The University of Greenwich expects to save £10,000 p.a from the air handling costs of three campuses following the installation of ABB ACH550 variable-speed drives. An initial investigation found that much of the air conditioning plant is overrated and they could reduce the speed of the fans without adversely affecting the air flow.
ACH550 drives were selected as they are designed specifically to meet HVAC applications requirements including harmonics and EMC standards, and for easy integration with building management systems.

On the university’s Medway campus, they looked at the air handling equipment installed in several buildings and recorded motor and fan data. During the survey they found that many of the fan units had rated speeds and powers less than that of the motors. These were either being run too fast or the speed of the motor was being reduced by the pulley ratios on the belts driving the fans. When the original system was set up, airflow was adjusted by setting dampers on vents at room level.

Monitoring was carried out on an AHU fan motor on Anson campus. Over the two day test period, while running on normal direct-on-line operation, the 4 kW motor consumed an average of 3.353 kW, for a total annual running cost of £871. Running the motor for two days using an ABB ACH550 HVAC drive consumed an average of 2.087 kW at a total annual cost of £542.

These results were extrapolated to produce estimated savings for the motors in the other buildings, a total of 44 installations with a combined installed power of 127 kW. It was estimated that following the installation of VSDs on these fans, the fan applications would save some £10,472 a year in running costs, as well as reducing carbon emissions by over 57 metric tonnes per annum.
It has a five year target to reduce its carbon emissions and based on the first project,  has identified additional savings from further projects could cut running costs by another £4,000 and a cut in CO2 of 19 metric tonnes.

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