Clearance in duct is the distance between the top of the uppermost cable in the conduit and the inner top surface of the conduit. It should be at least 10% of the conduit inner diameter or one inch for large cables or installations involving numerous bends.

Symbol
$CC_{\mathrm{p}}$
Unit
%
Formulae
 $- D_{\mathrm{e}} + Di_{\mathrm{d}}$ 1 cable $- 2 D_{\mathrm{e}} + Di_{\mathrm{d}}$ 2 cables $- 1.366 D_{\mathrm{e}} + \frac{Di_{\mathrm{d}}}{2} + \sqrt{- \frac{D_{\mathrm{e}}^{2}}{2 \left(- D_{\mathrm{e}} + Di_{\mathrm{d}}\right)} + 1}$ 3 cables (triangular) $- \frac{D_{\mathrm{e}}}{2} + \frac{Di_{\mathrm{d}}}{2} + \sqrt{- \frac{D_{\mathrm{e}}^{2} \left(- D_{\mathrm{e}} + Di_{\mathrm{d}}\right)}{2 \left(- 2 D_{\mathrm{e}} + 2 Di_{\mathrm{d}}\right)^{2}} + 1}$ 3 cables (cradled) $- 2 D_{\mathrm{e}} + Di_{\mathrm{d}}$ 4 cables (diamond)
Related
$D_{\mathrm{e}}$
$Di_{\mathrm{d}}$