I'm having trouble finding the article that discusses the maximum distance allowed for conduit between boxes. Thanks.
Well, what kind of conduit?
Chapter 3 of your code book covers all kinds of conduit.
I was always told that you can't have more than 100 feet between boxes, but I can't find it in the code book.
How long is your fish tape?
The maximum length of conduit between boxes is the circumference of the earth. More than that and you will have over 360º of bends in your run. But seriously, it's not restricted by distance, it is restricted to 360º degrees of bends between pull points. I have pulled wire through 700'runs of conduit using a Mightymouse.
The only other restirction, is the pulling force and sidewall pressure that will result when the conductors are pulled into the raceway. If this is a long pull with large conductors, then you need to do a pulling calculation to make sure that the conductors won't be dammage when pulled into the raceway.
Don
Saw an artical in EC&M a while back that had calculations and formulas for pulling. Side wall and drag resistance, ect. thought I saved it, but.... lost somewhere in this box next to me....
I'll have to admit, I never learned them, and have gone on experiance for this type of thing, and over-build/design if at all worried....
Found it:
http://ecmweb.com/mag/electric_simple_calculations_cable/index.html
You can also check out this free online tension calculator.
http://www.electrician.com/electa1/ductwirepull.html