|Data Center Design|
Critical Environmental Design Considerations for UPS Battery Rooms
The Heart of any UPS system supporting a mission critical facility is the battery plant. When Commercial power is interrupted in mission critical facilities, businesses are placed at significant risk to lose revenues, clients, and / or corporate image. The emergency power systems, which the UPS battery plant is a significant piece of must perform up to expectations and support the facility through any and all power outages. Properly designed and constructed battery rooms in mission critical facilities will provide a safe, efficient, environmentally friendly place to house and care for critical UPS battery systems, enabling them to provide optimum performance when needed. This chapter will highlight those environmental design features that must be taken into consideration when designing and constructing and fitting out a UPS battery room that will result in more than just a physical room to house the string of batteries.
Battery Room Design Criteria/ Battery Room Positioning and Layout
The positioning of the battery room must be in close proximity to the UPS modules being supported. For voltage drop considerations, the UPS modules and battery systems should be in adjacent spaces. Battery room Layouts should be clean and designed to maximize the space usage .Proper code clearances should be maintained in and around battery strings for required maintenance support and life safety systems. Egress aisles, exit ways and maintenance aisles also must be maintained .IEC,NFPA, and local codes must be taken into consideration and complied with when appropriate.
Building Structural Issues
Due to the weight of lead acid batteries, column and floor loading can quickly become a problem. 2volts VRLA batteries racked 3 or 4 tiers in a limited floor area can easily impress a 200-300 Kg/sqft floor loading on the structural floor which transfers to the columns and footers. Although this issue arises in new construction and existing renovation and reuse projects, the greater challenge occurs in the renovation projects. While extensive, expensive reinforcing of structurally elements is usually required to accommodate heavy battery loading in renovation projects, building floor slabs, columns, and footers in new construction can be much more easily designed and constructed.
Battery Rack/ Cabinet Issues
Battery racks and cabinets should be designed and installed to meet the requirements for the seismic zone they are installed in. The racks and the cabinets should be designed and purchased to accommodate the weight and size of the batteries ordered and the quantities of the batteries installed.
Fire Compartmentalization Issues
In a properly designed facility, battery rooms will be isolated from other equipment areas (UPS modules, electrical switchgear etc) and people spaces by a two hour fire rated wall. Additionally, where space constraints permits and there are multiple, multi module UPS systems serving the facilityï¿½s computer loads, individual UPS battery support systems should be located in separate ,fire compartmentalized rooms. This design strategy would also apply to the large multi module UPS systems themselves. The principle is one of the containment and the isolation of a catastrophic failure on one system from affecting other systems and occupancies in the facility. A failure on one battery system supporting UPS ï¿½A ï¿½ will also not disrupt power to UPS B. This is particularly important in Tier 4 facilities where completely separate and independent dual power path systems are to be maintained.
Fire Detection/ Suppressions Systems
Individual battery rooms should be treated as separate zones for fire detection and suppression purpose .Each room should have VESDA system installed and connected to the central fire detection system. Additionally the fire suppression system should be installed to suppress any battery fire within the room should one occur. This system should also be connected to the central fire detection system.
All battery racks and cabinets associated with UPS systems should have grounding wires linking all the racks for safety reasons .Periodic inspections should be made of the grounding system to assure that the continuity is maintained.
Battery Remote Monitoring Systems
Depending on the Tier level this system to be considered .The battery system should be equipped with an individual cell monitoring system to alert the facility team on the condition of the batteries serving mission critical applications. Without an adequate cell monitoring system individual battery cell problems cannot be easily traced. This systems generally provide continuous battery performance data for short and long duration outages. These systems can be remotely monitored by the facility team so that they will have ample time to investigate.
Temperature Control Considerations
For optimal battery performance, battery room air-conditioning systems should be designed to maintain a uniform average ambient temperature of 25deg Centigrade. Battery room temperatures below 25deg Cent will increase life but degrade on the performance during periods of heavy discharge. However battery room temperatures above 25 deg will increase the performance but reduce the life of the battery. In situations where the battery rooms borders outside walls and unconditioned spaces ,with no air-conditioning facility then the wall and ceiling surfaces should be insulated, sufficient openings for the fresh air inlet and exhaust ventilation system to be provided to tap natural cold air (in permissible conditions) to help to achieve the uniform ambient temperature.
Hydrogen Gas Detection and Ventilation System
Battery rooms should be designed with adequate ventilation- exhaust systems which provides for continuous ventilation of the battery room to prohibit the build up of potentially explosive hydrogen gas. During normal operation gas discharge by the batteries are relatively small. However the concern is elevated during the times of recharge of the batteries immediately after a deep discharge from the batteries. Two fans are usually involved (1W + 1S) and connected to the hydrogen detection system which senses the gas build up to the preset level within the battery room and activates the fan to switch on and clear the accumulated gas within the battery room. These systems should be installed with remote alarming capability to report hydrogen gas build up and abnormal operating conditions.
Spill Containment and Eye Wash Station
Only if the Battery banks considered are flooded cell type than these provisions should be considered in case of DRY type which has gained popularity in recent days the same is not required.
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