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09/02/2011
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Operators of the Omnibus building in Reigate, Surrey, report savings of £20,000 per year on HVAC energy costs since installing ABB standard variable speed drives.
 Sited on a disused bus garage in the centre of the town, the building is a multi-tenant facility, with more than 65,000 sqft of office space.
"We were approached by Econowise Drives and Controls to investigate our HVAC system and look at the scope for using drives to cut running costs," explains building manager Martin Dalgarno, of NB Entrust.
Dave Lapsley, owner and director of Econowise, says: "The energy appraisal revealed that the motors driving the [HVAC] system pumps were all running at full speed, with flow control by mechanical throttling. We calculated that putting drives on the application could save around £20,000 per annum."
The firm installed 12 ABB drives – six on the chiller pumps, rated at 15kW, four on the LPHW secondary heating pumps, also rated at 15kW, and two on the LPHW primary pumps rated at 7.5kW.
Lapsley explains that Econowise opened all the valves and set the drives to maximum speed, reducing the speed until the water flow rate met the requirements of the building as detailed in the original commissioning information.
He also says that the building already had two variable speed drives operating an air handling unit, but explains thatthese were not running in speed control mode. So Econowise reprogrammed the PID controller on the exhaust fan drive to accept signals from a CO2 detector and drive it at an appropriate speed.
The two drives were connected so that the supply fan was driven at a speed to match the speed of the exhaust fan, hence maintaining design pressures.
Says Dalgarno: "The predicted savings of £20,000 a year have proven correct. 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."
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Author
Brian Tinham
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