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-   -   Why did my breaker trip? (http://www.diychatroom.com/f18/why-did-my-breaker-trip-64516/)

yummy mummy 02-15-2010 01:27 PM

Why did my breaker trip?
 
My breaker tripped this morning just out of the blue. There was no overload on it or anything.

I just heard this loud bang and then when I went downstairs a number of the lights were not working, and also the furnace was not working. The breaker takes care of the furnace and some light fixtures in the basement.

I pushed it back on and the same loud noise happened and tripped again.
The bang seemed to be coming from the area where the furnace is.

Any ideas as to why this would happen? Could there have been some outside problem that affected just that breaker?
Is the breaker malfunctioning?

Thanks very much.

Jim Port 02-15-2010 01:31 PM

Sounds like a dead short near the furnace. Open the junction box near the furnace with the breaker off and look for blackened spots or sign of arcing.

HooKooDooKu 02-15-2010 01:34 PM

Since you said it initially occured "out of the blue", my first thought would be a problem inside the furnance. After all, a furnance is not a static object. So it would make sense if something gave out inside the furnance and created a new situation.

yummy mummy 02-15-2010 04:44 PM

Thanks for you help.

I don't think I want to open anything, since I do not know what I am doing.

I tried to turn the breaker back on and now it works. Go figure. The furnace works, and the breaker seems to be ok.

I am still curious as to what would have caused it.

yummy mummy 02-15-2010 04:45 PM

Quote:

Originally Posted by Jim Port (Post 400298)
Sounds like a dead short near the furnace. Open the junction box near the furnace with the breaker off and look for blackened spots or sign of arcing.

Jim, what is arcing?

joed 02-15-2010 05:14 PM

Sounds like an issue with the furnace. Could be a problem with the blower. Find the 'bang' you will find your problem.

HooKooDooKu 02-15-2010 05:18 PM

Quote:

Originally Posted by yummy mummy (Post 400425)
Jim, what is arcing?

Arcing can be described as a short circuit through air. Basically, if two wires are brought close enough together with enough electrical potential (voltage) between them, a spark will jump across them. Think of a spark plug.
http://en.wikipedia.org/wiki/Electric_arc

Quote:

Originally Posted by yummy mummy (Post 400424)
Thanks for you help.

I don't think I want to open anything, since I do not know what I am doing.

I tried to turn the breaker back on and now it works. Go figure. The furnace works, and the breaker seems to be ok.

I am still curious as to what would have caused it.

Until I could locate the source of the original problem, I would worry that something was potentially broken in my furnance or elsewhere in the house where the wires for this circuit are located.

It may no longer be occuring now because what ever caused a short/arc has now been jostled loose or vaporized from the repeat occurance after resetting the breakers. So something still could have been damaged or is lurking to try again.

If you are uncomfortable with taking the cover off your furnance, I don't think it would be unreasonable to have an HVAC professional come and inspect it.

Jim Port 02-15-2010 05:18 PM

Arcing could look like burn marks or small globules of metal where a energized conductor was too close to a grounded surface.

micromind 02-15-2010 08:11 PM

This problem will almost certainly surface again.

Most likely a wire has rubbed on the metal frame of something (maybe inside the furnace, or even a J-box), and it caused a short circuit to ground (the metal frame of the furnace is grounded, as are metal J-boxes), re-setting the breaker likely blew it loose, and now there's a bare part of a wire that's very close to a grounded metal part. Sooner or later.....

The furnace is my first suspect, since they vibrate during operation. The problem could be inside the furnace, or the wire connecting it.

If you're handy with tools, myself or any of about a dozen others around here can walk you through locating and fixing it.

A picture of the furnace and where the wire runs to it would be immensely helpful.

Rob

yummy mummy 02-15-2010 09:33 PM

I really don't think I am confortable doing any of this myself.

Thanks for the information.

Maybe I will call the furnace guy. But if I call the HVAC guy, would he know anything about the electrical and why the breaker tripped?

Or should I call the electrical guy, but then how would he know about the furnace? :eek:

HooKooDooKu 02-15-2010 09:52 PM

A reputable HVAC contractor should be qualified to handle all aspects of installing and servicing a furnance. And that includes gas and electrical connections.

So you want an HVAC guy, not an electrician to check out the furnace.

Now if the HVAC guy can't find anything with the furnace, then an electrician might be needed to trace down what could be wrong with the other wires.

Another option (if the HVAC can't find anything) is to at least run a new dedicated circuit to the furnace (again, an HVAC guy should be able to handle that) and turn the breaker for the existing circuit running to the other outlets off until an electric contractor could look into anything wrong on that part of the circuit.

plummen 02-15-2010 10:16 PM

was furnace running when it tripped? try turning up the thermostat and stand by the furnace to see if blower motor dims lights when it comes on :thumbsup:

yummy mummy 02-15-2010 10:42 PM

I am not sure if the furnace was on when the breaker tripped.

At times when I have the iron on, I do notice that the lights in the room go a little dim, but just for a second, and then they are ok.

What does that mean, when they dim?

HooKooDooKu 02-15-2010 10:52 PM

Quote:

Originally Posted by yummy mummy (Post 400646)
I am not sure if the furnace was on when the breaker tripped.

At times when I have the iron on, I do notice that the lights in the room go a little dim, but just for a second, and then they are ok.

What does that mean, when they dim?

Speaking in general...

Wire has resistance, and the voltage drop across anything with a current flowing through it will have a voltage drop. It's not unreasonable to expect that the wire from the circuit breaker to the lights has enough resistance that of the 120v supplied by the POCO, you have a 1 volt drop in the wire from the power source to the lights, 118v drop in the lights, and 1 volt drop in the wire from the lights back to the power source.

Now if you go and add more current in that circuit, the voltage drop in the wire could go from 1v to 2v. In that case, the lights now only have 116v on which to operate on.

So if the lights go a touch dim when the iron is drawing power, that is to be expected. If lights dim when a motor first starts up and then brighten up, that's to be expected too, because a motor draws more current when it's starting up than when its running.

But if the iron continues to draw power and the lights undim, I can't explain that one. It should only be explained by an initial high power draw that then reduces. I don't see how that is happening in an iron, with the expection of an iron will cut off when it reaches its set temperature. Usually that takes more than a second.

J. V. 02-16-2010 11:10 AM

Mummy. Call an electrician or HVAC guy or gal to come over and find out where the problem is. HVAC people are usually excellent electricians unless they are just installers. We have installers in both trades. People that just perform mundane tasks repetitively for a very long time and they good at that task. Give them another task they have no idea. So, whomever you call, let them know that you need someone with troubleshooting skills. Don't take any chances. Get this resolved right away!

Like Jim Port said its most likely right in the j-box at the furnace. You could check this yourself by turning off the power and looking at the connections. As long as the power is turned off, you should not be concerned. Might save yourself a few hundred dollars too.


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