Covered vs. Uncovered Conductor

[clay.luna@tcatpulaski.edu]

My students were watching your raceway and conductor sizing dvd on 2011 code and had a question that I can not find the answer to. In Annex C you talked about a RHH wire that had an asterisk beside it and you commented that at the bottom of the page it said the asterisk stands for a conductor without cover.

I have researched this and cannot find the answer to their question. They have asked what is the difference in this section for covered wire vs. uncovered wire. This clearly does not mean bare vs. insulated, and I'm thinking it dosnt mean Coated vs. Uncoated like in Chapter 9 Table 8. So I told them I would find out and this should be coming straight from the horses mouth.

Thanks for the help.

 

[kwired]

My students were watching your raceway and conductor sizing dvd on 2011 code and had a question that I can not find the answer to. In Annex C you talked about a RHH wire that had an asterisk beside it and you commented that at the bottom of the page it said the asterisk stands for a conductor without cover.

I have researched this and cannot find the answer to their question. They have asked what is the difference in this section for covered wire vs. uncovered wire. This clearly does not mean bare vs. insulated, and I'm thinking it dosnt mean Coated vs. Uncoated like in Chapter 9 Table 8. So I told them I would find out and this should be coming straight from the horses mouth.

Thanks for the help.

First welcome to the forum.

Second it appears you are trying to directly ask Mike Holt a question, I will let you know that though Mike is the owner of the forum he generally does not participate in the forum, so you are stuck with the rest of us most of the time. Mike does start new threads - usually with links to other information on his site, but very seldom do you see him reply to content in any other threads.

If you could give us a little more detail of what the content of this video is all about maybe it can help someone address the answer a little better.

 

[texie]

My students were watching your raceway and conductor sizing dvd on 2011 code and had a question that I can not find the answer to. In Annex C you talked about a RHH wire that had an asterisk beside it and you commented that at the bottom of the page it said the asterisk stands for a conductor without cover.

I have researched this and cannot find the answer to their question. They have asked what is the difference in this section for covered wire vs. uncovered wire. This clearly does not mean bare vs. insulated, and I'm thinking it dosnt mean Coated vs. Uncoated like in Chapter 9 Table 8. So I told them I would find out and this should be coming straight from the horses mouth.

Thanks for the help.

RHH and RHW can be had with or without outer cover. The issue here is that they will have different overall physical dimensions and hence will occupy more or less space in the conduit fill calculation. Take a look at Table 5 in Chapter 9 and you will see the difference in overall size of each.
You might make your students aware that RHH conductors are used very commonly in licensing exam questions for this reason and to be very careful that they are using the with or without covering as required in the question as the answer will always be different.

 

[kwired]

RHH and RHW can be had with or without outer cover. The issue here is that they will have different overall physical dimensions and hence will occupy more or less space in the conduit fill calculation. Take a look at Table 5 in Chapter 9 and you will see the difference in overall size of each.
You might make your students aware that RHH conductors are used very commonly in licensing exam questions for this reason and to be very careful that they are using the with or without covering as required in the question as the answer will always be different.

What is this outer cover? Any pictures or links to examples?

 

[captainwireman]

In article 100-Definitions: Conductor, Bare and Conductor, Covered is spelled out if this helps the students.

 

[kwired]

In article 100-Definitions: Conductor, Bare and Conductor, Covered is spelled out if this helps the students.

But it doesn't tell us what an insulated conductor with an outer covering is.

I agree that when it comes to raceway fill this outer covering takes up space and must be considered, but just exactly what is this "outer covering" is the main question here.

 

[captainwireman]

A covered wire is generally the same material as insulation but not applied with the thickness to qualify as a UL listed insulation. In addition, cloth, paper, green coating on a grounding conductor in a cable assembly, and lead sheath are some examples. This was used in knob and tube style wiring and a modern day use is for decorative pendant fixture wires.

 

[kwired]

A covered wire is generally the same material as insulation but not applied with the thickness to qualify as a UL listed insulation. In addition, cloth, paper, green coating on a grounding conductor in a cable assembly, and lead sheath are some examples. This was used in knob and tube style wiring and a modern day use is for decorative pendant fixture wires.

The question in the OP is not about "covered" conductors, it is about RHH with or without an outer covering. RHH alone is a NEC recognized insulation, the question here is just exactly what is this additional "outer covering" that may be on this conductor?

 

[kwired]

Here is a link for a conductor with an outer covering that is likely one example of what is being referred to when they mention "with/without an outer covering"

http://www.vitalinkcable.com/commercial/PDF/Vitalink RHW US Market 2-23-11_Vitalink RHH only.pdf

I'm guessing that only certain conductor types are generally used with such outer coatings and to get dimensions for a conductor with such a coating you likely need to go outside the NEC and directly to the manufacturer as I can see there possibly being more than one type of such coating.


I have never run into such conductors before but occasionally crossed my mind when seeing this "without outer covering" in the NEC and thinking to myself "what is this covering they speak of?"

 

[Pcmaker]

I was going to ask this same exact question. Watching that DVD was confusing, especially when they mention cover and uncovered quite a bit. I thought by "cover," they were referring to the Nylon

 

[GoldDigger]

Looking at Table 310.104(A), I am forced to the conclusion that the "*" in the RHH and RHW entry Trade Name column is meant to indicate that footnotes 4, 5 and 6 all apply even though they are not called out separately.

I suspect that the "overall covering" being described is one which binds two or more of the basic RHH or RHW conductors into an assembly or which provides moisture or flame retardant characteristics which the basic insulation may not provide.

I do not think that it applies to the two layer insulation design of the wire in the linked PDF. I would call that nylon layer an integral part of the wire insulation and not a covering.

JMO

 

[kwired]

I was going to ask this same exact question. Watching that DVD was confusing, especially when they mention cover and uncovered quite a bit. I thought by "cover," they were referring to the Nylon

RHW or RHH does not have an outer nylon jacket, THHN and THWN do but that nylon jacket is included in the conductor dimensions in chapter 9.

 

[GoldDigger]

RHW or RHH does not have an outer nylon jacket, THHN and THWN do but that nylon jacket is included in the conductor dimensions in chapter 9.

The specific Vitalink cable linked in an earlier post has an XLPO outer jacket and is listed to meet RHH or RHW standards.
I suspect that this is included in the "without cover" dimensions too, but I did not look closely at the table in the PDF.

 

[kwired]

The specific Vitalink cable linked in an earlier post has an XLPO outer jacket and is listed to meet RHH or RHW standards.
I suspect that this is included in the "without cover" dimensions too, but I did not look closely at the table in the PDF.

IDK. I was trying search for an example of RHW with the mentioned "outer covering" as I always have noticed that note about it but never knew just what it was referring to. I had no real success with finding any answer other then that Vitalink cable possibly being an example of what that covering may be. Though I did not look into any details of that cable or if it is a different dimension then regular RHW.

 

[captainwireman]

"They have asked what is the difference in this section for covered wire vs. uncovered wire."

http://www.electrowire.com/telcoflex-a/

Am I missing something here?

 

[kwired]

"They have asked what is the difference in this section for covered wire vs. uncovered wire."

http://www.electrowire.com/telcoflex-a/

Am I missing something here?

IDK, looks to me like your product link is likely about same thing as my product link - just from a different manufacturer. What IDK is whether or not it is the type of product NEC is referring to when it mentions *with/without an outer covering.

Was kind of hoping someone with actual experience with such conductors the NEC refers to would step in and clarify for us, otherwise my link was just a shot in the dark at the only possibility I have found so far.

 

[captainwireman]

I wasn't jabbing. I have installed conductors, medium voltage, in underground vaults tied in by rigid conduit as per spec that were considered "covered" for fill calculations purposes. I didn't want to throw this into the mix because they were not RHH and probably would confuse more than clarify so I chose this link. If I have this wrong, I hope someone corrects me.

 

[captainwireman]

From American Electricians Handbook 17th edition:

Covered. Designating a conductor encased in material whose thickness or composition is not recognized by the National Electrical Code as electrical insulation.

2.19 38 Protective-covering materials and finishes

Nonmetallic
a. cotton
b. Seine twine or hawser cord
c. hemp
d. paper and cotton
e. jute
f. asbestos
g. silk
h. rayon
i. Fibrous glass

Tapes
a. rubber filled cloth
b. combination of cotton cloth and rubber compounds

Woven covers
Unspun felted cotton
Rubber jackets
Synthetic jackets
Thermoplastic jackets
Jute and asphalt

Saturant
asphault
paint
varnish

According to finish
1. Stearin pitch and mica flake
2. Paint
3. Wax
4. Lacquer
5. Varnish

Metallic
A. Pure lead sheath
B. Reinforced lead sheath
C. Alloy-lead sheath
D. Flat-band armor
E. Interlocked armor
F. Wire armor
G. Basket-weave armor