(2) Closed Building Loop
  A "Closed Building Loop" ground source heat pump system (also called water source heat pump system) is a common commercial application.  In this application, heat pumps are tied in parallel to a building "loop," or circulating water system.  The same water is circulated and later re-circulated through the heat pumps.  As the heat pumps engage in forced air heating, they remove heat from the building loop water; conversely in cooling mode they add heat to the building loop water.  For commercial applications with somewhat even heating and cooling loads or simultaneous heating and cooling loads this application is ideal; the heat rejected from the cooling units is absorbed by the heating units. This results in a free swapping of heat energy and the ultimate payback.  Typically a boiler and cooling tower are used to assure the building loop water temperature does not get too extreme.

  The Parkvale Building is located just outside of Pittsburgh, PA.  Built in 1996, the building is a prime example of a "Closed Building Loop" application.  This building has a series of rooftop evaporative cooling towers and a large boiler to maintain a consistent building loop water temperature.  To save on the cost of insulation, the boiler is set to maintain a minimum 60 deg F supply water temperature to the heat pumps.  Below are some pictures of the ParkVale building and its mechanical facilities.

ParkVale Building at Night	Rooftop Mechanical Room
Rooftop Evaporative Cooling Towers	Two 500,000 Btuh Boilers
Water Pump Controller	Two Alternating VS Water Pumps

  The Harney District Hospital is located in Burns, Oregon.  Completed in 2007, the building is another prime example of a "Closed Building Loop" application.  This building has a single rooftop evaporative cooling tower and a large boiler to maintain a consistent building loop water temperature.  To save on the cost of insulation, the boiler is set to maintain a minimum 60 deg F supply water temperature to the heat pumps.  There are over 60 individual heat pumps at the Harney District Hospital allowing for comfortable individual climate control in 60+ zones. The operating rooms utilize unprecedented variable speed air-flow technology, allowing heat pumps to maintain proper air-flow levels even through Hepa filters. Below are some pictures of the Harney District Hospital building and its mechanical facilities.

Harney District Hospital During Construction, 2007	Harney District Hospital Entrance
Operating Room Hepa Filters and Variable Speed Blower Motors	HydroHeat Horizontal Heat Pump w/ Hepa & Variable Speed Blower Motor
Two Alternating VS Water Pumps	Rooftop Staged Evaporative Cooling Tower