The proper design and installation of a geothermal system is a somewhat multi-disciplinary endeavor. It starts with an evaluation of the energy requirements for the application at hand. For residential applications in the northeast, we are usually looking at a heating dominant system. Commercial systems are often cooling dominant.
The heating and cooling requirements need to be determined as these will dictate the equipment sizing and loop dimensions.
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.
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.