Ceiling fan install - loud hum then unit goes dark


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Old 08-08-14, 09:33 AM
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Ceiling fan install - loud hum then unit goes dark

I just installed a ceiling fan from Lowes, and when we tried to power it on, there was a loud humming sound in the wall and the bulbs flicker, and then the whole thing goes dead (neither the fan nor the lights come on). There was a "popping" sound inside the unit. It didn't trip the circuit breaker.

I've had this happen on a previous ceiling light installation -- taking that one down and re-wiring it wasn't successful, but there also wasn't obviously anything wrong with the light (although I haven't yet checked the continuity, either).

The house is 1940s, and the insulation around the wires isn't great, but I wrapped them both in electrical tape so I don't think they were in contact. I've replaced quite a few other lights in the house with no problems, but these last two have me questioning whether I'm suddenly doing something wrong (likely) or whether there's something wrong with the wiring in the house.

I am a complete novice so any suggestions as to what the problem might be would be greatly appreciated!
 
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Old 08-08-14, 09:48 AM
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Welcome to the forums. Did you turn the breaker completely off and reset it? Often they do not appear tripped. How many cables or wires is there in the ceiling box? Do you know where power is derived? From the switch box, or the ceiling box? Did you modify any wiring in the switch box?
 
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Old 08-08-14, 11:04 AM
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One of two things happened:

1) The fan is wired on a dimmer switch.

2) You somehow wire the fan to 240 volts.

If there is no dimmer, use a meter and check to what you have for voltage. Be sure to set your meter to at least 240 volts.
 
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Old 08-08-14, 11:21 AM
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Thank you both for the quick replies! To answer a couple of the questions:

- Breaker is definitely not thrown; other stuff on the circuit is still working. The "hum" only happened when the power was on to the switch. Now when I throw the switch, there's no hum -- and nothing happens with the fan/light.

- There were two wires in the ceiling box, no obvious difference between them.

- The circuit has two switches on it; I think they're all in series, if I recall correctly. The other light that this happened to was on a circuit with a single switch, though.

- No dimmer switch.

- I can't rule out the possibility of 240V; the previous fan was probably 10-15 years old, and I didn't notice anything particularly unusual about the way it was wired up when I removed it. I will try to get a meter to check that out.


Thanks again.
 
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Old 08-08-14, 11:23 AM
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Originally Posted by Jake Blues
there was a loud humming sound in the wall and the bulbs flicker, and then the whole thing goes dead (neither the fan nor the lights come on). There was a "popping" sound inside the unit. It didn't trip the circuit breaker.
I've dealt with 1940s wiring added after the fact to an old stone farmhouse -

My first guess is that you actually have some sort of junction in the ceiling box,
e.g the original wiring had a ceramic pull chain fixture which passed current through the base,
the new wiring tried to pass all the current through the fan.

Second guess, you have 2 switches in the room and this light was wired with a
"Knob & Tube 3 way switch"



which means sometimes the center contact of the light is hot, and the fan is connected to the return e.g. grounded;
and sometimes the center contact of the light is return, and the fan body is hot.

Basically, one switch works fine, the other switch triggers a dead short if the fan is properly grounded.
 
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Old 08-08-14, 11:50 AM
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Thanks Hal! I only saw the two wires in the ceiling box, and those were both connected to the previous fan in the installation I removed. Is there an easy way to test whether there's a junction in the box as opposed to just hot/neutral?

I'm not sure about the switching either; both switches were open when we tested the light for the first time, and the humming was immediate, and then a pop, then nothing. And again, because I saw exactly the same behavior from a previous ceiling light, which was on a single-switch circuit, I am less suspicious of the switching being the culprit.

Thanks for your reply, I appreciate it!
 
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Old 08-08-14, 03:27 PM
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Originally Posted by Jake Blues
both switches were open when we tested the light for the first time,
Hmm, curious about that.

Two way switches aren't open/closed, but instead are connected / not-connected to a traveller wire.

<img src="http://www.fitdownload.com/wirimg/2-way-switch-wire-electrical-circuit-diagram.jpg" width="374" height="53"/>

So, if you have with 2 wires to the fixture,
one wire should be a neutral - at 0 volts no matter what the position of the other 2 switches is.
the other should be a switch wire aka traveller, hot or not, depending on what the positions of the other 2 switches are.

What do you see?
 
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Old 08-09-14, 04:33 AM
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I'm not sure; there are two wires coming out of the ceiling box, but they're indistinguishable, and I don't have a wire to measure which one is hot. I believe that I hooked the black (fan) and blue (light) wires to the same wire that the black wire from the previous fan had been connected to, but I can't be a hundred percent sure that I did so. But given that the previous fan seemed to work fine with this same wiring, I just can't understand what could cause this loud "hum" and then the failure of the part. I don't know if the light/fan is damaged or not, but I just don't get what could allow it to draw so much current that it could fry itself without the breaker tripping. That makes me wonder if wiring up to the wrong wires could be harmful.

Definitely need to get a meter, but any further thoughts anyone has about how something simple could cause something catastrophic would be helpful.

Thanks again.
 
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Old 08-09-14, 05:34 AM
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I lost a post somewhere, so restated......could we be talking of low voltage control wiring, based on the switch terminology used. Just curious.
 
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Old 08-09-14, 09:21 AM
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I'm not sure; keep in mind that I don't really know anything! I've switched probably a dozen lights in this house, and the extent of my knowledge is (a) turn off the main breaker, and then (b) connect the black wire in the light to the black wire in the box and same for the white wire. That's worked well enough for me in the past, but for some reason, the last two lights I've installed something has gone wrong, not sure what. There are only two wires that I can see in the box; my assumption was that they're hot and neutral, but if I should inspect the box more carefully to see if there's a control wire that's been connected in some strange way I can do that. What's weird is simply that the previous ceiling fan worked with no problems with essentially the same wiring approach that I'm using for the current fan. The only possible difference is that I may have wired the black wire from the fan to the neutral line instead of the hot line. It's older wiring so I wasn't sure whether there's even a difference or whether the wiring is symmetric. As I said, I'm quite deficient in my knowledge and understanding of this kind of thing.
 
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Old 08-09-14, 09:40 AM
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Originally Posted by Jake Blues
the extent of my knowledge is (a) turn off the main breaker, and then (b) connect the black wire in the light to the black wire in the box and same for the white wire.
Curious - did the new fan have a green wire, or the bare copper wire?

What did that get wired to?
 
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Old 08-09-14, 01:10 PM
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There wasn't a green wire coming out of the fan itself, but there was a wire connected to the housing (ie the plastic structure that holds the housing of the fan structurally), which I just tied to the screw that was connecting that to the ceiling box.
 
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Old 08-09-14, 03:09 PM
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Originally Posted by Jake Blues
to the ceiling box.
So, two guesses-

Ceiling box is metal?

Wiring is solid wire with cloth insulation in armored cable?
<img src="https://img2-2.timeinc.net/toh/i/a/tools/wiring-problems-12.jpg" width="300" height="300"/>
 
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Old 08-09-14, 05:35 PM
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Yes, I believe the ceiling box is metal.

Yes, the wires look like what you've shown; they're recessed enough that I don't see the "armor", and old and dirty enough that it's not obvious whether they're different colors or not -- they look pretty similar.

Thanks,

-J
 
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Old 08-10-14, 05:29 AM
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Quick update on this; I pulled the fan from the ceiling, and the end of the white braided wire from the fan is singed. The orange cap is burned and there's some wire in there.

Would this be caused by erroneously connecting white to hot instead of neutral (again, it's impossible to tell which is which from the box), or from getting inadequate contact between the braided wire from the fan and the bare copper wire from the box?

Also, there's no ground wire from the fan, there's just a ground wire from the plastic bracket that holds the fan. I tied it to the ceiling box, but there's no actual contact between that and the fan. Not sure where I would connect it to the fan, if indeed I'm supposed to.
 
 

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