Difference between open loop and closed loop radiant heating systems

Several decades ago, PEX replaced polybutylene (PB) in open-loop and closed-loop radiant heating installations and the landscape of geothermal heating systems changed forever. Many reasons have contributed to this evolution but the change was inevitable.
PEX tubing is flexible, easy to install and provides all the characteristics one would need to create a successful open-loop or closed-loop radiant heating system. Being less rigid than metallic piping offers a tremendous advantage for one. It handles the fluctuations in temperature found in radiant heating systems much better than its competition. It is impervious to corrosion and requires no additional chemicals since PEX installers can run PEX in extremely long runs. Rather than solvent-cement or heat fusion methods, the joints are formed with a variety of mechanical compression methods. It is both freeze and break resistant, another enormous advantage when dealing with PEX piping that can be buried deep underground or placed in concrete masses called gypsum concrete or gypcrete.

Geothermal heating systems can be trenched, excavated in a deep bed or drilled. Open-loop systems, for instance, tend to use a well to pump water using an aquifer, which passes through the pump’s heat exchanger, and then discharges the water into another well or a nearby river. In theory it is much more efficient than a closed loop systems because it pulls the heat out of a steady stream of water from deep in the ground. However, open-loop systems are prohibited nowadays in many parts of the country because of water quality concerns.

PEX tubing is approved for hot-water heating systems (open or closed-loop) in all model plumbing and mechanical codes across the States. A closed-loop system uses a continuous loop of PEX tubing as a heat exchanger. The tubing is connected to the heat pump and with the proper antifreeze solution, it is circulated throughout. Unlike an open-loop system that consumes water from a well, a closed-loop system recalculates its heat-transferring solution in the pipe; working in a closed-controlled system. Approximately, two to three gallons per minute per ton of capacity are necessary for effective heat exchange.

The potential for harmful bacteria is much less in a closed system as well. The federal Centers for Disease Control websites (www.cdc.gov) say that 8,000 to 18,000 people contract Legionnaires' disease each year, with the illness fatal in 5 percent to 30 percent of the cases.

System components are less expensive in a closed-loop system when compared to an open-loop system since it requires bronze or stainless steel fittings instead of cast iron. Closed loop systems have become the most common of geothermal heating. When properly installed, a closed loop system is economical and reliable.

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