Fill through a small condut/cable/knockout entry

[lakee911]

We specify, in our spec, a minimum of 3/4" conduit. A lot of instruments have only 1/2" NPT conduit/cable entry locations. In this case, the Contractor uses an adaptor and connects up 3/4" conduit or flex.

If we have a case as stated above and the conduit fill is too high for 1/2" conduit, but fine for 3/4" conduit, would it be a code violation?

In other words, is the conduit fill code enforced for a very small opening of very short length?

Thanks,
Jason

 

[augie47]

Where you normal conduit fill is 40% (over two wires), a "nipple", 24" or less, allows fill to 60% (Table 9 Note 4) . Do these transitions exceed 60%.

 

[lakee911]

Maybe I'm missing something here ... my Table 9 only has two notes. Where do I find such a table?

These transitions are less than 24"

Thanks,
Jason

 

[Dennis Alwon]

Maybe I'm missing something here ... my Table 9 only has two notes. Where do I find such a table?

These transitions are less than 24"

Thanks,
Jason

Chapter 9 Note #4-- first page of the chapter -- not Table 9

 

[lakee911]

I found it! I don't think it applies though...

"Where conduit or tubing nipples having a maximum length not to exceed 600mm (24 in.) are installed between boxes, cabinets, and similar enclosures, the nipples shall be permitted to be filled to 60 percents of their todal cross-sectional area, and 310.15(B)(2)(a) adjustment factors need not apply to this condition.

I would classify this adapter as a "fitting", not as a "conduit" or "tubing nipple." Even so, it does say "between between boxes, cabinets, and similar enclosures." This would be installed between an instrument housing (which is a similar enclosure) and conduit (which is not a similar enclosure).

Thoughts?

(On a side note, I think that the second occurance of "nipples" should be replaced with "conduit or tubing nipples" in this section.)

 

[Dennis Alwon]

I see it as it is. If you have a transition to a smaller pipe then that section must meet the 60% fill. For a few inches I am not sure why it would matter but....

 

[augie47]

Point well taken. To be more "Code" correct, add a box at the transition.

 

[lakee911]

Point well taken. To be more "Code" correct, add a box at the transition.

Yup. Might have to. Thx.

 

[don_resqcapt19]

Jason,
Are you saying that you have an instrument with a 1/2" conduit opening and that the size and number of wires required to make this instrument work would exceed the permitted conduit fill for 1/2"?

 

[marti smith]

And is there already electrical apparati within the area of penetration that would not permit a larger hole to be made in the field?

 

[lakee911]

Jason,
Are you saying that you have an instrument with a 1/2" conduit opening and that the size and number of wires required to make this instrument work would exceed the permitted conduit fill for 1/2"?

Yes.

And is there already electrical apparati within the area of penetration that would not permit a larger hole to be made in the field?

Sometimes that is an option, but very rarely are people willing to take the risk of damaging something. In the case of a cast aluminum enclosure, reaming the existing hole and threading it would be a lot of work for someone in the field.

 

[lakee911]

< deleted >

 

[iwire]

Jason,
Are you saying that you have an instrument with a 1/2" conduit opening and that the size and number of wires required to make this instrument work would exceed the permitted conduit fill for 1/2"?

Yes.

Why is that?

 

[infinity]

Here is using these KO enlargers:

Very common for jobs with a 3/4" minimum sized conduit and where you cannot or don't want to enlarge the fixture KO to 3/4".

 

[don_resqcapt19]

Jason,
If the wire won't fit in the opening provided by the manufacturer, I would expect that you are not using the wiring that the manufacturer expects you to use. Can you give us a more detailed example ...size, number and type of conductors along with a part number for the equipment?

 

[jusme123]

Where you normal conduit fill is 40% (over two wires), a "nipple", 24" or less, allows fill to 60% (Table 9 Note 4) . Do these transitions exceed 60%.

...where is the nipple, he is transitioning from 3/4" to 1/2" in a conduit run?

 

[iwire]

...where is the nipple, he is transitioning from 3/4" to 1/2" in a conduit run?

I think in the OPs case the reducer is directly secured to the enclosure so the length of the reduced part is likely less than 1" long.


That said there is no prohibition in changing conduit size in the middle of a run as long as the conduit fill requirements are maintained.

 

[Dennis Alwon]

so the question remains in the 1" of nipple change is the 60% fill req.? I say yes but it does seem absurd in this case.

 

[jusme123]

...IMHO, the conduit fill is based on the smallest diameter conduit in the run (box to box), regardless how many transitions are made or how short they are.

 

[iwire]

so the question remains in the 1" of nipple change is the 60% fill req.? I say yes

I say yes as well.

But I am as curios as Don is about why the factory opening is not enough to bring in the needed conductors.

In my experience that is usually caused by someone specifying a conductor that is larger then needed. Or if the wire size must be increased for long distances they should also specify a job box near the device to reduce the conductor size back down.