Residential hot water energy analysis: Instruments and algorithms

Abstract A system has been developed for practical disaggregated measurement of residential hot water energy consumption. Since hot water energy use is primarily determined by occupant behavior, the significant phenomena occur at the points of use, not at the water tank. To measure with flow meters at each use point would be costly and esthetically undesirable in occupied residences. Drain traps are even more costly and intrusive. This paper describes the development of an instrumentation system based on a single flow meter at the tank, with temperature probes at each tap. A microprocessor-controlled data-logger samples water flow each minute; when water is flowing, it records volume and temperatures. A computer program was developed which examines the minute-by-minute temperature and volume readings, deduces which tap used water, and delimits distinct events. It also calculates pipe heat loss and heat delivered to the end use. The algorithm is evaluated for reliability of the inference rules and heat calculations.