3-Way Junction Box in Attic + Burnt Wires

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  #1  
Old 08-28-05, 08:32 PM
chosmer
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3-Way Junction Box in Attic + Burnt Wires

I recently had a contractor install a skylight. He cut a circular hole in my roof to install a sono-tube. He didnt touch any electrical stuff when he was up there.

After he was finished, I noticed some lights didnt work. Naturally, I called him and he came back. After examining, he found a junction box (might not be the right term) (Its about 3inches square metal box with a cover) with 3 white wires comming in. Each of the white wires is broken down into black, white, and green. It appears as if the plastic black nuts holding some of the wires together had melted and that he may have disturbed them while doing his work.

One of the things that doesnt function now is a dining room light on a dimmer. There are 3 75W bulbs in the chandelier on this dimmer.

The dimmer switch is part of a switch panel with 2 other switches that dont work. I tested each of these with a voltmeter to find that they have no current. Each of the 3 switches in this panel are standard 2 way swtiches, with both leads attached to black wires. I can only assume then that this entire switch panel is powered by one of the AWG wires comming down from the attic. The whites are all joined and the blacks are switched to the three different lites.

Up in the attic where the junction box is, As near as I can tell (the wires are a mess), the wires were attached to each other by color - Black-Black-Black, White-White-Whie, Green-Green-Green, etc. Should I assume this? Is there a standard way these junction boxes are wired?

Im assuming that one of these is live and that the other two are feeds off of it. I can test this with a voltmeter.

I thought about replacing the dimmer with a standard switch, since I have heard that the dimmers can cause trouble. Is this true?

I plan to climb back up into my attic and snap a picture. After that, Ill pull on some of the wires gently to see how much slack they have.
It looks like Im going to have to cut some of the wire since it looks like the short has burned some of the insulation off some of the wires. If my slack comes up short, what can I do to extend the wires?

Am I proceeding the right way, or missing something.
 
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  #2  
Old 08-28-05, 08:54 PM
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Whoa there...... slow down...

You've got a short in the wires.... possibly caused by the previous work... Sounds like it arc'd and burnt up inside the box a bit. Before you go tugging on wires..... remember, they're possibly still live and will short again if you touch the wrong things..... 120v can kill.

Your switches sound as if they've got no power. One of the black lines isn't connected properly, probably in the junction box. Or possibly the breaker has tripped in the main box due to the short you experienced. All the switches should be fine.

You are correct in assuming that the "colors" go together. Black/Black White/White Green/Green.

While you should have a qualified electrician check out your problem..... if you decide not to............ Determine which breaker the lines are on. Turn it off.... double check your wires for current before touching them.... ONCE YOUR SURE THEY'RE OFF.... clean up the mess.... strip off bad insulation and replace the wire nuts. This is the time to "Tug" on your wires to make sure your wire nuts are on tightly on all three sets of wires. Replace the cover on the box securely. After this it's time to turn the breaker back on and, hopefully, your problems will be solved.

You may get a lot better advice in this forum. Take it. I do lots of DIY projects, including electricity.... and always assume, often incorrectly, that others have the same basic knowledge.
 
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Old 08-29-05, 03:16 AM
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chosmer,

first as previously stated...WHOA.......hold on for a sec.


Ok....you stated:
Up in the attic where the junction box is, As near as I can tell (the wires are a mess), the wires were attached to each other by color - Black-Black-Black, White-White-Whie, Green-Green-Green, etc. Should I assume this? Is there a standard way these junction boxes are wired?

Im assuming that one of these is live and that the other two are feeds off of it. I can test this with a voltmeter.
The wiring itself if worked before is probably right and yes generally in a junction box as you describe it is what is called a " pass-through " for a lack of better term meaning it is just a junction of wires and the box is the method of access for this.

I then have a question to ask you before you go messing around with the wires...

1.) Is the melted or discolored portion located up the cable or just at the wirenuts inside the junction box?

The problem could be a number of things, the joint in the wirenut could have come loose and caused an arc inside the wirenut and the dimmer being a resistance impedance device could have caused the arc to get worse and thus heat melts plastic....and now the wires are not making contact on that circuit...

The problem can also lead us to wonder WHY the breaker did not trip..did you CHECK the breaker panel....???? Also what brand service panel do you have and is it fuses or breakers.....all lead me to other questions....

What i am getting at is their may be a underlining problem here that needs to be addressed, if it were me doing the service call I would be placing an AMP Probe on that circuit and trying to read the amps being drawn...but thats me....I get anal like that....

If you are destine to do something yourself I would suggest that you know 100% you are not dealing with live voltage before you mess in the box as the issue could still be their...so I would suggest a low cost voltage detector they sell at home depot which detects voltage without actually touching a live wire....know it is totally OFF.....

Now remove the wirenuts........seperate the wires out and KNOW 100% they are not touching anything....and then and only then turn the power back on and test the lines to see that voltage is coming into the junction box...

Once you have done that.....turn off the circuit again....and using NEW wirenuts make up the joints EXACTLY as they were before....

Lastly....you stated
He cut a circular hole in my roof to install a sono-tube. He didnt touch any electrical stuff when he was up there.
Ok...did HE say that or you said that....famous last words as no one wants to take blames for possible issues....never assume it....if possible check all around the installation locations for this skylight...from point of entry to the ceiling location above in the attic....

He could have stepped on a wire by mistake...( not that he did..just saying ) and it pulled on one of the cables....thus pulling a wire loose in a wirenut and then caused a arc....which built up heat and well you get the picture so eliminate everything...

Lastly.....we would LOVE a pic of it.......can learn alot from a picture so get a close up and then a shot from back a bit...so we can see the wires leading into the box....
 
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Old 08-29-05, 06:02 PM
chosmer
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Will Get a Picture

Thanks alot.
This is all really sound advice.

Just so you know, I had sense enough to turn the power (main breaker) totally off before I crawled up in the attic.

I will snap a picture as soon as it gets cool enough to go up there again...(Its really hot up there right now)

Is there a way I can post the picture as part of this thread?? I cant find the link.
 
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Old 09-05-05, 07:44 PM
chosmer
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I have the Pictures now.

I have pictures of the junction box now...should I email them?
 
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Old 09-05-05, 09:24 PM
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Find a public photo site to host them, then lin to them here, so all can see them.
 
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Old 09-06-05, 05:14 AM
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First question:
Is the wiring aluminum? If so then consulting a professional electrician is your safest bet.

You did state "the plastic black nuts holding some of the wires together had melted".
I'll refer to a previous post today and state that when wires are not pre-twisted, OR if a wire nut is NOT properly installed, this is a pretty common outcome if the load on the circuit is reasonably high. I have seen this MANY times for exactly these reasons.

Typically the breaker will not trip as it does not see this as and overload or short. The bad connection creates and enormous amount of heat at the splice because of the resistance. This does not raise the amperage of the circuit.

Normally, just cutting back on the wires and re-making the splice properly is all that's needed.
 
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Old 09-06-05, 06:32 PM
chosmer
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Link to the Photos

Heres the link to the pictures.
You dont need to sign in or enter any information in order to view them.
Just click on the top picture itself and then you should be able to view them as a slideshow.

http://www.kodakgallery.com/I.jsp?c=...v&x=0&y=1ggzay
 
  #9  
Old 09-06-05, 07:24 PM
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chosmer,

Hard to tell from those pics but it looks like corrosion on your ground wires and I would venture to say others as well. Speedy brings up a good point however, if the connection was weak due to a bad connection or corrosion....

Either way make sure the wire is not damaged other than the melted wire nut issue...if the wire looks fine itself then you should be fine. I see from the pics the old Wire Weasel is at it again......Always leaving TOO little in the box that old wire weasel.....

The first thing I teach at the local college....leave 6" or 8" in the box from the point the wire enters the box...give us guys something to work with...lol...

Anyway, I doubt the skylight fella did anything except maybe cutting the hole in the roof and possibly letting moisture get to the box...who knows but unless I am seeing things it looks mighty green in that box and it sure is not the wire jacket....
 
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