Ungrounded Conductors From Same Circuit on Same Breaker?

[ggunn]

Everyone in here knows the difference between series and parallel circuits. The only question is whether 310.4(A) applies to the aforementioned ring configuration. Whether it does or not depends of your interpretation of the term "connected in parallel". The Article gives us some aid in this by parenthetically stipulating that the definition of parallel within the context of the Article is "electrically joined at both ends".

I am of the opinion that the ring circuit does not fit this narrow definition of a parallel connection. I do not mean to say that I don't think that parallel paths are there in the ring circuit, just that the parallel conductors that 310.4(A) addresses are not addressed by the Article. Furthermore, when I look at the article in the context of what issues it is addressing in the section in which the Article appears, it looks even less likely to me that that the ring circuit is within its scope.

Beyond that, I leave it to the lawyers to interpret that section of Code if an electrical fire should ever occur in a structure where this ring configuration was implemented. Short of that, I don't think we are going to settle the issue in here. I don't think anyone's mind is going to be changed by this "discussion". I know that mine isn't.

Just how many angels can dance on the head of a pin, anyway?

 

[charlie b]

Basic electricity rules do not require identical conditions for each element in a parallel path.

True. But irrelevant.

Can you not have a 10 ohm resistor connected in parallel with a 25 ohm resistor? Can you not have a 10 foot conductor connected in parallel with a 25 foot conductor?

Yes, both are true. But both are irrelevant.

I will not give in unless someone can prove that you can not physically parallel two components of differing qualities.

Certainly you can. Still irrelevant.
? Take two wooden boards, say 1” x 6” x one foot long each.
? On the first board, insert into the wood a pair of screws, about two inches apart.
? On the second board, insert into the wood a set of three screws, laid out in the pattern of an equilateral triangle, spaced about two inches apart.
? On the first board, take a pair of resistors (any values you like, then need not be the same). Twist the left hand leads of the two resistors together, wrap them around the left hand screw, and tighten that screw. Then twist the right hand leads of the two resistors together, wrap them around the right hand screw, and tighten that screw.
? On the second board, take another pair of resistors (any values you like). Twist the left hand leads of the two resistors together, wrap them around the left hand screw, and tighten that screw. Next, wrap the right hand lead of one resistor around a second screw, and also wrap a short wire around the second screw, and tighten the second screw. Finally, wrap the right hand lead of the second resistor around the third screw, and also wrap the other end of the short wire around the third screw, and tighten the third screw.

On the first board, the two resistors are in parallel. On the second board, they are not. Period. The fact that there exists a resistive element (i.e., a wire) that is used to “electrically connect” the right side of one resistor to the right side of the other resistor is sufficient to cause the two resistors to not be in parallel. That, my friend, is the very definition of “parallel,” and is the essence of the disagreements on display in this thread.

This is first day or two stuff in a basic electricity class isn't it?

No, it’s our first lesson in the use of language. Here is the lesson: Quote from person #1: “The sky is blue.” Quote from person #2: “No you are wrong, the grass is green.”

It is constantly brought up on this forum the fact that grounded neutral current flows back to the source through all possible paths. Are these paths not parallel to one another? The lowest impedance paths carry most of the current, but all other parallel paths are carrying some current.

You ask us to verify that the paths are parallel (i.e., that the sky is blue)? Ok. I’ll verify that. Now I will assert that the components are not “in parallel” (i.e., that the grass is green). Can you not grasp that we are talking about different things? NEC 310.4 is all about placing wires in parallel with each other. It is not talking about parallel paths for current to travel from a source to a load.

 

[roger]

Just how many angels can dance on the head of a pin, anyway?

Is the head of this pin absolutely flat or is it convexed?

Roger

 

[cowboyjwc]

So in your opinion can you run 2 14AWG conductors from a 15 amp breaker to a receptacle? (most will say no you are paralleling the conductors). Yet many say add a second or even more receptacles and now this is not parallel conductors. What if you just added one receptacle and it happens to be in same enclosure as first (like a 2 gang box) and there is only 3 inches of conductor between the two receptacles. You have almost exactly the same thing.

Nobody is going to convince me that the two home runs are not parallel to each other. I agree they are not necessarily identical parallels but they are indeed parallel paths.

310.4 does not mention overcurrent protection. It just says conductors 1/0 and larger shall be permitted to be connected in parallel. Then parts B and C explain that they need to have same characteristics such as size, length, termination method, etc.

It is my opinion that the circuit in question does contain conductors that are connected in parallel, they are not the same length, and they are smaller than 1/0 AWG, therefore they are not allowed by 310.4. I also think it would be a better idea to just run a larger conductor in the first place if voltage drop is an issue.

Excepttion to 310.4(A) does allow conductors to be connected in parallel for instruments and control devices. This only makes sense. How can you get an "either/or" function out of dry contacts if you can't connect them in parallel?

Do I think there is a problem with using this setup? No. But I don't think it complies with 310.4.

I am not calling this "parallel conductors" I am calling it "conductors connected in parallel" which is the wording that is also used in 310.4

I totally disagree with the "Absolute Wording or Intended Meaning" theory you mention. The NEC says what it says. Absolute wording is part of the reason why the NEC is updated every three years. Sometimes the absolute wording is not interpreted the way the intended meaning was intended so three years later the absolute wording gets changed again. Intended meaning is simply reading it the way you (or somebody) want it to read. If absolute wording can be interpreted in more than one way than more than one way is what it means even if not intentional by the code making panel that wrote it, they have three more years to get it the way they wanted it.

As far as interpretation of what is written we have definitions in art 100 and we have definitions in some sections that apply to when a term is used in that section. If a word is not defined in either of those places then an english language dictionary is the source of a definition of a word. If there is more than one definition then there can be a problem. There is no definition of conductor in art 100. There also is no definition of parallel conductor there. 310.4 also does not use this terminology as I already mentioned above.

The red highlight is where you've made your mistake, this is not what the OP stated. In the original question he ran a #14 wire from the breaker to a receptacle and then at the end of the run he ran a #14 wire from a receptacle to the breaker. He didn't run two #14 wires to a receptacle.

 

[handy10]

Somewhat related to this discussion

Somewhat related to this discussion

This thread may be too long already, but I have a question that is related. What is the purpose of the NEC rule regarding parallel wires? I believe that the purpose is to permit pulling smaller wires in parallel if they are larger than a minimum size. This allows an 800kcml wire to be replaced by 4 200kcml. The rest of the rules (length, neutrals, etc) are to insure that if one or more of the wires is lost there is not a major problem because the remaining wires are too small. In the OPs description,it sounds like (if there is anything in parallel) both of the wires are 14AWG. Therefore, if one wire is cut, the circuit will continue to function safely. I agree with those who hold that the situation the OP describes is passable, but I also think that it is a poor idea. Unless the distance between receptacles is very large, all the receptacles will receive the power they require without the loop back to the panel.

 

[don_resqcapt19]

This thread may be too long already, but I have a question that is related. What is the purpose of the NEC rule regarding parallel wires? I believe that the purpose is to permit pulling smaller wires in parallel if they are larger than a minimum size. This allows an 800kcml wire to be replaced by 4 200kcml. The rest of the rules (length, neutrals, etc) are to insure that if one or more of the wires is lost there is not a major problem because the remaining wires are too small. ...

The rules for parallel conductors are based on keeping the current the same on all of the conductors that are installed in parallel. If you lose on of the conductors of the parallel set it is very likely that the others will be overloaded.
Also for you 800kcmil conductor, that would likely be replaced with two 250kcmil or with three 2/0s...not four 200's. One of the advantages of using parallel conductors is the fact that you can use less copper than you would use with a single conductor.

 

[charlie b]

Another advantage is that it is easier to physically handle the conductors, so the labor costs are reduced.

 

[taylorp]

The red highlight is where you've made your mistake, this is not what the OP stated. In the original question he ran a #14 wire from the breaker to a receptacle and then at the end of the run he ran a #14 wire from a receptacle to the breaker. He didn't run two #14 wires to a receptacle.

And the electrical difference is?

 

[roger]

And the electrical difference is?

In the original scenario the conducrtors are not in parallel, in the second scenario they are.

Roger

 

[readydave8]

Is the head of this pin absolutely flat or is it convexed?

Roger

should be safety pin in keeping with ring cirduit theme; does it even have a head?

 

[cowboyjwc]

In the original scenario the conducrtors are not in parallel, in the second scenario they are.

Roger

Roger is the only one that understands me.:happyyes:

 

[iwire]

I sure would like some to explain how the conductors in a ring circuit are not electrically joined at both ends. :?

In my opinion they are and that makes them parallel conductors to the NEC.

 

[weressl]

Kwired gets the prize. The guy's explanation was, "So that the last light on the circuit is the same brightness as the first one." I laughed and said something like that's not how voltage drop works...even though the circuit would work.

In this situation though, would an AFCI breaker hold? I might get the call from the bullpen if the breakers don't hold and we need a professional to put this job to bed...just wondering.

Actually the guys reasoning may not be accurate. It will depend on what else is plugged into the interceeding receptacles, how far is the first and the last one from the source, etc.

The phone company uses it to protect against open circuit and some network protocolls are still using the same scheme.

 

[ggunn]

I sure would like some to explain how the conductors in a ring circuit are not electrically joined at both ends. :?

In my opinion they are and that makes them parallel conductors to the NEC.

Wire is not a zero resistance conductor. If you model the ring system as a resistor network with a resistor for every conductor, including the conductors between receptacles, the two conductors from the panel are clearly not electrically joined at both ends. They touch the resistor network in different places.

And of course, you could say that even a terminal block has SOME resistance, so with the above interpretation, even conductors connected at both ends on blocks aren't in parallel. This is the kind of thing that makes lawyers rich.

So at the end of the day, you have to pick a threshold for what is parallel and what is "electrically joined".

 

[david luchini]

I sure would like some to explain how the conductors in a ring circuit are not electrically joined at both ends. :?

In my opinion they are and that makes them parallel conductors to the NEC.

I think the question would be: what are the two ends in the ring circuit. There is not two ends to the circuit. It is electrically continuous in a loop. So how would conductors be electrically joined at "both ends?"

 

[Rick Christopherson]

I sure would like some to explain how the conductors in a ring circuit are not electrically joined at both ends. :?

Is the current that is entering the first mutually shared node equal to the current exiting the next mutually shared node? No, because one of those conductors has several other non-mutual nodes in between. As Charlie suggested above, it's a parallel path, but not a parallel conductor.

 

[charlie b]

Let’s try this another way. Let’s forget (for a moment) the 15 amp circuit with its #14 wire connected in a ring to a number of receptacles. Let’s talk about a 600 amp circuit, and let’s talk about 1/0 THHN wire, and let’s talk about single phase heaters that draw 80 amps each.

The general idea of parallel conductors is that we can take three 1/0 conductors (ampacity 230 each), connect them in parallel, and have a total ampacity of 690. So let me build a ring circuit, starting at the 600 amp breaker, and running one 1/0 to a single phase heater, and running from there to a second heater, then to a third, fourth, fifth, and sixth, then back to the same breaker. Run a neutral wire in a ring to the heaters in a similar fashion, but let’s just talk about the ungrounded conductors. For this circuit, you cannot say I have violated the portion of 310.4 that gives a minimum size for parallel conductors.

I will have used a total of seven conductors (breaker to heater 1, then to heater 2, then heaters 3, 4, 5, and 6, then to breaker). So, using the philosophy that these seven conductors are “electrically joined at each end,” and are therefore “in parallel” (in the context of 310.4), I can infer that I have a total ampacity of 1610 amps (7 times 230). And since the total load is only 480, I have a code-compliant installation. Would you accept that?

I would not. For it looks to me very much like a run of 1/0 (ampacity 230) is carrying a total load of 480 amps. The seven wires are going to behave as though they were in series, so they are not “sharing” the total load. Even if you consider that half the current will leave the breaker on each of the two wires connected to the breaker, that still gives 240 amps leaving the breaker on wires that are only rated for 230.

Conclusion: This is not a "parallel" situation.

 

[iwire]

Is the current that is entering the first mutually shared node equal to the current exiting the next mutually shared node? No, because one of those conductors has several other non-mutual nodes in between. As Charlie suggested above, it's a parallel path, but not a parallel conductor.

My question has absolutely nothing at all to do with how electricity behaves and has everything to do with the wording in the NEC. Which tells us that for NEC applications parallel conductors are those conductors that are electrically joined at both ends.

From the 2008 NEC, please not the last words of the section.

310.4 Conductors in Parallel.
(A) General. Aluminum, copper-clad aluminum, or copper
conductors of size 1/0 AWG and larger, comprising each
phase, polarity, neutral, or grounded circuit conductor shall
be permitted to be connected in parallel (electrically joined
at both ends).

IMO there is no reason to talk about nodes or current, the NEC has set the rules for what the NEC considers parallel conductors.

 

[iwire]

I think the question would be: what are the two ends in the ring circuit. There is not two ends to the circuit. It is electrically continuous in a loop. So how would conductors be electrically joined at "both ends?"

They are joined at each termination and the fact it is a circle or ring means there are all electrically joined at each end (IMO)

 

[Rick Christopherson]

My question has absolutely nothing at all to do with how electricity behaves and has everything to do with the wording in the NEC. Which tells us that for NEC applications parallel conductors are those conductors that are electrically joined at both ends.

From the 2008 NEC, please not the last words of the section.


IMO there is no reason to talk about nodes or current, the NEC has set the rules for what the NEC considers parallel conductors.

If they were electrically joined at both ends, then the current entering and leaving the shared nodes would be equal. Electrically joined at both ends does not mean you can have an entire circuit's worth of conductors in the middle and still be electrically joined. You can't ignore all of the nodes in the middle and call that a single conductor.

If I had 10 amps entering what you want to call a single conductor, then how many amps are leaving it? You can't answer that because it's not the same conductor.