OT: Weird wiring

[J. Clarke]

Please forgive me--this is a bit of a rant.

I went to put a new fixture at the top of the stairs--the old one is physically too small to hold anything bigger than a 60w incandescent (by physically I mean you can't put the globe on if anything bigger is in it, and that includes CF and LED that are larger than 60W equivalent and in that location a 60 just isn't enough light.

Well, went to kill the power to the circuit and discovered chaos.

First: Turned the switch off Checked socket with a voltage sensor Still voltage on the circuit Par for the course in this house Switch is in the neutral leg Add to list of stuff to fix.

Next: Screwed adapter into socket and plugged in tracer Traced signal in breaker panel Not one, but _two_ breakers showed signal Turned both off Went back upstairs Checked for voltage again No voltage--good Flipped switch--checked again Voltage--not good Back to the panel Identify third breaker, turn off Now no voltage

Replaced fixture, turned breakers back on, everything works, I didn't die.

But now I have the real mystery--how is this effing light managing to be connected to not one, but _three_ separate branch circuits?

Every time someone tells me that wiring should be done by a "professional" I run into another example of egregiously bad wiring installed by a "professional".

Well, I know now how I'm going spend some part of my vacation. And I hate to admit it but I'm getting too _old_ to be rolling around in fiberglass pulling wires for fun and no profit. I know, I should hire an electrician but then I'll have to watch him.

[invalid unparseable]

Been there; done that - we're living in a house that once belonged to a mechanical engineer who thought he could do everything - no surprise that the ceramic tile isn't level (the easy swing of the trowel from side to side and failure to use a level on each tile that leaves a valley down the middle of the hall) plus some "How did he do that?" electrical wiring.

[DerbyDad03]

It's possible that you are dealing with an Edison circuit, also known as a "shared neutral" or "multi-wire branch circuit". Granted, Edison circuits usually only involve 2 breakers, but I think I could imagine one with 3.

In a typical Edison circuit a cable with 2 hots and a single neutral has the

2 hots tied to separate breakers. That 3 wire cable runs to a junction box from which a pair of 2-wire (hot and neutral) cables emerge. Those 2 circuits share the single source neutral from the 3 wire cable.

If you only turn off one breaker, you will often get some voltage that bleeds back through the neutral at the supposed-to-be-dead fixture. If you used a meter as opposed to a voltage sensor, I'll bet that it's not the full 120 VAC.

Now - although this is not something that I have ever seen - expand that to a 4 wire source cable (3 hots and a single neutral) to the first junction box and you've brought that 3rd breaker into the picture.

I don't know if a "super-Edison" (I made that up) would be allowed by code, but I can certainly imagine someone grabbing some 12/4 Romex and running one.

[DerbyDad03]

To add onto to my previous post about multi-wire branch circuit I found a Q&A related to a section of the code that relates to Device Removal. In that answer, the code commentary mentions 4 wire circuits, so assuming that I am extrapolating this correctly, a 3 breaker Edison circuit might be a thing. On the other hand, I believe that standard 3 wire multi-branch circuits require that the 2 hots be on opposite phases. I'm not sure how that can be done with 3 breakers.

I'd sure like to hear from an electrician or electrical inspector on this one. It looks like Greg Fretwell (electrical inspector down in Florida) still hangs out in alt.home.repair. It might be worth checking this out with him.

Nice guy...talked me through installing a panel interlock and 30A inlet so I can safely plug my portable generator directly into my house.

Anyway, here's that code snippet I mentioned. I only post it because it mentions "3- or 4-wire circuits".

...Begin Included Snippet...

US NEC 300.13(B) Device Removal. In multiwire branch circuits, the continuity of a grounded conductor shall not depend on device connections such as lampholders, receptacles, and so forth, where the removal of such devices would interrupt the continuity.

The code commentary on that notes:

Grounded conductors (neutrals) of multiwire branch circuits supplying receptacles, lampholders, or other such devices are not permitted to depend on terminal connections for continuity between devices.

For such installations (3- or 4-wire circuits), a splice is made and a jumper is connected to the terminal, unless the neutral is looped; that is, a receptacle or lampholder could be replaced without interrupting the continuity of energized downstream line-to-neutral loads (see commentary to 300.14).

Opening the neutral could cause unbalanced voltages, and a considerably higher voltage would be impressed on one part of a multiwire branch circuit, especially if the downstream line-to-neutral loads were appreciably unbalanced.

This requirement does not apply to individual 2-wire circuits or other circuits that do not contain a grounded (neutral) conductor.

...End Included Snippet...

[krw]

I'm with you there. I've seen stuff in relatively new houses that looks like it was done by an absolute moron. Our downstairs bathroom in our VT house (built in '87, we moved in, in '93) had a cheap contractor's fixture above the vanity. SWMBO decided that a new light was in order. I took the old one off and discovered that there was no box behind it. In further inspection, I found that the romex came up in the wrong wall box. Did they run another line down to the unfinished basement? No. Did they notch the 2x4 to get the wire into the right wall cavity? Nope. They notched the sheetrock and ran it around the stud, then papered over it. Nice.

In our hose before that, there were no boxes behind outdoor fixtures hanging on brick. Now what to do?

I'm sure it wasn't done by an electrician but a friends basement was wired in zip cord.

I'm doing a *lot* of wiring in our basement and I'll guarantee that it's done as well as any residential electrician would do.

[krw]

I don't see three.

And his switch is in the neutral. That's enough to make your head hurt.

4-wire cable? It's used in dryer cables but it's a lot larger than what you'd find in a lighting circuit.

I don't see how to do it with only one cable. Using two is _really_ scary.

[DerbyDad03]

Maybe. We're not there to check. The white wire can be used as a switch leg but it's supposed to marked as hot. I'm not doubting that JC knows what he's looking at cuz he's there, just saying that things are confusing enough here that something else might be being missed.

Southwire makes a 12/4 non-metallic cable and 14/4 MC. Both are standard sizes for lighting circuits.

Again, 12/4 or 14/4 could be used. Yes, 2 cables would be scary, run-away scary.

However, I don't see how it doing it with 4 wire cable could be code considering that 2 of the 3 hots would have to be on the same phase in a normal residential situation. Bad! See my other post where a 4-wire multi-branch circuit is mentioned in the NEC 300.13(B) commentary. 4-wire cable is apparently used in multi-branch circuits, but it's certainly not something I've ever run across. I'm guessing it's only used (properly) in a 480V 3 phase system.

And of course I'm not saying that this is what 100% what JC is dealing with, but how else could a single fixture be interacting with 3 breakers? An actual voltage reading with only one (or two?) breakers off might tell us something. I know that the voltage will vary by what other loads are sharing the neutral when only one breaker in a normal 3-wire multi-branch circuit is off. All JC's voltage sensor is telling him is that some amount of voltage is present.

[pyotr filipivich]

[e-mail] on Sun, 21 Mar 2021 20:22:06 -0400 typed in rec.woodworking the following:

OTOH, "I have this wire, so I don't have to go buy 'new'."

[Scott Lurndal]

Technically, 12-3 w/g is a 'four-wire cable' and along with 14-3 w/g is used heavily in lighting circuits; to wit, in three and four-way switched circuits.

[J. Clarke]

I'm pretty sure this wiring is all original to the house, which was commercially built.

[DerbyDad03]

That doesn't negate OTOH, "I have this wire, so I don't have to go buy 'new'."

The original electrician may have had the 4-wire cable in his truck and used it to save, or make up for lack of, 12/2 or 14/2 wire.

Multi-wire circuits can also be cheaper (less cable cost) and less labor (run one

14/3 cable instead of running two 14/2 cables).

As noted earlier: This is all speculation on my part.

[krw]

Sure, I do that all the time with 240 circuits - paint the white wire with a red sharpie. I have sharpies in my electrical tool caddy for that reason.

It can't be something the average electrician would have on his truck.

[krw]

Doesn't all w/g cable have a bare copper wire as the ground, now? I know it used to be green but I haven't seen that in forever. Sure, /3 is all over the place but /4 is a different animal, at least in residential. Obviously it makes sense with 3-phase circuits.

[Clare Snyder]

Could only occur on a 3 phase circuit - and BY LAW all edison circuits MUST use a "tied breaker" - and in a fused panel a "ganged pull-out" which makes it IMPOSSIBLE to shut off power on one side only.

Using a "tracer" is fraught with possibilities - including "induced cross-talk" The REAL test is if the light functions with any ONE of the 3 circuits enabled singly - or only with one of the three. Are all of the 3 on one side of the panel? If so check if all 3 neutrals are tied together - in which case they may all be connected to each other, but not properly connected to the incoming neutral

[DerbyDad03]

Obviously we're having a discussion about a bunch of unknowns here, but I think you'd have to agree that that statement isn't particularly relevant.

Even if there was such a class of electricians known as "average" which would somehow preclude them from having 12/4 on their truck, we have no idea what type of electrician wired JC's house.

An electrician that worked for a company that wires everything from single family residential homes to condos to multi-use commercial buildings could certainly have this type of wire on their truck.

In another post, JC said that the house was "commercially built". Not quite sure what that means or if it relates to the type of electrician that was involved.

[Clare Snyder]

Very common if wired with a "switch drop" -

Again -not unusual

Notuncommon with a "fox and hound" transmitter - crosstalk between 2 adjacent cables shows up at 2 breakers - or 3 (or possibly even 4)

You finally found the REAL power source.

Did you turn them on one at a time and check to see when the light camne on?? My bet is when you turned the first 2 on the light still didn't light - and the third (REAL power source) breaker caused the light to come on. Go back and try, then get back to us with your results.

Only on 3 phase - where you get 110 and 208 instead of 110 and 220

[DerbyDad03]

By *law* or by *code*?

I did mention both code & 3 phase circuits earlier. Of course, we don't know if code was followed.

As noted earlier, a meter reading would certainly tell us more.

He also should confirm that the neutral is actually switched or if it's just a unmarked white conductor used as part of a switch leg. Unmarked would be a code violation, at least in the US.

[J. Clarke]

It's a 3 way. Have to turn two breakers off with the switch in one position before the light goes out. If I flip the switch, then I have to turn the third breaker off to make it go out. I didn't try multiple combinations of breakers and switch positions--the light is up two flights of stairs from the breaker panel.

Putting the basement lights on their own circuit is another project that I guess I should handle while cleaning up this mess.

[krw]

I think it is. I'd have to guess that the moron who did this didn't plan it in advance.

Residential, I would assume. At least the industrial/commercial electricians I know don't work residential and certainly wouldn't put together an abortion like that.

I don't know any of those. It's a different class of electrician, IME. Maybe someone moonlighting but that doesn't fit with a "commercially built house".

I assumed he meant that it wasn't made by a homeowner but he can speak for himself.

[krw]

They're the same in many/most jurisdictions. The NEC is written into the law.

Only if done right. I know many who've made that mistake.