plant of a data center.
Due to the increased complexity of today’s critical facility systems, it is not possible for one person to be an expert in all commissioned systems. The complexity of the HVAC, building automation, electrical, fire and life safety, and security systems requires discipline specific specialists in each area. For example, the CxA may have an incredibly strong background in building automation systems with the ability to determine if a control loop is properly tuned, but may not be well-suited to identify the requirements of and be knowledgeable in testing generator paralleling gear with load shedding. It is necessary to pull together multiple experts in the various disciplines to perform the discipline specific Cx activities.
The costs of commissioning
When considering the total initial cost of the Cx effort, keep in mind all the work performed by all the team members is included in the total cost. The two key words are total and initial. Total cost includes time spent by the CxA, contractors, equipment suppliers, construction management, and the design team. Cx has cost implications far beyond the initial hours spent by the team members during the Cx process; however, we will only focus on the initial costs for this discussion.
The total Cx costs can be divided into two primary groups; the CxA and the contractor. The contractor group includes the general contractor and/or construction manager, subcontractors, and equipment suppliers. The owner and design team also have costs directly related to the initial Cx effort, however, they are typically insignificant compared to the CxA and contractor group. The Cx approach greatly determines the total initial Cx cost and establishes how those costs are divided between the CxA and the contractor.
Figure 1 illustrates the relationship between the CxA involvement in a project and how the total cost is divided between the CxA and contractor. The percentage of the total cost attributed to the contractor varies inversely with CxA involvement. The percentage of the total cost attributed to the CxA varies directly with CxA involvement. The Cx approach will dictate where on line A-B a project resides.
For more discussion on Cx costs and how to hire a Cx provider, download the complete paper presented at the National Conference on Building Commissioning, April 21-24, at www.peci.org/ncbc .
The complex, redundant nature of crucial facilities requires Cx processes and teams with commensurate breadth, depth, and experience. Owners need to decide early what level of assurance their facilities require for safe, reliable, and cost-effective operations. And then owners need to contract and empower an independent third-party Cx authority to see the job through.
|Prendergast and Whorton are project managers/commissioning providers for many of GBA/ViroCon’s commissioning projects with more than 11 and 14 years experience, respectively. Riley is the lead electrical engineer for all of GBA/ViroCon’s commissioning projects and has been providing electrical systems start-up and commissioning services for more than 15 years.|