thhn and/or thwn

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thinfool

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Ok..I have been reading the thhn=dry, thwn=wet or dry discussions.

Please help me here....who and where has anyone, in reality, found any thhn wire? Everything I buy and install is combo thhn/thwn wire. If I owned a supply house, no one would sell me thhn as I would have to grill every customer as to how it would be used, otherwise I could suffer legally for not informing him as to its restrictions. (it may be his responsibility to know what to use...but remember the gal who is now rich because she had a Hot cup of coffee at McD's?)

Furthermore, it would be yet another line of items that I would have to keep in inventory. ugh.

Finally, the type of wire used in NM has to have a spec. It may be the same for each mfr, or it may be different, but it has a spec. So the following comes to mind:
Why arent the conductors labelled? Just so the mfr can save a step for reasons of cost?
Why can't the type of conductors used be labelled either individually or on the outer jacket?

If, indeed, all nylon covered wires are now thwn, who cares if it is used inside lt conduit?

What was the agenda when all of these issues were created by the folks who wrote the standards? IMO, it seems that the motive was to confuse and complicate rather than facilitate.

JP :D
 
Re: thhn and/or thwn

I don't really know for sure but I would guess that based on your assumptions, the manufacturing process that makes THHN would be the same for THWN. Like you I have never seen simple THHN. Are they the same? Probably. Will that comply with the NEC? I don't think so, unless the conductors are so marked. Could we simplify the process by making THHN and THWN the same product? Absolutely.
 
Re: thhn and/or thwn

Thinfool
"It is a complicated world we live in." :D

It takes a tremendous effort to keep well informed these days for our industry, as technology (and ideas) are moving in front of us at "lightning" speed.

THHN/THWN is a conductor insulation that has been manufactured with a copolymer, hence the dual listing. Just remember when using this type of conductor, that THHN is rated at the 90 degree C column, and THWN is rated at the 75 degree C column.

The reason that manufacturers are not putting any labeling on the conductors they manufacture for NM cable is a standard/code requirement for them. Because the conductor is required to be a 90 degreee C rated conductor, but can only be used as a 60 degree C rated conductor - a lot of "extra" cushion in the design for safety reasons.
 
Re: thhn and/or thwn

Originally posted by pierre:
Because the conductor is required to be a 90 degreee C rated conductor, but can only be used as a 60 degree C rated conductor - a lot of "extra" cushion in the design for safety reasons.
Click to expand...
This is fine...as the cable can be rated for use at 60c, but the conductors could be labeled as thhn/thwn so that if they were removed from the jacket, the other ratings could apply. Professional tradesmen change ratings on a daily basis when they derate conductors according to the place and manner in which they are used.

While I am on a roll here...can someone tell me if RHW has been discussed on Mike Holt? It is still in the code, but the only place that I can imagine that it may still be installed in a new location would be in a special jurisdiction...ie, NYC. And even there it would be rare.
 
Re: thhn and/or thwn

We install a lot of large RHW, typically a spec from the engineers on our projects.

In my opinion RHW tolerates installation in colder temperatures than THHN/THWN.
 
Re: thhn and/or thwn

"so that if they were removed from the jacket, the other ratings could apply."

Not really, removing the jacket from the conductors of NM cable and using them as a 90 degree C conductor for a different application does violate the fact that conductors are to be marked 310.11(A) and (B) for the SHEATHING of NM cable.
 
Re: thhn and/or thwn

"If I owned a supply house, no one would sell me thhn as I would have to grill every customer as to how it would be used, otherwise I could suffer legally for not informing him as to its restrictions"

Jp that comment does not water at all.It is not up to the supply house to say in what manner what ever they sell is and isn`t to be used.Using that way of thinking then anyone who purchased a MLO panel would be asked where is the disc. for that split service.Or told that it can`t be used on a back to back service.
If I purchase material it is my bad if used in a non code complying manner.
 
Re: thhn and/or thwn

Originally posted by thinfool:
If I owned a supply house, no one would sell me thhn as I would have to grill every customer as to how it would be used, otherwise I could suffer legally for not informing him as to its restrictions. (it may be his responsibility to know what to use...but remember the gal who is now rich because she had a Hot cup of coffee at McD's?)...

JP :D
Click to expand...
A bit of a tangent, but there was more to that liability suit than spilling hot coffee in her lap. Also, it would take more than a bit of ignorance from a supply house to create a lawsuit of that magnitude.

Some facts about the Mickie D's case.

McFact No. 1: For years, McDonald's had known they had a problem with the way they make their coffee - that their coffee was served much hotter (at least 20 degrees more so) than at other restaurants.

McFact No. 2: McDonald's knew its coffee sometimes caused serious injuries - more than 700 incidents of scalding coffee burns in the past decade have been settled by the Corporation - and yet they never so much as consulted a burn expert regarding the issue.

McFact No. 3: The woman involved in this infamous case suffered very serious injuries - third degree burns on her groin, thighs and buttocks that required skin grafts and a seven-day hospital stay.

McFact No. 4: The woman, an 81-year old former department store clerk who had never before filed suit against anyone, said she wouldn't have brought the lawsuit against McDonald's had the Corporation not dismissed her request for compensation for medical bills.

McFact No. 5: A McDonald's quality assurance manager testified in the case that the Corporation was aware of the risk of serving dangerously hot coffee and had no plans to either turn down the heat or to post warning about the possibility of severe burns, even though most customers wouldn't think it was possible.

McFact No. 6: After careful deliberation, the jury found McDonald's was liable because the facts were overwhelmingly against the company. When it came to the punitive damages, the jury found that McDonald's had engaged in willful, reckless, malicious, or wanton conduct, and rendered a punitive damage award of 2.7 million dollars. (The equivalent of just two days of coffee sales, McDonalds Corporation generates revenues in excess of 1.3 million dollars daily from the sale of its coffee, selling 1 billion cups each year.)

McFact No. 7: On appeal, a judge lowered the award to $480,000, a fact not widely publicized in the media.

McFact No. 8: A report in Liability Week, September 29, 1997, indicated that Kathleen Gilliam, 73, suffered first degree burns when a cup of coffee spilled onto her lap. Reports also indicate that McDonald's consistently keeps its coffee at 185 degrees, still approximately 20 degrees hotter than at other restaurants. Third degree burns occur at this temperature in just two to seven seconds, requiring skin grafting, debridement and whirlpool treatments that cost tens of thousands of dollars and result in permanent disfigurement, extreme pain and disability to the victims for many months, and in some cases, years.
 
Re: thhn and/or thwn

Allen, I actually agree with you for a change.

Now I don`t care who you are that`s funny :D
From you I`ll take that as a compliment .I think
:confused:
 
Re: thhn and/or thwn

Allen you have been around here a long time and have over a 1000 posts. Yet you still have not figured out how quoting works.

Click this
quote_ubb6.gif
on the upper right of the post you want to quote.
 
Re: thhn and/or thwn

Originally posted by iwire:
Allen you have been around here a long time and have over a 1000 posts. Yet you still have not figured out how quoting works.
Click to expand...
1297 since he re-registered. :)

Edit: of the 1297 posts, strangely only six feature a space between paragraphs. Twelve feature code references. 1290 feature the forum limit of eight smilies per post. :D

I tried talking Pierre into quotes, some people are just resistant to change. :D

[ October 22, 2005, 10:12 PM: Message edited by: georgestolz ]
 
Re: thhn and/or thwn

I didn`t know so many of you were keeping track of my posts and the # of posts since I reregistered ,George where did you go to investigate that :D
 
Re: thhn and/or thwn

Oh and George it has only been 1289 posts of a max 8 graemlins per post :) :cool: Had to max out at 8 just for you..........
 
Re: thhn and/or thwn

One last thing,I am so honored that there are people here that have kept track of my posts and faults in my posts.That actually makes me feel good since you have nothing better to do then keep track of me.Maybe I can get my own section since I am so watched :D What about it Mike? uhhhhh Mike uuuuhhhhhh Mikeeee lol.
 
Re: thhn and/or thwn

edited

[ October 23, 2005, 02:58 PM: Message edited by: ryan_618 ]
 
Re: thhn and/or thwn

Thought this might help ,


Type NM-B nonmetallic-sheathed cable (commonly called "Romex?" in the industry) is Listed by Underwriters Laboratories Inc. for use in accordance with the National Electrical Code? (NEC?) under the product category "Nonmetallic-sheathed Cable (PWVX)." Guide Information for this category can be found in UL's Online Certifications Directory and on page 84 of UL's 2005 General Information for Electrical Equipment Directory (White Book).

In the mid-1980s, the outer jacket of this cable changed from an impregnated, braided covering to polyvinyl chloride (PVC), and the internal conductor insulation went from a 60 C to a 90 C rating. This newer cable is typically referred to as Type NM-B.

Section 334.10(A)(1) of the NEC states that Type NM cable shall be permitted for use in "normally dry locations." Article 100 of the NEC defines a dry location as:

Location, Dry. A location not normally subject to dampness or wetness. A location classified as dry may be temporarily subject to dampness or wetness, as in the case of a building under construction.

The older, braided jacketed version of this cable has less resistance to water ingress than the newer, PVC jacketed version, and if subject to immersion, such as from flooding, the suitability for continued use is unknown. Any cable of this type that has been subjected to flooding should be replaced without question.

In general, cables with PVC insulation and jacket can withstand immersion in clean water for a short period of time without being damaged as long as the ends are not immersed. For example, a building may be subject to rainfall while under construction, and water may come in contact with the outer jacket of nonmetallic-sheathed cable. This is not prohibited by the NEC. The UL Standard for Safety for Nonmetallic-Sheathed Cables, ANSI/UL 719, requires Dielectric Voltage-Withstand Tests after 24-hour water immersion of cable samples (with ends in free air). If the ends of the cable are immersed for any period of time, however, the internal paper wrapping around the bare equipment-grounding conductor will absorb and transfer the water into the cable assembly. The water may then start degrading the insulation or possibly corrode the conductors. If the cable comes into contact with contaminated water, the contaminants may also act on the insulation or conductors. Over time, failures can occur.

In a flooding situation, there is no way of knowing how long the cables were immersed in water, or what types of potentially corrosive substances may have been in the water that flooded the cables. As was widely reported after Hurricane Katrina, raw sewage and chemicals were known to be in the floodwaters afflicting the Gulf Coast region of the United States. Nonmetallic-sheathed cable has not been investigated by UL for this type of exposure. Therefore, it is not possible for UL to state that cable in a particular installation is acceptable for continued use after having been subjected to the flooding.

The safest approach is to replace any nonmetallic-sheathed cable that was immersed in water for any period of time during the flooding.

For more information on Type NM-B nonmetallic-sheathed cable, contact Austin Wetherell in Melville, N.Y., by phone at +1-631-271-6200, ext. 22818; or by e-mail at Austin.Wetherell@us.ul.com.
 
Re: thhn and/or thwn

Originally posted by allenwayne:
I didn`t know so many of you were keeping track of my posts and the # of posts since I reregistered
Click to expand...
It :) is :( the :eek: only :D reason ;) I :p come :cool: here. :eek:

[ October 23, 2005, 09:41 AM: Message edited by: iwire ]
 
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