# Voltage Drop to outlet 350 feet away



## litenin20 (Feb 8, 2013)

Hello I am new to site, I am Union journeyman electrician, and I just started with new company on a short call. I am already getting into it with foreman.. We are running 4 120v outlets in a warehouse on 1 circuit 350' from panel. Foreman is running 3/4 emt with #12 thhn wire. My arguement is that he has to figure for voltage drop, I come up with #4! His arguement is he wired all the lights in the entire buildiing using #12 some alot farther away. Am I missing something here???? If i am wrong I want to know what I am not understanding.


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## Speedy Petey (Jan 10, 2007)

He doesn't HAVE to figure for VD, but he should.
What are the receptacles going to be used for?


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## litenin20 (Feb 8, 2013)

They are going to feed a desk with a computer on it nothing else specific


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## chicken steve (Mar 22, 2011)

are there prints?

~CS~


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## Speedy Petey (Jan 10, 2007)

litenin20 said:


> They are going to feed a desk with a computer on it nothing else specific


Then WHY so far? I find it hard to believe there's not a closer panel.
And why use such a large number for figuring VD if it's just a desk?


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## litenin20 (Feb 8, 2013)

I haven't figured vd since i was back in apprenticeship. Panels are all on one end of warehouse. There aren't any closer, but I thought you had to figure vd based on maximum amps at outlet of 16a for 20a receptacle. I normally just run pipe and pull wire, but seems like it should be larger than a 12 to me doesnt the code say has to be less than 3% drop?


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## Speedy Petey (Jan 10, 2007)

VD in the code is a suggestion, not a requirement. Even many journeymen and masters are confused by this.


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## JohnR (Apr 12, 2010)

And even when VD is done, it is usually calculated on the expected load.


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## Big John (May 23, 2010)

Assuming 120V actual, anything more than an 8 amp load on that puts you beyond a 10% VD, which is what I'd call the worry point.

So if they plug in a vacuum cleaner or a microwave, yeah, it's gonna struggle. I agree, it's not the best design, but I think it will be fine for most loads.


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## Techy (Mar 4, 2011)

Florida building code only allows for 3% VD on a branch circuit. 2% for services. 

13-413.AB.1 Voltage drop.

13-413.AB.1.1 Feeders and customer-owned service conductors. Feeder and customer-owned service conductors shall be sized for a maximum voltage drop of 2 percent at design load.

13-413.AB.1.2 Branch circuits. Branch circuit conductors shall be sized for a maximum voltage drop of 3 percent at design load.


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## uconduit (Jun 6, 2012)

I wouldn't worry too much about it. You can put the 12ga in and you're just following orders. But, nevertheless, voltage drop is something to consider


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## FanelliBT (Dec 14, 2012)

I would figure the current of the outlet in commercial space based on the 180VA requirements for outlets. 

I would say you are fine

** edit ** ignore this I just thought about it more I am wrong lol


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## uconduit (Jun 6, 2012)

Ok i'm bored so I tried doing the voltage drop calculations


12ga stranded 2.05 ohms/1000ft / 10000 = * .00205 ohms/ft*
350 (source) + 350 (return) = *700 ft*
R(total)=R(1)+R(2) etc, 700ft * .00205 ohms/ft =* 1.435 ohms resistance*

volts=current * resistance (1.403 ohms), volts / resistance = current (8th grade algebra)
vrms *3%* = 120*3%=3.6 volts, *2.57 amps*
vrms* 5% *= 120*5%=6 volts, *4.27 amps*
vrms *10%* = 120*10%=12 volts,* 8.55 amps*

or by breaker size, full load
%drop=[(current * resistance) / 120] * 100% = 
15 amps, * 80% = *12 amps*, 100*12*1.403/120 =* 14%*
20 amps, * 80% = *16 amps*, 100*16*1.403/120=*19%*


ok lets say the current is 16amps and the goal is 5% vd
5%*120v=6volts
solve for ohms
e=ir, e/i=r
6volts/16amps=.375 ohms total, 

.375ohms * 1000 ft / 700 ft = 0.535 ohms/1000ft conductor =6 gauge copper

6volts/12amps=.5 ohms total

.5 * 1000/ 700 = .714 ohms/kft conductor = 8 gauge copper close enough

----------------------
this might be completely wrong so be advised....


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## JohnR (Apr 12, 2010)

I dunno guys, I had a boss once, that said if the voltage was 480, there was no VD. So at 120V there should only be a 1/4 of a VD.:whistling2::laughing:


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## farlsincharge (Dec 31, 2010)

Speedy Petey said:


> VD in the code is a suggestion, not a requirement. Even many journeymen and masters are confused by this.


That astonishes me. It has been a requirement here for as long as I have known and is being more strictly enforced every year.
I'm wiring a 40x100 shop right now and have #10's going to some of the 15a receptacles.

Maybe if the manufacturers can find a way to profit from it somehow it will become a requirement there.


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## hardworkingstiff (Jan 22, 2007)

Techy said:


> 13-413.AB.1.2 Branch circuits. Branch circuit conductors shall be sized for a maximum voltage drop of 3 percent at design load.


What loads do you use on the general purpose receptacles for the "design load"?


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## ampman (Apr 2, 2009)

Techy said:


> Florida building code only allows for 3% VD on a branch circuit. 2% for services.
> 
> 13-413.AB.1 Voltage drop.
> 
> ...


the building code has requirements for VD


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## running dummy (Mar 19, 2009)

Big John said:


> Assuming 120V actual, anything more than an 8 amp load on that puts you beyond a 10% VD, which is what I'd call the worry point.
> 
> So if they plug in a vacuum cleaner or a microwave, yeah, it's gonna struggle. I agree, it's not the best design, but I think it will be fine for most loads.


Yea, wait until the broad that sits at that desk plugs in her mega 1500w lips heater :laughing:


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## Bbsound (Dec 16, 2011)

At least pull some #10


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## Hippie (May 12, 2011)

Bbsound said:


> At least pull some #10


He's on a 2 week call, he's getting sent back to the hall as soon as they are done, its not something I would be concerned with enough to argue. I wouldn't even bring it up.


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## Eric Daniel (Feb 8, 2013)

farlsincharge said:


> That astonishes me. It has been a requirement here for as long as I have known and is being more strictly enforced every year.
> I'm wiring a 40x100 shop right now and have #10's going to some of the 15a receptacles.
> 
> Maybe if the manufacturers can find a way to profit from it somehow it will become a requirement there.


Question, once you get to the receps., (say they're close together but far from the feed...hence the 10ga.), do you keep running 10 ga from box to box, or pick up with smaller from the first box on?
Thanks.


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## farlsincharge (Dec 31, 2010)

Eric Daniel said:


> Question, once you get to the receps., (say they're close together but far from the feed...hence the 10ga.), do you keep running 10 ga from box to box, or pick up with smaller from the first box on?
> Thanks.


No, you can reduce wire size. As long as it doesn't put you over three percent.


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## litenin20 (Feb 8, 2013)

True I am only on a 2 week call, and in all reality don't really matter to me what they do I am going to just do what they want. but that doesn't mean that they are right. that is why I was seeing what others are doing. The way I interpret the code I would use 16 amps and figure vd. since that is max allowed on 20a receptacle. but thats the problem the interpretation!


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## uconduit (Jun 6, 2012)

litenin20 said:


> True I am only on a 2 week call, and in all reality don't really matter to me what they do I am going to just do what they want. but that doesn't mean that they are right. that is why I was seeing what others are doing. The way I interpret the code I would use 16 amps and figure vd. since that is max allowed on 20a receptacle. but thats the problem the interpretation!


If this is what it takes for boss-man to realize his mistake then so be it. After pulling it try plugging in a standard hairdryer while measuring the voltage on a voltmeter. If you think it will hurt his feelings then don't bother.

lets say you plug in a so-called 1875watt hair dryer I predict:

17.6 volt drop, so instead of 120volt it would read 102.6volts
30% less watts 




1875watt nominal/125volts nominal=15amp (assuming appliance rated at 125volts)
125volt/15amps=8.33ohms (assuming appliance rated at 125volts)
120volts/(1.435+8.333)ohms=12.29amps 
12.29amps*1.435ohms=17.6volts
102.4volts*12.29amps=1258watts


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## chicken steve (Mar 22, 2011)

Speedy Petey said:


> VD in the code is a suggestion, not a requirement. Even many journeymen and masters are confused by this.


yes & no

VD is found addressed via informational notes in 210, 215, 310 as a design suggestion .....

But if there's nothing identified _specificly_ , VD becomes a moot point , and the design becomes generic

This is why many architectuals just spec out #10's on a 20A OCPD for the first 100-200' of home runs ....can you say don't ask, don't tell? :whistling2:

The kicker is when a specific piece of equipment makes it's debut, along with manufacturers specifics that it's voltage be within certain parameters

So we go from info notes , to 110.3(B) , where the warranties on 208 motors running on 180V's , and overloads that pop due to it are on the table of reality, as well as code compliance

~CS~


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## Eric Daniel (Feb 8, 2013)

farlsincharge said:


> No, you can reduce wire size. As long as it doesn't put you over three percent.


Thanks.


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## BBQ (Nov 16, 2010)

farlsincharge said:


> That astonishes me. It has been a requirement here for as long as I have known and is being more strictly enforced every year.


Can you post the code section?

To me VD is not a safety issue and should not be a code issue.


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## hardworkingstiff (Jan 22, 2007)

BBQ said:


> Can you post the code section?


 Is it in the Canadian electrical code or is it a local amendment?


> To me VD is not a safety issue and should not be a code issue.


I don't have an argument against that, but I will say it would kind of make my life easier if a set standard was in place. Makes it easier if the competition doesn't upsize conductors for VD. I see the problem of assigning loads to GP receptacles when they may really never get loaded, or, could have some relatively heavy loads.


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## chicken steve (Mar 22, 2011)

they tried after the debute of the ideal 61-164 &5 Lou, there were some inspectors insisting on #10 rx home runs residentially....it would have amounted to kaos to size every branch circuit up.....~CS~


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## btharmy (Jan 17, 2009)

litenin20 said:


> Hello I am new to site, I am Union journeyman electrician, and I just started with new company on a short call. I am already getting into it with foreman.. We are running 4 120v outlets in a warehouse on 1 circuit 350' from panel. Foreman is running 3/4 emt with #12 thhn wire. My arguement is that he has to figure for voltage drop, I come up with #4! His arguement is he wired all the lights in the entire buildiing using #12 some alot farther away. Am I missing something here???? If i am wrong I want to know what I am not understanding.


Just a word of advice. You may be right, but you are on a short call. If you want to get hired on full time, I would suggest not arguing with the foreman as a new hire. Last thing he wants is some "bench warmer" coming out and starting trouble. It is a sure way to not get hired. As far as the V.D. issue, I agree with you completely, it may be problematic with any substantial loads, but that is the foreman's problem, not yours. If you were a full time employee with a track record of quality work, he may have heeded your advice more readily. As long as it is not a blatant safety violation just do it to the best of your ability and move on.


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## Big John (May 23, 2010)

running dummy said:


> Yea, wait until the broad that sits at that desk plugs in her mega 1500w lips heater :laughing:


 Someone on here call them "muff heaters." That is now in my vocabulary of slang. :laughing:


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## chicken steve (Mar 22, 2011)

lol, well i'd say it rather disgraceful to have voltage droop around those! ~CS~


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## farlsincharge (Dec 31, 2010)

It is in the CEC. No more than 3% in a branch circuit and no more than 5% from point of distribution. Which leaves feeders at 2% essentially.
If the load is unknown it is taken at 80% of overcurrent.


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## chicken steve (Mar 22, 2011)

farlsincharge said:


> > It is in the CEC. No more than 3% in a branch circuit and no more than 5% from point of distribution. Which leaves feeders at 2% essentially.
> 
> 
> point of disribution meaning serving Xformer or SDS...?
> ...


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## uconduit (Jun 6, 2012)

I get #4 too. Is this the formula people are using? 

Conductor Resistance (Ω/kFT) < Allowable Resistance (Ω/kFT)

Table 8 Conductor (Ω/kFT) < 500 x Voltage x Percentage / Amps x (Length in ft)

Allowable Resistance (Ω/kFT) = 500 x 120 volts x .03 percents / 16 amps x 350 ft = .321 

.308 #4 < .321


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## running dummy (Mar 19, 2009)

I always use some variation of:

2KIL/Acm=Vd


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## BBQ (Nov 16, 2010)

hardworkingstiff said:


> I don't have an argument against that, but I will say it would kind of make my life easier if a set standard was in place.


In my opinion voltage drop should be addressed in the job specs. 

Just not in a 'safety code'.


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## BBQ (Nov 16, 2010)

farlsincharge said:


> It is in the CEC. No more than 3% in a branch circuit and no more than 5% from point of distribution. Which leaves feeders at 2% essentially.
> If the load is unknown it is taken at 80% of overcurrent.


Can you do more than just tell us that.

Can you look up the section and post it?

I ask because those same figures are in the NEC as well .... as suggestions not as a code requirement.


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## chicken steve (Mar 22, 2011)

I can only imagine a large facility starting with rows of 2" emt w/heavy strut out of the MDP's....~CS~


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## BBQ (Nov 16, 2010)

We did a food distribution warehouse in PA, it was 45 acers under roof.

Anyway all the roof top GFCI 20 amp outlets where in fact supplied with 4 AWG copper.


http://maps.google.com/maps?oe=UTF-...a=X&ei=CH0XUY2eLu2I0QGljoDABg&ved=0CDAQ8gEwAA


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## chicken steve (Mar 22, 2011)

Was there a specific issue BBQ ? ~CS~


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## BBQ (Nov 16, 2010)

chicken steve said:


> Was there a specific issue BBQ ? ~CS~


Job specs.

But I think if a HVAC contractor tried to run a vacuum pump at the end of 300-400' of 12 AWG there would be an issue.


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## chicken steve (Mar 22, 2011)

understood.....

we had a 500' 480V1200A feeder derated to 800A's with the introduction of a rather _huge_ elevator motor here. 

elevator guys...._meh!_

~CS~


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## farlsincharge (Dec 31, 2010)

BBQ said:


> Can you do more than just tell us that.
> 
> Can you look up the section and post it?
> 
> I ask because those same figures are in the NEC as well .... as suggestions not as a code requirement.


Section 8 - 102

(1) voltage drop in an installation shall 
(a)Be based upon the calculated demand load of the feeders or branch circuit
(b)Not exceed 5% from the supply side of the consumers service to the point of utilization; and
(c)Not exceed 3% in a branch circuit


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## BBQ (Nov 16, 2010)

farlsincharge said:


> Section 8 - 102
> 
> (1) voltage drop in an installation shall
> (a)Be based upon the calculated demand load of the feeders or branch circuit
> ...


Thank you.

Here is what the NEC says




> *Informational Note No. 2:* Conductors for feeders as defined
> in Article 100, sized to prevent a voltage drop exceeding
> 3 percent at the farthest outlet of power, heating, and
> lighting loads, or combinations of such loads, and where
> ...


For us it is just a suggestion, not a requirement.


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## Deepwater Horizon (Jan 29, 2013)

BBQ said:


> We did a food distribution warehouse in PA, it was 45 acers under roof.
> 
> Anyway all the roof top GFCI 20 amp outlets where in fact supplied with 4 AWG copper.
> 
> ...


That place is tiny. :laughing:


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## BBQ (Nov 16, 2010)

Deepwater Horizon said:


> That place is tiny. :laughing:


:yawn:​


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## Deepwater Horizon (Jan 29, 2013)

BBQ said:


> :yawn:​


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## BBQ (Nov 16, 2010)

Deepwater Horizon said:


>





















:laughing:


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## Deepwater Horizon (Jan 29, 2013)

BBQ said:


> :laughing:​




OK, you got me. :laughing:

Did you hook up any generators?​


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## BBQ (Nov 16, 2010)

Deepwater Horizon said:


> OK, you got me. :laughing:
> 
> Did you hook up any generators?


I had to go to Hyannis yesterday to fix a permanent one. (I hit reset and it started ... I am an electrical superman.  )

Mike S and Bill C hooked one up in Hingham, 2 other guys did one in Prov last night and we may have some more to do today or tomorrow. The CT crew has done a few and have one to do today.


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## Deepwater Horizon (Jan 29, 2013)

BBQ said:


> I had to go to Hyannis yesterday to fix a permanent one. (I hit reset and it started ... I am an electrical superman.  )
> 
> Mike S and Bill C hooked one up in Hingham, 2 other guys did one in Prov last night and we may have some more to do today or tomorrow. The CT crew has done a few and have one to do today.


Mike S? :blink: And how has Chugs been lately? :laughing:


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## BBQ (Nov 16, 2010)

Deepwater Horizon said:


> how has Chugs been lately? :laughing:


I went by his house on the way home from the cape, it was 4PM or so and he was still digging out. He lives on the side of a large hill, his backyard is almost bare grass due to the wind ...... but it was all blown around into his front yard and driveway. He had drifts as tall as him ... really. :laughing:

But he had his 1930s gravely walk behind tractor outfitted with a snow blower, he was having a ball. :thumbup:


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## Deepwater Horizon (Jan 29, 2013)

BBQ said:


> I went by his house on the way home from the cape, it was 4PM or so and he was still digging out. He lives on the side of a large hill, his backyard is almost bare grass due to the wind ...... but it was all blown around into his front yard and driveway. He had drifts as tall as him ... really. :laughing:
> 
> But he had his 1930s gravely walk behind tractor outfitted with a snow blower, he was having a ball. :thumbup:


I know, I had to go to his house once and I saw his collection of scrap metal...errr...I mean old engines and equipment. :laughing:


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## chicken steve (Mar 22, 2011)

nice...

i bet that'd get the feathers off a chicken pronto!

~CS~


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