AFCI breakers tripping every 7 days

Discussion in 'Electrical Forum discussion & Blog' started by hmk123, Jun 23, 2008.

  1. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,714
    Location:
    Central Florida
    Are those non-tripping AFCIs on the same leg as the tripping ones? If so, we can probably rule out line-side problems. If not, try moving one of them to the suspect leg and see if it will join its cousins and trip weekly.

    Another test- when you reset them, reset them at different times and see if the problem associates with one particular breaker. You could probably do that tonight. Turn one off and reset it at, say, 6:30, and the other at 7:00. Then a week from tonight grab your popcorn and gather 'round at 6:25 or so and see what happens. They should still both trip at the same time, but at either 6:30 or 7:00, which would point the finger at one particular branch circuit. To confirm that, swap the hot wires on the two breakers and again reset them 30 minutes apart. Come back the following week and see if the problem does, in fact, occur on the same circuit.

    You might be able to rule out the outdoot GFCI by tripping it manually and leaving it off.

    Of course, in any experiment you should always change only one independent variable at a time, so with each test taking a week, this is going to be a career, not a job. I hope I live long enough to hear what the problem was...
    Last edited: Jun 30, 2008
  2. alternety

    alternety Like an engineer

    Messages:
    651
    Location:
    Washington
    If you have a friend with an oscilloscope you might be able to see something on the line when it trips. If there is something there it could be very quick. A scope with storage would be helpful (e.g., one based on a PC).

    Be careful using test equipment on the power line. Understand what ground is on the scope vs the line and what probes are isolated. Failure to understand can cause a sudden loud noise, bright light, and a funny odor. If there is a foreign signal coming from somewhere you might see it.

    Have you tried a different brand of breaker in one of the slots.

    I believe that from the discussions above, the time to trip is a function of actual time of reset and not wall clock time. This tends to preclude interference from the power company side of the panel. Make sure you don't have something getting power from those circuits that you don't know about.

    Mind dump of possibilities follows. A timer for something that upsets the neutral or ground after 12 hours (outside lights) sump pump, sprinkler control, ventilation fan, alarm clock, video recorder, computer, something with a defrost cycle (unplug your frig 10 minutes before the scheduled trip), air conditioner, house air recirculator. A 120V load on a 240V circuit (e.g., stove, air conditioner, clothes dryer). Alarm system. Backup power system (generator or UPS). Fish tank. Cable box. Something that exercises something each week (circulators in hydronic heating systems).

    Something could be erroneously sharing the neutral. For AFI and GFI, there must be a single continuous neutral/hot combination. If anything uses that neutral and another hot (or vice versa) it will trip breakers.
  3. hmk123

    hmk123 New Member

    Messages:
    20
    Thanks for the great help guys! So unfortunately am not so familiar with some of the terms and so can only assume what a "leg" means. There is one over the ground power feed into the house. The other AFCIs are on the main, original panel which also has the meter next to them. We then added one more room and and a garage and for that we needed a side panel in the garage. Now we added another bedroom and a bathroom. So there is a new side panel in the garage for that. Now it actually goes main panel, new side panel and then over the old side panel for the garage and media room. In that new side panel there are actually 3 AFCIs. The two outer ones are for lights and outlets in the bedroom. The middle room is for the bathroom and needs to be changed because it is supposed to be GFCI. That middle one never trips. I will reset both of them tonight and doing it a bit later for one of them to see if they will both trip again at the same time.

    So other than lights there is a microwave, a small fridge, a toaster, an AT&T settop box, a TV and a lamp on those circuits. There is also a gas fire place in that room that has an on/off switch.

    I will try to put the devices on power strips coming from other outlets. But the strange thing is, it did this already when the room was not occupied and there was only occasional use (lights, a tool being plugged in). The smoke detector is still disabled for now. There is no sprinkler system, fan or anything like that.

    I finally got the number of the electrician that our contractor used and will call him today. Not sure if there is anything in the walls that I don't know about :)

    About using different breakers: was told in a Square D panel I can only use their breakers. Is that not true? We changed them once from 15A to 20A (will have to revert that again). But that did not help.

    The oscilloscope sounds like a good idea. Will probably do that after few more try/errors. For now I know it is not the dimmers nor the smore detectors. Plus the breakers were changed once.
  4. hmk123

    hmk123 New Member

    Messages:
    20
    One other things. The bathroom has Occupant Sensors. Even though I think they are all on the one AFCI that is NOT tripping I need to double check that. I just looked up some models on the Internet and it seems like they have a learning function on room usage. Some seem to adjust weekly. Something to look into I guess.
  5. hmk123

    hmk123 New Member

    Messages:
    20
    Just checked... Those sensors are on a different, non-AFCI breaker.
  6. scrunchielaura

    scrunchielaura New Member

    Messages:
    10
    Location:
    California
    The AT&T settop box, is it hooked to a phone line? Or does your area have bidirection cable hookups (ie cable internet)? I wonder if the box is "phoning home" every 7 days to report any pay per view viewing. (My DishNetwork satellite box has a phone connection that it uses to do just that. After the third time it knocked me off the internet (dialup) or tried dialing while I was talking on the phone, I yanked it's phone cord.)

    You mention having two breakers that both trip together. Are the TV and settop box plugged into different circuits? Try plugging both into one power strip so that they both run off the exact same receptacle.
    Last edited: Jul 4, 2008
  7. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,714
    Location:
    Central Florida
    There's probably a better term for it... most residential power comes into the house on three wires -- 2 "hot" wires and a "neutral". The way things work, you will see 120V between either of the hot wires and the neutral, and 240V between the two hots. Each hot is often called a "leg".

    The way most panels are set up, each leg is connected to a metal "bus" that runs the length of the box, one on the left and one on the right side of the box. When the circuit breakers are plugged in to the panel, the ones on the left are not all connected to the left leg, as you might expect -- rather, they alternate left, right, left, right ... on each column of breakers down the panel.

    Thus, in your subpanel, since the 2 AFCI breakers are not adjacent, but rather separated by one other breaker, they are on the same leg. This leads me to suspect the problem is common to that leg of the house power. That's why I suggested swapping one of the AFCIs with the middle breaker -- to put the AFCIs on separate legs, and then see if they both still trip, or if only one does. If one does and one doesn't, then the problem is isolated to one leg only.

    If that happens, you then have the choice of moving the tripping AFCI to the same leg as the non-tripping AFCI (thus masking the problem), or exploring further on the symptomatic leg to find where you actually have an arc fault occuring.
  8. Tundra

    Tundra New Member

    Messages:
    11
    Location:
    Yellowknife, NT
    When it became code here we changed out breakers for arc fault up at the mine (about 250 of them.....real joy doing that hot by the way). We had quite a few that would trip right away but this was usually fixed by tightening all the connections and taping them over. There was one that we finally attributed to a staple that was too close or something and had to be re-pulled. It held and worked with a normal breaker for several years with no issues.....:confused:.

    I didn't read all of the postings but do you have a weird load like a small fridge or freezer on this? We had some issues with some loads.....small humidifier, coffee pot....keep in mind there was 500 rooms and most had items like these.....just a few for whatever reason didn't work. Don't know if the dimmers would do it or not but the electronics may do something weird to it....but that's a shot in the dark but you could try pulling them out of the scenario as well.

    Good luck

    t
  9. Bill Arden

    Bill Arden Computer Programmer

    Messages:
    584
    Location:
    MN, USA
    Can you take a picture of your meter or see if it says DCSI or TWACS ?

    The TWACS system from DCSI pulls 90 amp pulses to send data back to the substation.

    It looks like we will all be adding Cap filters in the future. I had to add one earlier to get X-10 to work better after the power company replaced the meter with a newer AMR unit. (HuntTech)
  10. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,631
    Location:
    Cave Creek, Arizona
    7 days

    You mentioned that if it happened on Sunday, the next time would be sever days later on Saturday. If it happens on Sunday, then the following Sunday is seven days later. When is it occurring?
  11. rgsgww

    rgsgww New Member

    Messages:
    53
    Location:
    Ia
    Hey hmk123 what really happened? Have you found out yet? I have this afci laying around that I never got the time to install...I want to know what happened before I slide this in.
  12. hmk123

    hmk123 New Member

    Messages:
    20
    Sorry, we had visitors so I wasn't on here. It did trip again yesterday (Saturday). Both always trip at the same time. So this time, five minutes before I turned off the one to the plugs. Sure enought at exactly 8:48pm last night the other one tripped. So that breaker is supposed to only feed the lights (most of them recess lights). I checked the clock and it was to the minute. So next week (it will be now on Friday since it is on the seventh, not eighst day) I am going to turn the other breaker off (the ones with the lights) and see if the one that was shut off yesterday will trip by itself. I will take a look at the meter in the morning and see if it says DCSI .
  13. scrunchielaura

    scrunchielaura New Member

    Messages:
    10
    Location:
    California
    Q1: The AT&T settop box, is it plugged into the "plugs" circuit that you turned off yesterday/Saturday?

    Q2: Reading between the lines, I assume you have another TV and settop box elsewhere, correct?
  14. hmk123

    hmk123 New Member

    Messages:
    20
    Yes, that settop box was on that circuit that was turned off. And yes, there are 3 other of their boxes in the house.
  15. RRW

    RRW New Member

    Messages:
    91
    Location:
    Illinois
    How a about a refrigerator going in to defrost mode on a regular schedule?
  16. hmk123

    hmk123 New Member

    Messages:
    20
    The fridge was on the circuit that I turned off a few minutes before the one with the lights tripped. Also, the two breakers already did this when there were no appliances in the room (only the occasional tool usage). The lights have been in there ever since it has been doing this. I just don't get how anything on that circuit could be keeping time. We changed the light switches from dimmers to normal switches and it did not make a difference.

    I still need to do a photo of the meter. But it does not say DCSI or TWACS on it.
  17. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,714
    Location:
    Central Florida
    God, this is getting exciting!
  18. hmk123

    hmk123 New Member

    Messages:
    20
    Sorry, no update last week because I forgot to pay attention. But both tripped again at the same time. I didn't realize it right away. So I did reset both breakers about 30 minutes later. Tonight, about 15 before they were supposed to trip, I turned off the other one (this is the circuit for the lights). Sure enough, now right to the minute the breaker with the plugs still tripped. I assume it now has to do something with the ground, since it is shared by both? I guess next thing is to swap one of them for a regular breaker and see if the regular one stays ok and the AFCI trips. This for sure is strange.
  19. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,714
    Location:
    Central Florida
    I would repeat the experiment turning off the receptacles. I assume you haven't swapped one of them to the other service leg?
  20. hmk123

    hmk123 New Member

    Messages:
    20
    I did that two weeks ago. I turned off the one with the receptacles and that time the lights tripped. So it is either one of them (or both if both are turned on) that trip exactly 7 days later.
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