The system includes a central fluid heater or cooler and an electrically driven centrifugal pump which pumps fluid therefrom to a supply main from which individual lines lead to each unit supplied. Return lines from each unit bring the used fluid back to the heater or cooler. The supply main is provided...http://www.google.de/patents/US4509679?utm_source=gb-gplus-sharePatent US4509679 - Energy use monitoring system
