# Element C of equivalent thermal circuit

Element C is only relevant for cables in air. The factor $T_{4iii}$ is the external thermal resistance due to air in the steady-state, calculated according to IEC 60287, expressed as a quantity per conductor or equivalent conductor.

Symbol
$T_{C}$
Unit
K.m/W
Formulae
$\frac{T_{4iii} q_{4}}{n_{c}}$
$T_{4iii}$
Used in
$T_{B}$