Virtual Reality (VR) systems have reached the consumer market which offers new application areas. In our paper, we examine to what extent current VR technology can be used to perform local or remote usability tests for technical devices, e.g., coffee machines. For this, we put virtual prototypes of the technical devices into VR and let users interact with them. We implemented four interaction modalities that are suitable for low-level smartphone-based VR systems up to high fidelity, tethered systems with room-scale tracking. The modalities range from a simple gaze pointer to interaction with virtual hands. Our case study and its counter evaluation show that we are able to detect usability issues of technical devices based on their virtual prototypes in VR. However, the quality of the results depends on the matching between the task, the technical device, the prototype level, and the interaction modality.