Tips on tracking down cross-wired circuits?

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  #1  
Old 12-28-12, 01:43 AM
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Tips on tracking down cross-wired circuits?

I've meticulously mapped out every single electrical unit in my house to the circuit breaker. While this is great to have, it unfortunately led me to realize that my hard-wired smoke detectors are cross-wired with one of my other "run of the mill" circuits. Knowing that's a bad thing, I'd like to get them separated.

In my old house, I had two circuits that were cross-wired where if I turned on both, they would pop the circuit. But in this case, either breaker will power the circuit and both can be on at the same time if I recall correctly (haven't tested this in a bit, but pretty sure that's the way it was working).

In any case, are there any tips or tools for tracking this down? For that matter, does the circuit operation give any particular hints as to how it might be wired?

I know I'm probably ahead in the game in that I already know all the load points, but am not looking forward to untwisting the wires in every single location if at all possible, particularly since one of those points is a light on a 16 foot ceiling with a chandelier on it.

Any help will be greatly appreciated!
Don
 
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  #2  
Old 12-28-12, 06:33 AM
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.


I believe smoke alarms are purposely supposed to be wired to a common lighting circuit.

This is to prevent you from shutting off the breaker in a nuisance alarm situation.

This would then leave the house unprotected.....the code guys will come along and confirm.


.
 
  #3  
Old 12-28-12, 07:07 AM
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My dad had an alarm business for 30 years and told me that hard-wired fire alarms needed to be on their own circuit so that a fire couldn't melt a wire and pop the whole circuit, thereby disabling fire protection during a fire, which makes sense to me.

Now, to my original issue...the only way to kill the circuit is for both breakers to be off. If either breaker is on, the circuit still works. For that matter, if both breakers are on, the circuit still works. Specifically, in my panel, breakers 9 and 13 are the two involved here (so they're not even right next to each other).

I keep one breaker off because it seems to me that there's a risk of overcurrent with this setup.

Did I clear it up or make it worse?
 
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Old 12-28-12, 08:04 AM
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I keep one breaker off because it seems to me that there's a risk of overcurrent with this setup.
Absolutely !


Circuit 9 and 13 are on the same phase.
If they were next to each other they would be on opposite phases and you would get an immediate short.

I have never ever heard of using two breakers to power one circuit.

You can't even determine what is only on 9 and only on 13 since both are tied together.
Sorry to say it but you are going to have to go thru each location involved with both breakers and check the wiring. Hopefully it's not in that ceiling light.

I've always wired hardwired smoke alarms on their own circuit with a locking circuit breaker.


Good luck !
 
  #5  
Old 12-28-12, 08:18 AM
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Thanks Pjmax! That makes a ton of sense.

I think I'm going to start with the smoke detectors. They are a firex g-6 and are not supposed to have more than 6 together and there are 7. I have a feeling someone figured they needed the extra circuit to "power" the additional unit.

Thanks!
Don
 
  #6  
Old 12-28-12, 08:22 AM
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You are correct.

You have the potential of 30 amps on that circuit if both breakers are on.
 
  #7  
Old 12-28-12, 11:42 AM
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My dad had an alarm business for 30 years and told me that hard-wired fire alarms needed to be on their own circuit so that a fire couldn't melt a wire and pop the whole circuit, thereby disabling fire protection during a fire, which makes sense to me.
By NEC requirements,
Originally Posted by Halton
smoke alarms are purposely supposed to be wired to a common lighting circuit. This is to prevent you from shutting off the breaker in a nuisance alarm situation.
Not to prevent you from shutting off the circuit to kill nuisance alarms, but so that the power to the detectors cannot be tripped or otherwise opened without your being aware of it.

Originally Posted by PJmax
I've always wired hardwired smoke alarms on their own circuit with a locking circuit breaker.
So have I, in commercial settings. That's how it's done there. Just not in a dwelling unit.

Now, to my original issue...the only way to kill the circuit is for both breakers to be off. If either breaker is on, the circuit still works. For that matter, if both breakers are on, the circuit still works. Specifically, in my panel, breakers 9 and 13 are the two involved here (so they're not even right next to each other).
Yes. This is where you started, isn't it. As PJ said, you can have both on at once because spaces 9 and 13 are separated by one space (i.e., not next to each other) and are both fed from the same leg of your service - unlike the case in your old house.

I don't know that you have the potential for 30A there. What I do know from a similar experience is that I couldn't get either breaker to trip when I deliberately shorted hot to neutral across a receptacle on those circuits. That means that you essentially have no protection for anything in the double-fed area.
I keep one breaker off because it seems to me that there's a risk of overcurrent with this setup.
A good temporary precaution, but let's get it fixed.

I'm probably ahead in the game in that I already know all the load points, but am not looking forward to untwisting the wires in every single location if at all possible, particularly since one of those points is a light on a 16 foot ceiling with a chandelier on it.
And you know which two breakers. That's a great start.

From what you've said, you're not aware of any light or receptacle that's fed by either Circuit 9 or Circuit 13 and not also fed by the other. If that's the case, the double-tap is most likely located in the panel, in a covered J-box between the panel and the first device that's supposed to be on each circuit (if there is such a J-box), or in a device box very close to the panel. Right now the box above the chandelier is looking like a long shot. I hope it stays that way.

I would start by having a careful look at the wires connected to breakers 9 and 13. Unless you're very comfortable working inside a live panel, grab a powerful flashlight and kill the main breaker before you uncover the terminal connection area.

Tell us what you find there, and/or post a picture of it, and we can go from there.
 
  #8  
Old 12-28-12, 12:19 PM
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I was in the panel not too long ago to add a circuit for a new bathroom in the basement (dedicated, 20A, GFCI) and it looked very clean in there actually. Although I don't have a pic right this second, I recall it looking good. I'll look again and grab a pic, but I'm thinking this isn't where it is.

The logistical issue I have, of course, is that the circuits instantly disappear into the walls, so, if there is a junction box somewhere, I may never be able to find it.

I have a basic question though...why do you think the tie-in is close to the panel? I would think that if they are tied together, they are tied together, right? I mean, even if the last outlet on both circuits were tied together, you'd just have a big loop and everything would still be "powered" by both breakers. Isn't everything in parallel anyway? I wouldn't figure there would be a way to power only part of 13 from 9 - everything should be able to draw power from either breaker...right? Or am I just missing something?

On a side note, one of the smoke detectors turns out to have never been connected to anything anyway. It's mounted, but the wires are stuffed in the ceiling. No idea if it was built like that or the previous home owner was an idiot and yanked the wires, but the connector isn't even there.

Thanks!!
Don
 
  #9  
Old 12-28-12, 05:27 PM
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A likely source of why a circuit is supplied from two different circuit breakers is a half-switched receptacle (one side always on and the other side switch controlled) that has been replaced without the intertie link being removed.
 
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Old 12-28-12, 06:30 PM
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You have the potential of 30 amps on that circuit if both breakers are on.

Picture the two breakers in parallel. Both breakers are handling the load. So both will allow their 15 amps to pass before tripping. 15 + 15 = 30

You do know at least one thing connected to 9 or 13......the chandelier
 
  #11  
Old 12-28-12, 06:50 PM
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7 Lights (8 fixtures, including a 3-way), 6 plugs, and 7 smoke detectors. Two of the lights are pull chain, so that makes 27 boxes to open and look (including the chandelier). yay. I at least know that one of the smoke detectors is at the end of a run, so that one's eliminated. So, 1 down, 26 to go I guess...

I'm going to have to open all the smoke detectors and put new connectors for the replacement smokes, so that'll be 6 more I'm going to have to look at anyway. I do have a "suspect" location, based on the layout of the house and a guess of the run for the smokes due to the one that I already opened that's at the end.

Grunt, slog, grunt, slog. Just wish I had my dad's sounder handy...
 
  #12  
Old 12-28-12, 10:40 PM
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I have a basic question though...why do you think the tie-in is close to the panel? I would think that if they are tied together, they are tied together, right? I mean, even if the last outlet on both circuits were tied together, you'd just have a big loop and everything would still be "powered" by both breakers. Isn't everything in parallel anyway? I wouldn't figure there would be a way to power only part of 13 from 9 - everything should be able to draw power from either breaker...right? Or am I just missing something?
That's correct. It's a hunch, not a prediction. But, given that the wiring paths in a house look like the branches of a tree and tend to get further apart as the distance from the panel increases, it's a reasonable first guess that this happened closer to the panel, rather than further away.

The logistical issue I have, of course, is that the circuits instantly disappear into the walls, so, if there is a junction box somewhere, I may never be able to find it.
Since all splices must be made inside accessible boxes, there should be no box that is hidden from you.

A thought: Do you have any 2 (or more) gang switch boxes in the area fed by the two breakers? If so, I'm wondering whether one of those might have been fed with both of these circuits, and someone inadvertently tied them together there.
 
  #13  
Old 12-30-12, 05:04 PM
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Well...something no one suggested...a wire tracer. My dad had an older version of this one. It led me to my suspected location, specifically the light switch. Popped it open and there were 4 romex in there. One for the light, two hots, and one that looked to be the smoke detectors. Turns out the two hots were the suspect breakers - all tied together. Seems they decided to use that as a junction box and just tied everything together.

A bunch of testing and yelling downstairs to my wife to switch different breakers on and off and looks like I got lucky and it was the end of the run for #9 (which is all my plugs/lights). So, I tied #9 hot to the light switch and put the other two together (#13 and smokes) and voila! Everything seems to be separate now!

I want to make another run at verifying all this tomorrow but I needed to let my poor wife out of the basement!

I'll post back tomorrow with (hopefully) my conclusive testing that I did indeed find the problem spot.
 
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Old 12-30-12, 06:52 PM
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I want to make another run at verifying all this tomorrow but I needed to let my poor wife out of the basement!
You'd better let her out if you expect dinner
 
  #15  
Old 12-30-12, 06:55 PM
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You'd better let her out if you expect dinner
LOL - that's EXACTLY why I let her out!!!
 
  #16  
Old 12-30-12, 08:54 PM
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And if someone had suggested that you go out and buy a $275 tester would you have taken the advice seriously?
 
  #17  
Old 12-30-12, 09:29 PM
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And if someone had suggested that you go out and buy a $275 tester would you have taken the advice seriously?
No, I would have looked at a cheaper alternative, like this one

I'm not b1tching. I'm just saying that it was an option - a helpful one at that - that didn't come up.
 
  #18  
Old 12-31-12, 02:28 PM
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Well, gentle folk, that was indeed the problem. And that line out that I figured fed the smokes seems to have gone to the one in that room, as it was the first in the series (hot in, hot out, but only one interconnect wire). So, I now have a whole new set of smoke detectors installed AND my circuit panel is clean and organized with no cross-wired stuff!

For posterity...

The tracer was a help, but knowing what was on what circuit was completely invaluable. For anyone reading this, take the time and map all the circuits in your house precisely. You never know when it will come in handy - like when we had a flood upstairs and I knew exactly which circuits to turn on or not.

Between the tracer and knowing the circuit, my first guess was the only one I needed. That was huge - and I'm sure glad I didn't need to open that 16ft light!

Thanks for the help guys!

Happy New Year!!!
Don

PS - Can someone show me where exactly in the NEC it says to wire smoke detectors to a common lighting circuit? I sure couldn't find it but I'd like to know for reference, especially since mine is *not* that way.

PPS - Any thoughts on how much it would have cost me to hire an electrician to find that cross-wire?
 
  #19  
Old 12-31-12, 02:54 PM
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P.S. mine is not "that way" either.
Mine are on their own circuit with breaker lock.
That's the way I feel most comfortable.
If the house gets sold I'll change it then.

Happy New Year....back
 
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