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Old 01-18-2013, 08:15 AM   #61
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SCARY oven fire! Why did it burn?


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Originally Posted by blott0 View Post
Hurray, I am the first person in 2013 to have this happen. What a bizarre experience. The element sure reminded me of a sparkler, until I unplugged the stove.

The really crazy thing about my situation is that I just had a final inspection done today on some electrical work I did. Nothing even close to the oven. I have no idea what would've happened if no one was at home, but if it turned into a really bad situation, you know I would've gotten blamed.
No, you are just the first to resurect this post. I changed out two of them already this year. First one was on Jan 4th and the second one was about a week ago. Similar problems, element burned and made a mess. New elements and they are good to go.

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Old 01-20-2013, 10:10 AM   #62
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SCARY oven fire! Why did it burn?


This failure spurs like an arc fault. The element churned out, but July completely. An electrical connection was still being made across the gap, creating a spark that got much hotter then the element tyically would. The arc, not really a fire per se continued until power was cut. So why didnt it quit when the switch was cut? Well, when you said that food cooks unevenly, I bet the thermostat in your oven is stuck on. The mode switch was maybe working, but when the failure occurred, the switch may have burned together in the higher current. I would replace the element AND replace the thermostat and any switches too.
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Old 01-20-2013, 06:51 PM   #63
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SCARY oven fire! Why did it burn?


I'm pretty sure this is not a true fire. It rather was an electric arc. Notice that when you unplugged the power, it immediately went out. Here's how I think it happened, and let me start from the beginning.

A stove has 4 prongs on the plug. These are Hot (0deg phase), Neutral, Hot (180deg phase), and Ground. You see the power transformer on the utility pole has 3 outputs, Hot-0deg, Neutral, and Hot-180deg. A grounding stake is driven into the ground near the pole and a cable goes from the neutral connector to the grounding stake. Also 3 lines run from the transformer to your house. At at your house there is another grounding stake or a metal water pipe is used, and a wire goes from that to all the ground contacts in your outlets. The neutral wire from the goes from the wire inlet in your house to all your outlets. The Hot-0deg wire goes from your wire inlet in your house to a breaker/fuse box, and hot wires for all the outlets in the house go out from there. The Hot-180deg wire goes to the breaker/fuse box and from there you have hot-180deg wires that go to just the 240volt outlets (such as your stove). At a 240v outlet, Neutral to Ground should be 0 volts. Hot (either one) to Neutral (or Ground) should be 120 volts, and Hot-0deg to Hot-180deg should be 240v. The heating element in your oven is Hot to Hot so it runs on 240v. A heating element consists of a resistive wire (nichrome or tungsten). A tube of ceramic insulation surrounds the resistive wire. A steel tube surrounds the ceramic insulator. Each end of the resistive wire should be connected to a Hot wire. The steel sheath should be connected to the metal chassis of the stove, which itself should be connected to the Ground wire.

As the heating element ages, cracks can develop in the resistive wire, thinning it at spots these spots will look brighter than the rest of the heating element. The current flowing through thinner spots will heat them more, eventually exceeding the melting point of the wire, causing it to "burn out". At this moment though an arc can strike across the small gap. the arc will be extremely hot and consume more power than the rest of the element. This will make this spot glow quite bright, and the rest of the heating element will get significantly dimmer than it was before. If you cut the power on your oven's switch at this point the arc will be extinguished. If you are unaware it is arcing, and it goes on for a long enough time, the heat from the arc can crack the ceramic insulation. Then the arc also will rise like a "Jacob's ladder" arc until it touches the steel sheath at a point that the ceramic insulation was compromised by cracking. At this point you will have 2 arcs, one from Hot-0deg to Ground and one from Hot-180deg to Ground. The heat from the arc will now melt the steel sheath. Since it isn't shielded by argon gas (like in arc welding or plasma cutting) though, the steel sheath will oxidize from the heat of the arc and won't be conductive (iron oxide rust is an insulator) so will fall away and not fill the gap where the arc is (which could stop the arc if it was conductive and did fill the gap). As a result, the arc on each side of the break in the heating element will keep arcing from Hot to Ground, slowly destroying the heating element (looking sort of like a candle wick slowly burning downward, but a LOT brighter, and it isn't actually a burning flame like a candle, but rather an electric arc). The more it goes on the less resistive wire there will be, so the more current will flow, and the brighter and hotter the arc will be. If allowed to "plasma cut" its way all the way back to the contacts where the heating element connects to the socket, it will then have NO resistance from the resistive wire (which previously was acting like a ballast for a mercury arc lamp). With no current limiting it will basically be a short circuit and your arc will turn into an "arc flash". However your circuit breaker will respond to an excess of current way before then (like 30A or whatever the oven circuit's circuit breaker in your house's breaker box is set for) and trip, stopping the arc.

However the moment you notice the arc you should turn off the power by turning off the knob on your stove. However if the arc is already proceeding to melt back the heating element on both sides, this may or may not work completely. If the switch only cuts off the Hot-0deg line, then the arc will still be going from Hot to Ground on one side of the element but will be stopped from the other side. This will require you to unplug the stove from the outlet, or manually switch off the oven's breaker in your house's breaker box if your oven is hardwired or the outlet is inaccessible. If the oven's setting knob switch cuts off both Hot lines, then turning the knob to "off" is all you will need to do to stop the arc on both sides of the element.

You should NOT throw anything onto the burner. It is not on fire. It is an electric arc. And whatever you do, NEVER throw flour. Flour burns, and when thrown it floats in the air, which if then it contacts the electric arc it can cause a mini "grain silo explosion" in your oven. VERY DANGEROUS. Also do not stare at a strong electric arc like the one from an oven element failure. It may look no brighter than a lighbulb glowing, but an electric arc in the air emits UV rays (air is mostly nitrogen, and the emission spectrum of nitrogen gas has a few strong lines in the in the UV region), and UV rays are dangerous to the eyes, the same reason you aren't supposed to look at a welding arc without proper eye protection.

You shouldn't necessarily need to call the fire department though, as it's not a fire, and unless there is evidence that the arc started a fire, there is no reason to call. If something in the stove is burning though, and ESPECIALLY if there is an electrical failure that causes the wall to feel hot somewhere or the electrical breaker box feels hot (possible indication of a fire in the wall or a short that might lead to a fire in the wall), then it's time to call the fire department. Only the fire department can properly handle a building on fire (flames inside the wall or other place in a building that's not accessible to the ordinary person with a fire extinguisher). If there's a fire in the oven though, a proper ABC fire extinguisher will put it out, and with there being no where else the fire could POSSIBLY have gone (being contained inside the all-metal oven), there's no possibility it spread to be inside a wall or something. So a simple fire put out with an extinguisher isn't in and of itself a reason to dial 911. But if there's reason to believe the fire spread (possibly inside a wall), then you ABSOLUTELY SHOULD call 911 IMMEDIATELY.

Last edited by Ben321; 01-20-2013 at 06:57 PM.
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Old 01-20-2013, 07:55 PM   #64
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SCARY oven fire! Why did it burn?


I think this diagram I drew might help explain it better.

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Old 11-11-2013, 02:01 PM   #65
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SCARY oven fire! Why did it burn?


We had a similar experience to everyone else with the bottom element of our oven catching on fire and looking like a sparkler as it burned its way around. We tried water and a dry fire extinguisher but only turning off the breaker to the oven stopped it from burning.

After removing some screws I was able to remove what remained of the element, leaving the two clips that attach to the element sticking out of the back of the oven about an inch or so apart. They did not seem to be damaged. We cleaned the oven cavity completely and because it is a double wall oven (GE Profile Performance Model # JT950S0Y1SS) I figured we could turn the breaker back on and at least use the bottom oven in the mean time. However when I did, the breaker immediately switched back to the middle position suggesting an electrical issue and my wife reported seeing some sort of flash/sparks inside the oven upstairs in the kitchen.

Do I need to install the replacement element in the upper oven for the rest of the oven to work or do I need to do something to the two clips to prevent arcing between then? Is there some sort of fuse or other component inside the oven itself that might have blown during the original fire and needs to be replaced?

Am not keen to replace the whole double oven if it can be easily repaired but don't want to spend $60 on a replacement element if the whole thing is a write-off.
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Old 11-12-2013, 08:06 AM   #66
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SCARY oven fire! Why did it burn?


I seriously doubt you have arcing between the two connectors if they're an inch apart. 120volts... even 240volts can't make a one inch jump. Notwithstanding, if the oven switch is off then one of those connectors is off and open completely (unless of course the contacts inside the switch/relay are welded shut)

Clearly you do still have a short there somewhere though (I would suspect somewhere on the non switched leg) and that needs to be cleared up before you can run again.
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Old 11-12-2013, 03:27 PM   #67
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SCARY oven fire! Why did it burn?


When I looked closer one of the two connections was unchanged but the other had fused to the side of the opening where the element connections come out of the back. Could it have arced onto the metal lining of the oven? It came loose without much effort and looked to be still in good shape. Our replacement element has arrived at our local store so may pick it up and give it a try tonight.
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Old 11-13-2013, 09:45 AM   #68
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SCARY oven fire! Why did it burn?


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When I looked closer one of the two connections was unchanged but the other had fused to the side of the opening where the element connections come out of the back. Could it have arced onto the metal lining of the oven? It came loose without much effort and looked to be still in good shape. Our replacement element has arrived at our local store so may pick it up and give it a try tonight.
That would be a short and the reason your breaker is tripping. Obviously the issue needs addressing before you install the new element. Buy a meter if you don't have one and test it out before firing it up.
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Old 12-08-2013, 05:14 AM   #69
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SCARY oven fire! Why did it burn?


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Originally Posted by Ben321 View Post
I'm pretty sure this is not a true fire. It rather was an electric arc. Notice that when you unplugged the power, it immediately went out. Here's how I think it happened, and let me start from the beginning.

A stove has 4 prongs on the plug. These are Hot (0deg phase), Neutral, Hot (180deg phase), and Ground. You see the power transformer on the utility pole has 3 outputs, Hot-0deg, Neutral, and Hot-180deg. A grounding stake is driven into the ground near the pole and a cable goes from the neutral connector to the grounding stake. Also 3 lines run from the transformer to your house. At at your house there is another grounding stake or a metal water pipe is used, and a wire goes from that to all the ground contacts in your outlets. The neutral wire from the goes from the wire inlet in your house to all your outlets. The Hot-0deg wire goes from your wire inlet in your house to a breaker/fuse box, and hot wires for all the outlets in the house go out from there. The Hot-180deg wire goes to the breaker/fuse box and from there you have hot-180deg wires that go to just the 240volt outlets (such as your stove). At a 240v outlet, Neutral to Ground should be 0 volts. Hot (either one) to Neutral (or Ground) should be 120 volts, and Hot-0deg to Hot-180deg should be 240v. The heating element in your oven is Hot to Hot so it runs on 240v. A heating element consists of a resistive wire (nichrome or tungsten). A tube of ceramic insulation surrounds the resistive wire. A steel tube surrounds the ceramic insulator. Each end of the resistive wire should be connected to a Hot wire. The steel sheath should be connected to the metal chassis of the stove, which itself should be connected to the Ground wire.

As the heating element ages, cracks can develop in the resistive wire, thinning it at spots these spots will look brighter than the rest of the heating element. The current flowing through thinner spots will heat them more, eventually exceeding the melting point of the wire, causing it to "burn out". At this moment though an arc can strike across the small gap. the arc will be extremely hot and consume more power than the rest of the element. This will make this spot glow quite bright, and the rest of the heating element will get significantly dimmer than it was before. If you cut the power on your oven's switch at this point the arc will be extinguished. If you are unaware it is arcing, and it goes on for a long enough time, the heat from the arc can crack the ceramic insulation. Then the arc also will rise like a "Jacob's ladder" arc until it touches the steel sheath at a point that the ceramic insulation was compromised by cracking. At this point you will have 2 arcs, one from Hot-0deg to Ground and one from Hot-180deg to Ground. The heat from the arc will now melt the steel sheath. Since it isn't shielded by argon gas (like in arc welding or plasma cutting) though, the steel sheath will oxidize from the heat of the arc and won't be conductive (iron oxide rust is an insulator) so will fall away and not fill the gap where the arc is (which could stop the arc if it was conductive and did fill the gap). As a result, the arc on each side of the break in the heating element will keep arcing from Hot to Ground, slowly destroying the heating element (looking sort of like a candle wick slowly burning downward, but a LOT brighter, and it isn't actually a burning flame like a candle, but rather an electric arc). The more it goes on the less resistive wire there will be, so the more current will flow, and the brighter and hotter the arc will be. If allowed to "plasma cut" its way all the way back to the contacts where the heating element connects to the socket, it will then have NO resistance from the resistive wire (which previously was acting like a ballast for a mercury arc lamp). With no current limiting it will basically be a short circuit and your arc will turn into an "arc flash". However your circuit breaker will respond to an excess of current way before then (like 30A or whatever the oven circuit's circuit breaker in your house's breaker box is set for) and trip, stopping the arc.

However the moment you notice the arc you should turn off the power by turning off the knob on your stove. However if the arc is already proceeding to melt back the heating element on both sides, this may or may not work completely. If the switch only cuts off the Hot-0deg line, then the arc will still be going from Hot to Ground on one side of the element but will be stopped from the other side. This will require you to unplug the stove from the outlet, or manually switch off the oven's breaker in your house's breaker box if your oven is hardwired or the outlet is inaccessible. If the oven's setting knob switch cuts off both Hot lines, then turning the knob to "off" is all you will need to do to stop the arc on both sides of the element.

You should NOT throw anything onto the burner. It is not on fire. It is an electric arc. And whatever you do, NEVER throw flour. Flour burns, and when thrown it floats in the air, which if then it contacts the electric arc it can cause a mini "grain silo explosion" in your oven. VERY DANGEROUS. Also do not stare at a strong electric arc like the one from an oven element failure. It may look no brighter than a lighbulb glowing, but an electric arc in the air emits UV rays (air is mostly nitrogen, and the emission spectrum of nitrogen gas has a few strong lines in the in the UV region), and UV rays are dangerous to the eyes, the same reason you aren't supposed to look at a welding arc without proper eye protection.

You shouldn't necessarily need to call the fire department though, as it's not a fire, and unless there is evidence that the arc started a fire, there is no reason to call. If something in the stove is burning though, and ESPECIALLY if there is an electrical failure that causes the wall to feel hot somewhere or the electrical breaker box feels hot (possible indication of a fire in the wall or a short that might lead to a fire in the wall), then it's time to call the fire department. Only the fire department can properly handle a building on fire (flames inside the wall or other place in a building that's not accessible to the ordinary person with a fire extinguisher). If there's a fire in the oven though, a proper ABC fire extinguisher will put it out, and with there being no where else the fire could POSSIBLY have gone (being contained inside the all-metal oven), there's no possibility it spread to be inside a wall or something. So a simple fire put out with an extinguisher isn't in and of itself a reason to dial 911. But if there's reason to believe the fire spread (possibly inside a wall), then you ABSOLUTELY SHOULD call 911 IMMEDIATELY.


I too was frustrated at the assumptions and incorrect ideas stated by posters on why this was happening, so I want to say: the above answer is accurate and true, (while including the small electronics engineering friendly details) and Ben321 saved me the effort of typing something similar.

Basically, the problem here in real easy to understand terms is:

The element got weak (for whatever reason, doesn't matter), and it started to spark (arc) inside, it heated up real hot, it broke (separated into two), and then started an electrical short to itself (using one half of the element, as you likely observed yourself), getting hotter as the element got "smaller" from being burned. It likely didn't trip the breaker (yet) because when the electricity goes through the element, the element restricts how much electricity can flow through. As the element gets smaller from being "Burned", it doesn't restrict as much, and at that point the breaker may (hopefully) trip.

If you're able to, you can likely fix this yourself really quick by turning off the oven, or if that doesn't work, unplug the oven. If that is not an option, turn off the correct breaker. If that is not an option, turn off the main breaker.

At this point, the spark/fire will likely be out and the element will be getting less red. You will have to let the oven cool for a good while before dealing with how you're going to replace the element. Make sure to have the power off while replacing it, and keep power off to the oven until the element is replaced, as it could start arcing again (depending how your oven is designed).

This is not a complete step by step, and doesn't cover safety and all that, it's just an overview really.

It is possible you may have several oven elements do this in your lifetime, especially if your particular stove does not "fully" turn off power to "both" ends of the element (this is not something most of you can determine on your own without electrical meters, etc).

Hope this quick summary helps someone.
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Old 12-08-2013, 09:07 AM   #70
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SCARY oven fire! Why did it burn?


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as the element gets smaller from being "Burned", it doesn't restrict as much, and at that point the breaker may (hopefully) trip.
As conductive material gets destroyed the resistance will increase, not decrease.
Quote:
If you're able to, you can likely fix this yourself really quick by turning off the oven, or if that doesn't work, unplug the oven. If that is not an option, turn off the correct breaker. If that is not an option, turn off the main breaker.
Yes, turn it off immediately, then turn off the breaker. It will be one of the large double pole ones. If the panel isn't marked it should be done. It's better to trip off all of them and figure it out later if in doubt. Unplugging a stove will take the longest in a typical setup.

If an element is looking funky, replace it before it fails.
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Old 12-08-2013, 10:49 PM   #71
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SCARY oven fire! Why did it burn?


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If you're able to, you can likely fix this yourself really quick by turning off the oven.
.
Simply turning off the oven most likely WON'T cure the problem.

As you have stated(in slightly different words):
An oven element uses not one but two 120 volt legs to make the necessary 240 volts to power the element. But the off-on switch on most ovens only controls ONE of the 120 volt legs. This means there is still 120 volts at the element and because the casing of the element is grounded the chain burning reaction will continue until the entire element has burnt itself up, or the other leg is disconnected through unplugging the stove or flipping the breaker.

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