# Branch circuit wire size



## gpop (May 14, 2018)

The calculator says #4 which would be a 2.88% voltage drop.


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## Kevin (Feb 14, 2017)

I'm not sure if NEC says the same thing my Ontario code says but it's no more than 3 percent from the panel to the point of utilization, and no more than 5 percent from the distribution point (transformer on the pole I believe) to the point of utilization. Might make a difference as to wire size.

Sent from my SM-G920W8 using Tapatalk


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## readydave8 (Sep 20, 2009)

xnuke;5052882
Here's an example - can someone tell me what wire you would install for a new hot tub said:


> 60 amp circuit? hot tub pulling no more than 48 amps?(guessing)
> 
> so you would not use 60 in calculations but rather actual load?


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## readydave8 (Sep 20, 2009)

Kevin_Essiambre said:


> I'm not sure if NEC says the same thing my Ontario code says but it's no more than 3 percent from the panel to the point of utilization, and no more than 5 percent from the distribution point (transformer on the pole I believe) to the point of utilization. Might make a difference as to wire size.
> 
> Sent from my SM-G920W8 using Tapatalk


nec does not have limit on voltage drop, that part still not a design manual


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## MDShunk (Jan 7, 2007)

readydave8 said:


> nec does not have limit on voltage drop, that part still not a design manual


Right on. The voltage drop is of little concern if the dataplate tolerates the actual realized voltage with the "normal" size conductor.


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## frenchelectrican (Mar 15, 2007)

readydave8 said:


> nec does not have limit on voltage drop, that part still not a design manual


Useally not unless it is specified by that equipment manufacter say something for X size conductor ( yuh ., ya will have to change depending on distance that about it) 

For high cycling loads I would upsize conductor larger if have to.


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## gpop (May 14, 2018)

I have never really done residential. Is the cost of wire that big of a deal when the customer is paying for it. If it was my own home then i might pay more attention to the manual and look for the correct amp draw as its never going to be a nice round number like 60. But if im not paying for the wire is it that big of a deal.


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## Dennis Alwon (May 9, 2009)

readydave8 said:


> nec does not have limit on voltage drop, that part still not a design manual


I believe fire pumps is the only area of the nec that has voltage drop parameters.



> 695.7 Voltage Drop.
> (A) Starting. The voltage at the fire pump controller line
> terminals shall not drop more than 15 percent below normal
> (controller-rated voltage) under motor starting conditions.
> ...


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## Mouser (May 4, 2011)

one other code article requiring a limited voltage drop is for Sensitive Electronic Equipment



> 647.4 Wiring Methods.
> (D) Voltage Drop. The voltage drop on any branch circuit
> shall not exceed 1.5 percent. The combined voltage drop of
> feeder and branch-circuit conductors shall not exceed
> 2.5 percent.


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## xnuke (May 10, 2018)

readydave8 said:


> 60 amp circuit? hot tub pulling no more than 48 amps?(guessing)
> 
> so you would not use 60 in calculations but rather actual load?



Good point, as far as a dedicated circuit. You would be right in the hot tub example for instance. However, if I run a 200' circuit to install a 120v 30 amp RV receptacle at the back of a garage, I don't have any idea what's really going to be plugged into that. In my world, there's no doubt someone will figure out how to plug their portable welder into that, or a space heater or something else that tests it's limit.


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## xnuke (May 10, 2018)

readydave8 said:


> nec does not have limit on voltage drop, that part still not a design manual




From what I can tell, this is the biggest difference among contractors - how they view this very statement.

The way I was taught, if it's IN the Code, then it IS Code. After reading your reply I pulled out my Code book just to verify first hand, and it is IN the Code... but as an Informational Note, so, I can see how someone would argue that it's not truly CODE. 

Since anything arguable really comes down to which side of the argument the AHJ takes, I called mine. I talked to the supervisor of the electrical inspectors here, and told him that when I calculate voltage drop and consider that installing a long circuit, I come up with wire size that other electricians wouldn't use and even the supplier asks "why are you using that?!" The AHJ told me that they might not be enforcing it well enough, but that I was absolutely doing the right thing. I asked if it was considered not enforceable because it was an Informational Note, and he said that they considered the Informational Notes to be enforceable, only the commentary blue text in the Handbook is not enforceable.

So, as far as the Boise, Idaho area, I guess I have my answer.


210 - BRANCH CIRCUITS
II. Branch-Circuit Ratings
210.19 Conductors — Minimum Ampacity and Size
(A) Branch Circuits Not More Than 600 Volts.
*Informational Note No. 4*: Conductors for branch circuits 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 the maximum
total voltage drop on both feeders and branch circuits to the farthest
outlet does not exceed 5 percent, provide reasonable efficiency of
operation. See Informational Note No. 2 of 215.2(A)(1)(b) for
voltage drop on feeder conductors.​


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## xnuke (May 10, 2018)

frenchelectrican said:


> Useally not unless it is specified by that equipment manufacter say something for X size conductor ( yuh ., ya will have to change depending on distance that about it)
> 
> For high cycling loads* I would upsize conductor larger if have to*.



How do you know if you have to? What do you go by?


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## xnuke (May 10, 2018)

gpop said:


> I have never really done residential. Is the cost of wire that big of a deal when the customer is paying for it. If it was my own home then i might pay more attention to the manual and look for the correct amp draw as its never going to be a nice round number like 60. But if im not paying for the wire is it that big of a deal.



Yes... It's more than a cost of material. Size matters.
In residential more than anywhere, IMO, the larger size causes more pain. At least for remodel work. Trying to fish through 2x4 walls, getting into attics in tight spaces, getting into recessed panels, handling wire/cable through crawl spaces or hot attics full of insulation - all that is so much worse when the wire is bigger, heavier and has a longer bend radius.
Personally, I would NEVER upsize wire just for the heck of it.


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## readydave8 (Sep 20, 2009)

xnuke said:


> From what I can tell, this is the biggest difference among contractors - how they view this very statement.
> 
> The way I was taught, if it's IN the Code, then it IS Code. After reading your reply I pulled out my Code book just to verify first hand, and it is IN the Code... but as an Informational Note, so, I can see how someone would argue that it's not truly CODE.
> 
> ...


That's ridiculous

Why is it called "informational note" and not in text above? Not to save ink


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## readydave8 (Sep 20, 2009)

xnuke said:


> I need help... I seem to be missing something.
> If I run a new branch circuit, say for an RV receptacle or a hot tub, the circuit should be sized to maintain no more than a 3% voltage drop, correct?
> 
> Either:
> ...


1 and 3 are both correct answers, for example if hot tub pulling 48 amps than 60 should not be used in equation


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## cabletie (Feb 12, 2011)

90.5 Mandatory Rules, Permissive Rules, and Explanatory Material.

(C)Explanatory Material.
Explanatory material, such as references to other standards, references to related sections of this Code, or information related to a Code rule, is included in this Code in the form of informational notes. Such notes are informational only and are not enforceable as requirements of this Code.

He seems to be a good inspector, but informational notes are not enforceable.


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## frenchelectrican (Mar 15, 2007)

xnuke said:


> How do you know if you have to? What do you go by?


There are some spots I just throw the codebook out of the window and use common sense with it. All it depending on the situation what ya looking at.


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## xnuke (May 10, 2018)

So far no one has answered the original question, regarding the example given.
*What would you run??*


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## telsa (May 22, 2015)

Hot tubs and RV receptacles get (usually) very occasional demand.

I'd go with a 5% voltage drop and not sweat it.

The heaters in a hot tub won't care, and the pump can handle 5%, no sweat.

You're not wasting that much power, and the conductors are not going to cook off.

The actual draw of a stored RV at someone's residence is trivial until its occupied, something that most suburbs won't permit. You can store it there, sometimes, but you're not supposed to be living out of it. 

End of problem.


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## matt1124 (Aug 23, 2011)

I have a customer that refurbishes Prevost motor coaches. You'd better believe they pull full amps with the air conditioners running without the bus engine on, and you'd better believe they run constantly in the shop in the middle of summer. 50 amp breaker @ .8 breaker loading, 200', in conduit, shop is 208/120 ----> #4 coppah


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## telsa (May 22, 2015)

matt1124 said:


> I have a customer that refurbishes Prevost motor coaches. You'd better believe they pull full amps with the air conditioners running without the bus engine on, and you'd better believe they run constantly in the shop in the middle of summer. 50 amp breaker @ .8 breaker loading, 200', in conduit, shop is 208/120 ----> #4 coppah


You're describing a commercial firm.

In my town, any residence caught doing what you're proposing would have the sheriff showing up ultra-fast. Around here, you can't even have such an RV outside. You have to build a custom garage for it. 

The OP wants to know what would be regular residential standards.


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## splatz (May 23, 2015)

xnuke said:


> Here's an example - can someone tell me what wire you would install for a new hot tub, 60 amp, 240v, 200 ft run? From what I can see, by the Code, #4 (copper) wire isn't big enough. What would you actually run?





gpop said:


> The calculator says #4 which would be a 2.88% voltage drop.





xnuke said:


> So far no one has answered the original question, regarding the example given.
> *What would you run??*


Actually I think @gpop answered it, I think your calculation was off and everybody's happy with #4. 

I agree with @readydave8 and @cabletie, the inspector seems well intentioned but must pull their head out of their butt with respect to the informational notes. Even aside from the bit that @cabletie posted about the informational note, even the language in the note is free of shall's, must's, etc. 

Now I am with the OP that if it's a receptacle, I do absolutely no speculating about the load they tell me will be on that receptacle. My goal is that my customers can rest assured that between when I put it in and when the building is torn down, if someone puts in a properly wired appliance with the proper plug, and they don't force a square peg in a round hole, it's going to work as it should.


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## eddy current (Feb 28, 2009)

Dennis Alwon said:


> I believe fire pumps is the only area of the nec that has voltage drop parameters.


That is surprising to me as the CEC is very clear on voltage drop allowances. 

We have codes and tables for calculating it. I’ve even had inspectors check it on long runs.


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## readydave8 (Sep 20, 2009)

xnuke said:


> Here's an example - can someone tell me what wire you would install for a new hot tub, 60 amp, 240v, 200 ft run? From what I can see, by the Code, #4 (copper) wire isn't big enough. What would you actually run?


The 200' run would be unusual inside, if I ran into that would probably run #2 aluminum
And switch over to #6 before tub (probably at dissconnect)

But the 60 amps is still confusing me, that tub may pull 32 and manufacturor still be asking for 60 amp circuit


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## sbrn33 (Mar 15, 2007)

I would run a 6-3 romex and call it good. Commercial application I may bump it to 4 but I doubt it.


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## gpop (May 14, 2018)

sbrn33 said:


> I would run a 6-3 romex and call it good. Commercial application I may bump it to 4 but I doubt it.


By code you can not use a #6 for 60amps as it would be under the 60c restriction for conduit/direct burial. Or am i reading that wrong.


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## MechanicalDVR (Dec 29, 2007)

telsa said:


> Hot tubs and RV receptacles get (usually) very occasional demand.
> 
> I'd go with a 5% voltage drop and not sweat it.
> 
> ...



You need to get out of Cali and travel the south a little.

Many around here live in RVs in the yards of relatives.


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## Switched (Dec 23, 2012)

MechanicalDVR said:


> You need to get out of Cali and travel the south a little.
> 
> Many around here live in RVs in the yards of relatives.


NO.... He and I can stay in Cali, the weirdos can leave. Damn... This would be the least populated state.


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## MechanicalDVR (Dec 29, 2007)

Switched said:


> NO.... He and I can stay in Cali, the weirdos can leave. Damn... This would be the least populated state.


Then you guys better get something going to push them due west or due south, just don't let them crazy things head east by any means.


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## Switched (Dec 23, 2012)

MechanicalDVR said:


> Then you guys better get something going to push them due west or due south, just don't let them crazy things head east by any means.


Ever see that John Candy flick "Wagons East"? From everyone I know that moves out of Cali, they go to the following places:

Texas
North Carolina
Oregon
Washington

I'll put out a memo to head to Virginia... Isn't that where your at Mech?:vs_laugh:


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## xnuke (May 10, 2018)

telsa said:


> Hot tubs and RV receptacles get (usually) very occasional demand.
> 
> I'd go with a 5% voltage drop and not sweat it.
> 
> ...



Another example I could have given was an RV receptacle circuit that we just installed. Client wants to park his RV in back of his business, so it was basically a residential job in a commercial setting. Two electricians before us gave him a bid for the job based on running #10 wire for his 125v, 30a circuit.

From panel to receptacle it was at least 165 ft. Calculation says #4 Cu wire. We ran #6. *(Again - what would you run??)*

As we finished the job, client asked if I'd pick up 85 ft of #10 SJ so he can make an extension cord to add to the 30 ft cable in his RV because he intends to park it down the fence line instead of up against his shop.

Just the voltage drop in the 85 ft to the receptacle would have been 10% (12.3v) if someone ran #10 wire. Then the guy adds another 115 ft after you leave, he's got an 18.6v drop. And there's no telling what he expects to plug in and use in the RV, maybe just the A/C, maybe not.

I get the idea there are a lot of guys that would be just fine with that.
If I was the client and figured out that I had <100v available because my electrical contractor didn't bother to consider voltage drop, I think I'd be pissed off. 

I'm feeling kind of alone here though...


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## gpop (May 14, 2018)

xnuke said:


> Another example I could have given was an RV receptacle circuit that we just installed. Client wants to park his RV in back of his business, so it was basically a residential job in a commercial setting. Two electricians before us gave him a bid for the job based on running #10 wire for his 125v, 30a circuit.
> 
> From panel to receptacle it was at least 165 ft. Calculation says #4 Cu wire. We ran #6. *(Again - what would you run??)*
> 
> ...


I would use a #6 copper and except a 3.65 drop knowing that a rv ac unit has a hard start installed as standard. (we ******* so we know what relatives need in them there rv's). 

What calculator are you using?


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## xnuke (May 10, 2018)

Switched said:


> NO.... He and I can stay in Cali, the weirdos can leave. Damn... This would be the least populated state.


A few years ago, when I lived north of Portland, Oregon I thought everyone in California was moving north up the coast.
Then I got to Idaho and realized those were just the few that didn't know the most direct route to Boise.


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## Switched (Dec 23, 2012)

@xnuke This is the difference between residential and commercial/industrial work. 

Generally in commercial and industrial, your values of the end product or usage are known, calculated and accounted for. So the right size conduit, wire, devices, etc. are installed. All of this because it has been specifically engineered.

Residential, well that's a total crap shoot.... 

Electrician: "What are you going to use this for?"

HO: "Maybe this... Maybe that..."

Electrician: "I need to know what will be used so I can correctly size it"

HO: "Can't you just install some big wire and a big fuse so I can use whatever?"

Electrician: :wallbash:


Don't worry about what other guys are doing so much. If you can sell it as an upgraded installation, as you seem to have done in the case of the RV receptacle, then you'll be seen as more knowledgeable to your clients. The other EC's may not agree with your thinking, but your cashing the checks they didn't get.

I tend to personally err on the side of caution with my installations, as I have seen to many homes completely inadequately wired for actual usage.

Does it cost more? Yes

Does it take a little longer? Yes

Am I loosing money? No

Is the customer happy? Yes


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## xnuke (May 10, 2018)

gpop said:


> What calculator are you using?



I've googled several to compare answers and don't see a difference between them, but I kept a shortcut to one that I use when I want a quick answer at a jobsite or something. I'd include the link, but evidently I can't until I've made 3 more posts. It's not an app, just a website.

If I'm at my desk though, like when I made the previous post, I use the formula and Code book (chpt 9).

*VD = (2 x K x I x L) / Cmils*

K = 12.9 Cu or 21.2 Al
I = circuit voltage
L = circuit length one way​
Am I doing something differently than everyone else??


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## xnuke (May 10, 2018)

Switched said:


> @xnuke This is the difference between residential and commercial/industrial work.
> 
> Generally in commercial and industrial, your values of the end product or usage are known, calculated and accounted for. So the right size conduit, wire, devices, etc. are installed. All of this because it has been specifically engineered.



Thanks for your post. You nailed it on the conversation with a HO.

I'm getting an EC company started, along with a partner, after spending nearly 15 years in Industrial maintenance working for major Pulp & Paper companies. Most of that time was spent as an electrical supervisor and/or planner.

You're right, and I just hadn't really thought about it. All of my background has me conditioned to do everything to the letter of the law or better. Reliability required for a multi-million dollar paper machine is a whole different level than my garage outlets.

I still have a hard time taking shortcuts.
I have a hard time standing on the top of a 6' ladder too though.
Maybe getting out of Pulp & Paper industrial settings will get me past both things. (I kinda hope not...)


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## Switched (Dec 23, 2012)

I think it was French who said sometimes you have to throw out the codebook, and like it says in the book it isn't a design manual, not to mention it is a set of minimum rules.

Most of us have been in the game long enough to know what works, what doesn't, how people use things, etc...

It isn't about cutting corners, it is about doing the best installation for the job. When that outcome is an unknown, then you can choose to do a minimum, medium, or prepare for worst case.

Whether that is wrong or a shortcut, that may all be in the eye of the beholder. The beholder is the end user, your customer. As long as the installation is "Safe", there is a lot of wiggle room.


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## MechanicalDVR (Dec 29, 2007)

Switched said:


> Ever see that John Candy flick "Wagons East"? From everyone I know that moves out of Cali, they go to the following places:
> 
> Texas
> North Carolina
> ...


I'm telling ya 'don't send us no liberal-progressive types' it might kick off a civil war!


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## sbrn33 (Mar 15, 2007)

gpop said:


> By code you can not use a #6 for 60amps as it would be under the 60c restriction for conduit/direct burial. Or am i reading that wrong.


You are probably right, but it is what I would do anyway. Although on second thought on a run that long I may run 2-4 Alum SE cable. That would save $400 or more.


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