A commerical combi boiler is a heating appliance that uses gas combustion to provide central heating and domestic hot water for everyday use. It consists of subsystems, each with its unique function, making material selection a critical design factor. The current threat of global warming further complicates material selection due to strict regulations related to carbon footprint. Consequently, composite materials, particularly glass fiber reinforced thermoplastics (GFRTP), have become a key choice to meet these requirements cost-effectively.Despite their favorable properties, GFRTPs have several disadvantages, the main one being the formation of weld lines. During the injection molding process, melt flow fronts meet at certain locations and create an unbounded region with mostly transverse fiber orientation which significantly decreases the local strength. Thus, it is crucial to examine the fiber orientations together with the molding defects in order to design robust components. This study aims to evaluate the mechanical robustness of a GFRTP component in a combi boiler. Anisotropic finite element analysis (AFEA) is utilized to incorporate the influence of fiber orientation and molding defects such as weld lines. Injection simulation is performed in Moldflow to identify weld line locations and fiber orientations. The multi-scale material modeling platform Digimat is used to transfer the obtained microstructural data from injection molding to structural simulation in ANSYS and collected micromechanical properties are homogenized into element-wise anisotropic material response. To accurately simulate the coupled molding and structural analysis chain, submodeling is utilized onto a single part model to account the effects of neighbouring parts and fittings. With the current method, high-fidelity simulations should be performed to investigate structurally weak regions during the design phase and strengthening measures can be taken to enhance the mechanical robustness of overall module.