We are attempting to understand conduit fill as it relates to bundled or wrapped wire (THHN). If a group of THHN (5-14 AWG & 5-18 AWG) are wrapped (to keep the group organized) vs individual THHN (5-14 AWG & 5-18 AWG). Would the wrap make a difference in the size fill calculation?
Conduit Fill - Wrapped THHN
- Thread starter ACI
- Start date
ptonsparky
Tom
- Occupation
- EC - retired
- Location
- New Jersey
- Occupation
- Journeyman Electrician
What kind of wrap are you referring to? Like a "quick pull"?
Ptonsparky,
How would the "wrap" make it larger conductors. We have the same number and size of THHN (wrapped or not wrapped).
ptonsparky
Tom
- Occupation
- EC - retired
- Location
- New Jersey
- Occupation
- Journeyman Electrician
I don't think that the NEC directly addresses wrapped conductors. It could be argued that they're actually separate conductors so normal conductor fill applies. Or it can be argued that they are in effect a single conductor then the rules for a single conductor in a raceway would apply. Without doing some calculations I wonder if it would even matter one way or the other.
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
If you mean a larger conductor as in based on the diameter of the wrapped bundle being a single conductor, I tend to agree. I would use common sense and caution. If the bundle is tightly wrapped, I would avoid fill over 30% if there were only two. For a single bundle I would likely avoid anything over 40% for multiple wires. However, if they are tightly wrapped, then using a caliper and using that diameter for a 53% fill would be acceptable IMO, I just wouldn't put myself through the attempt to pull that unless I absolutely needed to use the small conduit.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
That would only be beneficial (in terms of having the calculation meet the limits) if you have 7 conductors in the bundle (or 18 or more, possibly). That's because 40% / 53% = 0.754, and for a small number of circles packing inside a larger circle, the only number between 2 and 17 that achieves a density greater than that is 7 conductors (in the usual hexagonal pattern).
Circle packing in a circle - Wikipedia
Cheers, Wayne
Tortuga,
I would agree, we never consider individual wrapped THHN wires a cable. It is a "bundle", but we always consider these as individual THHN wires for the purpose of NEC calculations.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Tulsa Electrician
Senior Member
- Location
- Tulsa
- Occupation
- Electrician
I would say no. It is not a conductor.
I don't believe the NEC address it.
I have to admit I was thinking about it for a minute.
Then I was thinking what if I pulled two groups of wrapped conductors and how I would address the fill. Not for NEC fill rather pulling. It would be like two larger conductors and a ID/OD and a possible jam ratio.
I may need to run some number to see if it's applicable.
Using a number of wires into two bundles. Versus number of wires. Based on raceway size.
I would not think one would be doing two or more bundles per pull however they may.