For a C channel with the following dimensions:
b = width of the flange measured to the center of the web, inches or mm
c = Distance to the shear center, inches or mm
h = Height of section measured to the center of flanges, inches or mm
I = The second moment of area, in^4 or mm^4
t = flange thickness, inches or mm
If we apply load on this offset falling outside of the channel opposing the flanges there will be no twisting torque.
But usually in the construction C channels are rarely used as beams, the favorite section fo steel is I beams, or similar shapes because of their symmetry, a large relative I and the fact that they have been designed as beam and already include many requirements to be used as a beam by codes.
However, C channels in most cases (if ever) are used in situations where they are laterally braced by the floor slabs or roof sheathing so the torque created by loading, not through the shear center is resisted by those members.