MEGA MC Cable Installation & Application Guide - Southwire

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bending radius for cable under tension—When pulling MC feeder cable, the factor
that limits pulling tension is usually the pressure exerted on the cable sidewall when
pulling around bends.
When MC cable is pulled around a bend, the pulling tension causes pressure on the sidewall
of the cable. Sharp bends concentrate the sidewall pressure in a small area, so larger radiuses
allow higher pulling tensions.
When pulling MC cable through a series of bends, pulling tension is cumulative. If the radiuses are
all equal, the first bend will see the least tension and create the least sidewall pressure. As the cable
goes through the last bend of a series, it is subjected to all the tension required to pull it through the
earlier bends. The result is that the last bend typically will have the most tension and the most sidewall
pressure.
To avoid cable damage, it’s important to make sure that the radiuses around all bends are large
enough to keep the pressure on the cable sidewall within recommended limits. A typical sidewall
bearing pressure limit for Type MC cable is 300 pounds of pulling tension per foot of bend radius.
By this rule of thumb, a 36-inch bend radius would limit the pulling tension to 900 pounds.
NOTE: Be careful about relying on pulling-tension experience with pulling singleconductor
or non-armored PVC jacketed cables. In general, because of the
sidewall pressure created during the pull, interlocked armored cable under
pulling tension must use larger bending radiuses than those allowed for nonarmored,
non-shielded cables with the same number of conductors and the
same conductor size.
If there is any question about the sidewall pressure and pulling tension with MC feeder cables,
please refer to Annex A, “Calculating Roller Spacing and Cable Pulling Tensions.” These calculations
will help to determine whether your pull will be easy, difficult or impossible. If you have further
questions, or need additional help concerning your particular installation, please contact your
Southwire Project Engineer.
Fig. 1 - sheave ConFiguRation
Southwire MC inStallation Guide section 2. cAble riGGinG And instAllAtion