A massive saving in energy usage is being achieved by an international banking company on its air conditioning system following the installation of ACS 600 drives from ABB.
- 90% savings in energy
- £70,000 reduction in annual energy bill
- Hot water used effectively
- Drives co-ordinated with BMS
Equipment : One 9kW, one 22kW and two 75kW drives
Savings P.A. : £70,000
Coutts and Co is the international private banking arm of the Natwest Group in London. The bank recognised that the cost of energy would be a significant factor in its continuing operations. It wanted to reduce the operational costs of its air conditioning system. It also wanted to co-ordinate control of the indoor climate with an integrated Building Management System.
Under the previous regime, all of the pumps in the air conditioning system were operating at 100% power continuously. Maintenance costs were high and downtime had a marked effect on the efficiency of the plant.
ABB Inverter Solution
Variable speed drives were recommended for fitting to the pumps throughout the air conditioning system. Areas where pumps were identified that would benefit from the use of variable speed drives included the chilled, hot and condenser water systems. The medium pressure water system for the boiler room was also identified as giving suitable savings.
Four drives were fitted to the system. These included a 4kW and a 22kW drives as well as two 75kW variable speed drives. Sensors were fitted in the pipe work connected to the drives to help regulate the speed of the pumps and ensure optimum use of the water’s energy content.
ABB Inverter Benefits
The cost benefits were immediate with Coutts and Co able to save some £70,000 per annum. In addition, there were other benefits from reduced maintenance. Using variable speed drives meant that the speed of the pumps could be reduced to about 40 per cent of maximum speed leading to a marked drop in energy usage. The lower pump speed also reduces wear, saving on maintenance costs.
The hot water is also used more effectively resulting in a saving in gas costs. The return water is no 8oC lower than the outgoing water.
Confirms Mike Ingram, Facilities Manager at Coutts & Co: “The pumps are running at about 40% of maximum speed whereas before they would be running at 100% continuously. In addition, the hot water is used more efficiently, saving gas. Before we would pump water out at 40oC. Now the return water is at 32oC.” The systems is integrated with the Building Management System enabling easy control of the indoor climate.
Notes Mike Carman, Business Development Manager for HVAC at ABB: “This installation shows the staggering energy savings that can be achieved with variable speed drives. This is because the variable speed drive runs the motor at the speed needed by the process, rather than running the motor continuously at full speed irrespective of the requirements”.
Simple recirculation is the least efficient way of running a pump as the pump runs at full speed regardless of the output needed. Small decreases in pump speed regulated by a variable speed drive can give large energy savings.