Wireway Conductor Fill

[romex jockey]

The 10ft/10% exception applies to any reason why the ampactiy would be less, in the smaller portion of the length, given that it is still the same conductor. This doesn't include 75C rated terminations on 90C wire, but for all other reasons why ampacity would be less, it applies.

One example is stubs on a rooftop, where most of the run is inside the building, but this small portion is in direct sunlight and thus has an elevated ambient temperature.

Another example is if you have a wireway distributing wires among numerous pieces of equipment, and the final piece of equipment adds your 31st current carrying conductor. Yet for all the other equipment served by this trough, this is less than 10% of the total conductor length and less than 10ft total.

A blindspot to this rule is whether or not you are allowed to "double dip" it. Consider two portions of reduced ampacity, on opposite ends of the circuit, each individually less than 10%/10ft, but perhaps greater than this length limit collectively. Another blindspot is whether or not this only applies to continuous factory lengths of wire, or if you are allowed to splice it to an identical type of wire and still count the length.

well i guess a yes or no was too much to hope for here Carultch ......gotta say this captive heat vs. ampacity thing is difficult ..... ~RJ~

 

[jusme123]

My point is that if you place 5 factory 90 degree elbows end-to-end, it is still possible to pull the wire, probably even by hand. And this would be a violation by the letter of the code, even though the real life consequences are non-existent.

I'm aware that this is an unlikely case to encounter in real life, as most situations will have significant enough length between the bends, that the 360 degree rule is still a good "one-size-fits-all". Southwire makes a spreadsheet to calculate the pulling metrics of sidewall pressure and tension. And keeping track of this information is an important part of the puzzle of designing conduit runs.

...can you site the code article?

 

[kwired]

...can you site the code article?

How about 3XX.26 in each different raceway article.

 

[iwire]

How about 3XX.26 in each different raceway article.

Those sections require we provide pull points it does not require we use them.

 

[kwired]

Those sections require we provide pull points it does not require we use them.

Correct, but we still need to provide them whether used or not.