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My 10 year old son has asthma and we use an air cleaner in his room, along with a whole house UV system and another air cleaner downstairs.
Last night, he was up in his room doing some browsing on his computer. He heard a loud pop and then smelled something burning. I went upstairs immediately and unplugged the unit. Took it down to the garage and started to disassemble and investigate. A resistor fried on the circuit board.
I submitted a case to the CPSC this morning along with pictures. Was wondering if those more familiar with hardware would comment if this would have caught fire. I've never experienced something like this.
I can't say if that would have caught fire or not. Circuit boards are manufactured with flame resistant/retardant materials as a safety measure. Put enough current through them and generate enough heat and they will cook, putting off smoke and smelling really bad. If the circuit failure stopped the current flow, then probably no chance for fire, but if there was a short and excessive current flow then I don't know.
Most always, once you let the Magic Smoke escape from any Consumer electronic item, it just dies. Almost nil possibility of actual flames. They do smell funky though..........
All electrical and electronic components are manufactured with various amounts of smoke built into them. When they split in two and the smoke comes out they aren't any good anymore. As Kenneth and Randy stated, usually smoke and no fire because the circuit opens and cools down fast.
My only worry would have been all of the fuzzies on that think catching fire. The components themselves as stated are designed not to catch fire even if they do start smoking.
Is this a crossover of some sort? What is it in?
And the burned resistor is usually due to another component failing and causing a short. My guess would be that transistor failed and took out the resistor.
It looks like a power supply, essentially an AC to DC converter (full wave rectifier based on the four diodes and big capacitors). It's late and I'm not in full failure analysis mode - I do this for a living Mon-Fri so this is my day off.
There is nothing unique about your experience. These sorts of failures happen. Usually the result is as you experienced; device failure without anything more. However more can happen if there is a nearby fuel. I remember one case where a power strip/surge suppressor lying on a carpet failed sufficiently to ignite the carpet and burn down the entire home as it was unoccupied at the time. I suppose that it's prudent to keep the devices and the fuel separated and/or turn things "off" when unattended. If you'd like to hear more horror stories about this contact your local fire department. They usually have people who investigate such things.
I'm late to this, but I will agree with Fun71, even though, unlike him, I do not analyse electronics fir a living.
It looks as though more than one component failed here, probably one failure leading to another, and as though the ultimate effect was the same as a fuse blowing - disconnection of the current from the circuit.
If you want to check for sure, connect the unit to 110 through an ammeter, and/or connect it in a safe place (like in a cast iron bathtub, or outside on concrete), and check over several hours to see whether it gets hot.
Most always, once you let the Magic Smoke escape from any Consumer electronic item, it just dies. Almost nil possibility of actual flames. They do smell funky though..........
It smelled real similar to when I had a relay burn up on my first car, a 1984 Buick Skylark snow machine.
The chances of the board causing a fire is not as common as other issues which lead to the failure of the board in the first place. I've been on the FDNY for 19 years and an electrician for 30. It's usually not the appliance that causes the fires but how they are being fed. Extension cords are the #1 culprit. When I first got to the fire house one of the senior members told me we have more fires in the summer than in the winter in this area. After a few seasons I started seeing why. Very old houses, bad electrical work on some, but most of the time extension cords were overheated. Any heavy appliance should be plugged into a dedicated line. In NYC the electrical code requires a dedicated 20 amp AC receptacle within every room. Not sure if they wrote it in NEC 2017, but it should be nation wide. Most people don't know what a UL (Underwriters Laboratories) tag is so they usually don't look for it when they purchase something electrical. They buy cords from dollar stores and insure to much confidence in them. Of late the case is the SA or UL labels being counterfeited. So the only real safe bet is a dedicated line close to the appliance.
Looking at that board I'd guess that appliance is not drawing any high current so a regular receptacle, without an extension cord should be fine, but always check the name tag rating. By code (electricians law) a tag needs to be present on every appliance, motor, ect... As to why these appliance boards go, my opinion would be sales. If the company is not selling they are not turning a profit. The other reason could be a voltage drop. The smaller the wire the more likely this is to happen. Wire is nothing more than a resistor. Think of the wire in an incandescent bulb. The element heats up and the heat creates a glow. The reason it doesn't burn is the lack of oxygen. Again, within NYC #14 gauge wire is not allowed. It's been banned since about the 60's. I make a practice of never using it even out of the city(I use #12), but it is the most common wire used in homes. Voltage drop can happen in a number of ways but usually because a branch circuit is to long or there are a number of things drawing from the circuit. easiest way to remedy this is up the size of the wire during installation.
Then why doesn't the circuit breaker trip?
Circuit breakers trip in two ways, either a short circuit (which the breaker instantly opens at 10,000 trip amps on most house hold types) or from drawing to much current (amps). It heats an element and pop. If it doesn't get to either of those two it will not open. Sometimes other things indirectly become the breaker like extension cords or in your case the resistor in the appliance. That resistor is the secondary safety so it functioned as designed. With a tester the receptacle would show 110 volts +/- 10% which is fine, but under a load it could drop below the acceptable 10%. There is also the chance of the power company lowering the voltage output to conserve, like in large cities during heat waves, which further adds to the calculation.
Believe it or not this is the short answer. Not sure if this will confuse you more, but I hope it helps.
That did help, zeeke. Any additional knowledge on how it works is a good thing. CPSC report said they will let the manufacturer know. Question is, will they respond???
I had the same type of situation a few years ago with my refrigerator. To me and my wife it smelled like an electrical fire within the walls of my 110 year old home. As a precaution we called the FD. They unplugged all the appliances in the kitchen but couldn't find anything. They then brought in giant fans to get rid of smell to check if it would come back. No luck. 10 minutes after they left I plugged the refrigerator, heard a pop saw a small flame and sure enough it was a resistor that went out. Repair guy says very common, not usually dangerous but smells like a house ready to go up in flames.
The pop sound and paper wadding would point toward a capacitor not a resistor. You probably probably smelled the PCBs evaporating. Resistors are usually ceramic, and simply burn open on the inside like fuse. The capacitors function would have determined the fire likelihood. If it was buffering a circuit that would overload without it, your fire chances greatly increased. You did the right thing by unplugging it. The FD might have been a bit premature. I had a Cuisinart coffee maker go haywire on me 2 weeks ago. It got really hot, and smelled of burning plastic. I just unplugged and trashed it.
ah yes, capacitor you are correct. We could have simply replaced the capacitor but my wife was uncomfortable with that. So instead of a $50 part exchange we spent a heck of a lot more on a whole new fridge.
Don't get me wrong FD were there a while, maybe an hour and a half checking everything around the house. I went back and told them what I had found. They were young guys so maybe haven't experienced this before. I would have thought they would have been able to zereo in on that as the issue as it is not uncommon.
September 25th, 2016, 10:03 AM
