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FIXED 110.78890100 Dryer blowing circuit, power cord hot and melted

mpickell

Premium Member
Joined
Sep 28, 2011
Messages
92
Location
Pittsburgh
Model Number
110.78890100
Brand
Sears Kenmore
Age
More than 10 years
I have an "RV dryer" -- i.e., it is 120 volts for running in an RV or at a camp site. It is a Kenmore "Portable Dryer Model Series 88901" "Lady Kenmore Heavy Duty". I'll attach some pics.


This has run really well and drys great. However recently it has started blowing the circuit it is on -- it has not in the past year. I thought maybe it was that it was on the same circuit as a bunch of other stuff so i moved it to a dedicated circuit i had already set up. Both circuits are 20 amp (the first had other things, like lights, the washer, etc).

When I moved it I realized that the power cord was hot, which at the time I thought was maybe normal for a dryer. When i plugged it into the new dedicated circuit I did so with an extension code.

Today I went to get that extension cord to use for something else and I couldn't unplug the dryer. Turns out it was "melted" to the extension cord. I'm guessing the extension cord was 14 AWG, but this would mean the dryer was pushing >15 amps to melt this?

My question is: What could cause a dryer to start pulling way more AMPs than it should? This is a good dryer and i'd like to fix it. Could it be a bad cord? motor dying? I need to definitely replace the cord now, but I don't want to use this until I can figure out what is causing this.

thanks!
 

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rickgburton

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When i plugged it into the new dedicated circuit I did so with an extension code.
That's major cause of 120 Volt dryer failures. You're at the limit of current draw for the size wiring in your RV. That's without the extension cord. The extension cord adds more resistance. Use an amp meter or amp probe and check the current draw when the machine is running on timed dry, high heat.
 

mpickell

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That's major cause of 120 Volt dryer failures. You're at the limit of current draw for the size wiring in your RV. That's without the extension cord. The extension cord adds more resistance. Use an amp meter or amp probe and check the current draw when the machine is running on timed dry, high heat.

Rick,

Could you give me a little more info? Are you saying that
  • by simply introducing the extension cord I caused the melting,
  • there is probably not actually anything wrong with the machine (other than replacing the power cord, which i fried),
  • The reason it was tripping was that the 4AMP the dryer is drawing simply pushed over the 20 AMP breaker limit (ie "current draw for the size wiring")?

This is circuit I ran, 12 AWG wire direct off a 20 amp receptacle at the back of the campsite.

The dedicated circuit I put the dryer on is the same (12awg off 20 amp breaker) and had nothing else on it.. so it was a dedicated 20 amp circuit just for the dryer. Like I mentioned, the extension cord was probably 14AWG, but I would not expect the dryer (which says 4AMP) to melt the wire just based on the length of the extension cord? it was probably a 15ft cord.

Is the wire the issue -- I just need a new power cable and do not use an extension code with it? I don't need to consider something internal to the machine? This would make sense from what i saw... the machine worked fine when not tripping the circuit. I just have not heard of resistance issues like this with such a short extension cord.


I am going back to the camp this weekend and would like to know all the possible causes so i can bring up the potential replacement parts and return what I end up not using. This would be easier at home, but i can't measure amps/voltages until I go back up there.

Thanks!
 
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rickgburton

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When you turn on an electrical appliance, current is drawn through the wires and connections. The more energy the appliance requires, the more current that flows. If the flow of current exceeds the wire's specifications, the internal wire starts to heat up. Wires have electrical resistance, which means that they resist the motion of electrons, the electrons bump into atoms on the outside of the wire, and some of their kinetic energy is given to the atoms as thermal energy. This thermal energy causes the wire to heat up.
 

mpickell

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When you turn on an electrical appliance, current is drawn through the wires and connections. The more energy the appliance requires, the more current that flows. If the flow of current exceeds the wire's specifications, the internal wire starts to heat up. Wires have electrical resistance, which means that they resist the motion of electrons, the electrons bump into atoms on the outside of the wire, and some of their kinetic energy is given to the atoms as thermal energy. This thermal energy causes the wire to heat up.

ok, so is my assessment correct then?

  • don't use the extension cord,
  • replace the power cord
  • it won't work on the circuit i had it on. too much stuff on that circuit.
  • that's it. there's nothing actually wrong with the dryer

I appreciate the explanation, but i also want to make sure that i'm solving the problem.
 

rickgburton

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That's correct. 120 volt dryers use a lot of power. Most only have a timed dry cycle up to 120 minutes. The element is almost always on. That's a lot of current for a long time. In my first post I said to check the current draw when the machine is running on high heat. That will give you an idea how much. Here's another possibility. Over time the element can start to sag between the insulators. If it touches the housing it probably won't trip the circuit breaker because neutral and ground are connected. It changes the wattage of the element by using the machine as neutral.
 

mpickell

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Here's another possibility. Over time the element can start to sag between the insulators. If it touches the housing it probably won't trip the circuit breaker because neutral and ground are connected. It changes the wattage of the element by using the machine as neutral.

That's interesting... Can I check that visually? If it was touching... would that require a new element, or is that something that could be "tucked back in place" ?

I'm planning on replacing the cord, I am wondering if i should pick up the element as well since this is an old machine already.

Thanks!
 

rickgburton

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You can check it with a meter. Set it on the lowest Ω scale and measure from the element end to ground. Always remove at least one wire from the component you're checking. Remove power first.
 

mpickell

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You can check it with a meter. Set it on the lowest Ω scale and measure from the element end to ground. Always remove at least one wire from the component you're checking. Remove power first.

Ok, I have a meter and i'll check that.

What should i be looking for? Am I looking for a short? and if so, do i replace the element? If there is "infinite resistance" then i'm good to go and the element is not touching?

Thanks!
 

Jake

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Yes Rick is correct, I've seen that happen many times myself.

Here's the heating element for your model in case you need to order it:
279506 Element, Heating


Jake
 

mpickell

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B5582B03-3E71-48FE-B46F-B34E009B6A0A.jpeg944AC76D-630F-400E-8631-5E6CA4E3AD30.jpg

A couole thngs. This is the original outlet I had it plugged into before using the extension cord at all. I had not noticed this melting here before. So I’m guessing the extension cord was unrelated

i replaced the broken plug on the cord with this 20 amp male plug, which I cannot plug in because the thing has the pins the wrong way??!! You see in these pics that the plug does not match the 20amp receptacle. No idea what is up with this but I couldn’t measure amps because of that. I’m going to get a new plug tonight and fix it again

FFA2BE06-AD8E-4A89-8C28-89044E959CFB.jpg
I opened it up and cleaned it out. Very dusted with lint. Disconnected and inspected the heating element. I forgot to check if it was shorting before taking it out and cleaning and inspecting. However I did not see any part of the hearing element touching the metal, and after reinstalling it it definitely is not touching the metal because I checked continuity. The heating element itself is intact with a continuity test and a resistance reading of ‘10’ on my meter.

Once i I fix the plug I’ll test again and measure amps. But I wanted to know if this additional info changed the diagnosis. Could the motor be acting up and getting old, causing this? Are there electrical readings I can take on it to check it out before closing it up?
 

rickgburton

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Wrong plug. The wall outlet has a notch on the left terminal opening to indicate it's a 20 amp circuit and outlet. It uses the regular type plug. The one you're trying to add (and the reason it's on the opposite side) is a 220V AC plug.
 

mpickell

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Ok that makes sense. They throw all that stuff together at the store!

fixed the cord now and have a reading. Continuity check between heating element and metal casing around it is failing (as expected). So the element is not shorting.

Amp reading is 14 when I measure on the return wire only.

B33F6AFD-D2C4-4B9F-84F7-25CBD94225FC.jpg

Rick I really appreciate you sticking with me while I work through this. Do you have any ideas for next steps to check ? Does my evaluation of the heating element seem right or the resistance measurement?
 

mpickell

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36930CEA-DD60-4C7B-96D8-7198DA64296C.jpg

Ok, I ran it for two cycles, over an hour each. Amps measure around 13.5 on average. Is that normal? The face plate (pic above) says 4amps so i expected it to be around there instead? Cord did not get hot.

Sounds good to me if that amperage is right? I’m going to keep an eye on it but if the cord is t hot I assuming it is working now.

Could cleaning it out have fixed it? Or an new plug on the cord?
 
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rickgburton

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If you look on the tag it says MOTOR 4 amps. If you have an air fluff setting or no heat and run the machine it will be around 4 amps.
 

rickgburton

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In case you wanted to know: Your dryer was manufactured in February 1980
 

mpickell

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1980? I can't lie.. it is in really good shape for the age physically...

I ran this thing all week and had no issues...

Average running amps is between 13.5 and 14, and the cord has not been hot at all.

Thanks!!
 
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