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Quantum Controls helps Scottish hospital save £25,000 on electricity costs

Dumfries and Galloway Royal Infirmary is saving over £25,000 in electricity costs following installation of ABB variable speed drives by Quantum Controls.

Serving the Dumfries and Galloway area of south west Scotland, the hospital has nearly 400 beds. With a large demand for clean air to maintain a healthy and hygienic atmosphere, Dumfries and Galloway Royal Infirmary has a large number of air handing units (AHUs), representing a significant cost in energy. The hospital was keen to investigate the units to see if there was any scope to cut the energy use.

Doug Yorke, Energy Manager for Dumfries and Galloway Royal Infirmary, says: "We had experience of ABB drives previously and found them to be very reliable. The Quantum Controls representative got in touch with us at the right time, when we were considering using drives to reduce our energy use, so it all fell into place."

Quantum Controls, an ABB Drives Alliance member, was invited to carry out a survey of the fans within the AHUs that were running at fixed speed. The survey identified the AHUs in the main kitchen as a good candidate for a trial and energy usage report. Says Yorke: "The motors driving the AHU fans were 20 percent oversized and because they ran, unnecessarily, all of the time, it was wasting a lot of energy."

Quantum Controls logged the energy used on the kitchen AHU fan at a fixed speed for a week. The hospital then hired a variable speed drive from Quantum Controls to demonstrate the energy saved when the fan’s motor was run at a reduced speed, from 50Hz down to 42Hz. The fan was run under variable speed control for another week. A feature of the drive is a time clock allowing the AHU to be switched off over night. Quantum Controls produced a report showing energy and CO2 savings in the order of 30 percent at reduced speed.

It was also able to show that the reduction in speed had no effect on the air quality, a critical criterion for the hospital.

Following the trial, Quantum Controls won a competitive tender to supply and install 38 ABB variable speed drives on all the AHUs in the hospital, including in the Accident and Emergency department and in clean rooms next to the operating theatres. Motor sizes ranged from 1.1 to 11kW. The installation is now complete with the project giving a payback time of around two years.