A central closed loop system has all heat pumps in a central room; air or water is ducted and circulated to the heated or cooled rooms.
Commercial applications include chiller retrofits such as the Louisiana Association Building in Baton Rouge and the Daily YMCA in Bixby, Oklahoma, and a rooftop unit retrofit at Stockton State College in New Jersey.
Distributed systems use a central water pump and heat pumps serving individual rooms and areas. Types of buildings served included offices and schools, both new construction and retrofits.
The Oklahoma State Capitol Building uses more than 400 heat pumps. Since multiple units are heating and cooling simultaneously, the distributed system can provide heat recovery from core zones that have excess heat to perimeter zones that require heat.
A distribution system also permits location of relatively small individual units in restricted areas, such as historic buildings like Shields Tavern in Colonial Williamsburg.
Modular systems have dedicated heat pumps, water pumps and loops. This type of system allows for independent individual control, operation and maintenance.
Types of buildings suitable for a modular approach include schools, with modules serving individual classrooms, and other buildings where usage and environment are clearly separated. An example is the Bailey Middle School in Austin, Texas, where console units serve individual classrooms.
A hybrid system uses a cooling tower or other means to reject excess heat not needed for winter heating. The cooling tower reduces the size of the ground heat exchanger and the cost of installation.