Information on Electrical Conduit Bending
Protect your electrical system with properly bent conduit
By Richard Asmus
When electrical wiring runs from one point to another, solid tubes called conduit protect it from physical damage in high-activity areas, and from water and weather in exposed areas. And when several wires follow the same route, some electrical signals can interfere with others. Separate conduit runs keep these signals isolated. When installing conduit, it needs to be neatly bent to conform to building dimensions and to pass over or around obstacles.
Types of Conduit
Electrical conduit comes in sizes from one-quarter inch to 4 inches in diameter. Thinner-walled EMT (electrical metal tubing) protects wiring from lesser physical damage and reduces interference between wiring runs, but is not waterproof. Waterproof rigid conduit resembles water pipe, and can withstand severe shocks without crushing. Plastic conduits can provide some physical protection from shock and moisture, but do not isolate signals. Combinations of metal and PVC serve multiple functions. More expensive flexible conduit protects wiring in small areas where bending would be impossible.
EMT conduit up to 1 inch in diameter can be bent with a hand bender that has a 4-foot handle and a step to add power and accuracy by using your foot. The head of a hand bender can be removed from the handle and carried in a tool box. EMT conduit larger than 1 inch in diameter, and rigid conduit of all sizes, need to be bent with an electric or hydraulic bender, which can be quite heavy but can come with a tripod or on wheels for easier transportation and operation.
Bends for One Conduit Run
When a single run of conduit connects two items, a standard 90-degree or "stub up" bend goes around a single corner, either vertical or horizontal. With "back to back" bends, a conduit turns two corners with the same piece. An "offset bend" changes the conduit plane either to clear obstacles, or to rise up from a wall to enter a junction box. A "three-bend saddle" allows the conduit to clear an obstacle, such as another perpendicular conduit run. All but the stub up bend require skillfully crafted bends to stay aligned and neat.
Bends for Multiple Conduit Runs
When two or more conduit bends run alongside each other, it requires craftsmanship to bend the tubes straight and neat. With "parallel bends" the separate conduits are bent exactly the same for back to back, offset and three-bend saddles. But when two or more conduits make a bend along the same plane, such as to go from a vertical to horizontal run along a wall, "concentric bends" require a smaller radius for the inside bend, and wider bends for the outside runs. Extreme skill is required to keep the bends neat and parallel around a curve.
Bending conduit to fit neatly around corners and over and around obstacles is not easy. All types of conduit have a minimum bend radius that determines the smallest curve it can make without damaging the wires inside, while still maintaining its strength. Complex trigonometric principles apply to bending theory, and must be learned and practiced to make neat and professional-looking conduit runs. Many conduit manufacturers and suppliers, and many electrical organizations provide free conduit bending instructions. Check with your electrical supplier for a free pamphlet.
About the Author
Richard Asmus is a regular contributor to DexKnows.
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