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Posted By: sparkync Voltage drop?? - 11/13/07 07:54 PM
I have a 50 amp 120/240 camper power cord going 250 ft. I've been trying to find what the voltage drop is. Can anyone help me with the formula? Thanks Steve
I will have to assume the amperage at 50 amps max.
Posted By: kale Re: Voltage drop?? - 11/13/07 08:18 PM
You can use the calculator at http://nooutage.com/vdrop.htm, but you will need to know your wire gauge.
or http://www.elec-toolbox.com/calculators/voltdrop.htm will tell you your minimum wire size is going to be #3.
Posted By: sparkync Re: Voltage drop?? - 11/14/07 12:29 AM
A customer is wanting me to get this cord for him. He has a customer who is going to park a "medical RV" on his property. The RV will be approx. 250 ft. away. I'm thinking I need to discourage him from doing this at that distance. Sounds like he's going to burn something up in his RV with low voltage, as well as overheating the cable.
I don't know what the total amperage used will be, but his a/c unit, refrigeration equipment, etc. may take a toll from the lower voltage, especially if he need's #3 instead of #6. Plus the price of the cable is going to be around
$ 860.00 for that type of cable. I'm still looking for a second opinion here. I couldn't get the nooutage.com calculators, it wouldn't come up. Could be a mighty costly mistake if I get the wrong wire for him:( Thanks
Posted By: gfretwell Re: Voltage drop?? - 11/14/07 01:13 AM
I have an old BASIC program voltage drop calculator if anyone wants it. I can put it on my web site. It still runs with W/98, I suppose XP and Vista can do it
Posted By: sparkync Re: Voltage drop?? - 11/14/07 11:54 AM
Greg, I could probably use your voltage drop program if you could make it available. I have windows XP. Thanks , Steve
Posted By: sparkync Re: Voltage drop?? - 11/14/07 01:19 PM
Greg, what is your website? Thanks
Posted By: gfretwell Re: Voltage drop?? - 11/14/07 01:29 PM
This is in the ftp area

http://esteroriverheights.com/electrical/info.zip

This is a lot more than just voltage drop but the voltage drop is in "electrical". I suppose you could pare down the rest of the stuff if you are a BASIC guy but this thing is not really that big. I did not write this. It was an IBM guy I knew. Set your shortcut to run "info.bat"
Posted By: electure Re: Voltage drop?? - 11/14/07 02:03 PM
If you want help with the formula, here it is in depth.

http://www.selfhelpandmore.com/homewiringusa/2002/definitions/voltagedrop/voltagedropshowallp.htm
Posted By: JValdes Re: Voltage drop?? - 11/14/07 05:22 PM
Try the calculators listed above. I use them all the time, to save time.
Posted By: electure Re: Voltage drop?? - 11/14/07 07:41 PM
"Try the calculators listed above. I use them all the time, to save time."
You seem to be skipping over the thread to save time, too.

Read the thread carefully. According to the Original Poster:

"Can anyone help me with the formula?"
and
"I couldn't get the nooutage.com calculators, it wouldn't come up."


Try Googling "Voltage Drop Calculator" if that's what you want. Any one of a number of calculators should pop up.








Posted By: BigB Re: Voltage drop?? - 11/15/07 04:32 AM
Ever try Martindale's Calculator site? It is amazing. Here's a link to the electrical ones: http://www.martindalecenter.com/Calculators4A.html
Posted By: JValdes Re: Voltage drop?? - 11/15/07 08:51 PM
electure,
He asked for the formula, he got the calculators.
Whats your beef. I read all the posts.

If you require lenghthy responses on this forum just let me know.
Posted By: electure Re: Voltage drop?? - 11/15/07 10:58 PM
"He asked for the formula, he got the calculators."

The sentence should be self explanatory. Some members are here to learn, (my aged self included). In depth education is sound education. Unlike calculators, it explains the hows and whys.

As a matter of fact, until Greg was kind enough to post his calculator, SparkyNC got 1. (The other one wouldn't open on SparkyNC's computer.)



"I" don't require anything.
A moderator is just a member who's been around the site and carefully read/responded to a lot of threads, nothing more.

Posted By: kale Re: Voltage drop?? - 11/15/07 11:59 PM
It may be to your advantage to check into using a buck-boost transformer to reduce your wire size at the far end.
Posted By: ITO Re: Voltage drop?? - 11/16/07 08:52 PM
Originally Posted by sparkync
I have a 50 amp 120/240 camper power cord going 250 ft. I've been trying to find what the voltage drop is. Can anyone help me with the formula? Thanks Steve
I will have to assume the amperage at 50 amps max.


Wow, all that talk and still no formula?

VD = (2LIK)/CM

Or in English:

VD – Voltage Drop
L- Lengths
I- Amps
K- Constant for Copper (use 12.9 for CU and 21 for AL)
CM- Circular Mills (page 635 Table 8 of the NEC-2005)

Or you can back into it by:
CM = (2LIK)/ VD

So if 5% of 240 = 12v then…

(2 x 250f x 50A x 12.9)/12v = 26,875 cm

Go to page 635 Table 8 of the NEC-2005: Looks like # 6 is (26,240) so the next size up is #4 (41,740)


Posted By: electure Re: Voltage drop?? - 11/16/07 11:43 PM
The formula is in the link I gave, but not the answer wink
Posted By: HotLine1 Re: Voltage drop?? - 11/17/07 12:12 AM
Time to type.....
Voltage drop is a FPN in the NEC, 2% feeders, 3% branch for a total of 5%. But, it's a FPN, not 'Code'.

That said...thanks to Ito for doing that typing.

Kale:
The buck/boost solution is only recomended (IMHO) with a constant load. If you size the B/B for a 50 amp load, and it drops to 10 amps, you can/may get an overvoltage situation at the 'load'.

Sounds similar to my class Wed PM

Posted By: gfretwell Re: Voltage drop?? - 11/17/07 12:49 AM
If I was going to go with a transformer, I would go with 2. Step that up to 480 and back down to 120/240 but at that point bigger wire would probably be cheaper. Trying to boost the drop up at the far end is just paying extra to hide the waste heat you are losing along the way.
#1 al would get you in under 3% and probably not break the bank. #2al gets you up to 3.3% but that assumes 50a load and that would have to be a peak. I bet 40a would be a better working number. If you do that you can get in around 2.5% with #4 copper or the #2al.
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