Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 05-20-2013, 03:10 AM   #1
Newbie
 
Join Date: May 2013
Posts: 1
Share |
Question

Oven element "thermite"


My oven's broiler element just burnt out. I shut it off and the rest of the coil cooled off, but the blowout spot stayed bright-white hot, and began to travel along the length of the coil a couple of inches per minute, burning through the element's casing, sputtering and throwing sparks like a slow motion fuse. I googled this and found someone else's video --strangely enough the same model of oven as mine: There was little or no flame and I was unable to put it out even when I sandwiched the hot spot between two saturated sponges. I'm not a chemist but I'd swear this was some kind of thermite reaction: two compounds in the broiler element were reacting with each other at this super high temperature and didn't need any outside oxygen (or got it from the water in my sponges). Towards the end of the element, the remaining 6 inches began to glow (the regular red, not white), just like the video. Nevertheless I am sure the switch was off, and it's very unlikely the switch and element failed together. What strange chemistry goes on here?
--Jimfife

Jimfife is offline   Reply With Quote
Old 05-20-2013, 04:57 AM   #2
Electrical Contractor
 
Philly Master's Avatar
 
Join Date: Mar 2013
Location: SE PA
Posts: 1,137
Default

Oven element "thermite"


there are reports of a thing called a "RUNAWAY STOVE" ...you can google it ...
if you work on this make sure the breaker is off not just the stove ..

__________________
Philadelphia Master Electrician-Generac Dealer
Philly Master is offline   Reply With Quote
Old 05-20-2013, 05:18 AM   #3
Member
 
Join Date: Nov 2007
Location: Nashua, NH, USA
Posts: 6,944
Default

Oven element "thermite"


Possible explanation (some models only). The element is fed 240 volts (via both hot legs of the 120/240 volt circuit) but the knob switch cuts only one of the legs. A fault developed between the still energized nichrome wire inside the sheath and the (grounded) sheath.
__________________
Stop wasting time re-adjusting the pattern. Have several lawn sprinklers, one for each pattern.

Last edited by AllanJ; 05-20-2013 at 09:15 AM.
AllanJ is offline   Reply With Quote
The Following 2 Users Say Thank You to AllanJ For This Useful Post:
mpoulton (05-20-2013), Philly Master (05-20-2013)
Old 05-20-2013, 05:54 AM   #4
Member
 
Join Date: Mar 2010
Location: PENNSYLVANIA
Posts: 2,236
Default

Oven element "thermite"


Always unplug or shut off the breaker to the oven before messing around with the elements, especially with 2 wet sponges.
__________________
No Warranty Means- If it breaks in half you get to keep both halves.
COLDIRON is offline   Reply With Quote
Old 05-20-2013, 07:46 AM   #5
Member
 
Join Date: Oct 2012
Location: new mexico
Posts: 344
Default

Oven element "thermite"


Quote:
Originally Posted by COLDIRON View Post
Always unplug or shut off the breaker to the oven before messing around with the elements, especially with 2 wet sponges.


hmmmm, sounds like a fun time
redman88 is offline   Reply With Quote
Old 05-20-2013, 02:36 PM   #6
Semi-Pro Electro-Geek
 
Join Date: Jul 2009
Location: Arizona, USA
Posts: 2,550
Default

Oven element "thermite"


The nichrome wire in the element is insulated from the metal shell by a powdered material which is usually magnesium oxide. MgO is a great insulator and melts at an extremely high temperature. But an arc is hot enough to melt and vaporize it, and melted or vaporized MgO is conductive. So once an arc starts between the nichrome and the metal shell of the element, the overheated MgO insulator becomes a conductor and allows the fault to continue. There had to still be power involved - as AllanJ said, 120V may still exist between one end of the element and the sheath when the stove is off. A thermite reaction is not possible with an MgO insulator, because neither the steel shell nor the nichrome wire has enough reducing potential to strip oxygen from magnesium. If the insulating powder were something else, it might be possible.

__________________
I am a lawyer, but not your lawyer. And who cares anyways? We're here to talk construction. This is DIY advice, not legal advice.
mpoulton is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
oven element not glowing all the way around diysNovice Appliances 10 01-20-2013 07:55 AM
Electric oven element burned out but oven still hot Dhnothandy74 Appliances 2 07-29-2012 08:29 PM
Kenmore Oven Element Arcing Valerie1960 Appliances 2 01-30-2012 08:03 AM
Bottom (bake) element in the oven dead? elementz Appliances 3 04-19-2010 07:40 AM
Oven Blew Up at Connector with Element cynthiap Appliances 5 11-26-2008 06:30 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.