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Arc fault Tripping

3381 Views 21 Replies 6 Participants Last post by  Funk12doc
Really a novice here guys, so I'll do my best to summarize my issue and the troubleshooting I've already done....

I've got a fairly new home (2008) that has 3 arc fault breakers on the box. One of those covers a bathroom, laundry room, and bedroom combo. Have had zero issues with breaker tripping in the 4 years we've been here.

Recently, the breaker tripped in the middle of the night. No big deal, I figured the extra Christmas lights in the room (my daughters), coupled with the usual night light, sound machine, space heater, and clock probably overloaded the circuit. I flipped it in the morning and didn't have an issue for another week or so until it tripped again. It was after Christmas, so I removed the extra lighting and thought I would be fine. That's when the breaker starting tripping whenever I turned on the bathroom light switch. I then unplugged everything in the bedroom and bathroom. Had a nightlight in the bathroom and also a CO2 detector (why this was in the bathroom only my wife can explain?!?). Still the breaker tripped when I tried to turn on the bathroom light. To boot, the breaker will trip when I try to turn on the bedroom or laundry room overhead light as well. Not sure why this is happening. I've tested the outlets in those 3 rooms, and they all test and work fine using a small lamp. There is also a GFCI outlet in the bathroom in question, which I thought may have been the problem, but it tests fine as well.

Thought it could have been a bad breaker, but swapped it out and it still trips the new breaker whenever one of the light switches is turned on. Seems like I'm missing something obvious but can't figure it out.

I read thru an old post on this forum from 2009, but the OP bailed and never got to final resolution.

I have a square D breaker model QO I believe. Any help would be much appreciated and more than willing to answer questions and get back to the board with final resolution.

Many thanks!!!
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It sounds like you have a bad connection....

Go look up how an AFIC works.....interesting reading.

AFCIs are designed to protect against fires caused by electrical arc faults. While the sensitivity of the AFCIs helps in the detection of arc faults, these breakers can also indicate false positives, identifying normal circuit behaviors as arc faults. For instance, lightning strikes provide voltage and current profiles that resemble arc faults. This nuisance tripping reduces the overall effectiveness of AFCIs. Research into advancements in this area are being pursued.[4]
Also, AFCIs provide no specific protection against "glowing" connections, excess current, high line voltages or low line voltages. AFCI circuit breakers for use in a panelboard include a standard inverse-time circuit breaker. Glowing connections occur when relatively high electric current exists in a relatively large resistance object. Heat comes from power dissipation. This energy, when dissipated in a small junction area, can generate temperatures above 1000 degrees Celsius and can ignite most flammable materials.[5]
Bad wiring junctions can occur in utilization equipment, cords or in-situ wiring and especially in a defective switch, socket, plug, wiring connection and even at the circuit breaker or fuse panels. Terminal screws loosened by vibration, improper tightening or other causes offer increased resistance to the current, with consequent heating and potential thermal creep, which will cause the termination to loosen further and exacerbate the heating effect. In North America, high resistance junctions are sometimes observed at the terminations of aluminum wire circuits, where oxidation has caused increased resistance, resulting in thermal creep. No technology located in a circuit breaker or fuse panel could detect a high-resistance wiring fault as no measurable characteristic exists that differentiates a glow fault from normal branch circuit operation. Power Fault Circuit Interrupters (PFCI) located in receptacles are designed to prevent fires caused by glowing connections in premise wiring or panels. From the receptacle a PFCI can detect the voltage drop when high current exists in a high resistance junction. In a properly designed and maintained circuit substantial voltage drops should never occur. Proper wire terminations inside utilization equipment, such as appliances, and cords prevent high-resistance connections that could lead to fires.
I would look for a bad connection. If it was me, I would start with the light switch and lamp in the bathroom.

As a side note.....I belive the bathroom outlet is supposed to be on it's own are you saying that the outlet in the bathroom is also on the AFIC or is it just the light? Oh, and the laundry is also supposed to be on it's own....
Also make sure there not back stabed, if they are remove the wire and place it under the screw instead.
The GFI outlet in the bathroom is on the same circuit as the light. I do have a separate circuit for the dryer, but the outlets in the laundry and the overhead light in the laundry is on the same circuit as the bathroom and bedroom as well.

The GFI in that bathroom controls the outlets in the master bath, while the master bath lighting and smoke detectors are on another circuit together. I thought this was odd as well, b/c I thought the detectors were supposed to be on their own circuit.
Not sure what back stabbed is, could you explain further. Thanks!
Some recept have in addition to the screws, holes in the back that has a spring loaded connection. You strip the wire back and just shove (stab) it in the hole. Hence, the term "Back Stab". On the surface, this sounds great....easy to do.....

In reality, this one of the most common sources of bad connection in recept.
Would checking the outlet with a 3-prong tester identify this bad connection? I did that in the affected rooms and all outlets tested fine. Should I try testing all outlets in the house to see if something else is on this circuit that is not labeled?
I agree, check connections on that entire circuit.
The use of space heaters will exploit bad connections.
Would checking the outlet with a 3-prong tester identify this bad connection? I did that in the affected rooms and all outlets tested fine. Should I try testing all outlets in the house to see if something else is on this circuit that is not labeled?

It could be in a switch as well, you may need to pull receptacles and switches from their boxes to find it.
You could use a three prong tester, plug it in and try twisting the receptacle trying to recreate the tripped breaker.
Just don't go wild with it.:wink:
You are going to need to do a visual inspection of the connections to ensure they are tight. A three light tester will not show the integrity of the connections.
That is helpful. I will start looking inside the outlets to see if anything is amiss. I thought about replacing the switches, but when the switch in all 3 rooms tripped the breaker, I thought it was unlikely that all 3 were bad.

As these rooms are on the 2nd floor, it was suggested to me to get into the attic to see if I have any moisture or any other interference in the wiring up there. Thoughts on that?
Start by checking for loose connections. As others said, a large load like a heater can cause a connection to fail.
A bad connection at the start of your outlet chain will cause a problem even if your plugging into the last outlet....

If you have a voltmeter and an can test it that way. I made a pigtail that lets me plug in an iron and have my DVM leads hooked up at the same time. By measuring the voltage drop at the outlet of the recpt when you turn on the iron, you get a good idea of how good the connection is. You can also plug the iron into the top recpt of the duplex and meter in the bottom recpt of the same duplex.

In your case, you can do somewhat the same thing without a pig tail....plug the iron into the last recpt in your string of outlets. Then go to each outlet with your meter. Meas the voltage then have the wife turn on the iron. When you see a signifcant have a bad connection at or before that recpt.

Experts chime in....but to me, anything more than a 5Vac drop would be an issue.....if I recall, I think the most I see is around 2Vac...and that is on a long series of outlets.

One last thing....I installed AFIC's in the addition of my house (all bedrooms). I've been using a miter saw (10") upstairs in the master well as drills, etc. All on the AFIC. I have not had a single trip.
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If the heater caused the connection to fail, should I start at that connection where the heater was plugged in? Am I understanding correctly that the connection could be bad at a particular outlet even if I can plug something in there (ie. lamp, nightlight) and it works? I'm embarassed to say this, but when checking the outlet what specifically should I be looking for to identify the connection is bad?

Really appreciate all your help! I will have to wait to try some of this stuff when I get home tonight, but will continue to check the board throughout the day and be sure to post back this evening.
Sorry if this is too basic and you already know this part, in that case, disregard... To check each connection point (receptacle, light switch, light fixture) you would kill the power to the entire circuit and remove the recetacle/switch/light fixture from its junction box to check the black, white, and bare wires connected to that device; as well as any wires connected to each other in that junction box. You're looking for any connections that are loose and wires that may be touching each other (eg, white wire touching ground wire) or wires that could possibly touch when they are crammed back into the junction box.

If I were doing this, I would check the receptacle used for the heater, then the receptacle used for the christmas lights, then the problem switches, then the light fixtures controlled by those switches... then, if still having the problems, all other connections on that circuit.
So I started this evening by looking at the 2 outlets that were running the space heater at some time during the course of the first few trips.

Once I got inside the first outlet, I notice a screw just laying inside the box. It was about 1.5 inches and it appeared to be touching the exposed copper wire. I was optimistic that this was my problem, but I removed it, turned the breaker back on, but the light switch still tripped the breaker.

I got into the second outlet and noticed that wiring of the 2 outlets were different.

In outlet #1 there are 2 white and 2 black wires coming out of the back. Additionally, there is a white wire, black wire, and exposed copper wire wrapped around the screws on the side of the outlet.

In outlet #2 there are the 2 white and 2 black wires coming out of the back, but there is only the copper wire wrapped around the screw.

I haven't checked all of the outlets on the circuit of course, but just wanted to share this info to see if it should be leading me in a different direction before I get into the other outlets.

Many thanks to all of you still willing to read and assist!
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When you say "out the back", do you mean that the wires are pushed into the back of the outlet? If so...this is a 'back stabbed' outlet....and a good chance a source of your problems.

And on the second outlet, the wires are attached to the side screw as well as back stabbed?

It sounds like you should be changing all of your outlets to pigtails....

This is not the best picture...but should give you an idea of how it should look........and no, your wires should not be this long....most of mine are long because I still have drywall to do and I find it's easier for things to stick out like that so I can drywall around them.

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Ya, it appears mine are back stabbed. Why would the one outlet be back stabbed AND wire wrapped around the screw? Why would be there be 2 of each white/black back stabbed?
I tired to see if the back stabbed wires were loose but they are in there pretty good.
They may be in pretty good.....but you don't know how good those spring loaded connectors are making contact with everything else.

Trust me...pigtail is the best long term solution. I'm just a plain old home owner....and I learned the hard way....
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