Main site navigation

• Home
  • Corporate
  • Contractor
  • Consultant

• Our Approach
  • Ground Source Energy
  • Accreditations
• GSHP
  • Closed Loop
  • Open Loop
  • Process Coupling
  • Geothermal Piles
  • Renewable Heat Incentive
• Services
  • Design and Build
  • Thermal Response Testing

• Contact us

Closed Loop

This is the most common form of ground source heat pump (GSHP) system.  It relies on the circulation of fluids, usually water and antifreeze solution, within an underground system of pipes, installed in either vertical boreholes or horizontal trenches.

If adequate land area without hard rock is available, a horizontal loop installation is usually the most economic for smaller structures. Horizontal loops are often used for newly constructed homes and smaller commercial buildings.

A horizontal GSHP system uses a number of trenches. The piping can be configured in the trenches in several ways, namely a single loop in a narrow trench, multiple loops or slinkies in a wider trench.  The trenches need to be at least 1.2m deep and vary in length depending on the number of pipes to be buried and the required capacity of the system. 

An increasingly popular approach, especially in small scale residential systems, is a "Slinky" coil; a coil of plastic tubing spread out and overlapped in a trench and buried.  Slinky coils are installed in the same way as other horizontal geo-exchange systems, at the bottom of a wide trench.  A compact slinky will reduce trench length by about two-thirds; an extended slinky will reduce trench length by about one-third.  Specific design lengths will vary with the climate, soil and the heat pump's run fraction.

If the land area available is limited, or the system requires high heating or cooling loads, vertical loops can be installed for the geo-exchange.  Vertical installations are also be used where the land is too rocky for trenching, for existing buildings, and for large commercial or educational facilities.  To install a vertical loop, a contractor will bore holes into the ground, and insert a geothermal loop. The hole is backfilled, plugged or grouted, and the pipes are connected to headers in a trench leading back to the building.  The drilling depth is determined by a combination of site conditions, cost issues and system requirements.  A typical borehole depth is 100 to 150 metres.  Drilling boreholes for geothermal loops is much simpler than drilling to find well water for an open-loop system.  The borehole is generally of a smaller diameter, which reduces drilling time, and no separate well casing is required as the geothermal loop contains the circulant fluid.