Are my "semi-shared neutrals" a problem?

[leejosepho]

I just installed a pair of 3-way switches for the two lights for my basement stairway. The power goes to the switch at the top of the stairs, and the lights are fed by the switch at the bottom. However, one side of the light at the bottom of the stairway is connected to a neutral for a circuit other than the circuit that services the switch and light at the top. This configuration was not planned. Rather, I simply missed the matter of running yet another wire to be able to connect the bottom light's neutral at the top.

The two circuits involved are on opposing legs in the breaker panel.

Question: Will what I have be okay as long as I install a double-pole breaker for those two circuits? Their respective loads are each small and essentially equal.

[jar546]

No, this is an illegal connection and must be corrected if you want to comply with today's standards and be safe.

[leejosepho]

No, this is an illegal connection and must be corrected if you want to comply with today's standards and be safe.

Please try to help me understand what might be wrong or dangerous or whatever. Shared neutrals are not "illegal", and using a double-pole breaker for these two circuits would make it impossible for anyone to get hurt while working on either as long as the breaker is off.

[Cass]

If 2 separate circuits have a interconnected neutral and you shut off 1 circuit the circuit that is not off will keep the connected neutral "hot" because it is not off, it is still operating through the 2nd live circuit.

[jimbo]

In a shared neutral, the assumption is that the two loads are nearyly balanced, thus the current in the neutral wire is small. In your case, alth0ugh your loads are small, as you describe, you have UNbalanced the load to some extent. Is is really dangerous? Maybe not. But codes are written to avoid "maybes" and protect against something that some future homeowner may do, unaware of the shared neutral.

[jwelectric]

what might be wrong or dangerous or whatever.

It is very wrong for several reasons.

One is that unless you are going to be the only person working on the circuit no other person will understand just what is going on with the circuit and will rewire the entire circuit

Two all conductors of a circuit must be in the same raceway or cable. This stops inductive heating which can start a fire, see 300.3(B) of the NEC

The list goes on and on but the simple answer is the installation does not comply with the safety standards of today’s codes and is improperly installed.

If you were able to install the switch leg from the switches to the light it would be just as easy to install the grounded neutral with it so lets get this fixed right away.

[220/221]

Ever hear the term "he knows just enough to be dangerous"?

It applies here.


Although it helps to understand why, it's prudent in this case just to take the advice offered here and do whatever it takes to wire your switches correctly.

[GabeS]

Just curious. How do you guys wire a three way switch with 2 lights in between. Do you establish a regular 3 way connection with one of the lights and then just jump to the other light. And in that case can you just keep jumping to other lights if you want more than two?

[Speedy Petey]

It is ALWAYS easiest to run a 3-wire between switches. To go: switch-light-light-switch; you need a 4-wire between the lights.

The physical relationship between the lights and switches is rarely a concern.

[jwelectric]

Just curious. How do you guys wire a three way switch with 2 lights in between. A three way switch is wired no differently than any other switch. The only difference between a three way (with a four way in between) and a single pole switch is the use of travelers which alternate between the switches.



Do you establish a regular 3 way connection with one of the lights and then just jump to the other light. And in that case can you just keep jumping to other lights if you want more than two? Yes there can be more than one light up to as many as the overcurrent device will carry.

What Lee has done if very dangerous as he will now have current flowing through conductors that are not run together. When current is flowing through only one conductor it produces heat through induction.. Any metal that surrounds this single conductor such as metal boxes, staples, connectors and such will begin to heat. The more heat that is applied the more carbon will build up and the more carbon buildup the more heat that is produced and the carbon holds this heat. If two conductors are present in the cable or raceway that carries the same current, the two conductors will cancel each other out

If there is nothing more learned by the Do-It-Yourselfer on this forum it MUST be that electricity will work even when it is installed in a very dangerous manner. There is ONLY ONE correct way to make an electrical installation that is safe to both persons and equipment and just making it work is not the correct way.
If the person making the installation must ask this question they would be better advised to leave the work to someone else.

Please try to help me understand what might be wrong or dangerous
It is the lack of this knowledge that causes fires and death to the end user. A discussion forum is not the place for someone that does not understand the danger of electrical current to learn these dangers unless the discussion forum is set up in a classroom environment.
As many professionals have said and I must say that I agree, it is those questions that do not get asked, or an explanation of the dangers that causes someone to get hurt or cause damage to the wiring system or the building in which it is installed.

[leejosepho]

If 2 separate circuits have a interconnected neutral and you shut off 1 circuit the circuit that is not off will keep the connected neutral "hot" because it is not off, it is still operating through the 2nd live circuit.

Yes, and that was my very first thought just as soon as I realized I did not have the fourth wire Speedy Petey has mentioned ... and a double-pole breaker will resolve that "still operating through the 2nd live circuit" issue.


... you have UNbalanced the load to some extent. Is is really dangerous? Maybe not. But codes are written to avoid "maybes" and protect against something that some future homeowner may do, unaware of the shared neutral.

Understood, and this is not a final installation.


It is very wrong ...

No, just wrong (without the "very").


If you were able to install the switch leg from the switches to the light it would be just as easy to install the grounded neutral with it so lets get this fixed right away.

You bet, and it looks like all I need to do is to get about 30' of 4-conductor Romex or whatever.


Ever hear the term "he knows just enough to be dangerous"?

It applies here.

Now there is a case of something or someone being *very* wrong! If what you have said were true, I would not be here asking questions!


Although it helps to understand why, it's prudent in this case just to take the advice offered here and do whatever it takes to wire your switches correctly.

Agreed, but I would still first have to know "Why?" in order to help assure not having to go back and change even more yet later on.


... he will now have current flowing through conductors that are not run together.

Ah. That is yet another issue I did not know about ... and I will try to make and post a sketch to be sure I understand how things need to be.

[leejosepho]

Here is a sketch of what I have at the moment ...

I also have a bare ground connected everywhere, of course, but it is not shown in the sketch.

[jwelectric]

Here is a sketch of what I have at the moment ...

I also have a bare ground connected everywhere, of course, but it is not shown in the sketch.

Lee have you ever heard this statement?


Ever hear the term "he knows just enough to be dangerous"?

It applies here.

You have a serious problem with this installation and it needs to be addressed now.

[jar546]

It is ALWAYS easiest to run a 3-wire between switches. To go: switch-light-light-switch; you need a 4-wire between the lights.

The physical relationship between the lights and switches is rarely a concern.

See this crude drawing: http://www.remasinspections.com/images/3wayswitch.pdf

[leejosepho]

You have a serious problem with this installation ...

Please elaborate, you old windbag!
http://smileys.smileycentral.com/cat/28/28_2_2.gif
I am trying to be sure I get this right, and you have only editorial comment to offer. Has it ever crossed your mind to actually try to be helpful?!

I have one light sharing a common, and that needs to be corrected.

What is the alleged "serious problem" you have mentioned?

Your wife is correct.

[leejosepho]

See this crude drawing ...

Wow, and I thought mine was crude!

[jar546]

Wow, and I thought mine was crude!

The difference is that yours does not make any sense and I am being helpful by taking the time to provide you with crude but accurate drawings.

[220/221]

Heh heh....he called you an old windbag :D

Just fix it and everything will be right in the universe.

BTW, I DO give you credit for coming here to learn how to do it right.

[msgale]

See this crude drawing: http://www.remasinspections.com/images/3wayswitch.pdf
great sketches, nicely showing the choices,
thank you

[Cass]

This forum is for learning...Thanks jar...

[jwelectric]

Please elaborate, you old windbag! I am trying to be sure I get this right, and you have only editorial comment to offer. Has it ever crossed your mind to actually try to be helpful?!

I have one light sharing a common, and that needs to be corrected.

What is the alleged "serious problem" you have mentioned?

Your wife is correct.

Okay try reading this one more time.
Slow down and read it slowly so maybe it sinks in


What Lee has done if very dangerous as he will now have current flowing through conductors that are not run together. When current is flowing through only one conductor it produces heat through induction.. Any metal that surrounds this single conductor such as metal boxes, staples, connectors and such will begin to heat. The more heat that is applied the more carbon will build up and the more carbon buildup the more heat that is produced and the carbon holds this heat. If two conductors are present in the cable or raceway that carries the same current, the two conductors will cancel each other out

If there is nothing more learned by the Do-It-Yourselfer on this forum it MUST be that electricity will work even when it is installed in a very dangerous manner. There is ONLY ONE correct way to make an electrical installation that is safe to both persons and equipment and just making it work is not the correct way.
If the person making the installation must ask this question they would be better advised to leave the work to someone else.

It is the lack of this knowledge that causes fires and death to the end user. A discussion forum is not the place for someone that does not understand the danger of electrical current to learn these dangers unless the discussion forum is set up in a classroom environment.
As many professionals have said and I must say that I agree, it is those questions that do not get asked, or an explanation of the dangers that causes someone to get hurt or cause damage to the wiring system or the building in which it is installed.

[Terry]

I agree.

There are many things about electricity that I don't understand either.

I used to replace bath fans, NOT anymore.
I did one job that woke me up on that. There was something very different about it, and I was getting small shocks. I realized that I was clueless. That was the last one I did for anyone.

I don't know what the guy before me had done, but it was pretty weird.
And I wouldn't to this day, know what the right question would be.

[220/221]

I don't know what the guy before me had done, but it was pretty weird.

Don't feel bad. I run across things like that all the time. People can do a lot of damage when they know just enough to make the light come on.

[leejosepho]

Okay try reading this one more time.
Slow down and read it slowly so maybe it sinks in

Okay, I have again read what you wrote to someone else and now I understand ... and I thank you for your patience with me and for tolerating whatever attitude I had late last night. A hundred-dollar rebate I have been waiting for from one of the box stores arrived yesterday, and I will get the right wire (if they have it) tomorrow.


... [your drawing] does not make any sense and I am being helpful by taking the time to provide you with crude but accurate drawings.

I thank you for your effort, and your drawings have pretty much helped to confirm my suspicion about another circuit I will mention in just a minute. But first, maybe this will help as to mine:

I did not know how to draw the 3-way switches, so you see a switch with two wires connected at one end. Then, the little "c" indicates the respective commons for the two circuits involved. A piece of 14-2 w/ground takes power to the far switch, then a piece of 14-3 w-ground runs back to the other ... and that is the piece that needs to be 14-4 or whatever so the lower light can have a neutral connected at the box where the power arrives at the upper switch.

And now ...

My living room appears to have a 3-way circuit for the light/fan fixture on the ceiling, but that circuit has not worked properly as a 3-way since we first got this place over four years ago. Having learned a little about 3-way circuits over these past few days, I today spent quite a bit of time trying to make that circuit work like I had believed it should ... but now I believe that is not going to be possible, and here is why I say that:

After disconnecting all the wires and checking the switches to be sure they are good, I identified the runners going from one switch to the other. They are the two black wires in the picture below, and they show no resistance when they are nutted together on the other end. However, the upper black wire on that switch shows continuity (with some resistance) with the disconnected white wire when the pull switch on the ceiling light is on ... and that means I do not really have two runners, correct?

[jwelectric]

Here is a good example of why these type of discussion forums can not be used to give advice to someone looking for advice.

Although the subject matter did not change and others were asking questions not everyone reads all post.


Okay, I have again read what you wrote to someone else and now I understand ...

Although someone asked the question that Lee didn’t ask the answer was directed to the original post as much as to the person who asked the question the post was directed to.

There is no way that lessons in electrical can be given over a discussion forum simply due to the fact that there is no control over the reader of the forum.
Most will read only that parts that they agree with and ignore the ones they disagree with. In a classroom setting this can not happen as the person seeking knowledge will here (read) every question and answer.

Lee
How many conductors are in the box in the picture?
2- blacks and 2- whites?

[leejosepho]

Here is a good example of why these type of discussion forums can not be used to give advice to someone looking for advice ...

No, the problem there was your view of the entire world as a classroom with you at the front ... but I digress ... ;)


Lee
How many conductors are in the box in the picture?
2- blacks and 2- whites?

No, just two blacks and one white. And, the other end of this circuit has the same, plus a power lead ... and that is where I get lost. Based on many other wiring troubles I have already encountered and fixed around here, I suspect somebody before me either knew even less than me or never revealed his ignorance by asking questions.

I tried hooking the white wire in the picture below to the common, then connecting the power and blacks ... but that gave me absolutely nothing at the light on the ceiling.

[leejosepho]

See this crude drawing ...

When you have a moment, please take a look back and let me know whether my own updated version now makes more sense.

[jwelectric]

No, the problem there was your view of the entire world as a classroom with you at the front ... but I digress ... ;)



No, just two blacks and one white. And, the other end of this circuit has the same, plus a power lead ... and that is where I get lost. Based on many other wiring troubles I have already encountered and fixed around here, I suspect somebody before me either knew even less than me or never revealed his ignorance by asking questions.

I tried hooking the white wire in the picture below to the common, then connecting the power and blacks ... but that gave me absolutely nothing at the light on the ceiling.


In your little picture you have the following labeled.

One white
Two blacks
Power
Common??

This adds up to five

Two simple questions;

How many cables come into the box and how man conductors in each cable?

In my experience I have always seen two wire cable with one white and one black. In three wire cable it is one black one white and one read.
How has this box ended up with two blacks and only one white?

What are you calling a common? What color is this wire you are calling common?

In a three way switch configuration the common screw of the switch will always get either the switch leg or the supply. One switch will receive the switch leg on the common screw and the other switch will receive the supply on the common screw. There is no common wire.

Now as to this remark:

No, the problem there was your view of the entire world as a classroom with you at the front ... but I digress ... ;) Let me explain a little something that may improve our relationship.
You have come here seeking help. I am willing to assist you in this adventure of yours without any compensation. This makes you the student, the one seeking knowledge, and me or anyone else that is trying to aid you the instructor, the one standing in front of YOUR classroom not the entire world.
http://smileys.smileycentral.com/cat/3/3_3_101.gif

Then there are many that come and read the same thread trying to learn something about the same question you have making them a student of the same classroom. See how these discussion forums work? They aren’t a thing but the experienced trying to give freely of their knowledge to those that have neither knowledge nor experience making these forums nothing more than a quick lesson classroom.

Now do you want to accept the help or not?

[leejosepho]

In your little picture you have the following labeled.

One white
Two blacks
Power
Common??

This adds up to five

Yes.


Two simple questions;

How many cables come into the box and how man conductors in each cable?

In my experience I have always seen two wire cable with one white and one black. In three wire cable it is one black one white and one read.
How has this box ended up with two blacks and only one white?

Four cables come into the box by the door (second picture):

1) One with two conductors for the porch light (and irrelevant here);
2) One with a line (black) and a common (white) and no ground wire;
3) One with a black (runner?) and a white (for a purpose presently unknown);
4) One with a black (runner?) and a white that had been clipped short.

So, and concerning the circuit in question: The box ended up with two blacks and only one white when somebody long ago apparently ran a second cable to get only a black runner (and clipped its unneeded white).


What are you calling a common? What color is this wire you are calling common?

It is the white wire in #2 above that I am calling a common, and that cable is the one that brings power to the 4" box. The switch you can see in picture #2 is the switch for the porch light, and it is connected to the conductors in cable #2 and works just fine.


In a three way switch configuration the common screw of the switch will always get either the switch leg or the supply. One switch will receive the switch leg on the common screw and the other switch will receive the supply on the common screw. There is no common wire.

Understood ... but the white wire in cable #3 above might be the common side of the light if the white wire in picture #1 is its feed, and if so, it would need to be connected to the common in cable #2 in order to complete the circuit for the light.


I am willing to assist you in this adventure of yours without any compensation ...

Now do you want to accept the help or not?

Of course, and I thank you!

Give me about an hour and I will come back with an accurate sketch of the known absolutes related to this circuit. Logic suggests we might be able to figure out the unknowns after making some readings with the power off ...

[Cookie]

I am not putting anyone else down in saying this, Lee has an attitude that everyone could learn from.

[leejosepho]

I am not putting anyone else down in saying this, Lee has an attitude that everyone could learn from.

Well, maybe, but some people see me as a well-seasoned, passive-aggressive manipulator ...

But whatever the case, I greatly respect the vast knowledge and experience available here, and I am genuinely grateful to the many who freely share it.

JW: Here is a sketch, and my son-in-law is going to flip and pull switches while I record some readings. So, back in a while ...

[Cookie]

...I would still put a gold star on your head. :D

[jwelectric]

In your little picture you have the following labeled.

One white
Two blacks
Power
Common??

This adds up to fiveYes. But here you say:
No, just two blacks and one white. Which leaves the rest of what is in that box in question. We need to know every conductor that enters that box in order to figure out what the person that made the installation was doing.


Four cables come into the box by the door (second picture):
1) One with two conductors for the porch light (and irrelevant here);
2) One with a line (black) and a common (white) and no ground wire;
3) One with a black (runner?) and a white (for a purpose presently unknown);
4) One with a black (runner?) and a white that had been clipped short.
1- Yes it is very relevant as without know what is in the switch box it would be impossible to give an answer.
2- This is the supply (I think) which would have one black hot and one white grounded neutral but not a common.
3- Not a runner and we will figure out what the white is for as we go along
4- A bad idea although it was common practice just after the knob and tube days when electricians was learning how to use cable. This method has never been a code compliant method of installing three way switches.


So, and concerning the circuit in question: The box ended up with two blacks and only one white when somebody long ago apparently ran a second cable to get only a black runner (and clipped its unneeded white). I have never in 42 years of doing electrical work ever heard of a runner except for the young man that kept running back and froth from the job and the van or port-a-john.

It is the white wire in #2 above that I am calling a common, and that cable is the one that brings power to the 4" box. The switch you can see in picture #2 is the switch for the porch light, and it is connected to the conductors in cable #2 and works just fine. It is important that when talking about electrical circuits to use the correct terminology so there won’t be a lot of confusion.
We'll quit calling the grounded neutral conductor a common conductor. In premises wiring the grounded neutral is not a common conductor. On a three way switch there is a common screw and this screw will always get a hot or a switch leg.
If the porch light is using the 2 two wire cables then I would think that the two white conductors are under a wire nut and the two blacks are on the switch. Is this correct?
If this is correct so far then the three wires left;
3) One with a black (runner?) and a white (for a purpose presently unknown);
4) One with a black (runner?) and a white that had been clipped short
are for the three way switch. These wires will in no way connect to the conductors in the 2 two wire cables connected to the porch light.

Understood ... but the white wire in cable #3 above might be the common side of the light if the white wire in picture #1 is its feed, and if so, it would need to be connected to the common in cable #2 in order to complete the circuit for the light. Again it ain’t called a common wire just because it is white. It would be better to call it a “cracker” wire than a common wire. (a little humor there)
When you started this line of questioning about these three way switches in this post (http://www.terrylove.com/forums/showpost.php?p=174368&postcount=24) how many conductors and cables are in this switch? Is it is like the first one with a cut white wire in one of the cables? Are there three two wire cables in that switch box?
Give us a little more information here please.

I will venture so far as to say I don't think you are going to get the fan and light to work separately of each other just because there aren't enough switches.

[leejosepho]

We need to know every conductor that enters that box in order to figure out what the person that made the installation was doing.

There are two conductors (a black and a white) coming in to get power for the porch light;
There are two conductors (a black and a white) bringing power in from the panel in the basement;
There are two more blacks coming in from the "out" terminals of the 3-way switch across the room;
There is one more white coming in from somewhere presently unknown.


... the supply (I think) which would have one black hot and one white grounded neutral but not a common.

Yes, and I will try to remember "gounded neutral" rather than "common".


On a three way switch there is a common screw and this screw will always get a hot or a switch leg.

Understood and identified.


If the porch light is using the 2 two wire cables then I would think that the two white conductors are under a wire nut and the two blacks are on the switch. Is this correct?

Yes.


If this is correct so far then the three wires left ...

Yes, but remember we still need to power this 3-way circuit. The power for this 3-way circuit is not supplied at its other end.


3) One with a black (runner?) and a white (for a purpose presently unknown);
4) One with a black (runner?) and a white that had been clipped short are for the three way switch.
These wires will in no way connect to the conductors in the 2 two wire cables connected to the porch light.

Understood.


When you started this line of questioning about these three way switches in this post (http://www.terrylove.com/forums/showpost.php?p=174368&postcount=24) how many conductors and cables are in this switch? Is it is like the first one with a cut white wire in one of the cables? Are there three two wire cables in that switch box?
Give us a little more information here please.

The white and one of the blacks is a cable, the other black is a single strand and there are no more wires and no power coming into that box.


I will venture so far as to say I don't think you are going to get the fan and light to work separately of each other just because there aren't enough switches.

Beyond that, there is no separate fan wire going to the fixture.

[jwelectric]

In the box that only has one switch there is a cable with a black and white wire. This will be three wires for the three screws

In the box with two switches there is a supply of one black and one white, a switch leg going to the porch light, a two conductor cable and a two conductor cable with the white cut off.

Aside from the code violations of not having all conductors of the same circuit in the same cable which will result in the heating of the single conductor we don’t have enough conductors to make the three way switches work.

Try this. Use the single black wire in both boxes for the common screw of the three way switches. Use the two wire cable in each box for the other two screws on the three way switches and let me know what happens.

Leave the two, two conductor cables for the porch light as they are.

Edited to add;

If I am slow to answer it is because I am watching the ball game. NC is kicking a.............. somehting

[leejosepho]

If I am slow to answer it is because I am watching the ball game. NC is kicking a..............

... uh, apples?!

Anyway, case solved ...


In the box that only has one switch there is a cable with a black and white wire. This will be three wires for the three screws

Connected.


In the box with two switches there is a supply of one black and one white, a switch leg going to the porch light, a two conductor cable and a two conductor cable with the white cut off.

Yes, and the problem here is that whoever did the initial work evidently clipped the wrong white! It is the *other* white in that box we have been talking about that goes nowhere.

My son-in-law and I have pulled the fixture down from the ceiling to trace the wires that are there, and we found two cables nutted together as "hot" and "neutral" for the light/fan. However, the white in the cable going to the box by the front door is the one that is clipped, and we cannot find the far end of the other white in that box we have been talking about.


Aside from the code violations of not having all conductors of the same circuit in the same cable which will result in the heating of the single conductor we don’t have enough conductors to make the three way switches work.

Actually, we do ... but yes, I do understand this circuit needs to be completely rewired. In any case, the single wire in the far box is the black in the cable with the white going nowhere, and connecting the two blacks at the ceiling together would be the second "runner" or whatever for the "outs" on the 3-way switches. Then, the whites at the fixture could be the hot and neutral for the light ... but that would be dependent upon being able to make a solid and safe connection to the clipped wire in the box by the door ... and I do not know any way to do that.


Try this. Use the single black wire in both boxes for the common screw of the three way switches. Use the two wire cable in each box for the other two screws on the three way switches and let me know what happens.

My brain is too tired to contemplate that at the moment, but I will roll it around a little later this evening while my son-in-law and daughter are gone and my three grandchildren are ever-so-quietly just sitting and watching me think, eh?!


Leave the two, two conductor cables for the porch light as they are.

You bet, and I thank you and everyone else.