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 ID: 528011
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Slide1
Bending Electrical conduit
USING TRIGONOMETRYSlide2
Bending Conduit
Offset Bends are used when a conduit either needs to avoid an obstacle or needs to change elevation or planeSlide3
What Shape Does the Offset Make?Slide4
Where is the triangle?Slide5
Where is the triangle?Slide6
Trigonometric FunctionsSlide7
Trigonometry
Offset
Bend angle
θ
Adjacent
hypotenuse
Opposite
distance between bends
offset riseSlide8
How to put the functions into a calculatorSlide9
Find the value for each function
Use the angle of
Which answer is the easiest to use?
Slide10
Trigonometry
Offset
Bend angle
sin (
θ
)
=
O
H
csc
(
θ
) =
H
O
cos
(
θ
)
=
A
H
sec (
θ
) =
H
A
tan (
θ
) = O A
cot (θ) = A O
θ
Multiplier =
distance between bends
offset rise
Adjacent
hypotenuse
Opposite
distance between bends
offset rise
2 =
H
5
2
=
H
1 5
H = 2 x 5
H = 10 Slide11
Cosecant
hypotenuse
Opposite
Adjacent
30º
Cosecant of 30º = 2
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
10”
5”Slide12
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?Slide13
Try it Out
We know:
Our offset rise (opposite side) is 4”
Our multiplier (cosecant) for our 30º bend is 2
We need to solve for our distance between bends (hypotenuse
)
Adjacent
hypotenuse
Opposite
distance between bends
offset rise 4”
30ºSlide14
Try it Out
To find the distance between bends (hypotenuse) we multiply the off-set desired (4”) by our multiplier (2).
DBB = multiplier x offset
8”
= 2 x 4”
Adjacent
hypotenuse
Opposite
distance between bends
offset rise
30ºSlide15
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 obstacleSlide16
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 bendSlide17Slide18
Why is that 30º so POPULAR?
Easy math! – the offset multiplier is 2 and the shrink constant is ¼”Slide19
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
4
0” 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.
4
0”Slide20Slide21Slide22Slide23Slide24Slide25