Hydronic systems installed in buildings utilize water to transport thermal energy within the building for heating and cooling purposes. These systems can be closed loop, where the water is chemically treated and circulated indefinitely, or they can be open loop, where the water is not treated and is effluxed as a result of occupant activities, such as bathing or cooking. Water in an open loop system may circulate within the system for a limited time before it is extracted from the system by occupant activities and replaced with new water from the local water supply. The implementation of open loop hydronic systems is becoming more common in multi-unit residential buildings, even though a number of questions regarding the use of such systems remain unanswered. One concern regarding the use of circulated potable water for heating purposes is the potential effects on the occupant perceptions of the palatability of the service water being delivered to their suites. In an open-loop HVAC system (Heating Ventilating, Air Conditioning System), heating water is subject to repeated thermal cycles and continuous recirculation, which creates the potential for chemical alterations of the materials present in the water or leaching of materials from the equipment and piping. Through the use of Flavor Profile Analysis (FPA) established by the American Water Works Association, and a multi-unit HVAC system constructed in a controlled environment, the palatability effects of the operational system were evaluated for a number of scenarios. The collected feedback from the study participants was then tabulated to quantify the impacts of using potable water as a recirculating heating medium on the perceptions of the occupants. The resulting observations led us to conclude that utilizing potable water as a heating medium has a negligible effect on the palatability of water in the system for average retention times under one day, and a non-objectionable, but noticeable, effect for higher average retention times.
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