Electric oven tripping circuit breaker after turned on for 3-5 minutes

[petehall347]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

measure the lengths and bend your own to shape .

[redwire]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

Old ovens were just exposed wirewound nichrome and I know a woman that got zapped, the aluminium foil hit the element and it arced to ground, even though the oven was off. So much for a working DPDT switch.

Just replace the heating element, it's so much less hassle. If you have no money, maybe a scrap yard or junk yard has one you can grab.

[budm]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

Replace the heating elements, why fooling with safety.

[eccerr0r]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

how about this, all the attachment points of the heater element and the oven, put in a mica or something insulator there that isolates the shell from ground. Then connect one end of the power to the shell. Turn it on and let it heat up. The heater will expand and short against the outside shell, and the section between the short and the power end that you connected to the shell will stop glowing red hot... Bingo, located the short.

... but ultimately this experiment is useless, probably should pitch this heater, not really like they're repairable. I would think these things start straight, packed with the ceramic and the heater, and then bent. If the bending didn't cause a short then it's sold, else it's a manufacturing defect. Then those that are marginal or have future heat induced failures are the ones that need warranty replacement...

[clearchris]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

If it were me, and I weren't really concerned about safety (no one else in house, no animals, etc) which your picture of bare elements on a clay pot lead me to believe is true, I might set up an arduino and a relay, and just pulse it on and off over time. If you wanted to get fancy, you could hook up a thermistor to one of the elements and turn it off when it hits a certain temp. Hooking up the elements is series is a great idea. Slower is better with something like this. I definitely wouldn't run this unattended.

[sam_sam_sam]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

Here is my thoughts on this that once this has happen the element is not stable any more I would not recommend using it anymore

[beetle1303]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

i think you will find that the element wire has rusted and that is what is touching the casing.

It has become clear that the element coil touched the outer shell when heated up, and back to normal when cooled.

The hypothesis is: the centrally packed coil must have been exposed to moisture, and the magnesium oxide powder that packed it must have been deformed due to moisture (and probably still moist), and allows the coil to bend when heated and touched the outer shell.

The test is: to bake the element in order to dry up the powder, and hopefully the dry out powder will once again hold the coil centrally to prevent shorting to the outer shell.

The preferred method would be to bake the elements in another over at ~100c for few hours. But I don't have another oven...

Less ideally is the pass low voltage/current to heat up the elements, slowly, then repeat with increasing voltage/current for longer duration to dry out the powder. The problem is - I don't know if all this would work until I re-install the elements back into the oven. So I really don't want to spend all the baking times only to find it trip the house circuit breaker again..

So, please help me to devise a visual check of the baking process.

[stj]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

i think you will find that the element wire has rusted and that is what is touching the casing.

[beetle1303]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

I was doing a "slow bake". Each element is about 50 Ohms, and drawn about 5 Amps when power up independently. I feel the current is too high, so I connected them in series, total resistance ~150 Ohms, and drawing about 1.7 Amps.
The elements heated up slower and all is fine. But I can't tell if the elements are drying up well or already shorted...

So in order to "see" if the elements are still shorting when heated up, can I connect a light bulb between the element brackets and neutral so I know when to stop the baking when it leaks?

Can anyone help to confirm if this will work, and if so would a 40W incandescent bulb work?

If this is bad ideas or wiring is wrong, how else can I do this?

[clearchris]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

No way to say for certain, only thing to do is try it out!

[beetle1303]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

Something must have happened during the prolonged idling of the oven.

After more googling on this topic: https://www.plantengineering.com/art...ctric-heaters/

This is what I think:
When the oven is sit idling for a long time, significant amount of moisture sipped in and absorbed by the magnesium oxide powder via the terminals, or some minor cracks along the outer shell. The moisture does not 'wet' the powder uniformly, and caused some part of the evenly packed power to deform. The 'wet' part expanded and pushing the coil nearer to the edge of the shell. When heated up too quickly, the 'wet' part of the powder expended further and releases gas/vapor at the same time, pushing the already no longer centrally packed heating coil arced nearer or touched the shell, causing the earth leakage.

This, apparently, also happened to brand new ovens during long shipment via ocean, or brand new oven sitting idle in the showroom.

The suggested remedies are bake-out: put the elements in another ovens at medium temperature overnight, or passing low voltage over the element.

Do you think this is a plausible cause and remedies?

[redwire]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

I think there is a ground-fault within one of the heating elements.
Oven heating elements are in a metal tube with magnesium oxide powder for the insulator. The ends have a silicone seal.

The humidity reasoning is an old wive's tale. It's raining in everyone's oven? Even then, the element stays dry inside and cannot give high leakage current.

If the wire heating element pushed aside the MgO powder, it would cause a hard short once hot and then vanish after cooling down when the wire contracts.

[clearchris]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

If you think it's humidity related, attempt to dry them out. Reinstall, turn the oven on, turn off before it shorts, repeat until you think the elements are dry. I imagine it shouldn't take more than 5 or 6 times over the course of a few hours.

Edit: Or use a heat gun to heat the ends where the water probably is. Heat them a few times, let cool, repeat.

[beetle1303]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

There's a few things that will fry a heating element aside from a manufacturer's defect. You have things that will insulate the heating element and cause it to go high at one spot and burn it, like food residue or lime scale (in water heaters). Physical damage is pretty hard, these elements are tough. The other thing is a bad thermostat. If the thermostat doesn't properly turn off, the element will get too hot and burn. So when you replace the element, you should get a meter with a thermal probe and watch it. Periodically check it a few times after that too, if it's a mechanical thermostat, they don't always just go bad, instead, they get "sticky" and sometimes overheat the element.

If it did burn after a long time of being idle, I'd definitely take a look at the thermostat. An easy way, though not always conclusive, is to turn the knob and feel the click when the thermostat kicks in. You might not always feel the click turning on from cold, but after it's somewhat warm, you should be able to turn it both ways and feel it click on and off. If you don't feel the click, it might be bad. Don't confuse the "off" click with the thermostat kicking in, some have a dentent that clicks when you turn it all the way off.

Also make sure to clean the terminals, if you have a bad connection, this can also send the current high enough to pop a breaker. Sometimes the female spade connectors need a squeeze to tighten them up again.

Edit: if you do replace one element to test, make sure you are aware of where the thermostat bulb is. They are often placed near one heating element, and if that's not the element you put in, the thermostat isn't going to turn off, and you could burn a good heating element.

I am trying to digest, and do some experiments base on your input later.

But I want to describe my scenario a bit:
My oven is 2 years old now. It has upper dual-loop expose element and a lower single loop concealed element. It was used solely for baking bread weekly for the 1st year, and stopped using it till now.

I usually bake at 150-230C for 30-60 minutes each time using both upper and lower heating. The thermostat kicked in and out without incidents all those times. It started to trip within few minutes when first stated using it to warm up some pastry, consistently tripped within few minute every time now.

[beetle1303]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

This is the link I found most closely described what I am experiencing:

1. Oven not used frequently
When an oven is not used frequently, there is a very high tendency for it to trip when turned on to very high temperatures.

Why?
Oven tripping problems are inevitable especially in a country like Singapore where there is a high humidity level. This will cause moisture to form up in the heating elements of the oven.

When an oven has been heated up before, a small gap forms at the heating element holder. This is due to the difference in material between the heating element and the holder. As a result, any moisture in the atmosphere will cause this white powder in the heating element to become ‘wet'.

Originally designed to be an insulator, this powder has now become a conductor. Now with a conductance between the heating coil and the rest of the oven through the heating element, the oven will trip every time it is switched on. This is called an earth leakage trip.


https://www.fixwerks.com/the-beginne...s-and-repairs/

According to this link, the most likelihood would the outer shell and metallic holder of the element shorted when heated up.

Let me know what you guys think?

[clearchris]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

There's a few things that will fry a heating element aside from a manufacturer's defect. You have things that will insulate the heating element and cause it to go high at one spot and burn it, like food residue or lime scale (in water heaters). Physical damage is pretty hard, these elements are tough. The other thing is a bad thermostat. If the thermostat doesn't properly turn off, the element will get too hot and burn. So when you replace the element, you should get a meter with a thermal probe and watch it. Periodically check it a few times after that too, if it's a mechanical thermostat, they don't always just go bad, instead, they get "sticky" and sometimes overheat the element.

If it did burn after a long time of being idle, I'd definitely take a look at the thermostat. An easy way, though not always conclusive, is to turn the knob and feel the click when the thermostat kicks in. You might not always feel the click turning on from cold, but after it's somewhat warm, you should be able to turn it both ways and feel it click on and off. If you don't feel the click, it might be bad. Don't confuse the "off" click with the thermostat kicking in, some have a dentent that clicks when you turn it all the way off.

Also make sure to clean the terminals, if you have a bad connection, this can also send the current high enough to pop a breaker. Sometimes the female spade connectors need a squeeze to tighten them up again.

Edit: if you do replace one element to test, make sure you are aware of where the thermostat bulb is. They are often placed near one heating element, and if that's not the element you put in, the thermostat isn't going to turn off, and you could burn a good heating element.

[sam_sam_sam]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

My guess is that when you use the element more often there is no problem at point of time but there are issues that are not fatal

But when you let it sit for a moisture get into the ceramic material and causes an internal short or and rust when heating up the moisture reaction with the electricity causing current to flow to ground

This is just a guess at this point

[beetle1303]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

If this is the results that you got on this element then this one is bad

If you look at the element ( every inch of it ) with a magnifying glass you might see a place where there is a hair line crack or pitting in the outer shell this caused by hot liquid spilling on the element

This is also an indication of the element bad or going bad

There is also a situation where the bracket or brackets that hold the element up can cause issues as well

The medium is some type of ceramic material not sure what type

I am actually very convinced that the element is bad. All these tests are really just to satisfied my curiosity.

But what is puzzling me is that there seems to be many cases where electric oven tripped circuit breaker when re-use after a long time of unused. So what happened to the heating element when it is left unused for a long time? It would appear that the insulation turned bad for some reasons, and what would those reasons be??

[sam_sam_sam]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

OK.
To be safe, I put the element on the clay pot on a ceramic tile floor, wore a rubber gloves and rubber shoes. I turned on the power for few seconds at first, then left on for ~30 seconds then switched it off. The element didn't grow red but can smell the heat.
I then measure resistance between terminal and the outer shell - it fluctuated a lot for 20-30 seconds, stabilized ~60K Ohms.

Not sure at this level it will already trip the power, but most likely as the temperature goes up further, it eventually will.

Based on everyone's' input, it is already clear that the element is bad. For my own academic, I am just curious to see the outcomes.

I am guessing, based on what I have researched, that the old days oven heating element's insulating material was some kind of powdery form. When not used for a long time, it could absorbed sufficient amount of moisture around the terminals and becomes conductive.

If this is the results that you got on this element then this one is bad

If you look at the element ( every inch of it ) with a magnifying glass you might see a place where there is a hair line crack or pitting in the outer shell this caused by hot liquid spilling on the element

This is also an indication of the element bad or going bad

There is also a situation where the bracket or brackets that hold the element up can cause issues as well

The medium is some type of ceramic material not sure what type

[beetle1303]

Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

Just a coincidence. My friend fits 2 or 3 a week and those ovens are regularly used. The one that failed ion my oven is also used regularly.

Do they all, and yours, failed due to shorted to earth that tripped the power supply like mine?