No ampere adjustment for underground conductors

Status
Not open for further replies.
Jpflex

Jpflex

Electrician big leagues
Location
Victorville
Occupation
Electrician commercial and residential
How is this code supposed to be interpreted?

“adjustment factors shall not apply to underground conductors entering or leaving an outdoor trench if those conductors have physical protection…having a length not exceeding 10’ feet and if the number of conductors does not exceed four.”

I don’t have code book but I think code reference is found near section 310.15?

Am I supposed to interpret this such as if the entire length of underground conductors (which are progressing to leave their trench) including the conductors outside the trench cannot exceed 10 feet nor exceed 4 conductors in order to be exempt from ampacity adjustment factors?

I don’t know many underground trench lengths plus the height of the vertical runs outside of trench for termination that total 10 feet or less.

Unless they meant only the vertical sections outside of the trench not being over 10 feet but that’s not how the code was worded?

Therefore does underground trenched conductors over 10 feet become subject to ampacity temperature correction if over 4 conductors?
 
My interpretation is that you can have a very long underground trench, with less than 10 feet of wire as the wire enters the trench, and less than 10 feet of wire as the wires leave the trench, and not have to use adjustment factors for the 10 feet entering or the 10 feet leaving. You need to give the wires physical protection. If you have more than 4 conductors in the run, then adjustment factors do apply, no matter how long the trench is.
 
charlie b said:
My interpretation is that you can have a very long underground trench, with less than 10 feet of wire as the wire enters the trench, and less than 10 feet of wire as the wires leave the trench, and not have to use adjustment factors for the 10 feet entering or the 10 feet leaving. You need to give the wires physical protection. If you have more than 4 conductors in the run, then adjustment factors do apply, no matter how long the trench is.
Click to expand...
If I had a 50 feet underground trench with pvc conduit and came out of the trench with vertical pvc conduit 8 feet for one side of termination and another 8 feet coming out of the trench for the other side of termination, individually the vertical runs will be less than 10’ however the total vertical distance in feet “exiting” and “entering” the trench will exceed 10’ feet.

Therefore, all conduits that either enter or exit their trench more than 10 feet can have ampacity correction unless this code is permissive but not required? This is how it is worded by code.

If I reduce the ampacity of the vertices run that is over 10 feet, shouldn’t the rest of the underground conductors have the same ampacity?
 
charlie b said:
My interpretation is that you can have a very long underground trench, with less than 10 feet of wire as the wire enters the trench, and less than 10 feet of wire as the wires leave the trench, and not have to use adjustment factors for the 10 feet entering or the 10 feet leaving. You need to give the wires physical protection. If you have more than 4 conductors in the run, then adjustment factors do apply, no matter how long the trench is.
Click to expand...

I think that the intent is that 310.15(C)(1)(c) kind of acts as an exception to the Exception to 310.14(A)(2)...that is it permits up to 4 conductors to have no ampacity adjustment for up to 10' no matter how short the underground run is.

The exception to 310.14(A)(2) would limit the length without ampacity adjustment to 10% of the underground length or 10' which ever is less. However the exception to 310.4(A)(2) would permit you not to apply any ampacity adjustments and/or corrections to o 10% of the underground length or 10' which ever is less, no matter how many current carrying conductors are in the riser.
 
don_resqcapt19 said:
I think that the intent is that 310.15(C)(1)(c) kind of acts as an exception to the Exception to 310.14(A)(2)...that is it permits up to 4 conductors to have no ampacity adjustment for up to 10' no matter how short the underground run is.

The exception to 310.14(A)(2) would limit the length without ampacity adjustment to 10% of the underground length or 10' which ever is less. However the exception to 310.4(A)(2) would permit you not to apply any ampacity adjustments and/or corrections to o 10% of the underground length or 10' which ever is less, no matter how many current carrying conductors are in the riser.
Click to expand...
This seems to be a “permissive rule” so perhaps it doesn’t need to be followed? It’s worded stupid
 
Jpflex said:
This seems to be a “permissive rule” so perhaps it doesn’t need to be followed? It’s worded stupid
Click to expand...
It does not need to be followed, but it permits you to do something that the other rule does not permit. Not using the rule might require a larger conductor for the complete run.
 
Status
Not open for further replies.
Top