Formal verification of embedded control systems using closed-loop plant-controller models is getting increasingly popular. In this paper we propose a new method reducing complexity of model-checking on account of infusing non-determinism into certain parts of the plant model during formal verification process guided by a software tool. Net Condition/Event Systems (NCES) formalism is used for modular design of closed-loop models which are verified by ViVe and SESA model-checkers. Its performance is compared to modelling with finite state verified with SMV and UPPAAL and is proven to be superior.