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Old 12-16-2008, 06:00 PM   #1
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Electrical "arcing" problem?


Hi everyone, hoping to get some recommendations about a problem I'm having. Before I continue, I know the answer is "call a qualified electrician before your house burns down or you get electricuted". But I'd like to get as much information as I can to see if I can narrow down the problem a little. I have replaced light switches, installed and cabled new plugs and new sconces w/fixtures etc. I've been shocked before and all that. I'm no expert but don't live in fear of the unkown either. I won't be offended if you assume I know nothing and explain things in detail because it's been nearly two years since I did the last work.

Ok, here's the issue. I have a number of lights in the house that go dim, or "flicker" all in unison. This has happened about 6 times in the last month, meaning 6 episodes where for a half hour or an hour they exhibit this behavior, then stop and don't do it for a few days.

Facts about the house: Built in 1989 in San Diego area, I'm sure with the worst materials available.

Troubleshooting so far: These lights are definitely on the same circuit, no lights on any other breaker or devices exhibit this behavior. I've turned off the main, and looked carefully at what I can see behind the metal plate and I see no obvious evidence of "arcing", burn marks, discoloration that I've read could appear if a wire is finding a ground and "bzzt". I've listened to the breaker and I might be hearing a strange electricity-like noise but it's not a quiet area. One thing I could do, is I have a breaker that doesn't appear to go to anything we use and I could switch the wires to see if that solves the problem and if so, replace the defective breaker.

Other things I've done, I've tried turning off everything on that circuit except a single device at a time and the problem still persists for that single device. I guess, one question would be, could something other than a problem at the breaker affect all devices on the circuit?

I will note that there are no new fixtures or plugs on this circuit installed by me. I have replaced light fixtures but all the wiring etc. was already there. The part that sucks, is that this circuit happens to have a very high chandelier and a very heavy ceiling fan.

So I'm looking for troubleshooting steps that would be worthwhile or direction.

I would think that the problem if not at the breaker is either behind a plug or a light switch, assuming the wiring isn't totally messed up, and not behind the light fixture itself, does that sound right? or no?

Would it make sense to do something like, open a couple switches or plugs at a time and cap off wires firmly and track it down that way?

suggestions?

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Old 12-16-2008, 06:06 PM   #2
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Electrical "arcing" problem?


Dont switch the wires, that could be dangerous!

Is the breaker feeding the culprit circuit burnt? Start from the panel to the last thing on the circuit, checking and fixing connections.

If you find push ins, aka backstabs, get rid of them. Use screws. Check splices, if loose, tighten and replace the wirenut.

That "bzzt" should be normal, it should be 60hz

Does it sound like this, if so, its normal.

http://en.wikipedia.org/wiki/Mains_hum


Last edited by rgsgww; 12-16-2008 at 06:12 PM.
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Old 12-16-2008, 06:07 PM   #3
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Electrical "arcing" problem?


It definitely sounds like a loose connection. Cut the power to the circuit and check all the connections. Are all the lights that flicker on the same switch?
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Old 12-16-2008, 06:26 PM   #4
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Electrical "arcing" problem?


What kind of lights are these specifically?

Are they all on a dimmer? Switched together? All in same room?

Are there other lights on a different circuit which are on at the same time that you can see which don't flicker when these lights flicker?
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Old 12-16-2008, 07:24 PM   #5
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Electrical "arcing" problem?


Thank you everyone for your replies. Here are the answers:

- I've checked at the breaker very carefully and I can't find any burn evidence. But since this just began recently, maybe I haven't given it time?

- BIG QUESTION: How do I tell what is first and last on the circuit? And, related, if it is a device on the circuit, are you implying that something at the "end" of the circuit wouldn't affect something at the "beginning"?

- DUMB QUESTION: This is one of my top questions, even though it's dumb. Assuming that a light isn't on a 3-way, and assuming the switch is perfectly functional, it seems to me that if the light fixture itself has a bad wire, if it's turned "off" it shouldn't affect anything else. Is that right? It's just a dead wire at that point, right?

- all the lights that flicker are on the same circuit, not switch. there are outlets on that circuit too that have the problem.

- There are plenty of lights on other circuits that don't flicker when these do. None are "switched together" except the chandelier is on a 3-way. They are in different parts of the house. They are typical normal light bulbs, 40/60 watts. Except the one outside light which is a motion light, halogen, that might be the first one I check.
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Old 12-16-2008, 07:28 PM   #6
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Electrical "arcing" problem?


Put a 10A load (hair dryer, toaster) on an outlet powered from flickering light circuit.
50' (from the panel) of #14 AWG Romex (100' conductor length) should give a 2.5v drop in the measured voltage. #12 should give 1.6v.
Scale up or down for longer or shorter distances.

Double these ΔV values, or more, is cause for concern.
If it fails the test you need to go around and tighten connection screws and wirenuts in that circuit.
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Old 12-16-2008, 08:11 PM   #7
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Electrical "arcing" problem?


big answer
The wire starts at the panel and goes out. Most likely the fixture, receptacle, switch etc. closest to the panel is the first.

dumb answer
It depends. Your problem is something that is common to all the flickering lights. It may not be obvious. The neutral in the panel could be loose bu not look burnt. If you can find part of this circuit that does not blink when the rest does then the problem is between the good and bad. If it appears the entire circuit is flickering then I would start at the panel and work my way out. Electrician usually work in a logical sequence. The cable will follow a logical path once start tracing them.

If your receptacle use the back stab connection that a very common source of the type of problem you are describing. The problem could be in a working device.
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Old 12-16-2008, 08:20 PM   #8
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Electrical "arcing" problem?


Quote:
Originally Posted by morden5b View Post
Thank you everyone for your replies. Here are the answers:

- I've checked at the breaker very carefully and I can't find any burn evidence. But since this just began recently, maybe I haven't given it time?

- BIG QUESTION: How do I tell what is first and last on the circuit? And, related, if it is a device on the circuit, are you implying that something at the "end" of the circuit wouldn't affect something at the "beginning"?

- DUMB QUESTION: This is one of my top questions, even though it's dumb. Assuming that a light isn't on a 3-way, and assuming the switch is perfectly functional, it seems to me that if the light fixture itself has a bad wire, if it's turned "off" it shouldn't affect anything else. Is that right? It's just a dead wire at that point, right?

- all the lights that flicker are on the same circuit, not switch. there are outlets on that circuit too that have the problem.

- There are plenty of lights on other circuits that don't flicker when these do. None are "switched together" except the chandelier is on a 3-way. They are in different parts of the house. They are typical normal light bulbs, 40/60 watts. Except the one outside light which is a motion light, halogen, that might be the first one I check.
Depends on how the fixture is wired. It is not necessary dead. You have a loose / bad connection. Turn off power. Remove and throw away all outlets. Buy new ones, the best ones you can get (clamp down style are great, and they are not the same as push in, they only tighten when you turn the screw).

Tell us if you still have the problem once the outlets are replaced. Don't worry about replacing the switches right now.

There is really no reason to ever get a shock when working on electrical work. I work on enough of my stuff live on purpose and I have never been shocked by any of it and never plan to be. Be careful, just takes one shock to kill you.


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Old 12-16-2008, 08:51 PM   #9
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Electrical "arcing" problem?


You can determine everything which is on this circuit by turning off power and seeing what no longer works.

Usually there is some logic to these things and your panel may be labeled to indicate what the circuit is for pretty much, but there may be exceptions like your outside light.

Sometimes all lighting circuits are wired separate from outlets. Then if an outlet breaker trips, you still have lights.

Sometimes a bedroom will be on one circuit, another bedroom on another circuit.

Sometimes a living room and the bedroom wall opposite the living room will be on the same circuit. (Wires runs through wall, so it was easier and cheaper to also connect the outlets on the other side for the bedroom.)

Anyway once you identify all lights, outlets, and switches which are on this circuit, plug something into each outlet - maybe a nightlight. Look for an outlet where the light does not flicker when the lights are flickering (and closest to the next thing which does flicker). This or the outlet/switch/light next in line would probably have a bad connection.
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Old 12-16-2008, 08:51 PM   #10
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Electrical "arcing" problem?


Quote:
Originally Posted by morden5b View Post
How do I tell what is first and last on the circuit?
Let's say there are 2 outlets on a circuit. Put a 10A load on one of the outlets.

If it's on the upstream outlet, the voltage drop between the short slot of this outlet and the short slot of the other outlet will be zero (since there is no current flow).

If it's on the last outlet, the voltage drop between the short slot of this outlet and the short slot of the other outlet will not be zero. It will be 10A x the resistance of the Romex, about 130 mV for 5' of #14 cable.

Using this method you will be able to sort all the outlets in a circuit. It's easier to do than to say.

Last edited by Yoyizit; 12-17-2008 at 07:49 AM.
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Old 12-16-2008, 09:04 PM   #11
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Electrical "arcing" problem?


In the following picture, this outlet has some wires stuck into the holes in the back. This is called backstab and it is common for these connections to fail.

Better connections are the wires which are wrapped around the screws. You bend the wires with needle nose pliers.

Then better yet are outlets (usually commercial or industrial grade) which have clamps which tighten onto the wire when you turn the screw. These outlets are much more expensive than regular outlets.


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Old 12-16-2008, 10:28 PM   #12
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Electrical "arcing" problem?


Yoyzit, I now understand what you are saying, thanks, I'll have to buy a voltmeter/ampmeter to proceed that way which I might do. Everyone else too. For the record, I've replaced most of the outlets in the house already with ones you screw, though this circuit is the one that has a few I haven't yet. Of course, I could have made a mistake too. I also forgot to mention wired off of one outlet is a cable (preexisting) to the garden where my garden lights and fountains plug in, a huge question mark there! Now that I think about it, I'll start there, because this plug that is tapped into I'd wager is "first" as it's a few feet away from the breaker box on the other side of the garage wall. I'll keep you updated. The part that sucks is that because the flickering is pretty infrequent, I can make a change and not know whether it worked or not for a while.
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Old 12-17-2008, 07:50 AM   #13
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Originally Posted by morden5b View Post
Yoyzit, I now understand what you are saying, thanks,
Here's a better example:

Using a voltmeter and a 10A load, figure out what order three outlets (arbitrarily numbered 1, 2, & 3) are in and how many feet of #14 copper Romex are between each outlet.

Plugging the load into #1, #2 reads 0v and #3 reads 468 mV, so #3 is 18' upstream of #1.

Plugging the load into #2, #1 reads 260 mV and #3 reads 728 mV, so #1 is 10' upstream of #2 and #3 is 28' upstream of #2.

Plugging the load into #3, #1 and #2 read 0 so they are both downstream of #3.

The order is, #3 farthest upstream, then #1 18' downstream, then #2 10' downstream of #1.
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Old 12-17-2008, 12:31 PM   #14
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Electrical "arcing" problem?


As noted by others, in troubleshooting you look for a common cause when several items are all affected identically and a breaker certainly fills that bill.
I once had a similar problem where even turning on the stereo would blink the lights and it turned out to be the breaker even though there was no physical indication. Unless you have some oddball variety, they're not that expensive or that hard to replace if done with due prudence for safety.
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Old 12-17-2008, 02:11 PM   #15
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Electrical "arcing" problem?


Check the neutral connection in the panel for this circuit. It will be the white wire that comes from the same cable as the black (breaker connection) wire.

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