# Voltage Drop in Residential Settings.



## ilikepez (Mar 24, 2011)

So according to 210.19 we need to keep voltage drop below 3% for all branch circuits, and under 5% when we include feeders and the branch circuits.

I was calculating the voltage drop for 14 AWG for instance and found out that I could only make a 40' one way run on a 15 amp circuit. But I figured I might be doing something wrong because I see guys running 15 amp circuits with 14 AWG all over huge houses and they must have circuits that run at least 100 feet. 

Am I doing the calculation wrong or do a bunch of people just violate that part of the code?


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## user4818 (Jan 15, 2009)

You're assuming a full load of 15 amps. In reality, most residential circuits are not loaded anywhere close to 15 amps, hence voltage drop is not an issue.


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## HARRY304E (Sep 15, 2010)

ilikepez said:


> So according to 210.19 we need to keep voltage drop below 3% for all branch circuits, and under 5% when we include feeders and the branch circuits.
> 
> I was calculating the voltage drop for 14 AWG for instance and found out that I could only make a 40' one way run on a 15 amp circuit. But I figured I might be doing something wrong because I see guys running 15 amp circuits with 14 AWG all over huge houses and they must have circuits that run at least 100 feet.
> 
> Am I doing the calculation wrong or do a bunch of people just violate that part of the code?


If there running 100"s of feet of 14 then they really don't care about what they are doing so the NEC does not matter in this case.


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## ilikepez (Mar 24, 2011)

So what load should I assume for say ten outlets?


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## nitro71 (Sep 17, 2009)

The NEC doesn't require us to design for voltage drop. It suggests we should. Voltage drop is based off the amperage being used. Not the circuit ampacity. 3% is way to small to worry about. I don't worry about anything under 10% myself.


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## ilikepez (Mar 24, 2011)

nitro71 said:


> The NEC doesn't require us to design for voltage drop. It suggests we should. Voltage drop is based off the amperage being used. Not the circuit ampacity. 3% is way to small to worry about. I don't worry about anything under 10% myself.


Okay that makes sense. Looking at it more closely I understand what you're saying.


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## nitro71 (Sep 17, 2009)

If you are building larger, very expensive houses, with very long runs, you might want to consider using sub panels in strategic locations. But for your average 5000 square footer I wouldn't sweat it.


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## HARRY304E (Sep 15, 2010)

ilikepez said:


> So what load should I assume for say ten outlets?


 
1800 watts. each outlet is 180 voltamperes



*(I) Receptacle Outlets. 
*Except as covered in 220.14(J)
and (K), receptacle outlets shall be calculated at not less
than 180 volt-amperes for each single or for each multiple
receptacle on one yoke. A single piece of equipment consisting
of a multiple receptacle comprised of four or more receptacles
shall be calculated at not less than 90 volt-amperes per
receptacle. This provision shall not be applicable to the receptacle​outlets specified in 210.11(C)(1) and (C)(2).
​


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## macmikeman (Jan 23, 2007)

HARRY304E said:


> 1800 watts. each outlet is 180 voltamperes
> 
> 
> 
> ...


In a dwelling the 180 volt amps per receptacle outlet is not a requirement per the NEC. It is for non dwellings.
Its a design issue.


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## hardworkingstiff (Jan 22, 2007)

A few years ago I was reading about some studies Baltimore did in regards to VD. They decided that if it was kept below 10% on a full load (15-amps for a #14 circuit) that it was acceptable, and above that their study seemed to indicate an increase in fire incidents.


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## oliquir (Jan 13, 2011)

you are lucky it is a rule in CEC to follow voltage drop rule


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## Rockyd (Apr 22, 2007)

ilikepez said:


> So according to 210.19 we need to keep voltage drop below 3% for all branch circuits, and under 5% when we include feeders and the branch circuits.
> 
> 
> Am I doing the calculation wrong or do a bunch of people just violate that part of the code?


Informational Notes are *NOT code...and therefore unenforceable. *See 90.5(C).


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## brian john (Mar 11, 2007)

I just finished a large acceptance test for a military facility as part of the test, 25% of all receptacles had to be tested at no load and at 15 amps. 

Lot of paperwork. Because we do these test infrequently, I made a sheet showing voltage drop at different distances for #12, #10 fat 12, 15 and 20 amp loads. Surprising the distances are shorter than most electricians or engineers think.


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## Chris1971 (Dec 27, 2010)

brian john said:


> I just finished a large acceptance test for a military facility as part of the test, 25% of all receptacles had to be tested at no load and at 15 amps.
> 
> Lot of paperwork. Because we do these test infrequently, I made a sheet showing voltage drop at different distances for #12, #10 fat 12, 15 and 20 amp loads. Surprising the distances are shorter than most electricians or engineers think.



Care to share your info?


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## donaldelectrician (Sep 30, 2010)

*Care to share your info?*

I do not believe that NEC looks that hard in Residential . But we do .

I have seen , and walked off, Mc Mansion Remodels where the EE put all the 
Pans in one room ! Some runs could be 200' to 300 '

Hi Chris , Is Minnesota still without inspectors ? I read today that the Bars 
are in trouble , distributors can not get permit fees paid ? 
THAT HURTS ! 

Donald " Outstanding Citizen of the Conch Repuplic "


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## Chris1971 (Dec 27, 2010)

donaldelectrician said:


> I do not believe that NEC looks that hard in Residential . But we do .
> 
> I have seen , and walked off, Mc Mansion Remodels where the EE put all the
> Pans in one room ! Some runs could be 200' to 300 '
> ...


Hopefully the shutdown will be ending within a few days?


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## Rockyd (Apr 22, 2007)

brian john said:


> I just finished a large acceptance test for a military facility as part of the test, 25% of all receptacles had to be tested at no load and at 15 amps.
> 
> Lot of paperwork. Because we do these test infrequently, I made a sheet showing voltage drop at different distances for #12, #10 fat 12, 15 and 20 amp loads. Surprising the distances are shorter than most electricians or engineers think.


Without lookin the book, I'm guessing 50 to 55 feet...for # 12 to increase to a # 10


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## ralpha494 (Oct 29, 2008)

I don't know where it is, but last week I was researcing something concerning voltage drop, and there was a chart with the different wire sizes and how far you could go for 3% and 5% voltage drops. 

I kinda wish I saved the link now. But it's there if you look. If you were a really nice person, you would post the link for me.


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## macmikeman (Jan 23, 2007)

Nothing here a couple of dozen buck and boost can't fix..........:001_huh:


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## user4818 (Jan 15, 2009)

macmikeman said:


> Nothing here a couple of dozen buck and boost can't fix..........:001_huh:


That's a great idea - locate them strategically throughout the house for convenient point of use. For instance, one under the bathroom sink for the bathroom, one in each bedroom closet, two in the kitchen cabinets, and so on and so forth....


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## RIVETER (Sep 26, 2009)

ilikepez said:


> So what load should I assume for say ten outlets?


You should consider SPECIFIC loads when trying to determine if your wiring should be up sized. Other than that, it usually is not a concern that I know of in residential but then, I'm not one of them anymore.


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## oliquir (Jan 13, 2011)

for easy calculation i use this calculator 
http://www.nooutage.com/vdrop.htm


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## Rockyd (Apr 22, 2007)

ilikepez said:


> So according to 210.19 we need to keep voltage drop below 3% for all branch circuits, and under 5% when we include feeders and the branch circuits.


Informational notes are not code, therefore unenforceable. Recommendations for a smarter install perhaps, and a driver for a change order, but not code *see 90.5.*





> Am I doing the calculation wrong or do a bunch of people just violate that part of the code?


VD = 2 x K x I x D
CM​ 
2 = (#of conductors), if 3 phase -√3


K = is your constant 12.9 for copper, 21.2 for aluminum

I = is your amperage

D = Distance

CM = Circular mils


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## A Little Short (Nov 11, 2010)

ralpha494 said:


> I don't know where it is, but last week I was researcing something concerning voltage drop, and there was a chart with the different wire sizes and how far you could go for 3% and 5% voltage drops.
> 
> I kinda wish I saved the link now. But it's there if you look. If you were a really nice person, you would post the link for me.


Look here and go near the bottom for the voltage drop calc.


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## hardworkingstiff (Jan 22, 2007)

This will keep you close.

VD=IR= amps*resistance in the wire


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## BuzzKill (Oct 27, 2008)

ilikepez said:


> So what load should I assume for say ten outlets?


you could put the entire house on one recep.


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## Jimeatslead (Mar 23, 2011)

Not for nothing, but the job I'm on now specs #10 awg for any run longer than 100 feet on a 20 amp circuit. Now it's just small offices, but im in favor of it. I like to see it done myself.


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## brian john (Mar 11, 2007)

Corridor outlet located on the corner of hallway C104 and C103 fed from panel 2 CAC circuit breaker #1
Voltage Drop at outlet
No load measurement 116.9 VAC
10 Amp load measurement 107.1 VAC
Voltage drop from no load to 10 amp load 9.8 VAC
Percentage of drop based upon 117.0 VAC no load 9.5%
No load measurement at panel 2 CAC-1, 117.0 VAC (load connection of branch circuit breaker)
10amp load measurement at panel 2 CAC-1 116.8 VAC (load connection of branch circuit breaker)
Voltage drop from secondary termination in transformer TX2CAC to Load connection of CB-1 14.22 millivolts.

Corridor outlet located on the corner of hallway B104 and B105 fed from panel 2 AAC circuit breaker #7
Voltage Drop at outlet
No load measurement 117.3 VAC
10 Amp load measurement 103.7 VAC
Voltage drop from no load to 10 amp load 13.6 VAC
Percentage of drop based upon 117.3 VAC no load 12%
No load measurement at panel 2 AAC, 117.3 VAC (load connection of branch circuit breaker)
10amp load measurement at panel 2 AAC-7 117.0 VAC (load connection of branch circuit breaker)
Voltage drop from secondary termination in transformer TX2AAC to Load connection of CB-7 13.0 millivolts.


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## brian john (Mar 11, 2007)




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## BBQ (Nov 16, 2010)

My personal feeling and experience is that there are many times where voltage drop exceeds 10% and damn few times it makes any difference or causes any problems.

In other words we are trying to find a solution for a problem that does not exist.


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## brian john (Mar 11, 2007)

BBQ said:


> My personal feeling and experience is that there are many times where voltage drop exceeds 10% and damn few times it makes any difference or causes any problems.
> 
> In other words we are trying to find a solution for a problem that does not exist.


 
In the case above, the county said this school had VD issues and no other identical schools had the same issue. I told them I did not need to test but could do it all with math. They insisted on the test as they were suing the electrical contractor and the GC. They refused to believe me, until they made trips to the other identical schools and realized that VD is VD and that the math works. It is easy enough to estimate the distance and quickly calculate 120 VAC VD at the selected amperage.

They were freaking out about PCs, which IMO was not an issue, the real issue was the floor buffer 12 amp and the extension cord for the buffer was another 50'. And of course high capacity printers had some issues with the VD.

I got paid, I hope the EC got his.


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## lowend15 (May 23, 2013)

*Respectfully disagree*



brian john said:


>


As a caveat to those who may use this table:

I just spot checked your 120V single phase voltage drop calculation for 12 AWG and it is apparent the table is for conductor length, not circuit length. That could be very misleading. 

Basically, you are saying for 2% voltage drop for 10A on 12 AWG, one must be within 30 circuit feet, or 60 conductor feet. Especially in a setting where one is installing Romex, you are purchasing and installing circuit feet, not conductor feet.


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## Semi-Ret Electrician (Nov 10, 2011)

brian john said:


> In the case above, the county said this school had VD issues and no other identical schools had the same issue. I told them I did not need to test but could do it all with math. They insisted on the test as they were suing the electrical contractor and the GC. They refused to believe me, until they made trips to the other identical schools and realized that VD is VD and that the math works. It is easy enough to estimate the distance and quickly calculate 120 VAC VD at the selected amperage.
> 
> They were freaking out about PCs, which IMO was not an issue, the real issue was the floor buffer 12 amp and the extension cord for the buffer was another 50'. And of course high capacity printers had some issues with the VD.
> 
> I got paid, I hope the EC got his.


Brian, I saw something similar in a spec. house. The EC ran #14 from a detached garage (se panel). When the HO plugged in a Vac (15A) the smokes went off, due to VD. 

It was a slab house so I couldn't split the circuits or run a new 20A so I just suggested they plug the vac. into a bath or kitchen receptacle.


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