The application of incremental water source heat pumps to a closed water loop comprises a system which has gained wide acceptance among owners and designers of multi-room or multizone buildings in North America and Europe.

As the cost of energy, initial equipment investment, field erection expense, and operating and owning costs are continually increasing, it becomes increasingly important to incorporate a heating, ventilation, and air conditioning system which is practical and efficient, but also conserves available energy resources to the maximum degree possible, given the present state of the art. Whenever a combination of heating and cooling is required, and the heating and cooling loads vary from zone to zone, the closed loop heat pump system should be considered, not only for its true energy conservation characteristics, but for other advantages as well.

A brief review of what the closed loop system is, how it operates, and how it is an inherently energy conservation system, will promote greater understanding of its present operational limits, and of efforts to enhance the advantages of the system through the development of new generations of system components, and of innovations in system design.