BENDING ELECTRICAL CONDUIT USING TRIGONOMETRY Bending Conduit Offset

BENDING ELECTRICAL CONDUIT USING TRIGONOMETRY

Bending Conduit • Offset Bends are used when a conduit either needs to avoid an obstacle or needs to change elevation or plane

What Shape Does the Offset Make?

Where is the triangle?

Trigonometric Functions

Trigonometry ce hy p Opposite Offset offset rise dis ta n be tw ee ot en n be us e nd s θ Adjacent Bend angle

How to put the functions into a calculator

Find the value for each function •

Trigonometry Offset Opposite offset rise dis ta n hy p ce be tw ee ot en n be us e nd s θ Adjacent sin (θ) = O H csc (θ) = H O cos (θ) = A H sec (θ) = H A tan (θ) = O A cot (θ) = A O Bend angle Multiplier = distance between bends offset rise 2=H 5 2=H 1 5 H=2 x 5 H = 10

Cosecant 5” Opposite Cosecant of 30º = 2 hy po 10” ten us e 30º Adjacent The cosecant becomes our multiplier for a 30º bend, which is a constant value no matter what the length of the sides of the triangle The multiplier for a 30º bend will always be 2

Try it Out An electrician is running a conduit along a wall from the electrical panel to a box that will house a disconnect switch for a hot tub. The disconnect switch is mounted on a 4” deep structural post. The electrician must bend an offset so that the pipe will be on the same plane as the post. The electrician wants to use 30º bends What is the multiplier (cosecant) of a 30º bend?

1. Our offset rise (opposite side) is 4” 2. Our multiplier (cosecant) for our 30º bend is 2 We need to solve for our distance between bends (hypotenuse) Opposite We know: offset rise 4” Try it Out dis ta n hy p ce be tw ee ot en n be us e nd s 30º Adjacent

DBB = multiplier x offset 8” = 2 x 4” offset rise To find the distance between bends (hypotenuse) we multiply the off-set desired (4”) by our multiplier (2). Opposite Try it Out dis ta n hy p ce be tw ee ot en n be us e nd s 30º Adjacent

Shrink • When a conduit is bent around an obstacle, it “shrinks” in length • Shrink = the amount by which the total run that conduit can cover is reduced because of the extra length required to bend around an obstacle

Shrink • Bend angles have shrink constants • The shrink constant for a 30º bend is about ¼” • Shrink = C (shrink constant) x O (offset rise in inches) • Shrink needs to be added to your calculations before starting your bend

Why is that 30º so POPULAR? • Easy math! – the offset multiplier is 2 and the shrink constant is ¼”

Try it Out You are running a conduit along a wall from one lighting box to another lighting box. You encounter a 7 ½” tall exit sign which is 40” from the first lighting box. You must bend an offset so that the pipe can change elevation, get around the sign, and connect to the lighting box. You want to use 30º bends. 40”