The current study investigates the influence of thermal coupling on the dynamics of the component loops in a Coupled Natural Circulation Loop (CNCL) and compares it with the independent Natural Circulation Loop (NCL). A 1-D modelling approach based on Fourier series expansion is employed for the numerical study, incorporating the wall conduction and inclination of the common heat exchanger section. The work presents the long-term transient behaviour of component loops of CNCL for different substrate wall thicknesses and materials and for different inclinations of the CNCL, under the same initial and operating conditions as of the independent NCLs. The study reveals the dynamic nature of the CNCL system due to thermal coupling. It is observed that the component loops of the CNCL exhibited instability at higher heat flux values while the independent NCLs remained stable. In addition, the long-term transient nature at different substrate thicknesses is presented for different heat flux values. The study also showed the effect of substrate diffusivity on the nature of oscillations in the component loops. Moreover, an increase in inclination caused chaotic oscillations, until the HCNCL configuration is attained where the CNCL demonstrated stability.