Our unpleasant problem
A couple of years ago, I didn't know what an arc-fault circuit interrupter (breaker) was ... nor did I know that my home had one. Now I realize that one of these devices seems to have prevented a fire in my home. I must confess, the first time I heard about the device, I was not very happy. We noticed that one of our "circuit breakers" associated with a children's bedroom started tripping for no apparent reason. At first the breaker tripped every 2-6 months; then it started tripping every month. Finally it was tripping every week, and then every day. We tried unplugging everything from the related circuits, turning off lights.
Electrician - too expensive to solve the fault.
Eventually we hired an electrician to troubleshoot the problem:Wesco Systems Electrical Services
1416 North Main Street
1416 North Main Street
Pearland, TX 77581
Phone: (281) 485-9304
Fax: (281) 485-7311
TECL: #24619
(http://www.wescosystems.com/)
He noted that the circuit was protected by arc-fault circuit interrupter (breaker) such as the two shown below. We had problems with another circuit in our home (built by Pulte in 2004) and he examined it first. When he removed one of the light switches he found that it was very hot to the touch and the plastic components had become brittle. He replaced that switch and then proceeded to troubleshoot the circuit in question. He made sure the circuit was completely unloaded and that nothing was plugged in. We then reproduced the problem for him by loading the circuit up with home computer equipment and by turning on lights. The circuit soon tripped. He then opened several of the switches and electrical outlets but did not observe any problem. Because the electrician was unable to find a wiring problem that could explain the arc-fault trip after searching for 2 hours, he finally gave up. He suspected that there was a wiring problem, but he said it would take many hours or perhaps days to test each circuit point (switch, outlet, light, etc.) and to identify the cause, if it could be found at all. He was ready to leave when I suggested he at least try something to make some progress.
I suggested that he replace the arc-fault circuit interrupter because perhaps this device was defective and this was the problem. Although he could not determine that the device was indeed defective, he replaced the original arc-fault breaker (which I suspect looked like the one with the yellow sticker (#1) in Figure 1, below) with the one with the yellow button (#2). After this, we were unable to immediately reproduce the problem even by loading the circuit once again. We paid the electrician approximately $650 and we hoped that this corrected the problem. Considering that he spent several hours on trouble-shooting the circuit and replaced an arc-fault breaker, this was probably a fair price.
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| Figure 1. Two Arc fault breakers (arc-fault circuit interrupter) are shown in the home breaker box and are labeled #1 and #2 in the image. Two models are shown. The top one (#1) has a yellow "Test AF" sticker. The second one is below it (#2) and has a yellow unlabeled test button and was in the position of the circuit that kept tripping. The top one (#1) is original equipment that came with the home (built by Pulte in 2004). The second one (#2) was installed by an electrician in 2012 to replace a prior arc-fault breaker. |
More disappointment
I told my wife that I that the electrician had replaced the arc-fault breaker and one damaged (burned up) light switch in a separate circuit and that I hoped this corrected the problem. Unfortunately, the child bedroom circuit tripped again the next day. We tried unloading the circuit and left just one small light connected, but the circuit tripped again. The repair attempt above did not work. We called the electrician above back to let him know that the problem had recurred, but we never heard from him again. We knew it would be expensive to have him test every circuit, and we were not eager to spend thousands of dollars to test every electrical component in this rather large circuit protected by the breaker. We used some ugly extension cords and flashlights in the meantime as we considered our next move. It almost seemed like it would be cheaper just to replace parts of that circuit with new wiring than to trouble shoot the large amount of wiring where the problem could be hiding. Although it was possible that there was a wiring problem, I was beginning to sour on the fact that we had an arc-fault breaker, and that it was required by code. I would not be able to hire an electrician to replace it. I did not feel comfortable replacing it myself either. I considered that maybe this arc-fault breaker was tripping for a nuisance reason. Perhaps there was a minor wiring or device problem and the breaker tripped for no real safety reason.Very temporary workaround
Mysteriously, the circuit started to work a little bit. We would only use it with very light loads (a fluorescent overhead light, etc.). It would work for several hours and if the light was turned off, the breaker would not trip for several days. When the arc-fault breaker tripped, we simply reset it. This continued for about 10 months or so. Sometimes the arc-fault breaker would trip and could not be reset without tripping immediately again. However, if I waited a little while (minutes or hours), the arc-fault breaker could be reset and the circuit could be used at least briefly to put the kids to bed with their overhead light on.Fault detected & Conclusion
One day, the arc-fault breaker started to trip frequently. It simply would not reset, even if I waited a few minutes. Finally it reset, but then it would trip again. Then I tried resetting it twice in a row and my wife noticed an electrical noise and two bright flashes in a boys' bedroom. The flashes seemed to come from an electrical outlet behind a dresser. Upon closer inspection, the electrical outlet appeared to have some charring as shown in Figure 2 below: |
| Figure 2. Cooper Wiring Duplex Receptacle. Universal grounding duplex receptacle. 2-pole, 3 wire. 15A-125V, NEMA #5-15R. MFG# 270W. UPC #032664147807. To right receptacle hole has a burned / charred appearance. |
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| Figure 3 (a): Cooper Wiring Duplex Receptacle with heat damaged terminal visible on upper left and marked in red. Terminal on right seems normal and serves as a comparison. Noticed that the damaged terminal has a much darker screw and the copper wire appears to have slipped out from its ideal landing. Perhaps when the receptacle was pushed into the wall slot the copper wire slipped out? In any case, it appears to have been at risk of making a poor connection and heating up to create the fault. A similar "burned" terminal was seen on a light switch on a different circuit. I did not save the "burned" light switch. Because the circuit with the light switch did not trip the arc-fault breaker, it is clear that the arc-fault breaker does not detect this type of electrical wiring fault consistently. Perhaps this type of circuit wiring is susceptible to poor electrical connection and subsequent overheating. |
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| Figure 3 (b). Receptacle with damaged (overheated) terminal shown at top. |
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| Figure 3 (c) Bottom of receptacle showing burned terminal bottom right. |
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| Figure 3 (d) Normal side of the receptacle. |
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| Figure 3 (e) Repaired receptacle with cover. |
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