• Allowable Bends in Electrical Conduit per NEC code
• EMT Elbows Bends
• Electrical Conduit Math
• Electrical Steel Conduit
• ## Allowable Bends in Electrical Conduit per NEC code

BD, Bend Distance is the horizontal distance between bends. BO, Bend Offset is the depth of the obstacle to be passed over. S, Shrinkage is the effective reduction in horizontal conduit length because of the bend. Essentially, it is the difference in length between the hypotenuse and the base of a triangle. I will use these equations to generate the table shown in Figure 3. An additional formula for the straight pipe length is also provided Equation 4.

Figure 6 illustrates the geometry of the situation and the associated formulas. The radius of the conduit bender, called R, will vary for each conduit bender. Applying basic trigonometry to Figure 5, we can derive Equations 3, 4, and 5. Note that BD is defined slightly differently in that it represents the center-to-center distance between the bends.

Because conduit benders can have different bend radii see Figure 7 , this means that using a single table for all conduit benders may result in some error — particularly for large bend offsets.

Ideally, we would build a table for the conduit bender being used. I include this table with bend radius as a parameter on a worksheet in the Excel workbook associated with this post. Analysis Approach My focus here is on generating the traditional conduit bend table. In my workbook, I also include a tool using a more exact model.

There are a number of ways I could generate this table using Excel. The approach I chose was to: Generate a table of values for bend offsets of 1 inch. Generate separate tables of shrinkage and bend distances. I chose this approach because I wanted to experiment with arranging columns by using a helper row containing the ordinal number of each column and doing a horizontal sort. For demonstration purposes, I also included a tab where I used formulas to fill down the columns.

A third tab uses the conduit bender radius as a parameter. Reference Table Figure 8 shows the shrinkage and bend distance formulas evaluated for a 1-inch bend offset i. These values can be used as scale factors for other obstacle heights, which is exactly how the table in Figure 3 was generated. Figure 8: Reference Bend Table. Full Table Generation The table shown in Figure 3 is generated by multiplying the bend offsets by the scale factors in Figure 9.

I used Excel tables to perform this action. Conclusion I was able to duplicate the original table. I will be using this table for some conduit bending this weekend.

Take up is a amount of conduit length used to figure out where to place the marks on the conduit before the bend. Most hand benders have the take up stamped on the bender or on a sticker — usually on the bender handle. Find this first. It may vary between bender manufacturers. STUB — A stub is the length you need for the conduit to reach and is measured from the back of the bend or backside of the conduit.

LEG — The remaining length of conduit minus the stub. Grab the handle and using foot pressure on the bender foot and bend the conduit until it is just past being perpendicular with the floor. This is to allow for spring back. Check out this very informative video on how to bend a 90 degree with EMT. The reverse method for bending a 90 is an alternative that addresses this type of situation.

This method is also used in back to back 90 degree bends. When using the reverse method the take up deduction is no longer needed. This bend forms a short leg as if it were the stub and leaves the long stub on the ground as if it were the leg. Place the bender on the conduit with the hook pointing towards to short end and align the mark with the tip of the star.

Place one foot on the conduit and the other foot onto the bender foot. Grab the handle and using foot pressure on the bender foot and bend the conduit. To do it right, you could use both the basic and reverse method depending on the lengths of the stub you need. The video below shows you the proper way to make a back to back He uses 30 inches between bends which allows for plenty of clearance for the handle and bender show.

Essentially, it is the difference in length between the hypotenuse and the base of a triangle.

## EMT Elbows Bends

I will use these equations to generate the table shown in Figure 3. An additional formula for the straight pipe length is also provided Equation 4. Figure 6 illustrates the geometry of the situation and the associated formulas. The radius of the conduit bender, called R, will vary for each conduit bender.

Applying basic trigonometry to Figure 5, we can derive Equations 3, 4, and 5.

### Electrical Conduit Math

Note that BD is defined slightly differently in that it represents the center-to-center distance between the bends. Because conduit benders can have different bend radii see Figure 7this means that using a single table for all conduit benders may result in some error — particularly for large bend offsets. Ideally, we would build a table for the conduit bender being used. I include this table with bend radius as a parameter on a worksheet in the Excel workbook associated with this post. Analysis Approach My focus here is on generating the traditional conduit bend table.

In my workbook, I also include a tool using a more exact model. There are a number of ways I could generate this table using Excel.

The approach I chose was to: Generate a table of values for bend offsets of 1 inch. If however your offset is has to be greater than the diameter of the conduit, then the bends need to be added to the total count. This is typically an addition of 20 degrees two 10 degrees bends. Example of a box offset that is greater than the diameter of the conduit and should be counted in the total run count.

Do long sweeps count in the total?

### Electrical Steel Conduit

So as a rule of thumb, a long sweep is still a bend and adds friction to the conductors when pulling and therefore should still be counted as a bend when adding up the total. Where to get NEC book?

I would recommend spending a fraction of that and getting spiral bound print version. Check current prices for new and used here on Amazon. You have to manually click next on page and there is no search, copy or print function. How to bend conduit? A great video and resource I have found if you are looking to learn the basics of Conduit Bending can be found here.

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