King Energy LLC23 Clover Springs Drive, Willington, Connecticut, United States

After the dominant load has been calculated, the equipment can be specified.  The efficiency of the equipment affects the loop dimensions.  The ground loop should be thought of as your oil tank, and that it has access to sufficient heat /cool to get the building through the dominant period.  The equipment efficiency dictates the percentage of heat/cool that has to be provided by the ground loop.  The more efficient the equipment for heat, the longer the loop, and for cooling, more efficient equipment shortens the loop.  Loop dimensions are affected by soil and rock conditions as well as configuration, pipe size and design assumptions.  It is not recommended to reduce loop design to a simple ratio of feet of loop per ton of installed heat pump capacity.The distribution system into the space is relatively conventional, as long as the output air/water temperatures are adjusted for the lower temperatures associated with geothermal.  Some of the specialized skills and equipment needed for loop installation include heat fusion techniques for joining polyethelene pipe and grout equipment for backfilling bore holes.  The proper installation and maintenance of the equipment requires several common HVAC diagnostic items as well as a flush and purge cart.  The installation of the duct system, while apparently mundane, is rather important.  All duct connections need to be assured as being air tight and the insulation levels need to be carefully addressed.  There are several programs out there that  support geothermal heat pumps in particular, and energy efficiency in general.  We are VERY pro all.  It is our opinion that energy conservation, in general, answers to a certain pecking order.

A typical geothermal installation has three components, the ground loop, the equipment and the distribution system.  Of the three, the distribution system is the component most similar to conventional systems.  For new systems, ducted or radiant systems can be easily designed for geothermal heat allowing for the relatively low output temperatures of the geothermal heat pump, (90-110 degrees).  For retrofits, modern conventional duct systems designed for air conditioning are usually compatible with the air flow requirements of an air based geothermal system.  Water based distribution systems are more complex.  Most existing baseboard systems are not compatible with geothermal because they require higher water temperatures (180 degrees) than a geothermal can produce.  Radiant systems can be compatible, but special examination is needed to assure proper performance.  The equipment aspect of a geothermal system comes in several flavors.  The vanilla, and most often seen version, is a unitary air based, water to air, machine.  This unit looks a lot like a good sized refrigerator and it is set in the basement.  Duct, electrical, thermostat and ground loop connections are made, and off you go.  No fuel or refrigerant piping is required.  Some homes require remote air handlers due to space limitations.  This necessitates an air handler someplace outside of the mechanical room, connected to a compressor section usually in the mechanical room.  We call these split systems.  The equipment is connected with refrigerant pipes.  The most flexible, and complex configuration, is the water to water geothermal system.  The first water refers to the loop side. The second water refers to the output side.  Hence the unit outputs heated or chilled water.  This system most often utilizes mass tank(s) and can be combined with radiant heat, water based air handlers (both heat and cool), snow melt, pool heating, towel warmers and most anything you could imagine.  The ground loop is the feature of a geothermal system that sets it apart from convention systems.  I like to tell folks to think of the ground loop as their oil tank.  Reference to above, the ground loop is the ‘sink’.  The loop is sized to carry the home in question through the winter given the prevailing weather conditions.  The loop can be laid in trenches horizontally, or inserted into a well vertically, or sometimes, in a body of water (not everyone has one!).  The loop is constructed of high density polyethylene plastic pipe.  This stuff has been around and proven its durability for decades.  Configurations and pipe diameters are variable at the discretion of the designer and are often dictated by the site.  Heat of extraction and flow rates are key design criteria.  The loop is most often filled with anti-freeze solution.  We prefer 20% propylene glycol (non-toxic), but others use methanol or GS-4.  Ethylene glycol (Prestone) is frowned upon.  In an odd legacy, the loop circulating pump is still sometimes referred to as the ‘brine pump’, harkening back to the days that the antifreeze was a saline solution.  The important part to understand about the ground loop is that even if its -5 outside, the heat pump is seeing source temperatures (sink again) generally no less than 32 degrees, well within a heat pump’s efficient operating range.  The system maintains its output and efficiency regardless of outdoor air temperatures.

As boring as it sounds, insulation and air sealing, are by far the most effective means of conserving energy and saving money. 

By tightening up the envelope , savings can be maximized.  Get the envelope as tight as it can be done cost effectively, (new windows are great but expensive).  To aid in this effort, the utility companies offer conservation programs under the Home Energy Solutions (HES), that are specifically tailored to the needs of residential retrofits.  Advice and testing for new construction are available through the HERS system of approved building science specialists.  Support for all of these measures can be found at your electric utility as well as the state and federal government in the form of rebates or tax credits.  Details on all of these programs will change over time but subsidies are very much available and indicate the national will to improve on this front.