Conductor bending diameter limit

[CM Phillips]

A code official has rejected an installation citing 300.34. The inspector is indicating the panel feeder (in this case a 250 kcmil neutral) cannot exceed 175 degrees in one bend. First of all 300.34 applies to conductors over 600V, which this is not. Secondly 300.34 applies to bending radius being equal to or greater than 8 times the overall diameter of the conductor. Is there any other reference or requirements listed in the code that would prohibit a single conductor bend exceeding 175 degrees? I have not heard of any restriction, and can think of multiple "standard" practice installations where this would be violated if it were true. This installation is for a standard branch panelboard where harmonics, and similar concerns are not applicable.

 

[RUWired]

Is there any other reference or requirements listed in the code that would prohibit a single conductor bend exceeding 175 degrees? .

CM, you might want to check out table 312.6(A) for your application in the panel.With a 250 kcmil conductor,a minimum 4-1/2" space is required.I don't see any problem with making any 180 degree bends.
Rick

 

[charlie b]

If the bend radius is large enough, and if the box is big enough (and to be clear I am talking about conductors in a box and not in conduit), then you can wrap the conductor in circle after circle, even making a 3600 degree bend (i.e., ten turns) or more, if you like. Not a good design, mind you, and you may need to deal with supporting the conductor against the walls or sides of the box. But nothing prohibits it.

I have designed underground runs in ductbanks for which a conductor enters a manhole on one face, and departs the manhole in the face 90 degrees to the left. In order to make the transition possible, it was necessary to bend the conductor in a 270 degree turn to the right.

 

[Dennis Alwon]

CM, you might want to check out table 312.6(A) for your application in the panel.With a 250 kcmil conductor,a minimum 4-1/2" space is required.I don't see any problem with making any 180 degree bends.
Rick

I am not sure of this but art. 312.6(A) refers to table 312.6(A) and that is the width of the gutter.

Table 312.6(B) appears to be the bending space at the terminals. That would be 8 1/2" unless Note 2 applies than you can reduse by 2"

 

[RUWired]

Table 312.6(B) appears to be the bending space at the terminals. That would be 8 1/2" unless Note 2 applies than you can reduse by 2"

Dennis, 6(A) is for conductors not entering the opposite wall

(1) Conductors Not Entering or Leaving Opposite Wall Table 312.6(A) shall apply where the conductor does not enter or leave the enclosure through the wall opposite its terminal.

6(B) is for conductors leaving the opposite wall

(2) Conductors Entering or Leaving Opposite Wall Table 312.6(B) shall apply where the conductor does enter or leave the enclosure through the wall opposite its terminal.

I envision the wire coming down the gutter and making a 180 into the terminal
Rick

 

[CM Phillips]

Thanks for the responses! It appears I am referring to the correct code sections, 300.24 and more imporantly tables 312.6(A) and (B). These references only restrict bending radius and there does not appear to be any code restriction to maximum number of degrees the conductor bends in an arc. If our code official can give a specific argument, I will post for reference.

 

[mikeames]

you can wrap the conductor in circle after circle, even making a 3600 degree bend (i.e., ten turns) or more, if you like.

With 250 kcmils, thats one heck of an inductor

 

[jim dungar]

Thanks for the responses! It appears I am referring to the correct code sections, 300.24 and more imporantly tables 312.6(A) and (B). These references only restrict bending radius and there does not appear to be any code restriction to maximum number of degrees the conductor bends in an arc. If our code official can give a specific argument, I will post for reference.

These code sections do not address minimum bending radius. They only deal with physical space allowances which includes room for insertion/removal into the lugs.

Contact the manufacturer (don't look in the NEC) for minimum 600V cable/conductor bending requirements. I do not believe that THHN has any minimum. I do know that UL allows 90 degree (0 radius) bends in control panels.

 

[charlie b]

With 250 kcmils, thats one heck of an inductor

That's why I said it was a bad design.