From multiple industrial testing on chiller performance, refrigerant contaminants have been known as one of the main cause of efficiency loss. As the refrigerant is circulated throughout the refrigeration cycle, these efficiency loss causes great energy wastage and damage to equipment. This paper studies the possible impact of contaminants in a chiller system through the MATLAB simulations. The model block built by the external library namely, “Thermolib^®“, the model consists of the compressor, evaporator, condenser and expansion valve. The refrigerant R134a was used throughout the simulations. The thermodynamic properties of the R134a such as enthalpy, heat transfer coefficient and pressure of the system were adjusted to simulate the presence of refrigerant contaminants in the system. The simulation model was able to produce the accurate results that corresponds with existing industrial standards.