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Old 07-18-2016, 11:43 PM   #1
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Default how you guys caculate the voltage drop of wire bigger than 4/0?

in the CEC code book , the D3 table for calculate the voltage drop is only up to 4/0, so how you guys calculate the wire bigger than that?

any inputs will be thank you
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Old 07-19-2016, 12:49 AM   #2
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Quote:
Originally Posted by mike883 View Post
in the CEC code book , the D3 table for calculate the voltage drop is only up to 4/0, so how you guys calculate the wire bigger than that?

any inputs will be thank you
The SouthWire App
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Old 07-19-2016, 12:57 AM   #3
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Good question. Im thinking.....maybe verify circular mil area of the 4/0....and compare as a ratio of the CMA of the larger cable. Maybe im off track here, ( example )............ but CMA of # 14 is 4110. # 8 awg is approx. 4 times that.....16,510. Not exact, but close enough to compare. If you look at 4amps in both columns....# 14 is 15.3M....and # 8 is 61.7M. Not bang on, but pretty close to 4 X. Does this make sense??
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Old 07-19-2016, 07:35 AM   #4
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Use this http://www.elec-toolbox.com/calculators/voltdrop.htm
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Old 07-19-2016, 03:15 PM   #5
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The SouthWire App
Be careful using apps based on the NEC. Most times you will get what you are looking for, as our code is becoming more like the NEC each cycle, but be sure to read the notes given with the app.

Edit: I couldn't find a Southwire App that used the CEC, I tried a couple. Maybe electric guy can correct me.

Many apps out there that are based on the CEC.

Borgi
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Last edited by 51360; 07-19-2016 at 03:25 PM. Reason: Addition for clarity
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Old 07-19-2016, 08:20 PM   #6
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The SouthWire App
thanks, but I don't like this app
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Old 07-19-2016, 08:21 PM   #7
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thanks, but I don't like this either
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Old 07-19-2016, 08:21 PM   #8
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no one knows?...................
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Old 07-19-2016, 08:55 PM   #9
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no one knows?...................
Did they not teach you about Ω/1000' in trade school

And then Ohm's law from that ?
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Old 07-19-2016, 09:13 PM   #10
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Did they not teach you about Ω/1000' in trade school

And then Ohm's law from that ?
it doesn't work like that, for DC , you can use I=U/R no problem,

but for AC, you can't

do some research
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Old 07-19-2016, 09:23 PM   #11
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it doesn't work like that, for DC , you can use I=U/R no problem,

but for AC, you can't

do some research

Sorry, my bad, ... how many miles of cable are you talking about ... I will include impedance then
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Old 07-19-2016, 09:39 PM   #12
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I also want to know, but nobody has such question by far.
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Old 07-19-2016, 10:32 PM   #13
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Sorry, my bad, ... how many miles of cable are you talking about ... I will include impedance then
is it not the miles of the cable,
it is the kcmil
see below
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Old 07-19-2016, 10:47 PM   #14
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is it not the miles of the cable,
it is the kcmil
see below
And how many miles of cable would it take for that to be significant
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Old 07-19-2016, 11:59 PM   #15
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Originally Posted by Judoka View Post
Good question. Im thinking.....maybe verify circular mil area of the 4/0....and compare as a ratio of the CMA of the larger cable. Maybe im off track here, ( example )............ but CMA of # 14 is 4110. # 8 awg is approx. 4 times that.....16,510. Not exact, but close enough to compare. If you look at 4amps in both columns....# 14 is 15.3M....and # 8 is 61.7M. Not bang on, but pretty close to 4 X. Does this make sense??
You're not far off at all.

Quote:
Calculating Voltage Drop

In situations where the circuit conductors span large distances, the voltage drop is calculated. If the voltage drop is too great, the circuit conductor must be increased to maintain the current between the points. The calculations for a single-phase circuit and a three-phase circuit differ slightly.

Single-phase voltage drop calculation:

VD = [ 2 x L x R x I ]/1,000
VD% = [ VD/Source Voltage] x 100

Three-phase voltage drop calculation:

VD = [( 2 x L x R x I)/1,000] x .866
VD% = [ VD/Source Voltage] x 100

Where:

VD = Voltage drop (conductor temp of 75C) in volts
You can find formulas, like above, that you can use. But, good apps, ( you may have to buy them ), can do the math for you. Use an app that allows you to enter as many variables as needed.

For systems using wire sizes above 4/0, you may need to consult an engineered standard.

Borgi
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Last edited by 51360; 07-20-2016 at 12:07 AM. Reason: Spelling
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Old 07-21-2016, 07:28 AM   #16
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Quote:
Originally Posted by Judoka View Post
Good question. Im thinking.....maybe verify circular mil area of the 4/0....and compare as a ratio of the CMA of the larger cable. Maybe im off track here, ( example )............ but CMA of # 14 is 4110. # 8 awg is approx. 4 times that.....16,510. Not exact, but close enough to compare. If you look at 4amps in both columns....# 14 is 15.3M....and # 8 is 61.7M. Not bang on, but pretty close to 4 X. Does this make sense??
Quote:
Originally Posted by billyhunter View Post
I also want to know, but nobody has such question by far.
Since a couple of you were asking ...

Generally voltage drop with cables larger than 4/0 isn't an issue, because the runs are generally quite short (in my experience anyways).
If your running enough 750kcmil that VDrop is an issue, I'd think a transformer would be a cheaper option ! ( Assuming you've already used parallel conductors )

Anyways, manufacturer specs ALWAYS have the answer !

Here are a couple of charts, showing both AC and DC resistance values, for single and 3 phase, there are temp correction charts as well, and even reactance values for various conductor spacing.
At this level, your generally using engineered drawings, so these calcs are already done for you (at least in my experience)

If anyone is working in this, and would like the pdf, you can PM me and I can send it to you.
You may be able to find it on Anixter's website as well.
Attached Thumbnails
how you guys caculate the voltage drop of wire bigger than 4/0?-voltage-drop.jpg  

how you guys caculate the voltage drop of wire bigger than 4/0?-dc-ac-resistance.jpg  

how you guys caculate the voltage drop of wire bigger than 4/0?-reactance.jpg  

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Old 07-21-2016, 04:08 PM   #17
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Run parrallel conductors
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Old 07-21-2016, 04:10 PM   #18
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Also, check note 6 of table D3
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Old 08-04-2016, 09:47 AM   #19
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in the CEC code book , the D3 table for calculate the voltage drop is only up to 4/0, so how you guys calculate the wire bigger than that?

any inputs will be thank you
Mike ... I tried to email the doc, but your account doesn't accept incoming emails ??

I found a link for you though ... https://www.anixter.com/content/dam/...ook_Sec_07.pdf
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Old 08-04-2016, 10:55 AM   #20
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Here, again, 883 asks questions WRT answers he already has in hand.

Stop trolling.

Just post up your point without beating around the bush.

&&&&

I also must say that MOST of your queries are of interest to Electrical Engineers and kids trying to pass their exams.

They have no bearing on field practices for active electricians.

In this case, voltage drop on feeder conductors would ALWAYS be addressed by EEs.

For to even to become a concern, the feeder run would have to be mighty long -- hence a mighty bid building -- and a complex project.

Even master electricians are not allowed to weigh in on such affairs.

The EEs protect their turf.

&&&&&

You might find that you'll get true satisfaction only by dropping in on forums dedicated to EEs, because that is definitely where your head is at.

Indeed, hit the books, go to college,get your EE degree. It's plain that EE calculations and concerns obsess you.
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