Application of air-water heat pump in refurbished building with existing radiator system

Abstract

Strategic renovation of existing building stock is strongly promoted in Energy Efficiency Directive and Energy Performance of buildings directive. Measures at the envelope are usually combined with replacement of existing heating system. This paper deals with situation where existing radiator system are connected to heat pump instead of previously installed old boiler for heating. Designers of these systems rely on bin method which is well designed for new systems. However, in case of existing systems several factors determine the available power from heat pumps such as: oversized radiators, over-or under flow of hot water in existing system – both influencing the return temperature or inlet temperature to heat pump. It is demonstrated that in some cases available and declared capacity of the pump is overestimated which is result of neglecting previously mentioned factors. In this paper the adaptation of existing bin method according to standard EN 14825 is proposed which fits any existing system. Calculations are performed and results are presented for the baseline condition and three scenarios – two with radiator system and one with underfloor heating. Advances of improved methodology for calculation are highlighted and the conclusions are presented at the end.