Reigate, Surrey

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A prestigious building offering over 65,000 sq/ft of multi-tenant office space in Reigate, Surrey, has realised savings of £20,000 per year in energy costs for the buildings HVAC system following a project carried out by Econowise to install inverter drives.

Econowise were initially employed by the NB Entrust Ltd to carry out an energy appraisal of the existing system and investigate opportunities for energy reduction across the site. The survey revealed that the motors driving the system pumps were all running at full speed, with flow control achieved by mechanical throttling. It was calculated by the team at Econowise that installing VSDs on the system could save around £20,000 per annum in energy costs.

Following consultation with the client Econowise were instructed to carry out the installation works which included twelve ABB HVAC drives; six rated at 15kW on the chiller pumps, four rated at 15kW on the LPHW secondary heating pumps, and two on the LPHW Primary pumps rated at 7.5 kW. In order to configure the system to meet the original commissioning information provided by the building manager Martin Dalgarno, Econowise opened all the valves and set the drives to maximum speed, reducing the speed until the water flow rate met the exact requirements of the building.

Additionally the survey highlighted that two existing VSDs operating an air handling were not running in a speed control mode. Carrying out some reprogramming to the PID controller on the exhaust fan drive meant it could accept signals from a CO2 detector and drive the fan at an appropriate speed to remove the CO2. The two drives were connected so that the supply fan was driven at a speed to match the speed of the exhaust fan, enabling design pressures to be maintained at all times.

Martin Dalgarno commented, “The predicted savings of £20,000 were proven correct following an independent assessment. With an investment of around £14,000, this gave us a payback of under nine months. We have also gained other benefits such as reduced wear and tear on the motors and have had no problems with maintenance since the drives were installed”.