The Closed loop system employs a series of pumped underground closed circuits to collect heat. These loops are filled with anti freeze or refrigerant depending on the pump.

The size of the circuit will be directly related to the heat requirement of the house, i.e. the larger the heat load, the bigger the collector needs to be. Collectors can be arranged vertically or horizontally. The vertical arrangement is used when the space available is too small to fit a horizontal loop.