Multi wire branch circuit handle ties

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iwire

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Re: Multi wire branch circuit handle ties

Roger, I had never put that together, that is a good point.

I read once in one of the trade mags that solid wire was better for energy savings also, I did not understand it at the time, and still do not, any idea why it would save energy.

Bph, I get wound up because I do so many multiwire circuits I take it personal, which is my problem. keep your views coming.

I guess I should change the name from "iwire" to "Multiwire"

roger

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Re: Multi wire branch circuit handle ties

Bob,
I read once in one of the trade mags that solid wire was better for energy savings also, I did not understand it at the time, and still do not, any idea why it would save energy.
I don't really have an answer for that. I do know that the solid conductor does have a lower resistance per table 8 of chapter 9 (#12 solid 1.93 vs 1.98 for stranded) this would be self explanatory.

The only thing I can think of is, that given the AC properties of surface travel, the surface area would be greater in the solid and more symetrical.

If we were to take a given dimension and apply the circular multiplier of .7854 we would have an answer of X. Now if we took the same dimension and divided it by number of strands, divide these by .7854 and add the totals we come up with the same number, so that doesn't help

Now with the strands, if we look at the way they touch each other, we would loose that surface area, maybe thats the kicker.

Now with all that rambling, table 8 chapter 9 is DC properties, meaning full area vs surface.

Maybe one of our engineers or better knowledgable people than myself will chime in here.

Roger

[ March 18, 2003, 09:48 PM: Message edited by: roger ]

bphgravity

Senior Member
Re: Multi wire branch circuit handle ties

I will give it a shot. Solid wire has a cross sectional area that is completely filled with conductor. Stranded wire, even in the tight bundle under insulation will have tiny air gaps between the individual strands. This happens because the strands have a circular cross-section. So in effect, solid wire has a true complete cross section and stranded has the same cross section minus the little air gaps. Over disatnce and load, this may be the difference. Skin effect still applies. Take 7 pennies and place them in a hexagonal pattern as stranded wire typically is and you will see all these air gaps. Just a guess, I can not show any math for this.

iwire

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Re: Multi wire branch circuit handle ties

I always assumed (always bad to do) that stranded would be a little larger than solid to make up for the "air" space. I should spend some time at the back of the book

What was the topic "Multi wire branch circuit handle ties" how did we get here?

Thanks guys

[ March 18, 2003, 10:06 PM: Message edited by: iwire ]

hurk27

Senior Member
Re: Multi wire branch circuit handle ties

So that's where the term big headed comes from "the air gaps" LOL

Just funning

[ March 18, 2003, 10:09 PM: Message edited by: hurk27 ]

iwire

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Re: Multi wire branch circuit handle ties

hurk27, One of my coworkers who is also a close friend will say that to me once in a while when I deserve it.

I would not have put that up if I could not take some "funning"

I still have lots to learn, hammer me if I am wrong with something, I'll never forget again.

Bob

james wuebker

Senior Member
Re: Multi wire branch circuit handle ties

Remember everyone, we are talking about safety in this forum. Everyone had alot of good questions and answers but I haven't read anything about using a meter or some type of test devise.I mean that before you work on anything you should check the circuit to make sure what your working on is off. That's just a thought!

don_resqcapt19

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Re: Multi wire branch circuit handle ties

Guys,
Look at Chapter 8 Table 9 and do the math. There is at least as much actual copper in the stranded conductor as in the soild conductor. For example #12 solid has an area of 3.31 mm? and 7 strand #12 has 7 strands each with an area of 0.4778 mm? for a total area of 3.448 mm?. You can also see this is the "overall area" column where the solid has an area of 3.31 and the stranded an area of 4.25.
Don

[ March 23, 2003, 12:32 PM: Message edited by: don_resqcapt19 ]

bphgravity

Senior Member
Re: Multi wire branch circuit handle ties

Don, the total amount of conductor that is apart of the cross-sectional area may indeed be the same, but the interesting note is that the total area in stranded has gaps. These little gaps may be the reason of increased resistance, hence the ohm/KFt difference in stranded to solid. I stress the word MAY. I wear alot of hats, but EE is not one of the stronger ones. It is just interesting.

iwire

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Staff member
Re: Multi wire branch circuit handle ties

I finally went to Chapter 9 Table 8 and it looks like stranded is bigger than solid

Overall Diameter

#12 Solid 2.05mm

#12 Stranded 2.32mm

My thought before looking at the tables, was that amp rating was based on solid and when you made stranded you needed to make it larger because of the air gaps to stay at the same amp rating or we would have stranded and solid columns on 310.16

I should have looked at these tables before, but a table of numbers is pretty dull reading.

Thanks Guys, learning more all the time.

Bob

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