Abstract
In European countries with temperate climates, heating represents approximately 70% of the total energy consumption of a
residential building. Different Directives of the European Parliament and Council prescribe the enhancement of energy efficiency
and the reduction of energy demand of buildings. Consequently, the control of delivered heat is indispensable. The proper
operation of the control system is possible only for balanced central heating systems. In the case of central heating systems with a
constant supply temperature, the effects of mass flow deviation on the indoor temperature can be determined using only iterative
methods. In this paper, the indoor temperature variation is analyzed for different mass flow deviations, and the effects of
unbalancing are analyzed for a refurbished building.