This project was an expansion of an existing Critical Operations Facility/Data Center to essentially double the size of the Data Center and its supporting Energy Center (Electric Service Rooms). The project provided a completely redundant electrical service, and increased the overall cooling capacity, as well as changing the cooling system. The existing Data Center was 16,100 square feet, the existing Energy Center was 3,620 square feet and the Data Center Room and Energy Center were 13,650 square feet and 3,930 square feet respectively. This design also planned for the retrofit/modification of the existing Data Center to accommodate the increased mechanical and electrical loads from modern day data center components such as blade servers.
Due to the increased operating costs and heat loads which are now more prevalent in a high density Data Center utilizing blade servers, the cooling system selection was based on the result of a Life Cycle Cost Analysis which compared split system air cooled equipment, a condenser water system with compressorized units in the Data Center, and a central chilled water system utilizing chilled water units within the Data Center. The Life Cycle Cost Analysis resulted in the selection of the central chilled water system, basically due to system efficiency and reduced operating costs.
The chilled water system consists of three (3) nominal 225 ton air cooled, R-22 refrigerant, centrifugal chillers, and a 16° distribution loop differential (40°F - 56°F). Based on heat load data for the Day 1 build-out and projected loads for the future provided by the Owner, the cooling system load was determined to be 450 tons. Three (3) chillers were provided to provide an N+1 level redundancy. A packaged pumping system utilizing close-coupled end-suction base mounted pumps was designed as no mechanical equipment room space was available in the footprint of the building and all equipment associated with the chilled water system was roof mounted. The use of close coupled pumps allowed the overall footprint of the pump house/enclosure to be minimized while allowing required/appropriate clearance around all components for maintenance. The pump house also includes variable frequency drives for the circulating pumps, expansion tanks, chemical treatment systems, and the make-up water connection to the chilled water system. The chilled water system also utilizes a closed circuit fluid cooler to allow economizer/free cooling operation when outdoor air conditions are capable of providing sufficient cooling for the Data Center. This economizer is located on grade adjacent to the building as limited low roof space was available and roof penetrations were minimized.
The piping distribution system consists of two (2) independent chilled water loops located below a 24" raised floor. The piping loops are redundant in their entirety, from the roof mounted pump house to the equipment run out connections. Distribution is variable flow controlled by a prime valve and variable frequency drives that modulate circulating pump speed. The chilled water distribution piping is routed in a reverse return manner and connections have been provided for extension to the existing Data Center when the split air cooled system serving that portion of the facility is changed-out to chilled water.
Terminal equipment delivering conditioned air to the Data Center consists of perimeter computer room air conditioners (CRAC) units and vertical in-row coolers located within the rows of the high density racks of the Data Center. The CRAC units provide a general level of conditioning (temperature and humidity) for the entire Data Center footprint. These units are the standard downflow units that deliver conditioned air below the raised floor. The return air is ducted from a point just below the Data Center ceiling to minimize stratification of hot air. The in-row coolers provide both cooling capacity and required airflow to contain hot air (80°F - 95°F) in the hot aisles and provide room neutral air (±72°F) at the inlet to the blade server racks. This approach was utilized as maintaining proper airflow across the blade servers and proper cooling/heat removal is critical to the continued operation of blade servers.
The branch chilled water piping to the perimeter CRAC units consists of independent run-outs to each unit. Each run-out was connected to each chilled water distribution loop and an automatic three-way valve was utilized to automatically change from the operating loop to the standby loop in the event of a loop failure. The piping runouts for the vertical in-row coolers were extended to a maximum of four (4) units located throughout the high density racks. This approach was used to minimize piping runs and so that in the event of a piping failure in the runout to any group of in-row coolers, the entire cooling capacity for a row of racks would not be lost. The runouts for the in-row coolers were also provided with automatic three-way valves and a connection to each piping loop to allow automatic changeover from the primary distribution loop to the secondary distribution loop in the event of a piping loop failure.
In addition to conditioning the Data Center, the chilled water system also provided capacity for cooling of the Main Electrical Equipment Room, the UPS Room and the Battery Room. Independent environmental control units were utilized in these areas to maintain the temperature and humidity conditions within each room. N+1 level redundancy was provided by utilizing additional environmental control units. Ancillary systems for the Data Center included a 100% outside air air handling unit located above the lay-in ceiling. The unit was a packaged unit with a close coupled condensing section. Both the outside air and the discharge air associated with the unit were obtained through the exterior wall to eliminate roof penetrations. The volume of outside air was based on ASHRAE guidelines to maintain a positive pressure condition within the Data Center, thus minimizing/eliminating infiltration and providing dust control. An ancillary system in the Battery Room included a two speed ventilation/purge fan operated by a hydrogen sensor. The fan operated continuously on low speed but energized to high speed upon detection of hydrogen above the threshold setpoint of the hydrogen sensor.
The electrical system associated with this project included the provision
of two (2) 2 MW (1825 KW Prime rated) generators in addition to the
existing 1,750 KW (1600 KW Prime Rated) generator. The fuel oil system
for the new generators included two (2) nominal 3,000 gallon vertical
fuel oil tanks located within the building. In addition to the fuel
oil storage tanks, there is a supply and return side fuel oil transfer
pump/day tank configuration to provide positive displacement for the
fuel serving the generators as well as positive displacement for the
unburned fuel from the generators back to the main fuel oil tanks. The
fuel oil system also utilizes a filtration system and an automatic fill
The existing buss #1 consists of three (3) 500 KVA (400 KW) Liebert UPS systems connected in parallel with a future fourth for additional capacity or redundancy of the Liebert UPS system. The new #2 buss configuration consists of two (2) 800 KW APC UPS systems to be fully redundant to the existing Liebert UPS system. Each of the UPS systems extends through a bypass and controls to an UPS distribution switchboard, utilizing drawout breakers, similar to the existing service distribution switchboards and new paralleling service switchgear.
The UPS systems serve a combination of high speed static transfer switch to provide dual source feeds to existing machine room PDUs and the new machine room RPPs. The high speed static switches serving the new machine rooms are with transformers to step-down voltage, whereas the static switches added to backfeed the existing machine room are without step-down transformers.
Distribution to all the existing ECUs located in the existing machine room, to the ECUs in the new machine room and ECUs in the new energy center are by way of automatic transfer switch served from each Energy Center. Transfer switches are also provided to serve the chillers and pumps serving the new machine room air conditioning loads. 120/208 volt distribution from each Energy Center is also provided to serve the APC RC in-row units within the new machine room.
Plumbing for the Data Center/Energy Center expansion was limited. Under this project, the existing domestic water and fire services serving the building were modified to properly serve the Data Center/Energy Center expansion and the adjacent/connected People Space Expansion. The original facility had a nominal 500 gallon emergency water system to allow operation of the building for a limited time in the event of a municipal water system failure. Under the People Space Expansion project, this system was removed and a 15,000 gallon underground potable water storage tank was installed to allow facility operation up to five (5) days in the event of a municipal water system failure. The system design included an air compressor and backflow preventers which allow pressurization of the tank when the municipal water system fails to provide sufficient pressure and flow to the facility on an independent basis.
Fire protection systems for the facility included a combination of
wet type and preaction sprinkler systems extended from the existing
fire protection service room in the original facility.
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7526 Harford Road - Baltimore, MD - 21234-6944
Phone 410.254.5800 - Fax 410.254.7091
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