# Voltage drop



## knowshorts (Jan 9, 2009)

Without doing the math, I'd say #10 is fine. You didn't say what these outlets are for. You are pushing 80% of the breaker rating. Are these loads continuous? I typically won't even consider vd unless it's over 200'.


----------



## sparky723 (Jul 22, 2008)

Well, the outlets are for a rolling hotbox for chicken. Regardless, the load is still 15.8A.
I always considered vd over 100'. Anyway, check the math...10 seems too small.
Load will be considered continuous.


----------



## knowshorts (Jan 9, 2009)

I just dl'ed a vd calculator on my phone and with the info you provided, #10 would have less than a 5% drop.

Why not run a 12/3 to the 1st box and a 12/2 to the 2nd box. The additional circuit might be better in the long run.


----------



## rexowner (Apr 12, 2008)

10AWG, 90 deg F, I get a drop of 5.88 volts @ 15.8Amps, 4.9%, which sounds
fine. 12AWG->9.8V. 8AWG-> 3.8V (3.2%), 6AWG->2.4V, so 6AWG gets
you under 3%, but don't see why 4.9% wouldn't be OK. These phone apps
are great.


----------



## sparky723 (Jul 22, 2008)

I had re-measured the distance and got anxious about the wire size..Shouldve stuck to my original #10 anyway. They always say go with your first "guess".

Thanks, yall.

Btw- It wont be 12/3 because it will be a dedicated circuit on that 30A breaker.


----------



## brian john (Mar 11, 2007)

Try this

http://www.csgnetwork.com/voltagedropcalc.html


----------



## sparky723 (Jul 22, 2008)

0


rexowner said:


> 10AWG, 90 deg F, I get a drop of 5.88 volts @ 15.8Amps, 4.9%, which sounds
> fine. 12AWG->9.8V. 8AWG-> 3.8V (3.2%), 6AWG->2.4V, so 6AWG gets
> you under 3%, but don't see why 4.9% wouldn't be OK. These phone apps
> are great.


Did you use single or 3 phase system to get 5.9? I get 5.9 when using 3ph sys. but single ph. Sys. I get 6.2 with #10.


----------



## hardworkingstiff (Jan 22, 2007)

sparky723 said:


> . I will be installing 2 recpts. in the front of store and feeding from the back room.





sparky723 said:


> Btw- It wont be 12/3 because it will be a dedicated circuit on that 30A breaker.


Are you installing 30-amp receptacles on this circuit? If not, you should put that circuit on a 20A breaker.


----------



## sparky723 (Jul 22, 2008)

hardworkingstiff said:


> Are you installing 30-amp receptacles on this circuit? If not, you should put that circuit on a 20A breaker.


I have my choice. 20 amp plug most likely.


----------



## hardworkingstiff (Jan 22, 2007)

sparky723 said:


> I have my choice. 20 amp plug most likely.


See 210.21(B)(3)


----------



## rexowner (Apr 12, 2008)

sparky723 said:


> 0
> 
> Did you use single or 3 phase system to get 5.9? I get 5.9 when using 3ph sys. but single ph. Sys. I get 6.2 with #10.


Single. The difference may be I did it at 90 degrees F - I think the code
book tables are at a higher temperature, and then the program makes the
adjustment.


----------



## sfeyelectric (Dec 31, 2010)

knowshorts said:


> I just dl'ed a vd calculator on my phone and with the info you provided, #10 would have less than a 5% drop.
> 
> Why not run a 12/3 to the 1st box and a 12/2 to the 2nd box. The additional circuit might be better in the long run.


Voltage drop should not be higher than 3% so no 10 would not work

120v= acceptable voltage drop of 3.6volts
240v= acceptable voltage drop of 7.2volts


----------



## sparky723 (Jul 22, 2008)

sfeyelectric said:


> Voltage drop should not be higher than 3% so no 10 would not work
> 
> 120v= acceptable voltage drop of 3.6volts
> 240v= acceptable voltage drop of 7.2volts


So my 2nd calc. Was right using #6?....ugh!


----------



## knowshorts (Jan 9, 2009)

sfeyelectric said:


> Voltage drop should not be higher than 3% so no 10 would not work
> 
> 120v= acceptable voltage drop of 3.6volts
> 240v= acceptable voltage drop of 7.2volts


Oh, they would work. These are little chicken warmers with a max load of 7.9 amps each. Chances are they will not be turned all the way up. They are warmers, not cookers. You can go into any supermarket in this country and you will most likely find these hooked up to a #12 circuit. I would try to up-sell to a 10/3 and 2 separate circuits, but the chances of a market spending the extra money is probably not that great.

As far as voltage drop goes, the 3-5% for branch circuits and feeders is not code, it's a FPN.


----------



## sparky723 (Jul 22, 2008)

knowshorts said:


> Oh, they would work. These are little chicken warmers with a max load of 7.9 amps each. Chances are they will not be turned all the way up. They are warmers, not cookers. You can go into any supermarket in this country and you will most likely find these hooked up to a #12 circuit. I would try to up-sell to a 10/3 and 2 separate circuits, but the chances of a market spending the extra money is probably not that great.
> 
> As far as voltage drop goes, the 3-5% for branch circuits and feeders is not code, it's a FPN.


How is max load 7.9 amps when nameplate shows15.8?
you cant assume they wont turn it up.


----------



## knowshorts (Jan 9, 2009)

sparky723 said:


> How is max load 7.9 amps when nameplate shows15.8?
> you cant assume they wont turn it up.


My mistake, after reading your 1st post, I thought each warmer was 7.9 for a total load of 15.8 amps. That changes things. My original calculations are incorrect if each table warmer is 15.8 amps.


----------



## hardworkingstiff (Jan 22, 2007)

knowshorts said:


> Oh, they would work. These are little chicken warmers with a max load of 7.9 amps each. Chances are they will not be turned all the way up. They are warmers, not cookers. You can go into any supermarket in this country and you will most likely find these hooked up to a #12 circuit. I would try to up-sell to a 10/3 and 2 separate circuits, but the chances of a market spending the extra money is probably not that great.
> 
> As far as voltage drop goes, the 3-5% for branch circuits and feeders is not code, it's a FPN.


I would make sure I tried really hard to up sell wire size because of voltage drop issues to the point the customer will always remember he turned me down before I would consider the 12.

If he really has unacceptable voltage drop, you know he's going to blame you.


----------



## desar (Feb 6, 2011)

I have nothing better to due tonight wife's out.Formula :

cross sectional area = 2(10.4)(15.8)(180')/3.6volts = 16432 circular mills Ch9 table8 = #6

I used 3.6 volts because that's 3% of 120 volts. If that is the range you want to stay in. But if your feeding warmers the worst case is that they wont heat to 100%. The same thing if you hocked up 120 volts to a240 volt heater it heats slightly but not to heating at 240 volt.


----------



## drsparky (Nov 13, 2008)

Here is another calculator. You can never have enough cool references.
http://www.southwire.com/ProductCatalog/voltdrop.jsp


----------



## sparky723 (Jul 22, 2008)

drsparky said:


> Here is another calculator. You can never have enough cool references.
> http://www.southwire.com/ProductCatalog/voltdrop.jsp


Thanks for the calc....neat.
i rechecked with this calc. and got #6, too.
funny how a simple chicken warmer warrants a 50a and #6.
oh well, not my money..


----------



## hardworkingstiff (Jan 22, 2007)

sparky723 said:


> funny how a simple chicken warmer warrants a 50a and #6.
> ..


Shouldn't that be "funny how a simple chicken warmer warrants a 20a and #6".


----------



## Keyrick (Nov 10, 2010)

If there are any derating issues with this job you could go with #8 if you can live with 5% VD.


----------



## backstay (Feb 3, 2011)

@120 V AC 1ph 15.8 amps load
#10 = 7.09 VD which is 5.91%
#8 = 4.46 VD which is 3.72%
#6 =2.81 VD which is 2.81%


----------



## desar (Feb 6, 2011)

Because your using #6 for votage drop it doesn't mean to use a 50a breaker it's still a 20 amp breaker. The two chicken warmers are fixed resistors r= 120/15.8 = 7.59 ohms. This is the fixed resistance of the heater. 116/7.59= 15.28 amps .So voltage goes down ampacities go down so wattage output is lowered.


----------



## Keyrick (Nov 10, 2010)

desar said:


> Because your using #6 for votage drop it doesn't mean to use a 50a breaker it's still a 20 amp breaker. The two chicken warmers are fixed resistors r= 120/15.8 = 7.59 ohms. This is the fixed resistance of the heater. 116/7.59= 15.28 amps .So voltage goes down ampacities go down so wattage output is lowered.


You are correct. I will edit my post. Thanks.


----------



## sparky723 (Jul 22, 2008)

Fyi..
the 5 is right under the 2 on my # keypad. My bad. Its 20a. 
and there is only 1 warmer not 2. It is going to be moved from one location to the other.


----------



## nitro71 (Sep 17, 2009)

Try the demo for this software. I planned some lighting with the demo one time. Great software:
http://www.edreference.com/features.acseriesdrop.5.asp


----------



## backstay (Feb 3, 2011)

I use LectriCalc with my palm


----------



## Rockyd (Apr 22, 2007)

*VD*=2 x K x I x D
Kcmil​VD = Voltage Drop
2 = Single phase
K = Constant (12.9 for copper)
I = Amperage
D = Distance
Kcmil = wire size expressed in CM's see the Chapter nine table eight for size to # of wire.​


----------



## sparky723 (Jul 22, 2008)

Rockyd said:


> *VD*=2 x K x I x D
> Kcmil​VD = Voltage Drop
> 2 = Single phase
> K = Constant (12.9 for copper)
> ...


Lol..thanks.


----------



## Rockyd (Apr 22, 2007)

sparky723 said:


> Lol..thanks.


It's how we slay the beast Forums have got me out some ugly's in the past!


----------



## sparky723 (Jul 22, 2008)

Rockyd said:


> It's how we slay the beast Forums have got me out some ugly's in the past!


? Did I miss something?


----------



## Rockyd (Apr 22, 2007)

sparky723 said:


> ? Did I miss something?


Nope. Good to go!


----------



## jdce44 (Dec 9, 2010)

The termilas must be rated for 90c to use that table. most breakers and terminals are rated at 70c also did you add 1.25 to the cooker amp as the code requires. most appliances and equipment will have listed the electrical reqirements for the use of there stuff. voltage drop would be from panel to first recept total of both warmers then calculate from there to second recept. i would personaly run two dedicated cir. and size the breaker for the circuit over current protection. Its never a good idea to guess.its dangerous and foolish to guess. make sure you fully understand what it is your doing before you do it. Anyone doing electrical should have a up to date NEC code book and other ref. materials. And other electrician friends to descuss things with we are a family in the trade. I do think this site is a cool. A way to connect with other electricians, get information right or wrong openions guide and makes us ask and search for the right questians to the answers.


----------



## desar (Feb 6, 2011)

I beleive the question stated that the total amperage draw was 15.8 amps. That means that a 20 amp breaker could be used because 80% of the 20 amp breaker is 16 amps which what the breaker could be loaded to on a contiuous load ( 125% and 80% are the same)Then by sizing for voltage drop the size wire will easily carry the 125% of the continuous load.


----------



## Shockdoc (Mar 4, 2010)

VD.............................venerial disease


----------



## Rockyd (Apr 22, 2007)

Shockdoc said:


> VD.............................venerial disease


This is a family forum:no::no:. If you have VD here, we sure hope it's cureable with a big enough case of Kcmil. If not suggest you go off site and see more than just a Shockdoc :laughing:


----------



## kiyo (Jan 30, 2011)

rexowner said:


> 10AWG, 90 deg F, I get a drop of 5.88 volts @ 15.8Amps, 4.9%, which sounds
> fine. 12AWG->9.8V. 8AWG-> 3.8V (3.2%), 6AWG->2.4V, so 6AWG gets
> you under 3%, but don't see why 4.9% wouldn't be OK. These phone apps
> are great.


What app is it for voltage drop? I want it.


----------



## Shockdoc (Mar 4, 2010)

Rockyd said:


> This is a family forum:no::no:. If you have VD here, we sure hope it's cureable with a big enough case of Kcmil. If not suggest you go off site and see more than just a Shockdoc :laughing:


:laughing::laughing::laughing:


----------



## rexowner (Apr 12, 2008)

kiyo said:


> What app is it for voltage drop? I want it.


I use Electrical Wiring Pro on Android. There are others.


----------

