3 way switch wiring - how hard could it be I asked?

[MrBill]

14 minutes ago, Goose66 said:

@MrBill I don't know where this became so unnecessarily complex. If the OP rewires the circuit, most likely in the j-box at one of the fixtures, to have line (black) and neutral (white) go into each switch box, uses the red wire for load from one of the smart switches back to the light, and caps the red going to the other smart switch, then, bam, all good and to code - no fuss. Any suggestion that once you use a white wire as a traveler you can never go back and rewire it be a neutral is simply absurd.

You stated this:

4 hours ago, Goose66 said:

Also note that the diagram above of the circuit using/requiring 14/4 wire was obviously made before the price of copper got so high! 

And I replied that it was a code compliant diagram, CURRENT CODE requires the WHITE wire to be installed as neutral whether it is used or NOT, regardless of the price of copper.  Therefore I pointed out that it was a CODE COMPLIANT diagram, and why the code was created. 

You're absolutely correct in the OP of this threads case he must re-wire the circuit from wherever the source is and re-purpose conductors. 

If this circuit was being installed in new construction today, the 4th wire would be required if the circuit was created the way OP's circuit was created, it doesn't matter the price of copper, every switch location must have that circuits neutral wire present without re-wiring the circuit to get neutral.  That's why I stopped and said the drawing is made to be compliant with current electrical code, not because it was made before the price of copper shot up.

[MrBill]

22 minutes ago, SteveKlos said:

Also in case anyone is concerned I don't do work on electrical things unless I know what I'm doing and why...  And my post here was frankly a laziness on my part to not have to re-wire.  As I have watched the discussion ensue, I realized - yeah, I need to take the time to re-wire - it'll be safer, will be up to code and I can leave a label maker note in the capped off 3way switch box that indicates where the wires go in the case that a future owner of the house is ever curious.

Your best bet is to do exactly as you have said.  Install a smart switch in one location, and leave notes for the future about where the other wires starts and ends.  You need to figure out which fixture contains the magic splice tho, and get in and re-work that.

[apostolakisl]

12 minutes ago, MrBill said:

Your best bet is to do exactly as you have said.  Install a smart switch in one location, and leave notes for the future about where the other wires starts and ends.  You need to figure out which fixture contains the magic splice tho, and get in and re-work that.

Exactly what I had suggested before it was labeled as ~don't ever do that.  Trace out the wires so you know what goes where and then label it for all future activity.  And then of course once you know what goes where, there isn't really any excuse for connecting them wrong.

Edited October 6, 2021 by apostolakisl

[MrBill]

23 minutes ago, apostolakisl said:

He didn't do what I said or, despite tracing out the wires and knowing where they go, did something quite clueless in splicing two hots together from different circuits.   I would assume he did not trace out the wires but rather just started hooking things up wrong.  Plus, he would have had to shut off two breakers to get the power off, another clue.  I would also suggest replacing your sons breakers.  If they didn't trip prior to melting wire then they are bad.

It is very unlikely that two different circuits are going to the same switchbox.  If the switchbox is handling many switches, the chances go up, but if there is only one switch, then chances are pretty much zero.  Even if there are lots of switches, it would be very rare that two circuits are feeding it.  

Nothing wrong with taking pictures and I highly encourage (do it myself all the time), but the cat is out of the bag on this one.  He already didn't take pictures and disconnected.

Knowledge of the wire runs is never a bad thing and with said knowledge you then correctly connect them. 

Because you're interested, He was trying to do exactly what you said, but was in over his head.  It was a Multi-wire Branch Circuit (MWBC) feeding the kitchen counter circuits and the pantry light (where he was trying to install the motion sensor).  Because it was a MWBC it was fed by a two pole breaker (as required)(which was also a GFCI breaker, instead of counter outlets being GFCI themselves--the kitchen designer didn't want GFCI outlets "because they are ugly and have little green and red lights that don't belong in the tile colors", therefor it was a GFCI breaker instead) which is how he turned both circuits off from the start.  The reason the romex got hot is because when you directly connect opposite poles the wire becomes a heating element, it gets hot very quickly.  The reason it takes a few seconds to trip breaker is because every circuit breaker out there has a "trip curve" to prevent nuisance trips. Yes the trip curve will let the wire get hot... that happens very fast.. but the breaker trips before it gets too hot. The only thing that wasn't to code in the original installation is the kitchen counter outlet circuit shouldn't be feeding (under today's electrical code) anything else including the pantry light or the entryway light that that was also tapped into the circuit (I don't know but think they forgot to feed those two lights during pre-wire, on finish when they discovered they had covers unfed they made a "fix".

 

[apostolakisl]

1 hour ago, MrBill said:

Because you're interested, He was trying to do exactly what you said, but was in over his head.  It was a Multi-wire Branch Circuit (MWBC) feeding the kitchen counter circuits and the pantry light (where he was trying to install the motion sensor).  Because it was a MWBC it was fed by a two pole breaker (as required)(which was also a GFCI breaker, instead of counter outlets being GFCI themselves--the kitchen designer didn't want GFCI outlets "because they are ugly and have little green and red lights that don't belong in the tile colors", therefor it was a GFCI breaker instead) which is how he turned both circuits off from the start.  The reason the romex got hot is because when you directly connect opposite poles the wire becomes a heating element, it gets hot very quickly.  The reason it takes a few seconds to trip breaker is because every circuit breaker out there has a "trip curve" to prevent nuisance trips. Yes the trip curve will let the wire get hot... that happens very fast.. but the breaker trips before it gets too hot. The only thing that wasn't to code in the original installation is the kitchen counter outlet circuit shouldn't be feeding (under today's electrical code) anything else including the pantry light or the entryway light that that was also tapped into the circuit (I don't know but think they forgot to feed those two lights during pre-wire, on finish when they discovered they had covers unfed they made a "fix".

 

If you directly connect two legs of 120v split phase you have a pure short and your breaker must pop in milliseconds or it isn't working right. MWBC or otherwise doesn't matter, pure short should pop "instantly" or it isn't doing its job of protecting your house.  A pure short can very quickly destroy the wire, especially if you have any splices that aren't perfect.  A pure short that persists for a few seconds would be nasty.  It could easily be hundreds of amps going through some little 14 or 12 wire.  Those curves are meant to prevent transient and reasonable over-currents from popping breakers, like the inflow rush of turning on a vacuum, not a full out short. 

I would propose perhaps, if you connected the neutral wire coming off a load from one leg to the hot wire on the other leg, then you would get a 240 voltage going to that appliance and (with resistance appliance) a double amp which could put you at the edge and let it warm up the wire if it ran for a few seconds before popping.  Probably also destroy your appliance.

Either way, if he was in "over his head" then that is on him. 

In summary, knowing where all the wires go  and labeling can never be a bad thing.

 

EDIT:  It did occur to me that if it was a 20amp breaker and 14 gauge wire (of course not code) you would have enough resistance in the wire to prevent an "instant" popping of the breaker.  This is actually the reason for #12 wire on a 20amp breaker.  #14 can handle 20 amps, it just won't blow a 20amp breaker as quickly as it should when shorted.

Edited October 6, 2021 by apostolakisl

[larryllix]

28 minutes ago, apostolakisl said:

If you directly connect two legs of 120v split phase you have a pure short and your breaker must pop in milliseconds or it isn't working right. MWBC or otherwise doesn't matter, pure short should pop "instantly" or it isn't doing its job of protecting your house.  A pure short can very quickly destroy the wire, especially if you have any splices that aren't perfect.  A pure short that persists for a few seconds would be nasty.  It could easily be hundreds of amps going through some little 14 or 12 wire.  Those curves are meant to prevent transient and reasonable over-currents from popping breakers, like the inflow rush of turning on a vacuum, not a full out short. 

I would propose perhaps, if you connected the neutral wire coming off a load from one leg to the hot wire on the other leg, then you would get a 240 voltage going to that appliance and (with resistance appliance) a double amp which could put you at the edge and let it warm up the wire if it ran for a few seconds before popping.  Probably also destroy your appliance.

Either way, if he was in "over his head" then that is on him. 

In summary, knowing where all the wires go  and labeling can never be a bad thing.

Agreeing... if a dead short didn't pop the circuit breaker within 0.5 seconds, either there are bad wiring connections, or the main breaker would likely open up. Some breakers have dual curves (51, 50 ) where the longer curve gets cut it's time cut off by a (50) instantaneous element that beats the time curve. I am not sure whether that was ever implemented in some brands of circuit breakers though.

[apostolakisl]

Here is a great "red neck" video showing a short circuit.  6ms in this case.  My personal experience with ahemm, perhaps, maybe I might have accidentally bumped some hot wires to ground in the past, is that 6ms is about right.  Even the most transient of touches pops it.  All circuit breakers regardless of arc fault and ground fault are going to still do what this one did.  This is the most basic function of a breaker. . . protect the house.  Funny how people always thought circuit breakers were to stop electrocution, only the newer gfci ones do that, standard ones only protect people by preventing them from dying in a house fire.  They also protect your wallet from a costly repair.

 

 

[larryllix]

2 hours ago, apostolakisl said:

Here is a great "red neck" video showing a short circuit.  6ms in this case.  My personal experience with ahemm, perhaps, maybe I might have accidentally bumped some hot wires to ground in the past, is that 6ms is about right.  Even the most transient of touches pops it.  All circuit breakers regardless of arc fault and ground fault are going to still do what this one did.  This is the most basic function of a breaker. . . protect the house.  Funny how people always thought circuit breakers were to stop electrocution, only the newer gfci ones do that, standard ones only protect people by preventing them from dying in a house fire.  They also protect your wallet from a costly repair.

 

 

The other very common fallacy is that breakers and fuses limit the current flowing to their rating. They do not and cannot. These devices limit the damage by limiting the time before the circuit opens. Most residential breakers are rated at 10,000 AIR (amperes interrupting rating). If your supply transformer feed lines are very short from a larger than usual transformer supply, your main breaker may have to be a special type to handle the fault currents to avoid explosions from bad faults close to, or inside the main panel. A few feet of #14 conductor and connections typically limit currents at 120 volt to well under 10,000 amperes.

[SteveKlos]

On 10/6/2021 at 1:16 PM, Goose66 said:

If you aren't going to put a smart switch in the garage, then fine. But I'm OCD, so if there were a three-way switch in there before, I would want a smart switch operating as a scene controller (slave) in there now. Another advantage of this is that it could work as a bridge from the house Insteon network to the shed Insteon network, since they appear to be on different breaker boxes (although the shed breaker box is probably already downstream of a main one in your house). Or, you could take the opportunity to put an Insteon Keypad in and control lots of stuff in the backyard from the garage.

I'm OCD as well - that's why I'll put a note in the box and the fixture where the wires are located, then I'll simply put a cover plate over that particular box.  I completely get your perspective, but the fact that the switch box has wires coming into it from different breaker boxes caused my initial OCD to flare ?!

Just to give it a bit of context - the switch box is on the far side of the garage - many of our moving boxes are between the main entrance to the garage and that switch (the boxes will be either emptied or thrown out after a year because they clearly didn't have anything we needed)...  There really isn't any purpose to even have those switches available - they could just as well have been inline - ones for a security light, the other is the secondary switch for the outside lights in the shed.

For this house, we do have one keypad installed, but only because we needed to have separate control for a number of lights.  Beyond that, I use my phone for almost everything when I need to manage control of the gates, lights, garage doors, etc.  It's always on me, always convenient and once I installed a mesh set of Access Points, it's available almost everywhere on the property (would be everywhere if there was better cell service here).

[Teken]

Just some clarification as it relates to breakers in general. Breakers, like fuses, are intended to protect the wire from burning up.

It’s only because the same is designed and implemented by man that the human element is at play.

GFCI on the other hand are designed to protect human. AFCI’s were designed to detect micro arching within the buildings wiring in hopes of reducing fire within an enclosed space like a wall.

As with anything man has created many first generation of breakers were proven to be faulty by design. Anyone can relate to the first generation of nuisance tripping from GFCI / Breakers.

Those who have used power line Ethernet or power line communication like Insteon can also relate. Any home that has 1990 versions of anything need to inspect and replace the same. As they offer absolutely no protection because they were defective by design depending upon the maker.