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Author Topic: Voltage drop question  (Read 10211 times)

John Roberts {JR}

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Re: Voltage drop question
« Reply #30 on: April 17, 2017, 01:57:07 pm »

Ok sorry :), but IME no way  30ga carries 10A . 
I remember it like it was just last week, because it was...

30ga copper wire was something like 10+A...Aluminum or steel with higher resistance was less current.  I was surprised.

I remember from my old technician days when I would open up TO-3 transistor to analyze failure modes. If the 1 mil base wire melted that was more than one amp (rule of thumb from 50 years ago so not trustworthy). 
Quote
One of my past lives was elevator adjustor / troubleshooter at large...
Sometimes shorts would appear intermittently, based on momentary circuit logic, that couldn't be metered statically. 
It was easy to chew up a box of buss cartridge fuses trying to hunt the short down.
# of strands of 18ga to temporarily use as substitute during troubleshooting only was pretty common knowledge/practice. 
I don't remember it all so well anymore, but 1 strand carried less than 6A
OK you made me look it up again http://www.powerstream.com/wire-fusing-currents.htm  30ga copper 10.2A, aluminum 7.6A, iron 3.15A

18ga comes in different flavors, there is a 16 strand 30ga @ 10A each strand, 7 strand 26ga @ 20.5A each (copper).  There is also a 41/34 so 41 strands of 34ga @ 5.1A each...  So if you had 41 strand 18ga you are in your <6A ballpark.

There is also 18ga test lead wire with 192/41,   65/36,  413/44, etc...

I was surprised by the fuse current of 30ga wire, wish I had some 36ga or 44ga handy to make fuses with, but I didn't.

JR
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Mark Wilkinson

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Re: Voltage drop question
« Reply #31 on: April 17, 2017, 02:23:25 pm »

I remember it like it was just last week, because it was...

30ga copper wire was something like 10+A...Aluminum or steel with higher resistance was less current.  I was surprised.

I remember from my old technician days when I would open up TO-3 transistor to analyze failure modes. If the 1 mil base wire melted that was more than one amp (rule of thumb from 50 years ago so not trustworthy).  OK you made me look it up again http://www.powerstream.com/wire-fusing-currents.htm  30ga copper 10.2A, aluminum 7.6A, iron 3.15A

18ga comes in different flavors, there is a 16 strand 30ga @ 10A each strand, 7 strand 26ga @ 20.5A each (copper).  There is also a 41/34 so 41 strands of 34ga @ 5.1A each...  So if you had 41 strand 18ga you are in your <6A ballpark.

There is also 18ga test lead wire with 192/41,   65/36,  413/44, etc...

I was surprised by the fuse current of 30ga wire, wish I had some 36ga or 44ga handy to make fuses with, but I didn't.

JR

Nice research, thx.
That's a good example of you are the engineer, and I'm just the 'learned it on the job' dude !

I figure my remembrance is based on finer stranded 18ga. 
We did try to use pretty flexible wire, to manage all the long pulls through conduit and junction boxes.
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John Roberts {JR}

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Re: Voltage drop question
« Reply #32 on: April 17, 2017, 02:48:09 pm »

Nice research, thx.
That's a good example of you are the engineer, and I'm just the 'learned it on the job' dude !

I figure my remembrance is based on finer stranded 18ga. 
We did try to use pretty flexible wire, to manage all the long pulls through conduit and junction boxes.
Except that I'm an engineer (some might dispute that?) who mostly learned on the job...

I love the modern internet, there is a world of information at our fingertips if we just ask the right questions.

It wasn't this easy back in the day.

JR
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Mark Wilkinson

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Re: Voltage drop question
« Reply #33 on: April 17, 2017, 03:00:32 pm »

Except that I'm an engineer (some might dispute that?) who mostly learned on the job...

I love the modern internet, there is a world of information at our fingertips if we just ask the right questions.

It wasn't this easy back in the day.

JR

Funny...the engineer part that is..:)

Yeah, information was so much harder to come by 'back in the day'.
Information held alot of power back then, at least relative to today, I think....
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Tim McCulloch

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Re: Voltage drop question
« Reply #34 on: April 17, 2017, 03:22:34 pm »

Funny...the engineer part that is..:)

Yeah, information was so much harder to come by 'back in the day'.
Information held alot of power back then, at least relative to today, I think....

Topic swerve alert.  You have been warned. ;)

Commensurate with the greatly more accessible information is more accessible dis-information.  Lots of silly stuff on youtube that perpetuates "DIW"  Doing It Wrong.  There are musician/prosumer oriented forums (fora?) that contain dubious advice that gets repeated like gossip in a hair salon/barber shop.

I suppose the good outweighs the bad, at least I hope so.

In the Ye Olde Badde Dayz we relied on dead trees & ink.  I'd like to think the s/n was better back then. 8)

/topic swerve alert
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John Roberts {JR}

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Re: Voltage drop question
« Reply #35 on: April 17, 2017, 03:31:51 pm »

Topic swerve alert.  You have been warned. ;)

Commensurate with the greatly more accessible information is more accessible dis-information.  Lots of silly stuff on youtube that perpetuates "DIW"  Doing It Wrong.  There are musician/prosumer oriented forums (fora?) that contain dubious advice that gets repeated like gossip in a hair salon/barber shop.

I suppose the good outweighs the bad, at least I hope so.

In the Ye Olde Badde Dayz we relied on dead trees & ink.  I'd like to think the s/n was better back then. 8)

/topic swerve alert
In fact some of the "Audio Myths" I wrote about in the '80s, that were printed on those dead trees are still turning up like bad pennies today.

JR
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Kevin Graf

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Re: Voltage drop question
« Reply #36 on: April 17, 2017, 04:18:39 pm »

An old chart, shows 26AWG with a fusing current of 20.5 Amps. That would be the same as a pair of 29AWG wires. So one 29AWG wire would be 10.25 Amps.
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Speedskater

Jonathan Johnson

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Re: Voltage drop question
« Reply #37 on: April 17, 2017, 04:36:29 pm »

An old chart, shows 26AWG with a fusing current of 20.5 Amps. That would be the same as a pair of 29AWG wires. So one 29AWG wire would be 10.25 Amps.

Maybe we need Mike to run some tests with his glo-melt transformer.
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Stop confusing the issue with facts and logic!

John Roberts {JR}

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Re: Voltage drop question
« Reply #38 on: April 17, 2017, 04:49:51 pm »

An old chart, shows 26AWG with a fusing current of 20.5 Amps. That would be the same as a pair of 29AWG wires. So one 29AWG wire would be 10.25 Amps.
The link I posted earlier shows 26ga copper as 20.5A, 30ga copper as 10.2A 

JR
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Kevin Graf

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Re: Voltage drop question
« Reply #39 on: April 17, 2017, 05:28:46 pm »

The link I posted earlier shows 26ga copper as 20.5A, 30ga copper as 10.2A 
JR
Oops sorry.
I was going from the same link. But I had only printed the top part of the page (some years ago).
I had looked at the chart some hours ago. But when i got back to the computer, I missed your link.
Interesting the two smaller conductors will carry more current than one larger conductor of the same cross-section area.
I'll go back and print the entire page.
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Speedskater

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Re: Voltage drop question
« Reply #39 on: April 17, 2017, 05:28:46 pm »


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