House Neutral

[Quatrix]

Good Day,

I have a question regarding the neutral white wire in house wiring. Is it allowed to use a hot and a neutral from two different circuits? In other words, I want to connect a 15A receptacle to the hot black wire used in the network of two 3-way switches. Next, I was planning to grab a neutral from a different circuit and marry that to the hot black wire from the 3-way switch network to connect my receptacle. Is that allowed? Please let me know.

 

[nealtw]

I think, no because when you have two circuits that share a neutral the breakers are tied together

 

[afjes_2016]

As Neal stated sharing a neutral is only allowed in a MWBC (multi wire branch circuit) with tied breakers or double pole breakers so when one circuit trips the breaker the other breaker trips too.

Sharing neutrals in other than a MWBC can over load the neutral and cause serious problems. Many people do not realize that you can overload a neutral. Do some Googling on this and you will see how the MWBC differs from sharing a neutral from another circuit and how that may overload the neutral (Return). Hint - electricity entering your home is like your main water feed entering your home. The water comes in on the main water line and goes back out thru the drains to the sewer. Electricity comes in on the hot line and goes back out thru the neutral line. A flow-thru system just like water.

 

[hornetd]

That practice is specifically addressed by the language in

300.3 Conductors.
(B) Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cable bus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4).

None of the exceptions in 300.3(B)(1) through (B)(4) apply to residential installations. When you take the neutral conductor of one circuit and an energized conductor of another the you are making a circuit that is nearly certain to violate the requirement for all conductors of a circuit to be in the same pathway.

--
Tom Horne

 

[JoeD]

Definitely not allowed since the neutral would then be possible to carry the full current of both circuits. That means that if the two hots were on 15 amp breakers then neutral could possibly carry 30 amps.

If you can get the neutral from another circuit to the box why are you not bringing the hot from that circuit as well.

 

[WyrTwister]

Nope !

Go find a box with this circuit that contains both hot , neutral & earth ground and run a new piece of Romex from it , to the box you are dealing with . Do it right .

Wyr
God bless

 

[Quatrix]

The reason why I want to pull the neutral from a different circuit is because I have the white wire readily accessible from another 1-gang box. Assuming the white wire is good and all the remaining hot black wires have poor insulation my intent is to pull a hot black wire from a nearby 3-way switch network, similar to the circuit map #23 (attached).

From my understanding, a neutral can be overloaded if for example, a microwave and a toaster are both consuming power from same phase. If both of them are consuming 7A then the neutral will carry 14A through it. Now, if I have a juice maker consuming 5A and a food processor consuming 6A on the opposite phase then the neutral will have 14A-11A = 3A. Please correct me if I am wrong as this is very important.

Another interesting fact is that the total sum of amps inside of my panel (based on rated marking on circuit breakers) on the left leg equals 170A and the sum on the right leg is 180A. Before going any further why are these currents not balanced?

P.S. I have also attached an excerpt from a book on residential wiring, image of my panel, and image of the box with white neutral wire.
Please make any suggestions.

 

[WyrTwister]

Either do it ( knowing it is wrong / forbidden ) or don't do it . Why you wish to do it is immaterial . And discussing it is just a waste if every ones time .

Do not ask questions if you will not listen to the answer ( if it is not what you wish to hear ) . Again , it is just a waste if every ones time .

Wyr
God bless

 

[Quatrix]

Wyr,

First of all, if I'm wasting your time then don't reply to my question. Second, my question was not whether I need to do it or not, my question is whether there would be 3A flowing in the neutral based on my example. Read the post again!

 

[WyrTwister]

I did not reply to the question about the amperage . I did not waste my time reading the whole question . Neither do I spend time and effort arguing how many Angels can dance on the head of a pin .

I attempt to try to answer questions by people seeking to gain useful information to solve real issues .

If you wish to ask a math question , better you start another thread .

You do not have to be concerned about me answering your questions , in the future .

Have a nice day ,

Wyr
God bless

 

[EdInKentucky]

Is it allowed to use a hot and a neutral from two different circuits?

Quatrix,
I'm not a licensed electrician, but I feel that the above answers are a pretty clear ... "no".

 

[JoeD]

Hots on opposite legs of the service can share a neutral. It is called a multi wire branch circuit(MWBC). It has special rules including one that the two breakers must be tied together so they both go off if one or both are overloaded..

 

[hornetd]

The reason why I want to pull the neutral from a different circuit is because I have the white wire readily accessible from another 1-gang box. Assuming the white wire is good and all the remaining hot black wires have poor insulation my intent is to pull a hot black wire from a nearby 3-way switch network, similar to the circuit map #23 (attached).

From my understanding, a neutral can be overloaded if for example, a microwave and a toaster are both consuming power from same phase. If both of them are consuming 7A then the neutral will carry 14A through it. Now, if I have a juice maker consuming 5A and a food processor consuming 6A on the opposite phase then the neutral will have 14A-11A = 3A. Please correct me if I am wrong as this is very important.

Another interesting fact is that the total sum of amps inside of my panel (based on rated marking on circuit breakers) on the left leg equals 170A and the sum on the right leg is 180A. Before going any further why are these currents not balanced?

P.S. I have also attached an excerpt from a book on residential wiring, image of my panel, and image of the box with white neutral wire.
Please make any suggestions.

There is still only one answer here and it is not the one you want to see. What you are proposing to do is not the same as the example you are alluding to in your neutral calculation. You don't know what loads the neutral from one circuit and the energized conductor from a different circuit are already carrying. You also do not know if the non cancelling magnetic fields which are created by the current flow which is only traveling on one wire in each circuit will cause inductive heating at a point were it passes close to any piece of ferrous metal including through the wall of any metallic electrical box. That inductive heating will degrade the insulation of that conductor and eventually it WILL fail.

I have 35 years of line service as a Firefighter. I have helped extinguish many fires of electrical origin. When the investigators find that the origin is electric they call in the chief electrical inspector for the county. If they find a violation of the National Electric Code contributed to the ignition they inform the insurer. I'm only one firefighter; though now retired; in a very large organization and I was deposed twice in insurance cases. Both involved a fire of electrical origin were the owner had done his own work badly. In both cases the insurer was able to walk away from the loss without paying it. That is because an insurance contract is known legally as a "contract of utmost good faith." Both parties have taken on a very high level of responsibility to do nothing that would prevent the payment of an insured loss or make a loss more likely. One element of the insured's responsibility is to scrupulously obey the law in anything that applies to the insured property. That means that you do no work without the benefit of inspection by the authority having jurisdiction. That means you get a permit for any work that is subject to an adopted building or building utility's regulatory codes. If you fail to act with utmost good faith you have released the insurer from paying for any loss your bad faith actions may cause. The old adage would seem to apply here. "You pays your money and you takes your chance." Once you engage in unlawful electrical work you are taking the chance that each premium payment that you make will turn out to be "money down a rat hole."

No one who values their reputation is going to advise you to do what you are proposing to do. I'm with WyrTwister on this in that I would ask that you stop asking the folks here to validate your rather dangerous scheme. Those of us who try to answer the valid questions that are posed here want this forum to continue to be a place where people can get reliable advise about how to actually deal with electrical challenges. Validating your patently dangerous scheme does not contribute to that effort. I know that you will not except anything but agreement with your pet theory that this jury rig approach will work. So my reply is addressed more to anyone who might be tempted to apply your bogus approach to a problem that they have which seams similar.

--
Tom Horne

 

[Quatrix]

Good Day,

Thank you all for your input and recommendations, they are invaluable.

I would still like to re-iterate the questions in my post. If we try helping people, it would be good to first read their entire question before answering anything. On that note, I will start a new post with a ‘math’ question.