Thermal accumulation with PCMs is one of the ways to improve the existing capabilities of storing solar energy. Existing research has been aimed at small-scale experiments, therefore this work is part of an ongoing project to test a thermal accumulation system with volume of 367 litres that is closer to a volume of tank that can be used for small households. This paper presents the methodology for evaluation of experiments and flow rate impact analysis on heat transfer rates between PCM and water. It was found that for 120 kg/h, 360 kg/h and 600 kg/h flow rates the heat transfer rate is similar, which agrees with the findings from other authors. It was found that experimental system must be improved to reduce the impact from water in the system which is in the parts of the tank that are furthest away from the 10 sensors that has been placed vertically by the side of the tank. PCM containers used in these experiments are made out of HDPE that has large thermal resistance and therefore other options must be evaluated.