Trane WSHP-DS-6 manual Application Considerations, Closed Loop System

Application

Considerations

Closed Loop System

Closed loop systems (both ground source and surface water) provide heat rejection and heat addition to maintain proper water source temperatures.

Operating and maintenace cost are low because an auxillary fossil fuel boiler and cooling tower are not required to maintain the loop temperature. The technology has advanced to the point where many electric utilities and rural electric cooperatives are offering incentives for the installation of geothermal systems. These incentives are offered because of savings to the utilities due to reduced peak loads that flatten out the system demand curve over time.

For ground source geothermal systems, (See Figure 5), when building cooling

requirements cause loop water temperatures to rise, heat is dissapated into the cooler earth through buried polyethylene pipe heat exchangers. If reversed, heating demands cause the loop temperature to fall, enabling the earth to add heat to meet load requirements.

Where local building codes require water retention ponds for short term storage of surface run-off, a ground source surface water system, (See Figure 6), can be very cost effective. This system has all the advantages as the geothermal system in cooling dominated structures.

Another benefit of the ground source system is that it is environmentally friendly. The loop is made of chemically inert, non-polluting polyethylene pipe. The heat pumps use HCFC-22 refrigerant, which has a lower ozone depletion potential than CFC-12. Because the closed loop system does not require a heat adder, there are no CO2 emissions. Less electric power consumed reduces secondary emissions from the power plant. Therefore, the system offers advantages not seen by other central furnace or heat pump systems.

Figure 5: Ground source geothermal system

Figure 6: Ground source surface water system

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