Control solutions for variable refrigerant flow systems in office buildings

¹ Research on Energy Systems, University of Málaga (RE+), Escuela de Ingenierías, Arquitecto Francisco Peñalosa 6, 29071 Málaga, Spain
² Corporación Empresarial Altra, Marie Curie 21, 29590 Malaga, Spain
³ Airzone Italia, Via Fabio Filzi 19/E, 20032, Cormano, Italy

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

Variable Refrigerant Flow (VRF) systems are widely adopted as high-efficiency solutions for office buildings. In Italy, the Conto Termico 3.0 scheme promotes the replacement of fossil-fuel boilers with heat pumps, fully recognizing VRF systems as eligible air-to-air technologies when minimum seasonal efficiencies are met. This positions VRF as a key solution for building electrification and decarbonisation. However, conventional VRF configurations, with long refrigerant piping and numerous indoor units, often require large refrigerant charges. Given the high global warming potential (GWP) of typical refrigerants, reducing refrigerant inventory is a critical objective alongside improving energy efficiency. This study compares two VRF configurations in an Italian office building across different climatic zones in Italy. A conventional system with multiple indoor units per zone is compared with respect to an alternative configuration using centralized ducted units supplying multiple zones with motorized dampers and aggregated control. Simulations using a new VRF model in TRNSYS18 evaluate electricity consumption, refrigerant charge, thermal comfort, and economic performance that evaluates the viability of the control solution. Results show that the proposed zoned configuration reduces both energy use and refrigerant charge. This dual benefit aligns with Conto Termico 3.0 objectives, supporting both indirect emission reductions and lower refrigerant-related environmental impact.