Basic advice for an oven bake element house fire (GE JBP24B0B4WH)

Hi Red Green,

He's entitled to his opinion. Everyone is. At least he also provided additional help in his post. The guys who just complain and don't provide ANY discernable value are the ones who are the hardest to respond to.

I mean, there should be value in every post ..... but it's hard to find that in some people's responses.

Anyway, the good news is the GE Spectra oven is clean after the garden hosing, it's mostly dried out, and one of the last problems I'm researching is what happens when ABC powder stuck inside the oven glass heats up emitting copius nitrogen gasses.

Thanks, Donna

Reply to
Donna Ohl
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Hi NoSpam,

Actually, I called the numbers that Crumb Bum gave us and GE, after about a half hour of bouncing around, wrote up a work ticket for me and kindly shipped the element at an 80% discount and they even dropped the shipping.

The only thing I had to pay full on was the tax (which for California is over 8%).

The new genuine GE element should arrive soon from UPS at a total cost of about $38 off my credit card.

So, even though Crumb Bum must have been under the weather that day, he helped me get the parts for a great price (I think).

BTW, the GE parts representative kept touting "genuine GE" but I wonder if all the parts are the same. I'll bet they are.

Anyone know which brand of oven parts is any better or worse than the others?

Donna

Reply to
Donna Ohl

Hi dpb,

Oh my! Are you saying the neutral is connected to the oven chassis?!

If so, then the neutral is not grounded at the electrical box but at some point perhaps hundreds of yards away from the house. That means, under off-balance conditions, the neutral can have a voltage pressure to ground, which means the oven chassis can, essentially, be electrically hot under "normal" conditions.

Can that possibly be right that the chassis is connected to the neutral which carries current?

Donna

Reply to
Donna Ohl

Jeez, chill, lady. Read what I wrote again.

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Reply to
dpb

The element is normally fed from 240 V. The heat is generated in an inner resistance component which is completely insulated (electrically) from the element's outer metal jacket, which is grounded by touching other metal parts of the oven (and possibly by an explicit ground wire).

In normal operation, the jacket of the element is always grounded, so there's no voltage on it. *But* if the element breaks or the insulation between the core and jacket fails, you can get current flow between the centre core and the jacket - there is 120 V from *each* side of a broken core and the jacket. You could get an arc from the core to the jacket even with a gap in the element - the 240 V path through the element is broken, but there's still 120V at high current available.

The switch *should* disconnect power from both sides of the element and stop any arc when set to off. But if one side of the switch is shorted closed, it would still work normally while the element is intact (the other side would still switch the element on and off). So you may have a problem in the switch.

An arc is not a dead short, and the current is limited both by the voltage drop across the arc and any remaining element resistance still in series. So there may not have been enough current to blow a fuse. Fuses protect wiring from overloads - they aren't designed to prevent fires.

As for whether you should replace the oven: The powder from an ABC fire extinguisher is corrosive, so you need to clean it up very thoroughly. As long as it was confined to the interior of the oven, it may have been possible to clean it up by sweeping and wiping. But the oven is definitely *not* designed to have a garden hose sprayed into it! Unless the interior was already really clean, spraying water into the oven probably carried the corrosive powder into places you can no longer reach to clean.

Dave

Reply to
Dave Martindale

See my other reply. An arc by definition occurs across a gap which would be an open circuit if the arc was not there. And even when there is a gap in the element, an energized element has 120 V between the resistor core and the jacket (in North America).

You do need to interrupt the current to the electrical fire first. If turning the oven switch to off did not do this, turning off the oven breaker in the house electrical panel would have.

Sure it does. A switch, particularly if it's actually a thermostat, needs to open only one side of the 240 V line to do its job in normal operation. To stop an arc to ground, you need to open both sides of the supply to the element. There should have been some switch that does that, but maybe you didn't use it, or maybe it's defective. (Our oven has a separate Off/Bake/Broil/Clean mode switch, which is not part of the oven thermostat).

Because the wiring wasn't overloaded to the point of endangering the wiring. You can have a pretty dramatic arc without drawing enough current to blow a fuse. Why do you expect the fuse to blow?

Dave

Reply to
Dave Martindale

No, it's not. It is a big resistor surrounded by a metal jacket. The resistor is supposed to be insulated from the jacket by a high-temperature mineral insulation. In operation, the resistor is connected to 240 VAC, while the jacket is connected to ground. In North America, ground is also connected to the supply transformer centre tap, so there is *also* 120 V from the ends of the element to the element's metal jacket.

You seem to have a lot of misconceptions about things you think you understand. If the element is physically open with a large gap, the normal current path through the resistor is no longer available. But both sides of the remaining element are still "hot" with respect to ground, and you can get an arc from element interior to its jacket. Electrical arcs do not require anything flammable to "burn"; the electricity provides the energy. Arcs have resistance and limit the current, so there may not be enough current to blow a fuse (plus there's probably part of the element still in the circuit). Finally, the switch should have opened both sides of the 240 V circuit, but maybe it did not.

It makes perfect sense when you consider the actual situation with the grounded jacket around the element.

Dave

Reply to
Dave Martindale

On a modern oven with a 4-wire cord set, neutral and ground are separate. The oven frame is connected to ground, while neutral is connected only to the 120 V loads inside the oven (clock, lights, 120 V outlet if any).

Older ovens with a 3-wire connection use neutral as ground. This does pose some shock risk if the neutral ever becomes disconnected.

No, neutral and ground ought to be connected to each other (and to a ground rod) at your house electrical panel, not hundreds of yards away.

Under some conditions (old installation), yes. But since most of the loads in an oven are 240 V, there isn't much connected to neutral. And since the neutral for the stove isn't shared with any other circuit in the house, and neutral is connected to ground back at the panel, there should be very very little voltage on the stove neutral - unless it gets disconnected accidentally.

Dave

Reply to
Dave Martindale

This is correct... it is a dangerous failure mode...

Many appliances switch only one side of the 220 line so a fault to ground in the element can't be shut off with the switch...

You have to pull the plug or the breaker.

Yep it's a dangerous failure mode.

Mark

Reply to
Mark

This is correct... it is a dangerous failure mode...

Many appliances switch only one side of the 220 line so a fault to ground in the element can't be shut off with the switch...

You have to pull the plug or the breaker.

Yep it's a dangerous failure mode.

Mark

Reply to
Mark

My dear Donna,

Since you were nice to me, I'll be concomitantly nice to you in return.

While you know nothing about oven repair, I must admire your tenacity and desire. Most of the responses are from technicians like Smitty who simply mindlessly replace the part and move on with their lives, never taking the time or mental effort to dig down into they who-what-where- when-or-why. Their fix-it-and-be-done-with-it approach takes about fifteen minutes to complete so they can not comprehend why you are taking longer than they would for something so simple as replacing a heater element.

A LOT of repairs (probably 95% of all repairs) are done this replace- parts-one-by-one-until-the-system-works-again method so their approach has merit.

You can't count the number of times I've overheard the conversation "My cooling system is overheating. What shall I do?" with the fifteen- minute response being "just replace the thermostat". Don't think. Just replace. Ask a question or two like "where is it" and "what is the part number" but nothing more than that. Certainly don't take apart any failed item to understand why it failed. Why does it matter. It failed. You replaced it. What more is there to know. That is the Smitty mentality. There is nothing wrong with this move-on-with-your- life mentality. You just don't have it.

Only a few repairs (probably less than 5%) are done using a systematic and forensic approach which you seem to lean toward.

The systematic approach takes far longer than fifteen minutes and requires adequate documentation of the particulars. Many picayune questions need to be asked and answered. Far more than you've asked so far. Almost always, the errant part needs to be destroyed and the pieces analyzed to determine the true sequence of events and ultimate cause of the failure, which will suggest the appropriate solution. Most advances in knowledge are by this approach.

Most work is done by the fifteen-minute approach. Most advances are done by the systematic approach. You chose. You lose.This is not the message board for the systematic approach. We don't know how it works. And we don't care. We fix it. We get paid. We move on. You should too.

If you insist on the systemic approach, then you will find very few people here who have the patience to help you. Most don't want to admit they have no clue as all they do is remove two bolts and they're done. They can't comprehend why you still have questions after removing those two bolts.

My advice to you is for you to put the two bolts back in, plug the oven in, and if it works, you'll know as much as 95% of the people who responded to your initial question. If you insist on trying to figure out what happened, I suggest you post a closeup photograph of the element at the point of failure. I suspect you'll find the typical spiral pattern of the failed element burning through the metal casing and arcing to the oven itself until the power failed.

If you wish to better understand how the heater element works, I suggest as others have done, that you hack saw through both the failed and pristing section where you'll see the spiral pattern of the element embedded in the sintered ceramic surrounded by high temperature steel which will have failed at the point of arcing, in a barber-shop spiral down your element.

I no longer think you're a ditz. You're just different, in a sickly sweet nice kind of way!

Reply to
crumbbuma

I didn't see the Dave Martindale responses when I wrote the above but his (and those from dpb and Jack and trad) are the ones that command your attention. Read every word of what Dave Martindale just said. Read them again. Look at your parts. Look at your oven. Put two and two together. Then ask more questions if you still have them. Dave covered what happened pretty well.

If all you need is how to replace the element, read Smitty two-bolts and you'll be done in fifteen minutes.

Reply to
crumbbuma

GE has never been the same since Ronny quit advertising for them.

Reply to
Al Bundy

Any generalizations about which stoves have switches that switch both sides of the line, and which switch only one?

The last time I took apart a failed "infinite heat" control for a range element, I noticed that the bimetallic element that modulates the on/off time had only one contact, and thus switched only one side of the 240 V. But when you turned the control to "off", a second contact opened the other side of the 240 V circuit as well, so the element was supposed to be completely isolated in the "off" position. I don't know how typical this switch is. (And if the second contact stuck closed, you'd never notice in normal use).

Dave

Reply to
Dave Martindale

Hi Dave,

Is this what probably happened in my "typical" oven fire?

  1. Something (grease perhaps) was on the broil element in one spot
  2. The grounded jacket thinned in that one spot, ever so slightly
  3. Over time, that one spot cracked, ever so slightly
  4. Over time, stress increased on the resistor core encased in concrete
  5. At some point, the cantilever stress broke the inside resistive core
  6. I heard a "sound" as the air gap ionized to a conductive plasma
  7. The core melted, causing the plasma gap to expand (more sound)
  8. The super-heated plasma conductivity extended to the metal jacket
  9. The core-to-jacket arc melted the jacket "backward" in a spiral pattern
  10. I turned off the broiler but that only reduced to half the pressure
  11. The other 120v pressure still allowed the plasma to remain heated
  12. The plasma arc spiralled backward toward the remaining 120v pressure
  13. Opening the house circuit eliminated the pressure & the "fire" went out

Is this what happened? Did I miss any steps?

Donna

Reply to
Donna Ohl

That's it. I'M OUTTA HERE.

Reply to
PanHandler

Donna Ohl wrote in news:f5pHk.1972$ snipped-for-privacy@flpi150.ffdc.sbc.com:

He just wants to get in your pants :-)

Reply to
Red Green

Reply to
Old and Grunpy

I don't think we know why the element failed. Oven elements routinely get organic stuff (food) splattered or dripped on them, and the usual result is a bit of smoke as the organics stuff gets burned to carbon or ash, while the element is completely unhurt.

So, either your element was defective somehow (e.g. a gap in the insulation somewhere, or it was subjected to some unusual stress at some point. The initial failure could have been an open resistor core, but it could equally well have been the core touching the grounded metal jacket.

By the way, the insulating fill is not concrete - concrete contains lots of water and doesn't like being red hot. It's some kind of high-temperature insulator (e.g. a ceramic).

All of that's possible, though we don't know for certain.

Substitute "voltage" for "pressure". Electrical voltage is in many ways like fluid pressure, but they're not the same thing. This assumes you turned off the switch, but the switch only interrupts one side of the

240 VAC line.

Yes, turning off the house breaker removed the voltage, and the arc ceased. Turning off the circuit breaker for the stove alone would have accomplished the same thing.

We don't know for sure what happened (at least I don't). But the sequence is plausible.

Dave

Reply to
Dave Martindale

The WB44T10009 GE broiler element finally arrived (see pic) so we can continue the oven repair help tutorial.

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Warning to others (that I wish someone would have advised me)!

The hole for the temperature sensor screw in the new GE oven broiler heater element is way TOO SMALL!

You have to widen the mounting hole in the new oven broiler heating element for the temperature sensor in order for the screw to take hold.

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The temperature sensor screw itself won't go in no matter how hard you try. So I had to start with a smaller screw and then take progressively larger screws to stretch the hole in the new broiler heating element mounting plate in order to finally fit the original screw in. It has to be just right though, so be careful as it will not mount if you make the mounting hole too wide!

Reply to
Donna Ohl

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