Hospital nearly halves energy costs for AHU fans

ABB, variable speed drive, Medway Maritime Hospital
Huge savings in the energy used by fans in air-handling units at Medway Maritime Hospital in Gillingham have been achieved using ABB variable-speed drives.

The running costs of fans in air-handling units at Medway Maritime Hospital in Gillingham have been reduced by £9000 a year, a saving of over 40% on the previous £21 000 cost of running the fans in these AHUs. There is an associated reduction of 32 t of CO2 emissions a year. The payback was 2.5 years.

The savings have been achieved by installing ABB variable-speed drives (VSDs) on the fans. The installation involved ABB drives alliance partner Inverter Drives Southern installing 12 standard drives for HVAC with ratings from 1 to 11 kW.

During the day, the speed of the fans is set back to 90% and 80% at night. The drives are integrated with the building-management system.

The project was carried out with the help of a loan from Salix, a not-for-profit agency that provides interest-free loans for public bodies such as NHS trusts.

Trish Marchant, deputy environmental manager at the hospital, says, ‘We have been very happy with the contract and have been looking for similar applications that could benefit from VSDs. I have been tweaking the settings of the VSDs to get the right comfort levels in the building. This is one of the major advantages of VSDs — the flexibility to adjust the setpoint to suit the occupancy of the building. I would definitely recommend the use of VSDs in other similar situations, particularly for older AHUs where the motors may be oversized.’

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