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I have a mid 60's Thermador double oven (in stainless!) that was generally working fine. A couple months ago, upper oven stopped working. Last night, shortly after turning on the lower oven, we saw / smelled a few wisps of smoke coming from the side of the oven, against the wall it is mounted to (coincidentally, a couple feet below the breaker box on the other side of the same wall). Smelled more like an electrical issue than my cooking. (I.e., a good bit more pleasant.) Figured I should probably trip the breaker. (I do NOT believe this is a breaker issue, as the smoke was outside the closet that contains the breaker.)
Turned oven on this morning. No smoke. Elements got warm (not hot) slowly. Checked voltage across element leads while oven was on. About 50 volts.
Pulled all four heating elements. All have continuity. Checked voltage. 110 across the wires to the element when element disconnected. Noticed that the lights were rather dim. 50 volts to the oven lights. This was true regardless of whether heating elements were connected.
What do I need to replace? What are the chances I'll be able to find parts for this relic?
Fortunately, our Weber is working great.
Thanks.
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Rank: Advanced Member
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You have an electrical problem somewhere as you should see 240 volts across the elements. Should make no difference if they are connected or not.
Do not confuse this with measuring from one side of the element to ground/frame, see the last bit.
Am not sure how much you know about how 240 works so am adding the following:
240 is actually two 120 volt supplies that are 180 degrees out of phase. In other words when one is +120 volts the other is -120 volts (L1 and L2) giving you 240 between the two. The 120 volt supplies are referenced to Neutral in most cases this is also the ground re: unit`s frame.
Usually one side of the element is permanently connected to one of the supplies (always live). This is why it is very important to always remove power to the unit when replacing elements etc. Your controller then switches in the other line to provide the 240 volts across the element.
You are seeing 120 across the element so you probably have lost one of the 120 volt supplies and may have a wire that has shorted to the frame.
The 50 volts you see may just be ghost voltage since any current draw that would drop 120 volts down to 50 would be so high that it should blow the breaker.
The last bit
Now just to confuse you a little more.
Lets say every thing is OK and you turn the element on and measure from each side to the frame. Both will measure 120 volts but one would be the L1 side and the other the L2 side. You cannot tell which is which with a meter you need an O-scope so you could see and compare the waveforms.
Now lets say you disconnect the L2 side of the line. And again measure both sides of the element. You still see 120 volts to both sides when referenced to the frame. The reason is that one side will be that actual L1 voltage and since there is no current (voltage drop) across the element you also see it on the far side.
Hope this does not confuse the heck out of you but chasing 120 volts in the 240 volt element circuit can get confusing and I just wanted to point out the pit falls.
The first thing to check is are you actually getting 240 volts to the unit or out of the panel !!
The other first thing is to find out where that smoke came from, by the sound of it this will involve pulling the unit. |
THIS FORUM IS DEAD!!!!!!! |
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Rank: Member
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Joined: 4/4/2010(UTC)
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Great info. All understood. Will first test the leads from breaker to the oven and then will pull the oven.
I'm guessing your 'short to the frame' theory is correct, given the age of the oven and the likely condition of the wire insulation.
Thanks!
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