If the mechanical systems were to fail, the telecommunications equipment could fail within 15 min as space temperatures exceed equipment thresholds. A telecommunications provider must take extensive measures in the design, construction, and operation of the building’s mechanical systems to ensure a sustainable environment for the telecommunications equipment. A meticulously designed mechanical system will not operate effectively unless it is constructed and operated as designed.
A Clear Connection
MCI WorldCom’s Technical Facilities mission is to maximize reliability, survivability, maintainability, flexibility, and efficiency when constructing a new building or expanding an existing facility. MCI WorldCom engineers work extensively with the design engineers, contractors, and vendors to ensure their buildings meet the design mission.A critical part in meeting the level of reliability prescribed by the telecommunications industry is conducting a detailed and thorough commissioning process. This ensures that the design, construction, and operation of the building systems meet the reliability and survivability prescribed. The design and commissioning process ensures no single device will cause a system failure and, ultimately, a telecommunications failure.
Over the past few years, MCIW constructed several hundred thousand sq ft of telecommunications equipment space. MCIW’s commissioning process uses a 12-step program incorporating all facets of planning, design, construction, and system operation.
Step 1 — Design Criteria Log
MCIW starts the commissioning process by documenting the project’s design criteria or design intent. The design criteria evolve throughout the design process. Design engineers review MCIW’s design guide, which details the level of reliability and expectations of the equipment and systems operation. The guide focuses the consultants and gives them a basis from which to work in unison with MCIW engineers to form the design criteria.The project-specific design criteria document the building’s design basis and system operations. The criteria chronicle the design decisions relating to the construction and operation of the entire building. With regards to mechanical systems, the log states the operating conditions of the systems and the basis for these conditions.
Example: Chilled water supply-return temperatures are 48°F to 60°F. Chilled water supply temperature of 48°F keeps the computer room air conditioning units from performing unwanted dehumidification. In most cases, the log resides on the construction drawings. This provides a single-source document containing the design and operating basis for the building, the building engineer, and support personnel, since the building can expand multiple times. The design criteria give subsequent design teams the building background for integrating expansion with the existing building.
Step 2 — Commissioning Manual
The commissioning manual evolves from the construction drawings and the design criteria. Each piece of mechanical equipment on the drawings has a corresponding commissioning procedure in the manual. The manual chronicles how testing and commissioning proceed. Systematic descriptions detail the commissioning of each piece of equipment. The systematic descriptions detail the devices to test, how to test each device, the expected test results, and any related actions.The manual has two sections, with the first centering on individual equipment and components. Focusing first on the individual equipment or component level makes certain each device or sensor works properly. Once the component testing proves the devices operate properly, testing moves to a system level. Section II provides the system approach to the equipment operation. System operation details how one piece of equipment interacts with other equipment as a major event happens to the site. Section I shows the components act properly if a device fails or trips. Section II expands on the equipment failure and ensures the mechanical system as a whole performs properly.
Most MCIW systems have redundant or emergency systems to back up the main or lead equipment. For an air-handling unit providing cooling to the telecommunications equipment, a failure in the lead unit will signal the startup of the backup unit. This ensures the telecommunications equipment always receives proper cooling if a failure occurs. This is a simple example, but a more complex situation ensues with a loss of commercial power to the building.
Step 3 — Construction Documents & Commissioning Manual Review
MCIW thoroughly reviews construction documents several times during the design process. The review process identifies potential problems with the reliability and survivability of the site. The intent is to guarantee that the drawings provide sufficient detail to construct the building systems; configure systems and equipment to meet MCIW standards; and describe how the devices, equipment, and systems will operate and maintain the building.For large projects, MCIW uses a testing and balancing (TAB) firm to supplement the review process. The TAB firm provides expertise gained from hands-on exposure to air and water systems and experience in non-telecommunication settings. The TAB firm provides valuable information with regards to materials, equipment, and measuring devices not found in generic building specifications. Their review ensures valves, test ports, measuring devices, dampers, and access to components are properly located.
Other valuable information includes experience in sizing bypass lines, condenser water return, and filtering systems. A properly placed pressure tap or balancing valve can save quite a lot in operating costs, or the contractor having to return to the site to install the forgotten device.
Step 4 — Training
When constructing new facilities with different types of mechanical and controls systems, building support personnel need proper training. As the newer sites are larger, economies of scale predicate using chilled water systems over compressorized systems. Therefore, building support must receive training trained on chillers, cooling towers, chemical treatment, and controls. For buildings using DX-based systems, the engineer must understand the workings of small compressorized systems.More so, support personnel must be trained about the complexities of the building management system (bms). Programs are complex in nature due to the many pieces of equipment under control and the interaction of the building systems. Understanding trends and learning how to diagnose operational problems is the key to optimal performance.
Training on individual equipment does not provide all of the necessary information for operating the complete system. The support personnel must understand the cause and effect of the system components. For example, many different problems could cause a high chilled-water supply temperature. Combining training with commissioning provides the foundation for understanding the dynamics of the building systems.
Step 5 — Balance the Mechanical Systems
Balancing the system is critical to the correct operation of the building. Control sequences and equipment operation cannot perform correctly if the system is not balanced. MCIW only uses contractors with AABC certification because of the critical nature of the projects. A certified TAB firm uses the proper equipment with specially trained employees. The TAB firm is independent of the mechanical contractor to guard against any possible conflicts of interest. The TAB firm also confirms the equipment provides cooling and pumping capacities as selected. Then, the firm balances the system to certify that devices receive or produce the desired flow.
Example: An unbalanced chilled water system leaves balancing valves in an improper position. Pump produce higher- or lower-than-desired flow rates in various locations. Air-handling unit control valves don’t operate correctly because of pressure and flow variations through the coil. This translates to difficulty in controlling supply air temperature and ultimately hot and cold spots in the telecommunications equipment rooms. Equipment could then start to fail due to temperature fluctuations and severe hot spots.
Step 6 — Mandatory Commissioning Attendance
During commissioning, MCIW requires attendance of the mechanical contractor, building engineer, controls vendor, and design engineer, along with the MCIW mechanical engineer.Each party plays an integral part in certifying that the systems operate correctly. The mechanical contractor operates the equipment, since MCIW has not accepted the building. The building support personnel gain experience and training in the intended operation of the equipment. The controls vendor troubleshoots programming issues and reviews the sequences of operations. The design engineer assesses conformance to the design criteria and construction documents. The MCIW mechanical engineer directs and authorizes acceptance of the mechanical systems.
Full attendance allows for identifying the responsible party when corrective action is necessary. This is crucial in providing a documented step to the building acceptance as a whole.
Step 7 — Component Testing
MCIW’s equipment commissioning process begins by testing each of the system components. Personnel review the sequences and operations for each piece of equipment before testing the equipment. The review looks at the equipment testing procedures and the expected results of each test, so that everyone is knowledgeable of the proceedings and equipment operation. If problems surface, personnel will be able to properly identify them and make the necessary corrections with little discussion.
Component equipment testing confirms all devices and sequences work on individual equipment. As commissioning begins with the component testing, it will progress to the larger equipment and finally an integrated test of all building systems. First, testing begins with sensors to ensure they operate correctly, be it temperature, amperage, or airflow. Testing then proceeds to the equipment connected to the sensors.
Example: Testing begins with verifying operation of an air-handling unit freezestat. Tripping the freezestat will shut down the air-handling unit and the bms receives an alarm. Upon confirming that all individual sensors operate properly, testing moves to the supply air system as a whole. As MCIW has redundant units, testing proceeds to show that a failure with a unit will activate the redundant unit. The process repeats as the redundant unit operates as the lead unit and testing shows that the backup unit starts with the unit failure. Upon completion of Section I, the commissioning team begins integrated building testing.
Step 8 — Integrated Building Testing
Commissioning of individual pieces of equipment may not show how the entire system will respond if problems occur. Testing expands beyond just the mechanical systems to include the electrical and fire detection systems. An event with the electrical or fire detection systems directly impacts the operation of the mechanical system. A loss of power will cause a momentary shutdown of equipment, and it is necessary to know equipment will restart with power restoration. Initiating a general fire alarm must show equipment operates properly during the fire event. Integrated testing proves the equipment operates correctly as affected by other building systems. Section II of the commissioning manual describes how the building systems operate as a whole.Example: A failure to commercial power will cause the mechanical system to shutdown until the emergency generators start. Testing confirms that restoration of power will restart the mechanical equipment and all controls work properly. This includes tripping the main utility feed to the building. The results show chillers, pumps, towers and CRAC units drop off-line due to loss of power. The bms stays on-line as it receives power from the UPS. The bms issues equipment failure messages and successfully restarts the cooling equipment after the emergency generators come on-line. Testing continues by failing each device (chiller, pump, tower, etc.) to verify the redundant unit starts.
Step 9 — Resolving Problems
MCIW uses a 30-min rule for correcting programming or equipment problems. The time lost in waiting for the correction offsets remobilizing commissioning personnel. Mobilization includes positioning personnel in the proper locations and discussing the expected equipment operations. Waiting a short period for the corrections ensure processes are fresh and revisiting equipment operation are not necessary.For major corrections requiring more than 30 min, MCIW will move to the next piece of equipment to properly utilize valuable personnel time. Programmers or contractors can work off-hours to correct the problem without holding up the entire commissioning team. When coming back to a piece of equipment, MCIW will completely retest the equipment to verify equipment operation. With complex programming, major changes could affect other equipment operations. Complete retesting satisfies all parties on the equipment’s operation with every control sequence.
Step 10 — Off-Season Testing
One of the major mistakes in commissioning a building is expecting to complete the process during the initial system review. The initial system review only addresses testing the equipment under one seasonal condition. Most buildings take a full year to properly adjust all aspects of the building operations, as the changing seasons affect the conditions acting upon the building. A building will experience different operations during the year, and some devices may not be capable of operating during the commissioning process.Example: A heat exchanger and chiller switch-over cannot undergo full testing in the middle of June. Likewise, understanding the nuances of a fully loaded cooling system in January is not conducive to verifying proper building operation. Off-season testing confirms operation of the equipment during the winter and summer conditions, thereby making final adjustments for year-round operation.
Step 11 — Documentation
In order for the commissioning process to evolve, the project must document the results of commissioning events. MCIW engineers record the results for each step of the testing process in the commissioning manual. After each project, MCIW engineers modify or adjust procedures where improvement is necessary. This provides the basis for the next commissioning process.The documents provide each party with verification that the systems work as designed. A signed-off commissioning manual provides the building engineer documentation of the building system’s acceptance and provides a future reference. The manual documents that systems operate correctly, and thus provide the design engineers, TAB firm, and contractors with proof of MCI WorldCom’s acceptance of the building systems.
Step 12 — Engineering Support
MCIW project engineers provide design knowledge and system operation support to the building long after the construction crews leave the site. MCIW uses a resource network where the MCIW mechanical engineer supports the building and MCIW regional engineers with the building operations. The mechanical engineer answers questions on the building systems and provides aid in the design of system modifications. This forms a two-way communication process, as the mechanical engineer keeps tabs with the dynamics of building operations and gets feedback on how the systems truly operate. This provides valuable input for the design of the next facility or site expansion.Conclusion
Telecommunications buildings must possess characteristics maximizing reliability, survivability, and maintainability. As a three-legged stool cannot stand with one leg missing, a telecommunications building cannot survive by losing one of these characteristics. Verifying that the chillers operate to provide chilled water at the prescribed temperature ensures reliability. Verifying that a backup chiller, pump, or cooling tower operates during an equipment failure ensures survivability. Providing building support personnel with design intent and system training ensures the site’s maintainability. All must be present for the building to sustain telecommunications service.The 12–step commissioning process provides this confirmation to MCIW. MCIW feels that the critical nature of its facilities justifies the detailed commissioning process. A communications outage linked to a building system failure caused by not confirming the equipment operation would result in lost revenue far exceeding MCIW’s entire commissioning cost.
If operational problems surface from poor or no commissioning process, MCIW cannot wait the weeks, months, or sometimes years it takes to resolve problems with building systems. Commissioning is a proactive effort that MCIW uses effectively, rather than waiting for the ultimate (and more costly) reactive response associated with a building system failure. ES
