The efficiency of the HVAC installations in two London hospitals has been improved dramatically by installing more than 70 efficient motors and drives.
AS PART OF A programme of efficiency improvement work, undertaken in partnership with the Carbon Trust, the Hammersmith and Charing Cross NHS Trust has recently installed more than 70 high-efficiency electric motors and variable speed drives at its two London hospitals. The energy savings are expected to pay for the installation is less than two years.
The aim of the project has been to cut carbon emissions in line with Department of Health targets. An initial site survey highlighted opportunities for saving energy on fixed-speed fans and pumps used for heating, ventilation and air-conditioning at the sites. High-efficiency (Eff1) motors and variable speed drives were specified and are reckoned to be achieving a combined energy saving of up to 25% over the previous plant, which relied on mechanical throttling of pumps and baffles in the hospitals' air movement systems.The 72 new motors range in size from small 5.5kW pump drives to substantial 75kW machines, used for the main air movement fans. Field trials showed that replacing two-pole 18.5kW motors with the new high-efficiency motors (HEMS) could achieve annual savings of more than £500 per motor.
Deciding to change over to HEMs and drives was only part of the process. The installation had to be achieved with minimal disruption to the normal operation of the hospitals and to their patient care. "The work needed careful management and planning so that the installation engineers could be given access to heating and air conditioning areas throughout both buildings, where the pumps and fans were located," recalls the Trust's estates manager, lan Svenson. "We used relatively quiet times during the night for commissioning and switchover to provide an eight-hour window when individual areas such as operating theatres could be powered down."
Some of the smaller motors were wheeled in on trolleys and positioned by hand. Several of the larger motors required roof panels to be removed before they could be lowered into place using a small crane. This had to be done without affecting significantly the normal operation of the hospital.
The control and power management panels, including the drives, are controlled via a Trend building management system (BMS) using SCADA-like PC visualisation to make the new equipment visible to the hospitals’ facilities teams. The integration went smoothly, with a simple plug-in connection to the BMS.
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