Conduit Bodies Wire Fill

[augie47]

I know I'm digging up old bones and I have read several previous threads on the subject, but, I still find it difficult to answer the question when it comes up in the field.
I understand that conduit body dimensions must meet 314.28 when conductors are #4 or larger unless the conduit body is marked for fill. With that in mind, if a 1" LB is marked "Max Fill (3) #4 RHW" and we are installing (4) #4 THWNs in a 1" EMT can that 1" LB be used ?
314.28 references Table 1 Chapter 9. In that table my (3) RHW would have an area of .3999 where my (4) THWNs would be .3296

If that makes the THWNs allowable, would any combination of conductors with an area less than the (3) RHWs be allowable ?

 

[north star]

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"If that makes the THWNs allowable, would any combination of conductors with an area less than the (3) RHWs be allowable ?"

IMO, ..."yes!", as long as the conductors are rated for that particular
install.....Wouldn't smaller diameter conductors provide more area
within the conduit for air flow & heat dissipation? :happyyes:

% %

 

[kwired]

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IMO, ..."yes!", as long as the conductors are rated for that particular
install.....Wouldn't smaller diameter conductors provide more area
within the conduit for air flow & heat dissipation? :happyyes:

% %

More area would be provided but that is not the issue. Bending the conductor to be able to install it in the conduit body without damaging the insulation is the issue.

Most conduit bodies have very limited combinations of conductors marked on them that they have been tested for and this has been brought up here before, there needs to be a better way to mark them. Better example would be a conduit body marked for 3-#1/0 max, but maybe I want to install 6-#4AWG. Can I do it? What if I have 3 - 1/0 and a 4 AWG equipment ground? That is not the same as 4-1/0 at all, but I really do not know if it would be acceptable. Many times they are marked with three conductors and a size, but many times we are running three ungrounded, plus a grounded and maybe even an equipment ground, making the markings they do have meaningless for our installation.

 

[north star]

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Soooo, ...is this a manufacturing problem to be addressed by the NEC?

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[kwired]

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Soooo, ...is this a manufacturing problem to be addressed by the NEC?

* *

I don't necessarily believe it is responsibility of the NEC to address the problem. But if one manufacturer starts to test their fittings for more combinations of conductor possibilities and marks them for those possibilities somehow there is a good chance there will be more demand for their fittings, and pretty soon they all will be doing the same thing.

 

[don_resqcapt19]

Where the conductors are #4 and larger and where the dimensions of the conduit body do not meet the rules in 314.28, there are no provisions that cover installing condutors other than those listed on the conduit body.

 

[kwired]

Where the conductors are #4 and larger and where the dimensions of the conduit body do not meet the rules in 314.28, there are no provisions that cover installing condutors other than those listed on the conduit body.

And they never have many potential combinations of conductors listed, even though based on what is listed there it is likely there are many combinations that would pass same testing that applied to the ones that are listed.

 

[don_resqcapt19]

And they never have many potential combinations of conductors listed, even though based on what is listed there it is likely there are many combinations that would pass same testing that applied to the ones that are listed.

And with the code requiring the marking on the fitting, they don't have room to list all of the combintations that would work.

 

[kwired]

And with the code requiring the marking on the fitting, they don't have room to list all of the combintations that would work.

That is right, now we are back to there has to be a better way, should we go through the cycle again?

 

[don_resqcapt19]

That is right, now we are back to there has to be a better way, should we go through the cycle again?

The code needs to be changed to provide either a "field calculation method" or to permit listed combinations to be provided in the instructions and not marked on the fitting.

 

[infinity]

Where the conductors are #4 and larger and where the dimensions of the conduit body do not meet the rules in 314.28, there are no provisions that cover installing condutors other than those listed on the conduit body.

I agree, comply with the provisions written on the conduit body or use something else.

 

[chris kennedy]

I agree, comply with the provisions written on the conduit body or use something else.

What to use for four 500's and an EGC.