The NEC restricts the total number of bends in a single continuous run to 360 degrees or four 90-degree bends. "There should not be more than the equivalent of four quarter bends (360 degrees total) between draw points, such as conduit bodies and boxes," it specifies. "Conduit shall not be bent back on itself."
These restrictions are necessary because of the potential for damage that could result from too much bending. For example, if a section of cable is subjected to excessive bending stress, it may break, causing electrical failure. The risk of this occurring increases with each additional bend.
Additional bends in conduits are usually indicated by special fittings called "right angles". Two sections of conduit connected by a right angle have four corners instead of two. The extra corner provides more space for bending without causing damage.
Right angles are used in construction projects where multiple lengths of conduit are needed. For example, one end of one length of cable may need to be connected to the other end of another length of cable. A right angle is used to connect these lengths of conduit together.
Right angles are also used when several lengths of conduit must be routed through the same wall aperture. In this case, the interior walls of the conduit body are exposed until all the holes are cut, after which time the walls are covered with drywall or some other material.
In any section of conduit, no more than two 90-degree bends or equivalents are permitted between pull points. The only time this restriction does not apply is if the conduit is listed for horizontal lay-out and has the additional criteria that the outer radius of each bend is at least as large as the inner radius plus 1/4 inch.
The reason for this limit is that it is difficult to achieve tight radii with standard fittings. If the conduit is bent too sharply, the inside wall will touch first, leaving a gap between the walls. This creates a weak point where the pipe can split.
To make sure that your conduit runs are free of sharp bends, use 45-degree bends instead. These can be easily achieved with standard equipment such as tees and elbows. However, keep in mind that if you need to go into another compartment for more conduit, you will need to change directions. This means adding more 45-degree bends to the original route.
If you want to avoid changing direction completely, you will need to use special equipment for sharp bends. There are several types of connectors that can be used instead of elbows. For example, there is a connector called a "right angle clamp" that can be used instead of a 90-degree elbow.
Two 90-degree angles Between horizontal cable pull points, no more than two 90-degree bends are permitted, while no 90-degree bends are desired. When 90-degree bends are required, use sweeping bend products. The maximum pulling tension of the cables limits the number of cables that may be put in a conduit. The allowable load on each cable depends on the design of the cable itself; however, for PVC cable, we recommend a maximum of 20 pounds per foot (9.1 kilograms per meter). If the conduit is not large enough to accommodate all the cables you want to put in it, go over or around the conduits rather than through them.
Conduit is used to protect electrical wiring from damage and the weather. It allows the wires within to be hidden from view. Conduits are available in a wide variety of sizes and shapes. The type of conduit used should be based on how many cables will be placed in it. For example, if there are only going to be two cables placed in a conduit, then one-and-a-half-inch ID x three-quarter-inch OD metal conduit will do the job. But if there were ten cables with four conductors in each, then one-and-three-quarters-inch ID x three-quarter-inch OD plastic conduit would be needed.
The advantage of using metal conduit is its durability. The walls of plastic conduit tend to thin out under pressure, which can lead to collapse.