Conduit Fill

[timm333]

I have a question about NEC Table 1. For 4 conductors the maximum allowed fill is 40%, but this 40% assumes that there are two ninety bends in the conduit run. If there are more than two ninety bends, then the percent fill should be decreased by 15% for each bend. My question is that if there is no bend at all (straight run), then can the allowed fill be increased to something like 60%? Thanks.

 

[Ponchik]

Never heard of this before. (2) 90s in the run if more than that add 15%.

 

[Dennis Alwon]

I have a question about NEC Table 1. For 4 conductors the maximum allowed fill is 40%, but this 40% assumes that there are two ninety bends in the conduit run. If there are more than two ninety bends, then the percent fill should be decreased by 15% for each bend. My question is that if there is no bend at all (straight run), then can the allowed fill be increased to something like 60%? Thanks.

The number of bends has nothing to do with fill capacity.

 

[GoldDigger]

The number of bends has nothing to do with fill capacity.

It affects pulling tension, which is also in part a function of fill capacity, but the NEC does not address that directly in its limitations on either fill factor or cumulative bends.

 

[tkb]

I have a question about NEC Table 1. For 4 conductors the maximum allowed fill is 40%, but this 40% assumes that there are two ninety bends in the conduit run. If there are more than two ninety bends, then the percent fill should be decreased by 15% for each bend. My question is that if there is no bend at all (straight run), then can the allowed fill be increased to something like 60%? Thanks.

Where are you getting this info, it's not in Table 1?

 

[Dennis Alwon]

It affects pulling tension, which is also in part a function of fill capacity, but the NEC does not address that directly in its limitations on either fill factor or cumulative bends.

Sure, that is why we are limited to 360°.

 

[timm333]

I got the 15% info from "Step 3" on this link: http://ce.superioressex.com/uploade...guidelines/TG16-Conduit-Fill-Requirements.pdf

 

[tkb]

I got the 15% info from "Step 3" on this link: http://ce.superioressex.com/uploade...guidelines/TG16-Conduit-Fill-Requirements.pdf

Thats not code, it's to sell more conduit.

 

[timm333]

What about high voltage 138 kV underground cables, for example 138 kV cables? As NEC does not apply to high voltage, so can engineering judgment be used for sizing the conduits for 138 kV cables?

 

[GoldDigger]

Thats not code, it's to sell more conduit.

It would be awkward if am AHJ interpreted that as installation instructions for the conduit. :angel:

Sent from my XT1585 using Tapatalk

 

[Carultch]

I have a question about NEC Table 1. For 4 conductors the maximum allowed fill is 40%, but this 40% assumes that there are two ninety bends in the conduit run. If there are more than two ninety bends, then the percent fill should be decreased by 15% for each bend. My question is that if there is no bend at all (straight run), then can the allowed fill be increased to something like 60%? Thanks.

The only time when you can fill to 60%, is when the raceway is 2 ft and less in length. The details this doesn't address, is whether this is the length of raw raceway material, or if this is the length between enclosures, or if this is the length between the finished terminations with bushing surfaces.

The code required fill factor in all longer raceways, does not depend on the number of bends. It generally represents about 75% of the diameter, which is why single round wire in round raceway is 53%, two wires is reduced to 31%, and 40% is the fill factor for everything else.

 

[tkb]

It would be awkward if am AHJ interpreted that as installation instructions for the conduit. :angel:

Sent from my XT1585 using Tapatalk

If it were realistic it would be different.
Accorging to them, if I had 360° of bends, then I could only fill to 10°. :lol:

Now that I read it again, it looks like this is by a data cable company with data conduit recommendations.