My oven died

JakeCK

So the PoCo replaced the utility pole behind my house yesterday and when they reconnected everything we got a really nasty under voltage which I suspect killed the oven on my stove. All four burners still work, and the coil for the broil function works. Just the lower coil. 

It's a Tappan electric model number tef351ewb.

Anyone familiar with this stove or have a wiring schematic? I'm hoping it's something as simple as a fuse and not the control board but considering what happened...

On a side note this is the second thing I found that they destroyed during all of this.

JakeCK

I want to add that I can hear what sounds like a relay clicking when I try to set the oven. So maybe it's just the lower coil and it's just coincidence it died when the PoCo did they're thing? 

ChrisJ

Why would low voltage kill a hot surface igniter?

109A_5

Hello @JakeCK,

Poor image quality, but maybe better than nothing.

https://www.searspartsdirect.com/model/aa6qkr1r68-001269/tappan-tef351ewb-electric-range-parts

Wiring diagram on the inside of a panel ?

Was the oven in use at the time ? Under-Voltage rarely does permanent damage (other than some motor types), things often just don't work properly. Over-Voltage on the other hand is damaging. Was the Voltage corrected ?

Larry Weingarten

Hi, Might this help? https://www.partselect.com/Models/TEF351EWB/?msclkid=9e3db197e12a1f50257ed5cbda9880b7 I see some schematics that may be useful.

Yours, Larry

Jamie Hall

Can you probe the contacts for the coil (careful!) and see if -- or when -- you get voltage? But I see there is also a door switch, and it's not clear whether it is only for the light, or whether it's also an interlock for the lower coil. Wouldn't think it would be, but...

mattmia2

Jamie Hall said:

Can you probe the contacts for the coil (careful!) and see if -- or when -- you get voltage? But I see there is also a door switch, and it's not clear whether it is only for the light, or whether it's also an interlock for the lower coil. Wouldn't think it would be, but...

i'd start with an ohmmeter to check for continuity between the terminals of the element(it should be in the under 10 ohm range) and that it is open to the metal outer casing. if that is ok then i'd check the voltage to the element.

mattmia2

You may have had a bad neutral rather than an undervoltage. that could cause problems.

JakeCK

mattmia2 said:

You may have had a bad neutral rather than an undervoltage. that could cause problems.

I was just guessing an under voltage based on how different devices behaved while power was being restored. But it could have been any number of things. I do know I was still sitting in the dark on the john while some things started coming to life before finally the lights came on and flickered/dimmed a few more times. All the while all the ups' for my computer equipment was going ape s*** about it. 

It's just an odd coincidence that the day after I try to use the oven and got nothing. 

JakeCK

And no it was not in use at the time.

JakeCK

ChrisJ said:

Why would low voltage kill a hot surface igniter?

I was thinking maybe the control board got zapped, not necessarily the element it's self. And this is an electric. Why would it have an igniter? 

JakeCK

Trying to read those diagrams. They're all too low of a resolution. If I was an expert at reading them maybe I could make em' out.

ChrisJ

JakeCK said:

ChrisJ said:

Why would low voltage kill a hot surface igniter?

I was thinking maybe the control board got zapped, not necessarily the element it's self. And this is an electric. Why would it have an igniter? 

I assumed you had a decent stove. 

 

In all seriousness, when you said coil I automatically thought hot surface igniter.   My mistake.

 

109A_5

I find with power outages due to storm damage or local repair work. Turn off the main circuit breaker and/or all the branch circuits. Once power is restored verify the Voltage is correct before restoring power to critical or expensive devices. Just less headaches in the long-run and not hard to do.

109A_5

JakeCK said:

Trying to read those diagrams. They're all too low of a resolution. If I was an expert at reading them maybe I could make em' out.

The link to the document that @Larry Weingarten provided, the resolution is quite good if you zoom in.

mattmia2

unless there is more than one relay, if the relay is clicking it would seem the logic is behaving as it should. any chance it is fuses rather than a breaker and one of the fuses is blown but the control is 120v and on the side that has power?

Dave Carpentier

I cant see how the element would burn out if it was off at the time.
If all your surface heaters and the broil work, you probably have a good power supply to it.
Did you try turning off the breaker for a minute and then back on ?
(maybe the control board got into a freak-out mode ?)

109A_5

Often things fail and go unnoticed until another event happens and then the failure is found by inspection or other means.

I don't see any fuses in the wiring diagram.

JakeCK

Dave Carpentier said:

I cant see how the element would burn out if it was off at the time. If all your surface heaters and the broil work, you probably have a good power supply to it. Did you try turning off the breaker for a minute and then back on ? (maybe the control board got into a freak-out mode ?)

First thing I tried was to kill the breaker for a few minutes. 

Dave Carpentier

Might there be a more legible wiring diag on the inside of the back panel ?
You could probe for hots going to the bake element from the relays, the relay could be pooched (usually easy solder job, electronics part # right on the relay). If the relay isn't getting to command to close, then thats usually where I toss in the towel, as its a chip or such.
Mind you, possibly a glass fuse on the board ? (but thats a reach..)

Got an RV to cook in while you be Mr Takeapart ?

JakeCK

Ok, I got a schematic good enough to read. It looks like leg 2 out on the control board goes to both the bake and broil element, and then each element goes back to BK and BRL terminals respectively on the control board. There is also the temperature probe that has it's own terminals that could be the culprit, however since the broil element does heat it suggests that is ok unless the control board doesn't use temperature when set to broil? Since I can hear what sounds like a relay clicking when I turn it on suggests the control board is also working. Tomorrow I'll pull out the element and check continuity.

Lowe's appears to have it available, as does amazon. Both with in a couple dollars of each other. I might poke around some of the local appliance repair/part shops. Sadly there aren't many left anymore. In fact up until about 5 years ago there was one with in walking distance of my house.

JakeCK

109A_5 said:

I find with power outages due to storm damage or local repair work. Turn off the main circuit breaker and/or all the branch circuits. Once power is restored verify the Voltage is correct before restoring power to critical or expensive devices. Just less headaches in the long-run and not hard to do.

Ya know, I would have but I was asleep when they started all this. I work nights 6pm - 6am. The wife answered the door when they informed us and decided that what they were doing was not important enough to wake me up. Never mind all the times over the years where I have explicitly said that if the power goes out I want to know ASAP. If I'm asleep, I'll get up with a purpose. If I'm at work, I'll come home. If I'm on the other side of the country I'll do a orderly remote shut down of the network. And hope that the aquarium filter doesn't become toxic once the backup battery on that dies...

I have a generator just for these occasions. If only she would have woke me up. >:| Yes I'm still a little annoyed she didn't.

109A_5

Sometime wife's have other priorities.

Before you go to the trouble of getting a replacement heating element I would verify the suspected bad one is actually bad. Assuming you have a multi-meter. You need to get to the connection points anyways to replace it. I would compare the resistance of the Bake to the Broil element. Like @mattmia2 stated they may be in the 10 Ohm ballpark depending on their actual wattage.

If you are in an outage prone area there is equipment and strategies for the computer stuff to do an automatic orderly shut down and not come back on until manual reset is invoked.

JakeCK

109A_5 said:

Sometime wife's have other priorities.

Before you go to the trouble of getting a replacement heating element I would verify the suspected bad one is actually bad. Assuming you have a multi-meter. You need to get to the connection points anyways to replace it. I would compare the resistance of the Bake to the Broil element. Like @mattmia2 stated they may be in the 10 Ohm ballpark depending on their actual wattage.

If you are in an outage prone area there is equipment and strategies for the computer stuff to do an automatic orderly shut down and not come back on until manual reset is invoked.

I thought I said I was going to check it first.

Power outages are not that common here, maybe once every couple of years we'll have a longer outage. That said everything is on battery backup and will continue to run for 40-60 minutes no problem before most everything does a nice shutdown. But some stuff just isn't very intelligent and will occasionally go down hard. And I want everything to boot backup once power is restored.

Dave Carpentier

On my electric oven (whirlpool), when I set a normal bake temp, both elements come on until it approaches the set temp then the broil turns off and the bake continues as per expected.
So, I would hear a relay click when I started the oven even if there was an issue with the bake relay (or control side of it) because it would be the broil relay.
Not sure if all electric ovens do the same dual-element startup.
Do you get any cabinet heat when setting a bake temp ?

JakeCK

Dave Carpentier said:

On my electric oven (whirlpool), when I set a normal bake temp, both elements come on until it approaches the set temp then the broil turns off and the bake continues as per expected. So, I would hear a relay click when I started the oven even if there was an issue with the bake relay (or control side of it) because it would be the broil relay. Not sure if all electric ovens do the same dual-element startup. Do you get any cabinet heat when setting a bake temp ?

None. That's how we initially noticed it wasn't working. We had set it to pre heat and when checked the cabinet was cold still.

EBEBRATT-Ed

Call POCO and report the problem they will fix or replace they do it all the time.

A relative of mine lost power during a storm when the wires came down. Poco reconnected but "forgot" to reconnect the neutral.

This put 240 v across the hot wire and connected the 120 volt loads in series. Depending on the loads resistance some will live and some will die. Poco is replacing 3 of their appliances.

ChrisJ

EBEBRATT-Ed said:

Call POCO and report the problem they will fix or replace they do it all the time.

A relative of mine lost power during a storm when the wires came down. Poco reconnected but "forgot" to reconnect the neutral.

This put 240 v across the hot wire and connected the 120 volt loads in series. Depending on the loads resistance some will live and some will die. Poco is replacing 3 of their appliances.

Lost neutral and yet the only thing effected in the entire house is the electric stove that wasn't on? Even more so, the rest of the stove still works normally.

JakeCK

I pulled the element and tested it. My multimeter doesn't have continuity so I used the ohms. It gave me a null reading, no change. I tested the multimeter on a scrap 6" piece of 12ga wire and got a reading of about .9.

ChrisJ

JakeCK said:

I pulled the element and tested it. My multimeter doesn't have continuity so I used the ohms. It gave me a null reading, no change. I tested the multimeter on a scrap 6" piece of 12ga wire and got a reading of about .9.

You would test the meter by shorting the leads together. I'd expect to see a reading of between 0 and 0.2 ohms, give or take.

ethicalpaul

Continuity is typically just the ohmmeter at a 200 ohm range, no problem there.

Try some different ranges on the element, I don't know the expected resistance although no doubt someone here will.

.9 ohm sounds quite high for a piece of wire Maybe it was .009 or something. The gauge of the wire won't matter at the current the meter is putting through there.

ChrisJ

ethicalpaul said:

Continuity is typically just the ohmmeter at a 200 ohm range, no problem there.

Try some different ranges on the element, I don't know the expected resistance although no doubt someone here will.

.9 ohm sounds quite high for a piece of wire Maybe it was .009 or something. The gauge of the wire won't matter at the current the meter is putting through there.

Just a wild guess, probably 20 to 25 ohms.

JakeCK

Putting the leads together got the same reading. Yes I know just touching the leads does the same test just minus one connection point. 

Since I apparently do not know how to use a multi tool here's the reading touching the leads:

109A_5

If the element is bad it should read basically the same as it the probes are not touching each other. I would now expect in the 20 Ohm vicinity (did some research), plus the value on the meter with the probes touching each other. Compare to the other element. It will be in the same ballpark but I believe the Wattage is different.

ethicalpaul

It probably won't affect your testing of the element, but a reading of 1.2 when touching the contacts together isn't great.

Consider replacing it with a new $20 model that has a audible continuity feature, they are very convenient.

Your meter does have a signal injection feature which is interesting!

Correction: $10, and it also has signal injection

https://www.amazon.com/dp/B01ISAMUA6/

JakeCK

ethicalpaul said:

It probably won't affect your testing of the element, but a reading of 1.2 when touching the contacts together isn't great. Consider replacing it with a new $20 model that has a audible continuity feature, they are very convenient. Your meter does have a signal injection feature which is interesting! Correction: $10, and it also has signal injection

https://www.amazon.com/dp/B01ISAMUA6/

What can I say it was a cheap-o from Walmart.

ethicalpaul

It wasn't a personal judgment

PC7060

That meter is perfectly functional. It will give you reading in ohms up to 2000; may switch to kilo-ohms at the higher ranges. 

I’ve got several meters; the accuracy at the lower ranges varies; anywhere from 0.1 to 1 ohm is common. Spin the banana plugs in the sockets, may have some oxidation increasing the resistance. 

mattmia2

ethicalpaul said:

Continuity is typically just the ohmmeter at a 200 ohm range, no problem there.

Try some different ranges on the element, I don't know the expected resistance although no doubt someone here will.

.9 ohm sounds quite high for a piece of wire Maybe it was .009 or something. The gauge of the wire won't matter at the current the meter is putting through there.

e=ir

resistance is constant, you measure the current and voltage and you can calculate the resistance.

A little under 1 ohm isn't unusual given the error in the meter and the resistance of the various connections. The wire in the test leads and the wire under test have a lot less than 1 ohm resistance but reading a little under 1 ohm isn't unsusual.

Since the element is 240v and they are typically around 2000 w and nichrome is a thermistor, the resistance should be under around 30 ohms. If it reads infinity on the ohmmeter it is open and the element in the problem.

Typically they fail when they first turn on. Frequently they fail by shorting to the cladding so one terminal will have continuity to the cladding and the other will be completely open.

mattmia2

ethicalpaul said:

Correction: $10, and it also has signal injection

That little picture of a square wave on the function dial is a frequency counter.

ethicalpaul

> That little picture of a square wave on the function dial is a frequency counter.

No, it's a signal injector. I looked at the manual. I had to look because I had never seen that symbol on a meter before!

I do think a reading of about 1 ohm through the probes is quite unusual and inaccurate. It's a failure of something on the order of 1000% I would say.