Many years ago I did a pretty nice job diagramming and labeling the circuits in the 1982 main house panel. Curiously, one 15 amp circuit had a wire connected to it but no lights or switches related to it in the house. I figured the answer to this odd situation would come over time. Today, when the breaker tripped and cannot be turned back on without re-tripping I find an even more odd situation.

The black wire attached to this ? circuit is part of a four wire cable: black, white, red and ground. The white goes to neutral and the red goes to another 15 amp circuit, one that controls several lights in several rooms. That circuit seems OK.

So...

1. There is no explanation why all of a sudden the ? circuit tripped. This circuit has been live and happy since the house was built. The only action I can take, it seems, is to keep looking for a light or plug that is inactive...is there any other detective work I can do?

2. The builder was not the most careful, as we have learned over the years,...is there any logical reason to split the black and red to two separate circuits?

Thanks!

 

Sounds like a multiwire circuit. Are the two breakers vertically next to each other, one directly above the other? You need to open all the boxes on the red circuit and look for a 3-conductor cable (what you called a four wire cable).

 

Are there any receptacles on that circuit that are split; i.e. top is hot all of the time and the bottom is controlled by a switch, or vice versa? That could explain the red and black, and would give you a place to start. Otherwise, I would follow the circuit, typically starting with the receptacle or fixture nearest the panel, and work my way out from there, to determine where the second wire leads. A worst case scenario might be that it's not in use, tucked back someplace, maybe a wire nut let go on it, or whatever, causing it to be shorting out, so definitely worth chasing.

 

I ended up finding the circuit was dedicated to pipe heaters in the crawlspace of an addition to my home which included a bathroom. You don't want to miss that, if it applies, especially with the kind of weather we're experiencing across the country today.

Tony

 

I didn't want to clutter up a long initial post with this additional detail, but it may answer one of the questions posed:

The two wires referred to earlier, the black and the red coming from within the same cable, connect to two of four switches on two tandem circuit breakers, one right above the other. Imagine two tandems:

Circuit 1, 15 amp...connected to the ? black wire
Circuit 2, 20 amp...

Circuit 3, 15 amp...connected to the related red wire
Circuit 4, 20 amp...

Perhaps this relates to the "multi-wire" or "split" terminology.

Thanks for the quick feedback.

 

Is the voltage between the black and red 240 volts? If so it is likely a multiwire. However from your discretion it might be an incorrectly wired multiwire. We need the voltage reading to be sure. As written before you need to look for a box on the red circuit that has a 3-conductor cable, red- black- white.

 

Perhaps I am not understanding the request to take the voltage reading between the red and the black. When I touch the test probes to both the red and the black I get no reading.

However, recall that the black wire is no longer connected to the breaker. The breaker trips when the wire is attached and I attempt to reset the breaker, so I disconnected the black wire.

However, when I test each wire to ground I get 120 for each. So...the black wire is not connected to the circuit breaker but is hot (120). The red wire is connected to its circuit breaker and it is hot (120).

If you need me to check further I will be happy to.

The suggestion to find a junction box with a red wire is next...when I find it, is there a next step?

Thanks again.

 

Check between the terminals of the breakers that held the black and red wires for the voltage readings.

Since the two hots are in the same cable they run to the same area of the house before splitting. You may be able to see the black and red just be taking off a cover plate. A toner could also be used to trace the cable.

 

You need to check between the two breakers with the breakers on (problem wire disconnected).

Doesn't answer the question.

 

The 240 volt reading is present between the circuit breaker 1 and 3 referred to earlier. The breakers are both set, the black wire normally connected to 1 is disconnected and the red wire is connected to the 3 breaker.

Thanks for your patience.

 

It sounds like you're describing a group of four half-height breakers that are vertically adjacent on one side of your panel, and that these four breakers are, in order, a 15A, 20A, 15A and 20A breaker.

Is that accurate? If so, which two breakers are the two ungrounded conductors in this cable connected to? What wires, from what cable(s) are connected to the other two breakers in this group?

 

The OP sounds like they have a quad tandem. The inner two are linked and the outer two are linked. It sounds like they were properly wired as a MWBC. The issue is there appears to be a short on the one leg.

 

Nashkat1...your two questions:

Q. It sounds like you're describing a group of four half-height breakers that are vertically adjacent on one side of your panel, and that these four breakers are, in order, a 15A, 20A, 15A and 20A breaker.

A. Yes, perfectly accurate. These are what you refer to as half height.

Q. If so, which two breakers are the two ungrounded conductors in this cable connected to? What wires, from what cable(s) are connected to the other two breakers in this group?

A.
Circuit 1, black wire, cable A, 15 amp, unknown...breaker will not reset.
Circuit 2, black wire, cable B, 20 amp, plugs for family room and 1/2 office...overloaded circuit here caused this recent issue

Circuit 3, red wire, cable A, 1/2 office, bedroom plugs
Circuit 4, red wire, cable B, kitchen plugs

I hope this helps!

I will be offline til midnight PST...thanks very much to all the responders.

 

Dave, that set of breakers needs to be reworked or replaced to provide the protection you need.

Two quick questions:

• What positions are these four breakers in, and
• What is the make and model of your panel?

One quick point:
Either these circuits aren't connected and protected the way you described, or the problem with the circuit supplied by the black wire on the 15A breaker coincidentally happened at the same time that something happened on the circuit supplied by the black wire on the 20A breaker. Those two circuits should have no interconnection and no ability to affect each other.

 

The breakers are in the upper left corner of the panel. However, the OP is mistakenly calling them circuits 1,2,3,4. The breakers are twins.

The one breaker is 1U and 1L or 1A and 1B
The other breaker is 3U and 3L or 3A and 3B

I usually label the panel with the U(upper) and L(lower)

1U = 15A - unknown circuit (black)
1L = 20A - family room/office (black)
3U = 15A - office/bedroom (red)
3L = 20A - kitchen receptacles (red)

1U and 3U is one three wire cable 14/3
1L and 3L is another three wire cable 12/3

So if all my information is correct.... that would tell us that the unknown black wire of the 14-3 cable is located in the area of the office and bedroom. If you shut off breaker 3U and note which receptacles go dead..... you will most likely find the black wire of the 14-3 cable in one of those junction boxes if you locate the junction box that has the red wire in it.

 

And I label with lower case a and b for half-highs, as in 1a and 1b. But it makes no real difference. Either way clarifies the setup.

What you say makes sense except that I'm unfamiliar with twin or tandem breakers that have two different ratings. IMX, to get both 15A and 20A on a single leg with half-height breakers requires installing one half-inch 15A breaker and one half-inch 20A breaker.

Right now, if those breakers are arranged as the OP says they are, then neither MWBC can be protected so as to provide common disconnect. Swapping one set would allow one of the MWBCs to have a common disconnect. Adding more half-inch breakers to stagger the spacing of the MWBC pairs onto opposite legs is one way to provide it for both. Changing to full size breakers, if there's room in the panel, is, of course, another.

If the manufacturer of the OP's panel makes a quad tandem - or a "saddle" breaker, as I sometimes call it - that would be a quick and easy solution. But right now, with the breakers set in opposite order by rating, it appears that there isn't a quad tandem there.

Chasing along the 14AWG cable to find the fault is a good next step. Rationalizing the breakers so that proper protection can be provided will also be needed before everything is done.

 

I still have some here. The one in the pic is Bryant. Several companies did make them.

 

Good Morning to all. I have looked closely for any main panel designation but find no naming to indicate a brand or model. The Home is in California and was built in 1980-1982 era and the breakers are originally BRYANT...I now purchase what I refer to as Bryant-like replacements.

A moderator suggested I was mistaken in my calling these circuits 1, 2, 3, and 4. If there is a commonly accepted naming convention, I apologize. I was merely trying to describe that I can turn on and turn off four separate switches residing on two breakers. If I was to purchase a new "breaker", which I have done, I would be purchasing one unit that has both a 15 and a 20 amp switch. That unit is installed in the main panel by pressing its female mounting onto one of the main panel's male mounting points. Each switch on that breaker is attached to it's own "circuit".

Let's see of I can describe the positioning within the panel accurately this way:

In the uppermost left quadrant on my main panel there are actually three breakers. For the sake of clarity earlier I chose to ignore the left uppermost breaker...but here goes:

The first breaker is a GFCI unit that I will refer to a the GFCI "controller". The second and third breakers are the subject of this thread and to repeat...each is attached to the panel on a single male mounting point.

Yes...the moderator's picture is a correct example, except my 15 and 20 amp switches are reversed...in place my 15 amp is physically above the 20 amp.

 

Most panels have the odd numbers on the left side with the evens on the right side.

 

With all due respect, I'm not trying to gain consensus on a naming convention.

I am focused on four circuits that are somehow related...I'll call them John, Paul, Ringo and George if it helps. No, I don't know what snarkey means...but my wife says I can be sometimes.

I do appreciate all the great feedback thusfar.

 

Getting this back on track, the two things you need to do are:

• Measure the voltage between the two breaker terminals the black and red wires are connected to.
• Find the box on the circuit that is supplied by the red wire that contains the 3-conductor cable(red, black, white)*.

Do those two things and we will go from there.

*If you can't find a box with the 3-conductor cable on the "red" circuit then you will have to look further afield.

 

No problem. Matthew, Mark, Luke and John will work too.

Now that you've clarified the position of your existing breakers, I think I'll refer to them as 3a, 3b, 5a, and 5b. It's what I'm used to, and helps me visualize the connections behind them more easily.

The point here is that one set (5a and 5b) is connected to Leg A of your service and the other set (3a and 3b) is connected to Leg B. (See why PJ likes to use U and L for half-high breaker designations? ) Having the 15A and 20A breakers set up and connected that way insures that the two breakers serving each MWBC are on opposite legs. Unfortunately, since each pair is in one molded case, it also insures that neither MWBC can be provided with common disconnect.

Do you have any unused breaker spaces in your panel?

All of this is aside from the question about the tripping breaker, 3a. You can test that breaker by moving the red wire from 5a to it and seeing if it will hold with that attached. If it still trips you have a bad breaker. If it holds, the problem should be a short in the circuit fed by the 14AWG black wire, and you'll need to open boxes and rework connections along that chain until you find and correct it.

 

Thank you Ray.

I previously reported this:

The 240 volt reading is present between the circuit breaker 1 and 3 referred to earlier. The breakers are both set, the black wire normally connected to 1 is disconnected and the red wire is connected to the 3 breaker.

I believe this is the reading you are asking for.

 

Nashkat1,

No problem here either. 3a, 3b, 5a, and 5b makes sense here too.

You said: "If it holds, the problem should be a short in the circuit fed by the 14AWG black wire, and you'll need to open boxes and rework connections along that chain until you find and correct it."

The challenge here is that according to my original dilemma, there are no circuits currently identified with that black wire. As someone suggested earlier, should I open all the junction boxes associated with the red wire in the same cable as the unidentified black wire? With our new labeling, wires: 3a black and 5a red. Correct?

 

Bryant was bought by Eaton. The replacement "Bryant-like" breakers are Eaton's BR series.

The tandem quad breaker that will give you common disconnect protection for both of your existing MWBCs should be an Eaton BQ215220 breaker.

Now you need to do the detective work on that black wire.

 

Good, step one completed. Step two is from Nash: If there is a short as determined by that test then we go to step 3:

 

Well, the breaker my supply house sold me is referred to this way on their receipt:

C-H BR1520 1P 15A & 1P 20A 120V CB Part number 2651708

Looking at the breaker, it is an Eaton product.

 

Good, step one completed. Step two is from Nash:
You can test that breaker by moving the red wire from 5a to it and seeing if it will hold with that attached. If it still trips you have a bad breaker. If it holds, the problem should be a short in the circuit fed by the 14AWG black wire,

Yes, switching the red wire from one terminal to another was successful...the breaker was reset and held.

However,

If there is a short as determined by that test then we go to step 3:
Find the box on the circuit that is supplied by the red wire that contains the 3-conductor cable(red, black, white)

The challenge here is that according to my original dilemma, there are no circuits currently identified with that black wire. As someone suggested earlier, should I open all the junction boxes associated with the red wire in the same cable as the unidentified black wire? With our new labeling, wires: 3a black and 5a red.

Is that the next step?

 

When I open the junction boxes and determine that I have indeed found the unidentified black wire, can I assume what I am looking for is perhaps that it has come apart from its wirenut, for example?

If I locate the unidentified black wire in box 1 of 7 is is logical to assume it will or may appear also in boxes 2 through 7?

Thanks.

 

Yes.

No. Normally it appears in only one box and then splits off to whatever the black supplies. However there are exceptions so we just need to go one step at a time. If there is only one 3-conductor cable in the box it likely won't however if there are two 3-conductor cables it may be be in other "red" circuit boxes.

 

Thanks.

The last key question:

The challenge here is that according to my original dilemma, there are no circuits currently identified with that black wire. As someone suggested earlier, should I open all the junction boxes associated with the red wire in the same cable as the unidentified black wire? With our new labeling, wires: 3a black and 5a red.

 

You may have but to start with the one closest to the breaker box and as I wrote previously: There is the possibility the black wire was never used. It may just be capped off in one of the "red" circuit boxes.

 

I'm not explaining the question well, sorry. I'll try again. I'm trying to confirm that the junction boxes to search are those that I know contain the red wire that is part of the cable that also contains the unidentified black wire. This is because there are no circuits/boxes to search that I know are connected to the black wire. Is this the most logical approach?

 

As I have said in each reply look in the circuit boxes known to be controlled by the breaker that the red wire is fastened to. That is what I meant by "red" circuit. Please reread my replies.

 

There is one circuit, supplied by the 14AWG black wire and the shared neutral. There are no identified loads.

I would open them and troubleshoot in a very different pattern, but I do this all day every day. Because you don't, I'll repeat Ray's suggestion:

Do one step at a time. Terminate the wires to the breakers the way they were to begin with. Turn breakers 3a and 5a off. Start at the outlet (box) on that MWBC that is closest to the panel. Take all of the wires apart. Look for signs of an arc flash. Cap the ungrounded wires. Turn the two breakers back on. If they both hold, turn them both off and reconnect everything in that box. Use new wire nuts if the old ones don't look as good as new. Make pigtails to join wires of the same function that need to be connected to the receptacle. Terminate the pigtails to screw terminals - don't use any backstab terminals.

Turn the two breakers on. If they both hold, you corrected the short. If either one trips, turn them both off and move to the next outlet down the chain.

See Troubleshooting a dead receptacle or light....

That's one of the two combo 15A & 20A tandem breakers you have in positions 3 and 5 now. Have you ordered an Eaton BQ215220 breaker yet?

 

Since you don't know of any loads served by the black wire, where else would you look? This seems to me to be the only possible approach.

 

I said: "the breaker my supply house sold me is referred to this way on their receipt:

C-H BR1520 1P 15A & 1P 20A 120V CB Part number 2651708"

Hashkat1 said: "That's one of the two combo 15A & 20A tandem breakers you have in positions 3 and 5 now. Have you ordered an Eaton BQ215220 breaker yet?"

I should have been more precise above. That receipt refers to the replacement breaker I purchased two days ago by bringing the old breaker in and having them give me what I needed. So...a new breaker is in place...it is Eaton...but I do not see the same BQ215220 on it. The key reference on the unit seems to be BR1520.

 

Gentlemen:

I'm off now to find my fortune...correct that...to find my black wire inside its hiding place.

There is an old saying that goes something like: You can have great service or a high quality product at a great price quickly...(but you have to chose two qualities of the three: high quality, great price, timeliness). I've really never been good at old sayings. Anyway...I will report back when I find something just for the record.

I do want to thank you for great responses at a great price quickly. Couldn't ask for more!

Dave