MasterTheNEC
CEO and President of Electrical Code Academy, Inc.
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- McKinney, Texas
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- CEO
Have you read UL-83 and 44 as well in regards to multiconductor cable?
Cable Definition
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Have you read UL-83 and 44 as well in regards to multiconductor cable?
MasterTheNEC
CEO and President of Electrical Code Academy, Inc.
- Location
- McKinney, Texas
- Occupation
- CEO
OK....We will have to agree to disagree...and I am perfectly at peace with that...lol
I might have said the exact same thing before I started working closely with the wire and cable industry. I can promise you this way of thinking is not "only in my head" as this is exactly how the wire and cable industry thinks. In terms of the NEC, nothing in Note 9 of Table 1 says anything to the manufacturer other than a "multiconductor cable" can utilize the 53% fill. It says nothing about what type of cable "in terms of type", it simply says multiconductor cable. The conductors being used in the cabling process are those listed in 310.104 and so on.
You again can agree or disagree, as a previous AHJ I have no problem with them using the 53% on a factory pre-twisted "cabled" set of conductors in a raceway. In fact, I believe (as do other too afraid to get into debates) that having this factory cabled conductors, twisted to the specific length of lay tolerances that would reduce potential jamming effects, reduce the coefficient of friction with the pre-lubrication process and so on is acceptable.
And now that we do "pull" tests monthly, I do "pull" calculations nearly daily with side wall pressure tests, you could never convince me otherwise.
But hey.....to each it own but recognize others have opinions that differ from yours....some of you have a hard time swallowing that pill. :angel:
I might have said the exact same thing before I started working closely with the wire and cable industry. I can promise you this way of thinking is not "only in my head" as this is exactly how the wire and cable industry thinks. In terms of the NEC, nothing in Note 9 of Table 1 says anything to the manufacturer other than a "multiconductor cable" can utilize the 53% fill. It says nothing about what type of cable "in terms of type", it simply says multiconductor cable. The conductors being used in the cabling process are those listed in 310.104 and so on.
You again can agree or disagree, as a previous AHJ I have no problem with them using the 53% on a factory pre-twisted "cabled" set of conductors in a raceway. In fact, I believe (as do other too afraid to get into debates) that having this factory cabled conductors, twisted to the specific length of lay tolerances that would reduce potential jamming effects, reduce the coefficient of friction with the pre-lubrication process and so on is acceptable.
And now that we do "pull" tests monthly, I do "pull" calculations nearly daily with side wall pressure tests, you could never convince me otherwise.
But hey.....to each it own but recognize others have opinions that differ from yours....some of you have a hard time swallowing that pill. :angel:
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- Massachusetts
Yeah, someone here sure seems to have an issue with differing opinions.
mwm1752
Senior Member
- Location
- Aspen, Colo
NEC defines SE Cable as multi conductor/ with or without covering-- Triplex, Quadreplex by NEC definition is a cable IMO
338.2 Definitions
Service-Entrance Cable. A single conductor or multiconductor assembly provided with or without an overall covering, primarily used for services, and of the following types:
Type SE. Service- entrance cable having a flame-retardant, moisture resistant covering.
Type USE. Service -entrance cable, identified for underground use, having a moisture-resistant covering, but not required to have a flame-retardant covering.
338.2 Definitions
Service-Entrance Cable. A single conductor or multiconductor assembly provided with or without an overall covering, primarily used for services, and of the following types:
Type SE. Service- entrance cable having a flame-retardant, moisture resistant covering.
Type USE. Service -entrance cable, identified for underground use, having a moisture-resistant covering, but not required to have a flame-retardant covering.
MasterTheNEC
CEO and President of Electrical Code Academy, Inc.
- Location
- McKinney, Texas
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- CEO
lol..I have no problem with your opinion...as long as i'm entitled to one as well.
There's only one person that can entitle you to your own opinion...
...unless you're schizophrenic. :lol:
MasterTheNEC
CEO and President of Electrical Code Academy, Inc.
- Location
- McKinney, Texas
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- CEO
- Location
- Placerville, CA, USA
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- Retired PV System Designer
And in the wonderful world of the NEC (and other standards as well) it is quite possible for a Service-Entrance Cable not to be a cable in the more general sense.
Also, although the quote above says that services entrance cable does not need to have a covering, Type SE cable does. How do you reconcile that with the statement that SE cable does not have to have a covering.
Or else it simply means, as others have mentioned, that triplex is not SE.
We need to be careful not to think that SE and service-entrance (s-e for short) are the same thing. SE and USE are two examples of s-e, but both are required to have a covering.
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Ummm... no, Type USE is not required to have a covering. It's right there in the definition.And in the wonderful world of the NEC (and other standards as well) it is quite possible for a Service-Entrance Cable not to be a cable in the more general sense.
Also, although the quote above says that services entrance cable does not need to have a covering, Type SE cable does. How do you reconcile that with the statement that SE cable does not have to have a covering.
Or else it simply means, as others have mentioned, that triplex is not SE.
We need to be careful not to think that SE and service-entrance (s-e for short) are the same thing. SE and USE are two examples of s-e, but both are required to have a covering.
K8MHZ
Senior Member
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- Electrician
It most certainly is required to have a covering, that's right there in the definition.
Take a look at Table 310.13(a). Note the columns. There is one for insulation and a separate one for outer covering.
Type USE must have an outer covering.
What is getting confused is 'covering' and 'overall covering'.
For instance, single conductor THHN must have a nylon jacket or equivalent covering the thermoplastic insulation.
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In 2014 it's Table 310.104(A).
Now that you referred to it, please note this table references only single conductor and some single conductor cable... but not multiconductor cable. Take a look at the Trade Name column...
If you wish to get more specific... http://ulstandardsinfonet.ul.com/scopes/scopes.asp?fn=0854.html
Ultimately, multiconductor Type USE cable is not required to have an overall covering.
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mwm1752
Senior Member
- Location
- Aspen, Colo
2 schools of thought being discussed here -- straight up code -- Is it reasaonable. Code is the only one that can be enforced in this instance.
wwhitney
Senior Member
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- Berkeley, CA
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- Retired
Hello,
Counting three twisted conductors as a cable won't help you in terms of conduit fill. Because once you consider them as a cable, you have to use that cable's diameter. And if I did my math correctly, filling a large circle with three smaller circles uses only 64.6% of the large circle's area. So while with one cable you are allowed 53% of the conduit's area, you are only using 64.6% of that, or 34.2% overall. Which is less than 40%.
Twisting 4 conductors is a little better, I get a packing efficiency of 68.6%, which gets you up 36.4% overall. Maybe when I'm more awake I'll do the math for the general case and see if you ever get above 40% overall.
Cheers, Wayne
Counting three twisted conductors as a cable won't help you in terms of conduit fill. Because once you consider them as a cable, you have to use that cable's diameter. And if I did my math correctly, filling a large circle with three smaller circles uses only 64.6% of the large circle's area. So while with one cable you are allowed 53% of the conduit's area, you are only using 64.6% of that, or 34.2% overall. Which is less than 40%.
Twisting 4 conductors is a little better, I get a packing efficiency of 68.6%, which gets you up 36.4% overall. Maybe when I'm more awake I'll do the math for the general case and see if you ever get above 40% overall.
Cheers, Wayne
wwhitney
Senior Member
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- Berkeley, CA
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- Retired
See http://en.wikipedia.org/wiki/Circle_packing_in_a_circle
40/53 = 75.5%, so with 7 conductors at a packing efficiency of 77.8% you'd be slightly ahead by cabling the conductors. Otherwise, with under 18 conductors in the conduit, just leave them separate.
Cheers, Wayne
Good point. Although the Notes don't really say we have to use the diameter for such a cable. It only references the major diameter of cables with an elliptical cross section.
Wouldn't that be under 7 rather than 18...???
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- Location
- Placerville, CA, USA
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- Retired PV System Designer
Under 8, I think, since the improvement for 7 is very small.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
Let me rephrase that for clarity: for between 2 and 17 conductors in the bundle, you only come out ahead in the case of 7 conductors.
Cheers, Wayne
Does that mean you don't come out ahead for 2 through 6 ...AND... 8 through 17?
BTW, did you factor in overall diameter change for the twist? (Just kidding
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The way identically sized conductors pack into a circle has a density peak at 7 because six conductors fit perfectly around the seventh in the middle.
Kind of like the increased stability of atoms with full outer electron shells.
If you twist the seven without keeping one in the center you lose the otherwise small advantage you get at 7.
Kind of like the increased stability of atoms with full outer electron shells.
If you twist the seven without keeping one in the center you lose the otherwise small advantage you get at 7.
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Twisting with one in the center, the outer six will be on an angle. That'll make the cross sectional area of the six each somewhat elliptical. As such, they will not fit perfectly around the seventh. The circumscribing circle will be larger... making the density percentage lower.
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