A 1D cylindrical power-balance model of the radiation density limit (DL) gives a unified description of this phenomenon for stellarators, reversed field pinches and L-mode tokamaks (Zanca et al 2019 Nucl. Fusion59 126011). The DL scaling laws for the three different configurations are all derived from a combination of just two equations: (a) a single-fluid heat-transport equation; (b) on-axis Ohm's law with Spitzer resistivity, taken in a suitable limit for the stellarator. Here, we present a refined version of the model, alongside further experimental evidence supporting its successful application.