When supplying a hot-water supply of 50 C, 60 C and 70 C, air
temperature-sensing methods (Case 2, Case 4) keep up mean
temperature, but the water temperature ratio control slightly
differs. This means that when the water ratio control (Case 3),
which maintains an indoor mean temperature of 22.8 C with 50 C
hot-water, is supplied with a hotter water supply, the mean
temperature rises because it controls the flow rate with the return
water. In this case, the set point needs to be readjusted.