From the manufacturer's information.

www.anixter.ca/AXECOM/AXEDocLib.nsf/(UnID)/71C22AE23FF1A43580256F24006EF67A/$file/B-1_7.pdf

http://www.okonite.com/engineering/bending-ratios.html

http://www.lanshack.com/DesigningConduitRuns.aspx

http://www.tpub.com/ceb/68.htm

As PW has mentioned, the maker of the cable will publish the minimum bending radius to be used for their products. Failing such information, you can turn to one of the published national codes. For example, table #7 of the Canadian Electrical code contains minimum pipe bending ratios to be used in Canada.

NEC handbook has minimum bending radius for the various sizes of EMT.

If you are in the US, refer to the NEC. If elsewhere, consult your local or national standards and codes on electric wiring.

Remember that you must also de-rate the ampacity of your conductors based on percentage fill of the conduit and the ambient temperature.

Hi guest,

If I understand your question you are asking for the radius of the pipe bend. this is determined by the bender. Most 1/2 inch emt benders in the USA are designed to produce a 5 inch radius bend. 3/4 in produces a 6 inch radius bend.

It depends on what the cable is. Fiber-optic requires a larger radius

You can get EMT benders from any vendor that sells electrical supplies. They come in all sizes and they are marked so you can determine where the center of the radius is going to be.

A rule of thumb some people use is that the minimum ID radius of the bend should be 5 times the OD of the tube. This of course will vary depending on wall thickness and material, but it should get you in the ballpark. Local electrical codes in your area may have to be applied depending on what kind of cable you have inside (usually based on power carrying capacity). Of course you can always have a tighter "bend" by using a preformed 90 degree elbow fitting if space limitations are a concern.

Good morning,

There are many books (references) wherein this sort of information is available for a minimum cost.

One of the best inexpensive pocket-references for answers to questions like this is "UGLY's ELECTRICAL REFERENCES" by George V. Hart.

It is available from:

BURLESON DISTRIBUTING CORPORATION

3501 Oak Forest Drive

Houston, Texas 77018

Phone: 800-531-1660

713-956-6666

E-Mail: uglys@uglyselectrical.com

Website: www.uglyselectrical.com

The general rule of thumb for any cable is 10 times the diameter of the cable for the minimum radius this includes fiber optic cable, But it is best to consult with the cable manufacturer for the minimum bending radius, If you are pulling cable in to longer runs or runs with more bends you should use as large of a radius as possible to reduce the strain on the cable.