System Overview: Level 5 is currently fed from the old building chiller systems to the CW (Chilled Water) Fanwalls. The Fanwalls are designed with a supply air of 24°C under normal conditions to client’s server intake, with SLA temperatures limits of 16°C (low limit) & 30°C (high limit). Global Switch have built a new chiller system that runs under modern design practices and is more efficient and currently being offline heat load tested. The new hybrid chilled water system runs at elevated to the old system CW water flow temperatures. However, the supply air temperature of 24°C will remain the same because the Fanwalls were oversized at design for this migration. Under abnormal conditions estimated for approximately 0.55% of the year, the CHW system will operate in ‘Drift Mode’, meaning the supply water temperature is able to drift +3, resulting in higher supply air temperature expected up to 27°C. As part of the migration the Fanwalls airflow and valve control will be recommissioned and the modes of operation tested under strict script and control measures to ensure all parts of the system operate as designed.
Work Breakdown: There are a total of 18 fan walls to migrate over onto the new CHW system. There are 12 fan walls along the south cooling corridor, and 6 fan walls along the north cooling corridor. Working from East to west along the south corridor, the first fan wall units will systematically be hydraulically isolated from the existing CHW system and migrated onto the new system, the alarm set points will be adjusted for the new water temperatures of 20°C / 30°C and the flow rates recommissioned/balanced. Upon completion of all fan wall unit migrations, ‘Drift mode’ will be tested. This will be monitored until temperatures are stable, we do not expect the duration of this test to exceed 1 hour. Once temperatures are stable, simulated drift mode will be removed and system put back into ‘auto’. N.B. ‘Drift mode’ has already been tested in a vacant data hall during a heat load test, therefore the software has been proven. At no point during heat load testing were SLA’s breached. The SLA’s are in excess of 30°C for 30 minutes, if during testing of Drift mode the average room temperatures reach 29.5°C, back out plan will be implemented immediately which will return flow water temperature to 20°C and supply air temp to 24°C.
Risk / impact: Increased temperatures in the data halls / Breach SLA’s, risk of damage to equipment
Risk details: The room temperatures will be monitored throughout work effort.
Purpose of Project To migrate CHW systems on levels 5 from the current CHW system onto the new NE chiller quadrant, with new water temperatures of 20°C / 30°C.
Systems Impacted 1 fan wall unit will be impacted systematically however with the current loads within the data suite, the data hall will never be reduced to N.
Method of Procedure Yes, All works to be carried out in accordance with contractor RAMS and GS MOP.
Risk Analysis The fans walls will be migrated one unit at a time in a controlled manner. The system will be monitored to ensure cooling is stable prior to moving onto the next fan walls.
Mitigation Measures One fan wall to be migrated at a time. Room temperatures to be monitored throughout. BMS specialist on hand throughout work effort.