A ‘forward-thinking NHS Trust’ in Surrey has recently enlisted the expertise of specialist building services engineers, RAB Specialist Engineers (RABSE), to address the issue of coil clogging in the cooling plant at one of its main hospitals, and reduce the cost of running the equipment, via the installation of air intake filter screens.
Richard Betts, RABSE’s MD, explained: “Hospitals are a 24/7 operation, and have a significant need for cooling, which can be found at the heart of most HVAC systems. At the request of the Frimley Health NHS Foundation Trust, we recently surveyed two separate cooling systems at Frimley Park Hospital – one Alfa Laval Fin coil unit SCAG-8-5, and four Carrier 09GHCA178 Aquasnap air-cooled units. Annual energy consumption for these cooling systems alone is 1,618,000 kWh; they thus cost the Trust just over £194,000 per annum to run.
“We found the horizontal coil faces dirty with compacted dust, seed, pollen, and other debris, which, unless addressed, will be drawn into the fins. A US study by Pacific Gas and Electric identified that just 1 mm of debris on a coil fin would cause a 21% drop in efficiency, and increase energy consumption by up to 30 per cent. To address the issue, we installed RABscreen air intake filter screens to protect the coil faces, which will significantly reduce contamination, particularly in hotter weather.”
The air intake screens are produced using a polyester core and polypropylene overlay which, during air movement, creates an electrostatic charge. This captures the airborne particulate to prevent it reaching the fins. Needing no airflow or electrostatic charge, this system enables maintenance personnel to easily clean the air intake screens using a vacuum cleaner, hose, or brush.
Richard Betts added: “We would expect to see a minimum 10% reduction in running costs compared with similar sites, as the condenser is kept clean, and efficiently rejects heat. The air intake filter screens were secured to the coil support steelwork using marine grade, nylon drop tab fastenings. Should access to the fins be required, the screens can be easily removed and replaced.
“With an air resistance of only 17 Pascals at 3.05m3/s, these highly effective external filters will continue to protect the coils for at least 10 years, giving a return-on-investment of under a year. Thanks to the air intake screens’ fitting, the Trust should save at least £175,000 over the next nine years.”
