The right environment – for mice and men
Yaskawa Electric explains how the tricky task of providing the ideal environment for both laboratory mice and personnel was overcome
Jackson Laboratory, an internationally recognised research centre and established provider of genetically-defined laboratory mice, presented a unique challenge: to design an environmental control system suitable for both staff and animals.
The laboratory exists to advance the understanding of the genetic factors underlying the development of cancer. Each year it distributes nearly two million mice to universities and research laboratories around the world. In total, 12,000 research institutions in 56 countries depend on Jackson to provide more than 2,400 varieties of mice. Jackson uses rigorous quality controls to ensure the standardisation, health and genetic definition of mice involved in research. Controls include state-of-the-art heating, ventilation and air conditioning systems to provide the optimal environment to raise the mice, as well as control and maintain the working environment for Jackson staff.
Constant temperature and air flow Breeding and raising healthy laboratory mice requires constant temperature and air flow. On the other hand, the areas that Jackson staff use function most efficiently on an advanced variable air volume system, which delivers optimum comfort during working hours and off-peak setbacks for energy savings during evenings and weekends. The HVAC system, designed, installed and maintained by John Fitzpatrick, the laboratory's engineering and technical services manager, controls these dissimilar environments by applying Yaskawa AC adjustable speed drives. According to Fitzpatrick, the adjustable speed drives provide control in the "macro" environment of 46,500m2 in several laboratory buildings, and in the "micro" environment of the separate animal rearing cages. In the critical environment where animals are housed and raised, ingeniously designed supply and exhaust plenums actually serve as frames for the cages. Yaskawa's drives control the fan speeds on both the supply and exhaust sides of air handlers feeding these plenums. Ensuring optimum cage conditions on a constant basis involves maintaining constant discharge pressure, according to Fitzpatrick. He must also consider the heavy biofiltration that is to be designed into the system to provide a biologically clean supply of fresh air to the cages. This intense filtering requires that drives and motors be run hard and, as a result, have been de-rated about 15% to accommodate the additional filter load.
Substantial energy savings These same drive/motor installations that maintain constant discharge pressure in the cage areas also enable the laboratory to achieve extraordinary energy savings in its administrative and laboratory spaces. "Electrical energy savings from 15-20% are easily realised in areas using Yaskawa drives to provide Variable Air Volume (VAV) heating and ventilation control," Fitzpatrick said. "We consider this an extraordinary result, since we provide a minimum of 12 air changes per hour instead of the normal six and use 100% outside air instead of a conventional sequence." The laboratory savings result from the ability to programme the drive to operate fan motors at optimum reduced speeds instead of a constant 100% of capacity. It installed its first Yaskawa drive in 1992 and today has more than 50 P5 drives in operation at various locations. A communications option on four drives demonstrates how drives and, therefore, control and monitoring of the building environment can be achieved from a central point. The drives with communications cards and bypasses have been installed in one of the laboratory's production facilities for more than a year. By linking the drives and related equipment (boilers, chillers and air handlers) to a PC or other monitoring device, the system is able to provide effective control from a single point. As installed, the building management system provides a monitoring, alert and control system, while the adjustable speed drives control fan speed and air volume to match flow requirements. Advantages include reduced installation costs, since drives and controls are linked by simple, twisted-pair wiring. Additionally, the system provides improved maintenance capabilities, since a remote drive shut down by a fault condition can be brought back on line by commands from the central PC. System information fed back into the communication network also provides information to help maximise energy savings. The laboratory is evaluating the operation of the installation at the moment and is considering converting the remainder of the site to a communications-controlled drive architecture.
Trouble free experience "The demands of our biological environment and the welfare of our employees and laboratory animals creates a need for excellent service on a continuing basis. Yaskawa has responded with drives that are very dependable and flexible – in fact, trouble free," Fitzpatrick said. The laboratory's success with Yaskawa drives in meeting the demands of this challenging application, has lead Fitzpatrick to evaluate drive and communication combinations for a planned installation of a drive multiplexing system on the laboratory's main chilled water plant.
