posted
Our house was built in the 70s and for some reason has no built-in doorbell. We got a wireless doorbell that uses a battery in the button and has two plug-in receivers that chime when the button is pushed. Sometime in the last 2 or 3 weeks, the one of those receivers stopped working. Today, when I unplugged it to take a look, I burnt my hand on the plastic case near the plug (not bad, but enough to elicit a pullback and a little redness).
The plastic behind the plug is scorched brown. I took off the cover plate, and found out that the outlet is scorched, emanating from where the black wires are attached, and insulation on the wires is flaking off.
OK, first thing I'll do is turn off the breaker for this circuit. My next question is: how do I know if this is going on elsewhere? What could lead to this? It's not on either circuit I've done electrical work on. Neither outlet I've added gets hot. This makes me think the problem is systemic.
how does one find a good electrical inspector, and how much should it cost for them to a detailed inspection and report every problem like this in the house?
posted
Dag, I would call the fire department, and ask them first. They will probably inspect it and tell you what to do.
Posts: 10890 | Registered: May 2003
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posted
Hmm...The circuit is overheating, that's clear enough. What could cause that, though, is the quesiton.
This device you had plugged into it -- sounds like it couldn't (or rather shouldn't) draw enough current to heat the wires appreciably. But that's the first thing to check. Plus, what else did you have connected to that plug.
The other concern is what else is on that circuit, especially the part of it that connects THROUGH that wall outlet. The current may be simply passing over the plug to other parts of the circuit and the whole darn wiring is overheating.
But...maybe you have a ground fault or something in that circuit and the current is traveling massively behind the wall. There are things called ground fault checkers that you plug into the wall outlet to see if it's properly grounded, etc.
Now...let's see... What else is on that circuit? What else went off when you flipped the breaker switch?
Do you have any OLD appliances hooked up anywhere in the same vicinity?
What is the max amperage on the circuit breaker, by the way? I'm just surprised it's getting THAT hot and not blowing the circuit.
That actually makes me suspect that the wiring in the walls might be the wrong gauge. Or, you could have aluminum wiring. I don't remember why that's bad, but apparently there was a spate of fires because of aluminum wiring and I just don't remember what the issue or problem was with it. But most building codes don't allow it anymore.
Anyway, this is a long-winded way of saying that I'd have a real electrical inspector check it out. If there is a problem, you might want to see if this is something that your original home inspector should have noticed. There's a guarantee of sorts when you do a pre-buy inspection of a house. (assuming you hired an inspector -- most mortgages require it).
Good luck! Go feel around the other outlets in the house and see if you spot any other hot spots!!
posted
I used to be a commercial electrician and have done electrical work on my house and others. Maybe I can help.
First off, I'm glad you turned off the breaker. This shows common sense.
Second, if it's flaking off on one plug, then odds are that it's flaking on most of them. I recently replaced two light fixtures in my house that would not turn off anymore (they had broken pull chain switches). The wiring on both of the old fixtures was frayed and the insulation was falling off. Also, there were crappy splice jobs done with electrical tape. The whole electrical system in my house needs to be redone, especially since it isn't properly grounded.
Third, it will be expensive to replace the electrical wiring in your whole house, if that turns out to be needed. I don't think it's covered by insurance, but check. In Washington State, journeyman electricans make about $32 an hour. If they're working for a company, then labor costs go up higher. And this is not a short job, though the size of the house is a factor. Putting in electrical wiring when the house is being built is easy - putting it in afterwards is hard. Walls (the dry wall part, not the supports)will be ripped apart in some cases. Be prepared for sticker shock if you want an estimate.
Fourth, it's not an emergency, so save up for a few months first. Breakers and fuses were invented to prevent fires and electrocution. These protective devices will tide you over until you're in a better financial position. Don't take off any more plug covers live, and you won't get shocked. I assume this is the first time you've had a wiring problem? Don't let the contractor/electrical inspector scare you into anything rash or hasty. Get a few different quotes, too. This is big, like reshingling your roof. Some people put it off for years with no problems.
posted
Argh! Reread your first post and realized it wasn't shock, but heat! Hmmm, not good.
Bob mentioned a lot of good things. The circuit should not be getting that hot, no matter what is plugged into it. The breaker should trip if the device is pulling a huge amount of current. Heat comes from what are called "I squared R losses". If that particular plug, was just connected poorly, that could cause the scorching, though the breaker should have tripped...it might just be that the outlet plug is old, though. That would be lucky. Turn off the breaker and check the other plug outlets.
Aluminum has a problem because it doesn't handle heat well for long periods of time. Know how they melt aluminum in aluminum factories? They pass large amounts of current through it to heat it up! So yeah, aluminum is not good except for low voltage applications.
Edit: Just to add, I make the assumption that your house is wired according to code. This could be a bad assumption. If Bob is right and crappy electricians did the wiring for your house, then the wires could be the wrong gauge, there could be aluminum wiring, the connections could be poorly made. Sullying my fellow electricians' good names woould not be my first choice, though.
posted
JNSB...yeah, that heat thing triggered a memory about aluminum wiring and it's sort of a 1970's vintage thing, if I recall correctly.
I doubt Dag's house has aluminum wiring, I was just trying to recall what the issue was.
Question Dag -- was it still hot when you unplugged that doorbell thing? Or did you run and turn off the circuit right away so you don't have data on whether it was cooling off or not?
(note, don't run the experiment. I wouldn't turn that circuit breaker back on until I'd had someone check it out, personally).
quote:Bob mentioned a lot of good things. The circuit should not be getting that hot, no matter what is plugged into it. The breaker should trip if the device is pulling a huge amount of current. Heat comes from what are called "I squared R losses". If that particular plug, was just connected poorly, that could cause the scorching, though the breaker should have tripped...it might just be that the outlet plug is old, though. That would be lucky. Turn off the breaker and check the other plug outlets.
Wow, thanks for the great advice Bob and JNSB.
I talked to my dad, and he suggested the possibility it's just that plug, too.
I would replace an outlet, but some of the wire is damaged, and I want an electrician to pass on it. So I'll call one in just to replace the outlet and look at the other outlets on the circuit tomorrow. I'll probably take the cover plates off myself before he gets there, just to check it out in daylight.
I'm not going to take off the receptacle. I'd love the electrician to look at it and say, "Here's your problem - looks like they didn't tighten the screw enough."
I certainly won't agree to anything else than replacing the circuit unless I can see the physical damage he finds. The worst part is we may be putting the home on the market in a few weeks.
posted
Cuz aluminum melts at a far lower temperature than copper, and then burns furiously. Once there is a short in aluminum wire, it can burn like a fuse even afterthe short is disconnected by an automatic circuit breaker or manually or the current itself melts out the short.
Plus it corrodes via galvanic induction between the aluminum wire and the copper/brass/bronze or stainless steel terminator screws (for connecting to electrical outlets) and wires (for lights, ventilation fans, etc) far far more easily than copper, which is another potential cause for shorting. The aluminum end corrodes, the exposed wire drops against the outlet box, shorts, and "FIRE!"
quote:I doubt Dag's house has aluminum wiring, I was just trying to recall what the issue was.
We have aluminum on two circuits from when the basement was finished. This circuit is copper, though.
quote:Question Dag -- was it still hot when you unplugged that doorbell thing? Or did you run and turn off the circuit right away so you don't have data on whether it was cooling off or not?
The outlet was hot when I pulled off the doorknob, and stayed hot for at least 30 seconds. But I didn't check after that.
quote:Was it humming at all?
No humming. The scorch marks were on the copper tab where the blacks attach, and ran up one of the wirest about 2 inches. If the scorch marks indicate arcing endpoints, then there was lots of arcing from one of the screws where the black attaches to about 3 or 4 different points on the receptacle and wire.
The back of the doorbell (which is white plastic) was discolored to about a coffee color, ranging from black to coffee with 2 creams, and it was cnetered on the plug that goes into the black side of the receptacle.
posted
Well...keep us posted. I hope it's just this circuit.
Worst case, you could cook hot dogs on that wiring and turn it into a selling point when prospective buyers come through.
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We just covered mandatory disclosures in professional responsibility, too.
Although if it's a bad receptacle, I do not have to tell anyone about it. Bad circuit, I probably do.
Posts: 26071 | Registered: Oct 2003
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quote:Cuz aluminum melts at a far lower temperature than copper, and then burns furiously. Once there is a short in aluminum wire, it can burn like a fuse even after the short is disconnected by a circuit breaker or manually or the current itself melts out the short.
Um, although I agree with the lower melting point bit, I have a problem with your terminology. It "burns furiously"? We aren't talking about magnesium here. "...it can burn like a fuse" is confusing because you're obviously making the analogy to a fuse for a firecracker or a stick of dynamite, not an electrical fuse, which doesn't burn but melts the filament inside, causing an open in the circuit.
"...or the current itself melts out the short." What in the wide, wide world of sports are you talking about with this sentence? This blurb makes absolutely no sense. I think you might be trying to say that if aluminum wiring caused the short, then the heat resulting from the short (and the high current) would cause the wiring to melt, removing the connection that caused the short.
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I'll start by saying that it's irresponsible of me to make such a diagnosis long distance. Then I'm going to do it anyway.
You say the plug-in-chime-mechanism was hot when you pulled it out of the outlet? I'm assuming there's an actual bell tube and striker in this chime. It's not a digital with a piezo chime sound. Yes?
Chimes don't draw a lot of current, but the coil that drives the striker can heat up quite easily if the contact that triggers it sticks. It's actually quite common. And it's probably why the chime stopped working earlier. The coil in the chime was probably energized the whole time from when it stopped working, and just kept getting hotter.
If you had an actual short in your house wiring, the breaker should have tripped. But since it was the chime solenoid heating up, the heat remained local, and there wasn't enough draw on the circuit to heat up the breaker and trip it. It's as if the solenoid was acting as a heating element in a hair dryer - that doesn't trip the breaker either.
So the long and short is that I don't think there's anything wrong with your house wiring, provided the heat didn't damage the outlet. I'd pull the receptacle out of the box, and look for heat damage on the wiring itself. Then I'd put a new receptacle in, just because we know the receptacle got hot by having the chime plugged into it. And I'd get one of those ground fault testers Bob talked about to make sure the wiring is all put back together properly. They're good to have anyway. You can check all the other outlets in your house.
Anyway, all this is assuming I understood your description properly. So check to see if the heat seems like it all came from the plug-in unit. Once it's cool, open up the chime and look to see if the heat came from a solenoid coil inside. It should be pretty obvious.
Posts: 3735 | Registered: Mar 2002
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quote:You say the plug-in-chime-mechanism was hot when you pulled it out of the outlet? I'm assuming there's an actual bell tube and striker in this chime. It's not a digital with a piezo chime sound. Yes?
Sorry, it's digital, not mechanical. All solid state, no moving parts, with a cheesy speaker.
It's one plastic box about 3 inches square, with a plug sticking directly out of the back, so it lies flat against the wall.
The doorbell thing is slightly discolored. The receptacle is actually charred - insulation eaten up on about 2 inches of the black wire, and scoring on the receptacle itself. I think I'll take the doorbell apart to check, but all signs point to the wall, not the doorbell. Unfortunately.
posted
Yes. The downside is we'd have to move. The upside is I'd actually live in the same apartment as my wife. We're still up in the air waiting for things to clarify.
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I've been meaning to ask if this newly-married-living-most-of-the-week-apart deal is a lawyer thing.
The only other couple that I knew who did it (well, other than the one where the wife went back to Canada to visit her parents and then wasn't allowed to return to th US for three months) was also a law student and his wife. They've been sharing a house for some time now (in an entirely different state, having moved back to L.A.), but they did the only-weekends-and-the-occasional-midweek-day-together for a couple years, I think.
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quote: m, although I agree with the lower melting point bit, I have a problem with your terminology. It "burns furiously"? We aren't talking about magnesium here. "
Aluminum actually has such a high oxidation potential that it would spontaneously combust simply by exposure to air.
What keeps aluminum from burning is that as soon as the metal is exposed to air, the surface becomes covered with an impregnable layer of aluminum oxide, which prevents oxygen from reaching the metal inside.
When machinists turn aluminum on a lathe, it heats up a disproportional amount compared to the heat of friction that's normally associated with cutting, because the newly exposed metal is oxidizing, and giving off heat.
Also, once aluminum is melted, if it touches water, it will rip the oxygen off the water molecules and release hydrogen, which of course explodes as soon as it hits the air. The explosion then spatters molten aluminum all over everything.
They take water very seriously in aluminum plants.
Posts: 3735 | Registered: Mar 2002
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quote:Ah! Yes, that would be a big upside. [Smile]
I've been meaning to ask if this newly-married-living-most-of-the-week-apart deal is a lawyer thing.
The only other couple that I knew who did it (well, other than the one where the wife went back to Canada to visit her parents and then wasn't allowed to return to th US for three months) was also a law student and his wife. They've been sharing a house for some time now (in an entirely different state, having moved back to L.A.), but they did the only-weekends-and-the-occasional-midweek-day-together for a couple years, I think.
Maybe a law student thing. I can tell you with absolute certainty, it won't be a "lawyer-thing" in our family. Once I'm out of school, we'll be together.
It's hard. Very hard sometimes. But we're only 2 hours apart, so we can see each other every weekend, plus breaks. The strange thing will be if we have to sell the house soon, I'll be commuting up here from Charlottesville and staying with a friend 4 nights a week during the summer.
Glen, the doorbell is damaged only on the outside. I plugged it in another outlet and it still works. I quickly unplugged it in case it's the cause of the problem, but I'm thinking not.
quote: Maybe a law student thing. I can tell you with absolute certainty, it won't be a "lawyer-thing" in our family. Once I'm out of school, we'll be together.
*nod* Ok, that was true for them too, pretty much. He had a summer internship and she finished up her last semester at Yale, and then they actually got to live in the same place.
I know from talking to her that it is very difficult. I don't think I could do it.
posted
Yeah, I wouldn't use that bell again anyway, even if it's not the cause, it got heated up too.
I have some friends that got married in Louisiana, while she lived in Michigan and he lived in New York. They were married for almost a year, I think, before she moved to New York.
They weren't lawyers, but he was a ph.D engineer and she was finishing her doctorate at U-Mich.
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posted
Any chance you got a 1 year coverage included in the house purchase? I had one on my TX house and I kept it as coverage for my renters in case anything breaks. Great stuff, that insurance.
posted
Ok, well I said it was irresponsible to diagnose long distance. Sounds like you will have to do some work, at least from the the outlet that got hot to the previous junction box.
So, back you your original question:
quote: how does one find a good electrical inspector, and how much should it cost for them to a detailed inspection and report every problem like this in the house?
I would go to your town building inspector. You could just hire an electrician, but my experience with electricians (even licensed ones) is that they tend to just see "the job" rather than looking at the whole system. My town put me in touch with an underwriter - essentially he sells insurance, but his job is to look at the system to see that it's safe. So he looks at the system as a whole, rather than just looking at the outlet.
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I thought it said Ethical Help-Dangerous situation. So I was a bit surprised to hear about a doorbell.
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quote:Also, once aluminum is melted, if it touches water, it will rip the oxygen off the water molecules and release hydrogen, which of course explodes as soon as it hits the air. The explosion then spatters molten aluminum all over everything.
This only happens with MOLTEN alumnium. Your average room temperature aluminum has to be dropped into acid to react and form hydrogen. And the only reason they hydrogen would be combusting is if there was a spark or it was hot enough to be above the ignition temperature.
ALUMINUM does NOT spontaneously combust in Air, unless it is heated and vaporized into gaseous form, even if you scrape the protective coating off. Otherwise we'd be having kids go up in flames while drinking from soda cans. I quote from the CRC Handbook.
quote: Pure alumnium, a silvery, white metal, possesses many desireable charactiristics. It is light, nontoxic, has a pleasing appearance, can easily be formed, machined or cast, has a high thermal conuctivity and has excellent corrosion resistance.
Aluminum plants have far different conditions from your average aluminum so this is a giant false alarm. You've got to get over 600 degrees F before there is any cause for concern.
posted
I guess there are deep ethical issues that also need to be explored. Is it really ok to fit something that is broken? Maybe it is broken for a reason you do not understand? Maybe if you fix it you will be ruining some master plan that you just can't see?
I see your quandry. Good luck with these tough questions.
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posted
I'm not sure I want to know how long it's been going on and what would have happened had I not tried to fix the doorbell.
The situation was dangerous because it could lead to a fire, but there was no immediate danger of shock or anything. The burn mark was gone by this morning.
All in all, I'm starting to think I'm lucky to have noticed it. It would have been luckier for it not to happen, of course, but I'll take this over a row fire any day.
posted
OK, it turns out it was one of the aluminum circuits. This was the only bad outlet. They showed me how to test with a ground fault tester, so I'm going to buy one of those.
They also inspected the panel and made sure all the connections were tight. No problems there.
Thanks for all the advice, everyone. I'll keep an eye on things, but it looks like it's not too bad.
quote: ALUMINUM does NOT spontaneously combust in Air, unless it is heated and vaporized into gaseous form, even if you scrape the protective coating off.
Glenn:
quote: What keeps aluminum from burning is that as soon as the metal is exposed to air, the surface becomes covered with an impregnable layer of aluminum oxide, which prevents oxygen from reaching the metal inside.
Already covered.
quote: Aluminum plants have far different conditions from your average aluminum so this is a giant false alarm. You've got to get over 600 degrees F before there is any cause for concern.
Actually you have to get over 1400 Degrees F. But how hot is an electric spark? An aluminum wire will burn very nicely thank you if electricity is arcing from it. And once lit, it can be difficult to extinguish, because it can pull oxygen from unexpected sources.
[ March 11, 2005, 04:25 PM: Message edited by: Glenn Arnold ]
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posted
It isn't just the oxide Glenn, yes the oxide is a nice protective covering, but even if the stuff was completely exposed it wouldn't "burn".
Though I guess you could argue that forming the oxide on the surface is a oxidation-reduction reaction and burning is oxidation, so therefore it is burning but that's a stretch. Burn in the classical sense is an exothermic reaction with flame and you don't get that. Even doing vapor deposition experiments.
The delta G (Gibs Free Energy) of elemental aluminum is ZERO. Which means that it has no inclination to change state at all. As is your Delta H or enthalpy. Gaseous aluminum has a Delta H of 330 KJ/mol which is more of a concern. You have to have something going into the system in order to convert ground state Aluminum into Gaseous Aluminum. Electricity may be sufficient to do it. Part of the reason why Al will burn with electricity flowing through it is because energy is being added to it from a source. Remove that, and the burn will likely stop pretty quickly.
I agree Aluminum isn't as good of a wiring as Copper. But I still stand by my statment that exposed elemental aluminum (without electricity running through it) will *not* burst into flames oxide protection or no.
AJ (I will revise this statment to say in metal ingots Aluminum is inert. Aluminum powder is explosive because of the high surface area to volume ratio increases the rate of the natural oxidation process we've already discussed, but even it generally needs to be in the presence of water vapor as well as oxygen to facilitate the electron transport. This can happen in a humid atmopsphere. MANY benign substances can become risky when ground into fine powder, which is why grain silos explode.)
I see your point. You don't like the word "burn" because you're looking for a conventional flame. Hence the need for Al to be in a gaseous state. (Steel usually isn't in a gaseous state when it's cut, but it's still referred to as burning, it just doesn't have a flame)
The surface of aluminum does oxidize when exposed to air, and that oxidation is exothermic. I agree that this oxidation does not produce a flame, nor does it continue. The question is: Why?
Other than the impervious oxide layer argument, I know of no reason why oxygen shouldn't diffuse into a mass of aluminum metal and turn it to alumina, releasing a lot of heat as it does. The Gibbs free energy is related to the state of order of the material. In order to sustain a reaction, the oxide layer needs to be disturbed. That's why I gave the description of the heat released as aluminum is turned on a lathe- as the lathe exposes more metal, the newly exposed metal oxidizes, and gives off heat.
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posted
Maybe you've got two hot phases going to that outlet, rather than one hot and one common. Cool...240 volts to a 120-volt device.
Posts: 2655 | Registered: Feb 2004
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posted
No wait, by receiver you mean the chime part, and that's what went bad? It's probably shorted out inside, maybe not a dead short that would trip the breaker, but low enough resistance to get hot.
Posts: 2655 | Registered: Feb 2004
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quote:JNSB you wouldn't know any good electricians in Illinois would you? Our house is going to need a complete rewiring itself in the near future.
Sorry, AJ. Though I do know some nuclear technicians there if you're having trouble with your reactor.
Posts: 1423 | Registered: Sep 2003
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quote:No wait, by receiver you mean the chime part, and that's what went bad? It's probably shorted out inside, maybe not a dead short that would trip the breaker, but low enough resistance to get hot.
It was the chime (cheap speaker, not mechanical chime) that was plugged in, but it was definitely the outlet that went bad. Electrician showed me where the wire had loosened.
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