COMFORT ASSESSMENT OF TANKLESS WATER HEATERS: REVIEW AND SUGGESTIONS

Today, a European standard procedure for the assessment of the comfort properties of domestic hot water modules is not available. Preliminary work on this subject is existing, though: Several years ago, the Swiss research institute SPF has suggested a procedure regarding the withdrawal capacity, energy efficiency and comfort, which is sometimes regarded as preliminary state-of-the-art version of an upcoming standardization procedure to be defined in the future. On this background, this paper discusses strategies for the assessment of the comfort properties of domestic hot water modules in terms of the control performance of adopting tapping events. The assessment is based on recorded temperature data, numerically damped by a simulation model for a generic pipe section. This model yields tapping temperatures, which are assessed by means of comfort criteria regarding both the temperature value as well as its rate of change. As tapping comfort measure, we propose the heat fraction during the first 60 seconds of a tapping event that is described as "comfortable" as a comfort figure.