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

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    #21
    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?

    Comment


      #22
      Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

      Originally posted by clearchris View Post
      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.

      Comment


        #23
        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.
        Last edited by clearchris; 05-04-2020, 11:40 AM.

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          #24
          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.
          Attached Files
          Last edited by redwire; 05-04-2020, 12:42 PM.

          Comment


            #25
            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?
            Attached Files

            Comment


              #26
              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!

              Comment


                #27
                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?
                Attached Files

                Comment


                  #28
                  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.

                  Comment


                    #29
                    Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

                    Originally posted by stj View Post
                    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.

                    Comment


                      #30
                      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
                      Last edited by sam_sam_sam; 05-09-2020, 09:39 AM.
                      9 PC LCD Monitor
                      6 LCD Flat Screen TV
                      30 Desk Top Switching Power Supply
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                      6 18v Lithium Battery Power Boards for Tool Battery Packs
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                      25 Servo Drives 220/460 3 Phase
                      6 De-soldering Station Switching Power Supply 1 Power Supply
                      1 Dell Mother Board
                      15 Computer Power Supply
                      1 HP Printer Supply & Control Board * lighting finished it *


                      These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                      1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                      2 Hem Saw Computer Stack Board

                      All of these had CAPs POOF
                      All of the mosfet that are taken out by bad caps

                      Comment


                        #31
                        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.

                        Comment


                          #32
                          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...

                          Comment


                            #33
                            Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

                            Replace the heating elements, why fooling with safety.
                            Never stop learning
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                            Comment


                              #34
                              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.

                              Comment


                                #35
                                Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

                                measure the lengths and bend your own to shape .

                                Comment


                                  #36
                                  Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

                                  Originally posted by petehall347 View Post
                                  measure the lengths and bend your own to shape .
                                  I have done this, and it's much less fun than it sounds, even with a pipe bender. The unbent ones tend to be more expensive than a replacement part too. I wouldn't have done it if I didn't need it custom. It was to add an extra defrost coil to a walk-in freezer that kept freezing solid.

                                  At least it worked great when it was done.

                                  Comment


                                    #37
                                    Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

                                    Thanks for all the input and feedback. I appreciate them.

                                    I am more interest in the learning than getting the oven working again. I mean I don't really the oven... So the quest for knowledge - identify root causes, probable solutions and fixes, etc, the journey is more fulfilling.

                                    Here's additional test outcomes:
                                    1) In a condone off corner of my living room (in from of my TV and laptop) , I wired up the elements: 3-element-in-series, 2-element-in-series, and 1-element-only.
                                    2) I tested them one at a time, with live, neutral and earth all connected to wall socket.
                                    3) I ran the 3-element-in-series for 1 hour, stopped for 10 min to cool, and repeated one more time. I repeated the same with the 2-element-in-series. All good, no power trip.
                                    4) I then repeat with 1-element-only, but only for 10 minute since it would have tripped in 3-5 minute. As it turned out: the single loop lower element and the inner of the double loop upper element both OK after 10 minutes. The outer loop of upper element tripped in ~3 minutes!

                                    So I have a working lower element, a half working upper element. And a more or less conclusion that baking the long idled elements for 1-2 hours won't fix the issue. I am guessing that baking longer hours might not help either.

                                    Now I have one last quest for knowledge:
                                    In trying to not tripping the whole house with each experiment, I found a spare RCCB in the storeroom. So I googled and research about this to see this RCCB can be wired up to prevent the power trip.

                                    I googled and watched some youtube on this topics, and drawn up a diagram did some Ohms' Law calculations.

                                    I am guessing this will work - please see attached pic.

                                    Again, this is purely academic - it will not fix the element issue, but will enrich my basic electricity knowledge.

                                    Advise and feedback will be very much appreciated.
                                    Attached Files
                                    Last edited by beetle1303; 05-11-2020, 09:14 AM.

                                    Comment


                                      #38
                                      Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

                                      I wouldn't do that. Now that you know the bad coil, reassemble the oven with the good coils. Put the bad coil in and bake a low temperature. Obviously don't connect the bad coil, put it on a rack or don't attach the wires.

                                      Edit: make sure you tape off any bare ends so they don't contact the case or anything else.
                                      Last edited by clearchris; 05-11-2020, 12:27 PM.

                                      Comment


                                        #39
                                        Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

                                        Originally posted by clearchris View Post
                                        I wouldn't do that. Now that you know the bad coil, reassemble the oven with the good coils. Put the bad coil in and bake a low temperature. Obviously don't connect the bad coil, put it on a rack or don't attach the wires.

                                        Edit: make sure you tape off any bare ends so they don't contact the case or anything else.
                                        Good idea. I would re-install both lower and upper elements, and not connecting the bad element loop as you suggested. Then turn on at lower temperature for a few hours to see if the make any difference.

                                        On the RCCB to isolate oven elements from tripping the house, I would like to know why you wouldn't do it - is it wired wrongly, or it wouldn't work as intended?

                                        In fact, I have wired up the RCCB with the leakage wired to earth wire. When the element leaked, the house main RCCB tripped but the RCCB at the element side did not. I googled and gathered that with both RCCB of same 30mA rating, the main RCCB will trip first due to inherently already having some level leakage within the household circuits.

                                        Comment


                                          #40
                                          Re: Electric oven tripping circuit breaker after turned on for 3-5 minutes

                                          I'd just not use the RCCB because it would require ripping more out of the oven or the wall socket. If you hook it up as you said, I'd consider that safe enough to not worry about additional protection. For the record, hooking up the elements on a clay pot was a bit dicey to me, but I'd be fine without an extra breaker in line if everything was hooked up in the oven.

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