Ch.9/table8 Resistance on uncoated/coated

[cwain]

please explain the differance of uncoated and coated wire? I think I am using this chart wrong. The way I have been using it is when I am getting the resistance of bare copper , I use the uncoated column and when I am checking resistance of ,say THHN insulated conductor I use the coated column.

 

[cwain]

several people have looked at this but no replys . I s that becouse no one knows or what ? come on now.

 

[hardworkingstiff]

I am of the understanding that the coated is a tinned conductor. I don't know it that is correct, but that's my understanding.

 

[cwain]

more comments please

 

[Chamuit]

I've always taken it as uncoated is bare and coated is insulated.

 

[cadpoint]

First off I don't know why you’re swapping between, coated and uncoated.

A coating is put on a single stand of wire because copper will be attack many other compounds and
element that will eat it up. One could basically think of the coating as rust inhibitor.

The coating is not an insulator but a dielectric, dielectric being an insulating material or a very poor
conductor of electric current.

So with the coating you notice the resistant goes up, also remeber that AC voltage wants to run on the outside of the wire (skin effect) and that little bit of coating adds up, thus increasing the resistance as shown in the table.

I would think you'd always want to use a coated wire, unless qualified otherwise.

 

[cadpoint]

Well I just realized that it a DC Resistance in the chart, DC Power uses all of the wire, the full circumferance of the strain.

The skin effect is way less in DC verses AC but still present in a DC wire... the type of insulation can also change the add or detact from a wire properties similar to THHW and others in two different collumn in 310.16, but this change is based on temperture.

 

[cwain]

First off I don't know why you?re swapping between, coated and uncoated.

A coating is put on a single stand of wire because copper will be attack many other compounds and
element that will eat it up. One could basically think of the coating as rust inhibitor.

The coating is not an insulator but a dielectric, dielectric being an insulating material or a very poor
conductor of electric current.

So with the coating you notice the resistant goes up, also remeber that AC voltage wants to run on the outside of the wire (skin effect) and that little bit of coating adds up, thus increasing the resistance as shown in the table.

I would think you'd always want to use a coated wire, unless qualified otherwise.

therefore I take it that coated wire does not mean insulated wire. correct?

 

[yired29]

First off I don't know why you’re swapping between, coated and uncoated.

A coating is put on a single stand of wire because copper will be attack many other compounds and
element that will eat it up. One could basically think of the coating as rust inhibitor.


The coating is not an insulator but a dielectric, dielectric being an insulating material or a very poor
conductor of electric current.

So with the coating you notice the resistant goes up, also remeber that AC voltage wants to run on the outside of the wire (skin effect) and that little bit of coating adds up, thus increasing the resistance as shown in the table.

I would think you'd always want to use a coated wire, unless qualified otherwise.

I believe coated was used when rubber insulation is used, copper and rubber don't mix.
I always use uncoated unless it is given that it is coated.

 

[yired29]

therefore I take it that coated wire does not mean insulated wire. correct?

Definition
Conductor, Insulated. A conductor encased within material of composition and thickness that is recognized by this Code as electrical insulation.

 

[yired29]

330.104 Conductors.
Conductors shall be of copper, aluminum, copper-clad aluminum, nickel or nickel-coated copper, solid or stranded. The minimum conductor size shall be 18 AWG copper, nickel or nickel-coated copper, and 12 AWG aluminum or copper-clad aluminum.

Take a close look at Table 310.13 TFE and 310.18 PFAH, TFE

 

[Volta]

I've always taken it as uncoated is bare and coated is insulated.

Me too. Notice the wording of Note 1.

These resistance values are valid only for the parameters given. Using conductors having coated strands, different stranding type, and, especially, other temperatures changes the resistance.

So if coated strands changes the values, that must not be what is meant in the heading by "Coated".

 

[kbsparky]

Just took a Code class yesterday, and this was discussed. Instructor mentioned that most all your standard wiring (romex, MC, THHN, etc) is uncoated. Some specialty wires that have tin coating can be determined by looking at the conductor ends.

Coating is not insulation.

 

[cadpoint]

I believe coated was used when rubber insulation is used, copper and rubber don't mix.
I always use uncoated unless it is given that it is coated.

I think all two or three of Us have been using the wrong terms, maybe its just me, my thinking has been corrected but not quenched as to a researching for the answer; as to the correct use to a "Coating" not insulation that is put on a wire when manufactured. That is just put on to protect it from corrosion. Maybe I'm just flat out wrong!

I tried researching the FPN as listed under table 8. I also tried to search the other numbers listed with-in. It's not light reading and not to say direct to the point of the OP. I didn't dig deep, I'm sure the definitions are in there, but I gave up.

I did go to Southwire and found there general sudo vague, one might even consider it quite finite, "Wire and Cable Terms/Rating" page.

Take a look at CONDUCTOR INSULATION / CABLE JACKETS, one might come to the same conclusion as previously stated.

 

[yired29]

I think all two or three of Us have been using the wrong terms, maybe its just me, my thinking has been corrected but not quenched as to a researching for the answer; as to the correct use to a "Coating" not insulation that is put on a wire when manufactured. That is just put on to protect it from corrosion. Maybe I'm just flat out wrong!

I tried researching the FPN as listed under table 8. I also tried to search the other numbers listed with-in. It's not light reading and not to say direct to the point of the OP. I didn't dig deep, I'm sure the definitions are in there, but I gave up.

I did go to Southwire and found there general sudo vague, one might even consider it quite finite, "Wire and Cable Terms/Rating" page.

Take a look at CONDUCTOR INSULATION / CABLE JACKETS, one might come to the same conclusion as previously stated.

330.104 Conductors.
Conductors shall be of copper, aluminum, copper-clad aluminum, nickel or nickel-coated copper, solid or stranded. The minimum conductor size shall be 18 AWG copper, nickel or nickel-coated copper, and 12 AWG aluminum or copper-clad aluminum.

I think what is in red says it all. A coating is not insulation. This is also found in 332.104 Conductors, and 336.104 Conductors. Table 310.13 has it for TFE and PFAH wire types and this is not listed under insulation.

 

[yired29]

Take a look at page 5 on the following link.

http://www.nfpa.org/assets/files/PDF/Proceedings/Dini_paper_-_History_Residential_Wiring.pdf

 

[hardworkingstiff]

Take a look at page 5 on the following link.

http://www.nfpa.org/assets/files/PDF/Proceedings/Dini_paper_-_History_Residential_Wiring.pdf

Great link.

Beginning in Edison?s time, the original residential wiring systems used conductor insulation made of gum-rubber. This ?rubber? insulation was actually a mixture of ingredients including vulcanizing agents containing sulfur for curing. These various additives, especially sulfur, had a very corrosive effect on the copper conductor, so the copper had to be tinned.

If this article is correct, it looks like the coating is a reference to "tinned" wire?

 

[stjohnbarleycorn]

yes it is tinned wire. not insulation

 

[jumper]

I did a quick search and it is tinned wire. The tin is added to a smaller copper wire and the result is a coated wire of the same dimension as an uncoated wire, but has a slightly higher resistance.