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jamiedolan 01-02-2009 02:49 PM

Number of Strands in THHN
 
HI;

Can anyone tell me why they make THHN with different numbers of strands and if it really matters?

Is it just that more strands makes it easier to pull? Can I use 4 strand within the same fill limits and such as long as I am careful with it?

I found 6awg 500' 4 strand THHN for $156. Is that a pretty fair price for the 4 strand?

Thanks
Jamie

220/221 01-02-2009 02:53 PM

I've never seen 4 strand.

No matter what your wife tells you, size is all that matters.:eek:

micromind 01-02-2009 03:09 PM

THHN generally comes in 7 strand, or more commonly 19 strand up to 4/0. From 250 MCM to 500 MCM, it's 37 strand. 600 MCM to 1000 MCM is 61 strand. I can't remember the larger sizes, but 127 strand rings a bell. The more strands it has, the easier it is to bend.

Rob

Yoyizit 01-02-2009 06:04 PM

The number of strands have to do with the number of circles (strand cross sections) that fit inside a bigger circle (cable cross section), with minimum wasted space.
7 & 19 are magic numbers in this regard.

http://www.houwire.com/products/tech...conductor.html

InPhase277 01-02-2009 08:07 PM

Jaime, if you had ever worked with 500 kcmil and larger, you would know the benefits of more strands. I love big jobs, but I don't look forward to pulling the services that's for sure! We once did a large industrial upgrade at a glass factory and had to lay alot of 750 kcmil in a cable tray. But it was spec'd in what was called "locomotive cable". I don't know how many strands it had, but it was flexible enough to jump rope with. Unfortunately my boss wouldn't buy it for every big job:(.

But for #6, sure, 4 strand would be fine for runs that didn't have a bunch of bends in them. Overall, the amount of copper is the same.

frenchelectrican 01-02-2009 11:22 PM

Quote:

Originally Posted by InPhase277 (Post 205930)
Jaime, if you had ever worked with 500 kcmil and larger, you would know the benefits of more strands. I love big jobs, but I don't look forward to pulling the services that's for sure! We once did a large industrial upgrade at a glass factory and had to lay alot of 750 kcmil in a cable tray. But it was spec'd in what was called "locomotive cable". I don't know how many strands it had, but it was flexible enough to jump rope with. Unfortunately my boss wouldn't buy it for every big job:(.

But for #6, sure, 4 strand would be fine for runs that didn't have a bunch of bends in them. Overall, the amount of copper is the same.


The last Locomovite cable I know it have over 150 strands so they are extra fexibale and also they are multi voltage rated 600v and IIRC 2KV as well.

Merci,Marc

nap 01-03-2009 12:25 AM

#18-#2 7 strands
#1- 4/0 19 strands
250 mcm - 500 mcm 37 strands
600mcm- 1000mcm 61 strands
1250 mcm and 1500 mcm 91 strands
1750 mcm and 2000 mcm 127 strands

info per NEMA WC--8 1992 or ANSI/UL 1581-1998 for class B stranding

from NEC 2008 Table 8

4 strand? that would be very stiff wire.

J. V. 01-03-2009 01:43 PM

I worked in a plant one time and we used locomotive cable for all the large DC motor conductors. From the drive to the motor. It really made it so much easier, especially the connections and the ability to get them back in the motor peckerhead.
It did cost big coin, but this one was on them not me.

jamiedolan 01-03-2009 02:13 PM

I'm not positive how many strands were in the cable Lowes and home depot offered. But the 4 strand from the electrical supply was half price of lowes. My pulls for the hot tub are a bit rough, runs with 360 degrees of bends in them.
I am going to see if the electrical supply has something with a few more strands for a few bucks more.

Something I found that seems really weird, CH double breakers up to 60A are like $12-$14. The 70A double CH breakers are $45. Ouch.

Thanks for all the feedback.

Jamie

Gigs 01-03-2009 03:50 PM

I would not use very high strand count for house wiring. For an extension cord or appliance cord where flexibility really matters sure.

The thing is, once you get up to having very fine strands, oxygen in the sheath causes a loss of useful copper over the years. This is significant increase in resistance once you are talking about 150+ strands.


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