Voltage Drop Calculator

[jimmac49]

Anyone know where I can download or access a VD calculator. The site I have been using seems to be gone. Thanks

 

[raider1]

I just did a google search and found this one it needs javascript to work.

voltage drop calculator

Was it electrician.com that you were using. I found that that site has changed and no longer has the voltage drop calculator.

Chris

 

[charlie b]

There used to be one available from Mike Holt's home page (from the "free stuff"). But it was taken off a couple years ago, for reasons I do not know.

 

[infinity]

You could try this one:


http://www.elec-toolbox.com/calculators/voltdrop.htm

 

[jimmac49]

Thanks for the replies
Jim

 

[bob]

The caculator listed by raider asks that you input only 1/2 of the distance.
The VD is only 1/2 of the caculated VD at this location http://www.electrician2.com/ and 1/2 of the caculator I use.

 

[raider1]

Bob,

Thanks for pointing that out. I haven't tried to use that calculator, just did a google search to find it.

Again thanks for the link to electrician2.com, I had wondered what had happened to electrician.com. Now I know.

Chris

 

[peter d]

I use a pen and paper, and CM=(2KIL)/Ed and solve algebraically.

I guess I'm old fashioned. :lol:

 

[1793]

Most of the VD calculators solve for 120. How does one solve for 240? Do you drop the "2"(2KIL)/CM?

Edit for change to CM

 

[hardworkingstiff]

I just set it up in my spread sheet so I can use it anytime w/out internet access.

 

[ramsy]

My Target Voltage method, based on NEC 110.10 & 110.3(B), uses either table data or field measurements for the same variables.

1) One advantage of choosing your impedance here, lets you control the fault clearance STD used by IEEE 1100 (The Emerald Book). Even if you don't care about ASCC (Available Short-Circuit Current) and OCPD trip times, you have control of it in this calc..

That formula would be, ASCC = E/Z, line voltage(E) over line impedance(Z). According to Mike Holt, 120vac / 4.8 ohms = 25A, and 500 Seconds, or 8+ minutes to trip the breaker.

2) This calc includes a Power Factor for proper motor FLA in Tbl 430-150. Motor power-factor adjustment is critical for proper wire size.

For 90 and 80 percent power factor, the figures shall be multiplied by 1.1 and 1.25 respectively.

3) This Target Voltage method shows Choked Power and Choked Amps, so meeting equip. power needs, or lighting effects (Choked Watts / Watts)x100, is known before the install.

4) That link includes a proof for using any source voltage to match wire sizes by either the Volts Dropped or the Iimpedance results shown, using different NEC Tbl.8 wire Size and Length variables. But, the same calc. results could also be matched to Tbl.9 wire Size and Z. values.

5) Plugging the variables of that proof into a spreadsheet would be faster, but I believe getting familiar with the seperate table and field-measurement formulas for Power factor, Choked Power, Choked Amps, and Z, brings more skill-set leverage to my service ability, and more wage / renewal leverage to the bargaining table.

 

[charlie b]

Most of the VD calculators solve for 120. How does one solve for 240? Do you drop the "2" (2KIL)/CM?

Good question. First, as I understand it the "2" in the "(2KIL)/CM" refers to twice the one-way length. In other words, the "L" is a one way distance, and you double it to get the total VD.

Secondly, the amount of voltage drop is not a function of the source voltage. If a 120 volt source pushes 10 amps through a 100 foot #12 wire, you will get a VD of 3.95 volts, which is 3.3% of the 120 volt source. If a 240 volt source pushes the same 10 amps through the same 100 foot #12 wire (obviously, you will have to change the load, doubling its resistance, in order to make this work), you will get the same VD (along the conductors) of 3.95 volts, but that will be 1.6% of the 240 volt source.