electrical industry vsd news,electricaldigest.co.uk
ABB variable-speed drives (VSDs) are saving a hospital £9,000 a year on the cost of running its air-handling units (AHUs).

Medway Maritime Hospital in Gillingham, Kent, was becoming increasingly concerned by the energy consumption of the AHUs in the three plant rooms serving the hospital's Block A.

'Our main drive is to keep our CO2 contribution low, as well as cut energy costs, especially with the launch of the CRC Energy Efficiency Scheme,' said Trish Marchant, deputy environmental manager of Medway Maritime Hospital.

ABB Drives Alliance partner Inverter Drives Southern was asked to look into the application and make a recommendation for improving its energy efficiency.

Marchant said: 'We wanted a company that had experience of working in the NHS and that understood the demands made on a ventilation system in a building that was continually occupied.

'I found Inverter Drives Southern to be very confident in gathering the energy use data - they assessed the motors and estimated that they were oversized.

'Inverter Drives Southern then produced robust predictions that fitted with our own expectations,' she added.

Each plant room has one supply and three extract fans.

Inverter Drives Southern measured the power consumption and determined that the AHUs cost a total of more than £21,000 a year to run.

It predicted that installing variable-speed drives could cut this cost to around £12,000 per annum, a saving of £9,000 alongside 32 tonnes of CO2 saved per year.

The installation project involved Inverter Drives Southern installing 12 ABB standard drives for HVAC, with ratings between 1kW and 11kW.

At night, the speed of the fans is set back to 80 per cent, while in the daytime they are set to 90 per cent.

The drives are integrated with the building management system (BMS) so the night set-back is engaged by the BMS to a centrally controlled time schedule.

IDS worked closely with the hospital's BMS vendor to ensure the correct I/O for the drives.

'I have been tweaking the settings of the VSDs to get the right comfort levels in the building,' said Marchant.

'This is one of the major advantages of VSDs, the flexibility to adjust the set-point to suit the occupancy of the building,' she added.

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