Although most geothermal systems are forced air systems (using blowers and ducting) there are many applications for using warmed or chilled water. These geothermal systems are commonly known as “water to water” systems. The primary difference is the substitution of the coil (that air moves past in a forced air system) to a special heat exchanger (that permits circulated water to pass within).

Water to water systems are most commonly used for radiant systems. Geothermal systems do not provide water warm enough to practically work with existing cast iron radiators. Radiant systems utilizing newer style radiators with (3/4″ or 1″ copper tube with square aluminized fins spaced approximately 1/4″ apart), on some occasions may work with geothermal but usually require more radiation.

Retrofitting a geothermal system to an existing hydronic system needs to be done after careful engineering. Most existing gas, propane and oil boilers rely on radiators that are designed for 160 – 180 degree water temperatures. The common refrigerants used in geothermal systems are not capable of generating temperatures much above 126 – 128 degrees. For this reason it may be necessary to add additional radiation.

Concrete radiant floor systems are becoming increasingly popular. Engineering for concrete radiant floor systems typically utilizes 90 – 110 degrees.


Hydronic systems are also used in commercial and larger residential applications. The geo system is capable of both warm water and chilled water. A water coil cabinet with a blower can provide both heating and cooling in remote areas.

For example, a water to water geo could be placed in the basement with two blower coils in the basement (one to take care of the basement and one to take care of the main floor). Another blower coil in the attic (to take care of the second floor), a third blower coil in a knee wall space (to take care of a bonus room over the garage) and a final blower coil suspended from the garage ceiling (for the garage). Each of these being capable of heating or cooling and while controlled by a individual thermostats.


The typical A-frame located in the plenum of an air handler prompts dehumidification as it cools the air. Unfortunately, the forced air moves across the coil so quickly that it will not take as much moisture out of the air as it could if the air speed were slower. Additionally, the outer edges of the A-frame are not sufficiently part of the air stream to allow adequate condensation to take place for dehumidifying the air. Conversely, the coil setup in Geothermal systems Geothermal systems slow the air speed down by passing it through a 90 degree turn in the ductwork just before passing the coil. Additionally, the coil is square shaped, creating greater surface area than the triangular shape of A frames. These two differences account for dehumidification rates from two to four times greater than A frames, depending on how poorly the A frame performs.

Forced air heating and cooling

Hot water dedicated or desuperheater (generator)

Well vs Loop

Chilled Water

Product Specifications and Literature

CD subdirectories