# Thermal resistance of multi-layer backfill method

Overall thermal resistance between buried cable in a multi-layer backfill and the ground surface.

All resistances $R_q$ are calculated once for the side with shorter distance to backfill boundary, and once for the other side. The resistance to ambient is calculated by taking the average of the two values.

Symbol
$R_{CG}$
Unit
K.m/W
Formulae
$\frac{0.5}{\frac{1}{R_{q3}} + \frac{1}{R_{q2}} + \frac{1}{R_{q1}}}$
Related
$R_{q1}$
$R_{q2}$
$R_{q3}$