Article 376.56 splices in a wireway

Strathead

Senior Member
It is ironic how one can review codes for decades and still discover a code that one has never even heard of. So I was slammed with 376.56. I am sure someone with cut and paste ability will post the exact wordage, but here is my issue. If I read it correctly, it requires a maximum of 75% fill at any 2 dimensional cross section where splices or taps occur. But if that statement is correct it seems to me impossible to calculate. Or actually highly improbable and outside the capability of the average on site electrician or inspector. You would have to determine the area of the splice with in the case of a taped split bolt connector for example could be different at every point. Along with that the area of the wire at that same point, for the sake of argument let's say it is a conductor for a different splice and that "point" is cutting through the bend of the conductor. Infinitely every "point" would have a slightly different calculation and realistically you couldn't really make an educated guess as to the area at any one point.

What am I missing?
 

infinity

Moderator
Staff member
Location
New Jersey
IMO the fact remains that it's impossible to exceed 75% of fill in the area of the tap or splice so there is little need to perform any calculation but I do see your frustration with the actual wording.
 

Carultch

Senior Member
Location
Massachusetts
It is ironic how one can review codes for decades and still discover a code that one has never even heard of. So I was slammed with 376.56. I am sure someone with cut and paste ability will post the exact wordage, but here is my issue. If I read it correctly, it requires a maximum of 75% fill at any 2 dimensional cross section where splices or taps occur. But if that statement is correct it seems to me impossible to calculate. Or actually highly improbable and outside the capability of the average on site electrician or inspector. You would have to determine the area of the splice with in the case of a taped split bolt connector for example could be different at every point. Along with that the area of the wire at that same point, for the sake of argument let's say it is a conductor for a different splice and that "point" is cutting through the bend of the conductor. Infinitely every "point" would have a slightly different calculation and realistically you couldn't really make an educated guess as to the area at any one point.

What am I missing?
If you can comfortably close the wireway cover, without resorting to wedging it closed with a screwdriver, or banging it closed with a hammer, you've usually maintained the fill limits on splices.


The number is given to you as a guideline, so that you can anticipate this based on physical size of the splice devices while you are selecting the size of the wireway. In a 6x6 trough, this amounts to 5.2" x 5.2" region that you've saturated with wires and splices.
 

Strathead

Senior Member
IMO the fact remains that it's impossible to exceed 75% of fill in the area of the tap or splice so there is little need to perform any calculation but I do see your frustration with the actual wording.

Basically the a superfluous code requirement that is only there to create havoc with an aggressive inspector.
 

Strathead

Senior Member
The dimensions of Polaris lugs can be found here http://www.polarisconnectors.com or in their paper catalog.

Beyond that it is simple math to determine the area.
I contend that it is only simple math to BS the area. If the Polaris lug is sitting at a 3 degree angle relative to the cover, then it has a different area than if it is sitting at a 4 degree angle. This is a worse ambiguity than saying parallel conductors shall be the same length.
 

iwire

Moderator
Staff member
Location
Massachusetts
I contend that it is only simple math to BS the area. If the Polaris lug is sitting at a 3 degree angle relative to the cover, then it has a different area than if it is sitting at a 4 degree angle. This is a worse ambiguity than saying parallel conductors shall be the same length.
It's as hard as you make it.:roll:

Do the math straight up, hand the calcs to the inspector and put in their ball park to dispute it.

You will be so far from reaching fill, a small error is irelevent.
 

Strathead

Senior Member
It's as hard as you make it.:roll:

Do the math straight up, hand the calcs to the inspector and put in their ball park to dispute it.

You will be so far from reaching fill, a small error is irelevent.
I do agree with that, but it doesn't make it any less irritating to a type A slightly OCD person like myself!
 

wwhitney

Senior Member
Location
Berkeley, CA
I contend that it is only simple math to BS the area. If the Polaris lug is sitting at a 3 degree angle relative to the cover, then it has a different area than if it is sitting at a 4 degree angle. This is a worse ambiguity than saying parallel conductors shall be the same length.
There is likely enough space available that you could just assume the worst possible orientation for your calculation and still be under 75% easy.

Another option is to cut a small piece of plywood with area equal to 25% of the wireway's cross-sectional area, and then demonstrate that you can insert it perpendicularly into the wireway alongside the Polaris. The shape of the plywood would be chosen to avoid the Polaris and minimize the number of wires you have to push on.

Again, that would be more stringent than the written rule, but you likely have enough extra space to be able to do it.

Cheers, Wayne
 
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