Kenmore Dryer Fire

[Reidan]

Good Morning,
I have a Kenmore Series 90 Gas Dryer. Approx 5 years old. Model # 110.76912693-76912.

2 Nights ago the wife and I smelled something burning in our house. Upon investigation it seemed strongest near the dryer. Could not visibly see any smoke coming from the dryer, but the smell was inside the drum. Powered off unit by opening the dryer door and then unplugged the power. Opened the lower front panel and found some burned lint in the bottom of the dryer. It was not a lot of lint as we do clean it out at least once a year, But what was close to the burner assembly was indeed scorched. There was burned lint on both ends of the metal tube that surrounds the burner assembly.

I decided to inspect the dryer for visible damage before I made the decision to call a repair technician or to just replace the unit with a new one. I am a technician myself with a degree in Robotics. This includes Electronics, Pneumatics, Hydraulics, computer controls, etc. I have never been trained in appliance repair, but I have repaired my own home appliances before. I feel comfortable working on just about any kind of device. I may even attempt to repair the dryer myself. Which is what I am here looking for some guidance.

I started off with just a good visual inspection of the dryer to determine what happened. It looks as if the lint fire started where the metal shroud around the burner meets the duct that takes the heated air up the back of the dryer and into the clothes drum. There is about a ¼ inch gap where the pieces meet and it was covered in burned lint. I assume that the natural convection effect of the moving heated air would cause lint to be attracted to this opening and the lint built up around the opening. Then for some reason the lint ignited and resulted in a flash fire that (thankfully) burnt out very quickly.

After the visual inspection I used a shop vacuum to remove all traces of lint. Even opened up the blower duct and cleaned it out. Inspected all wiring and equipment to see if the flames damaged it. Everything seems to be 100% intact. No scorching or discoloration on any of the wires or components. Connectors are in good condition and are securely connected.

After the inspection I reassembled everything, but left front panel off. Got a fire extinguisher from the kitchen. Had the wife plug the unit back in and turn it on while I laid on the ground in front of the dryer and watched the operation. The igniter glowed a nice bright orange and the flame ignited quickly when the gas came on. But, the gas flame from the burner seems to be too large. It is exiting the end of the metal tube and going up into the back of the dryer.

The flame is nice and even as it travels down the tube, but when the flame exits the tube and enters the ductwork it becomes very turbulent. I assume that the 90% elbow in the duct and the air being sucked into the area where the tube meets the duct is causing this. This turbulence most likely helped the flame to come into contact with the lint built up around the opening, thus igniting the fire.

I have cleaned the lint from the bottom of the dryer before. After doing so I have inspected the burner to make sure it was working, but did not pay attention to the actual flame size. But, now that I had a lint fire I was paying particular close attention to the flame. And to me it just does not look right. I would think that flames hitting the duct on the back of the drum would allow the flames to get very close to the clothing. Not to mention it would make the back of the dryer very hot and possibly ignite anything that came into contact with the back of the dryer.

So, here are my questions. Is this flame normal operation for dryers, or do I have a problem in the gas regulator. What would cause this to happen? My assumption is that the two coils on the top of the gas regulator are what opens the gas valves and allows the gas to flow. Could a failure of one of these coils cause this to happen? If so, should I replace both coils? Could a bad spring in a valve cause it to happen?

There is a sensor of some kind on the top of the metal tube around the gas burner. If this sensor is giving a false reading could it cause the system to open the valve too far and allow too much gas to be burned?

Any other items I should check as a possible cause?


Thanks for your help and advice,
Patrick

[jeff1]

Hi,

JMO!

the gas flame from the burner seems to be too large. It is exiting the end of the metal tube and going up into the back of the dryer.

Most that I see fill the entire flame tube and some -lightly- turn the corner, but none have gone up the tube at the back.

Is this flame normal operation for dryers, or do I have a problem in the gas regulator.

From what you have described, no....pressure reugulator is possible for a little too much gas pressure.

My assumption is that the two coils on the top of the gas regulator are what opens the gas valves and allows the gas to flow.

Correct.

Could a failure of one of these coils cause this to happen?

Nope, they simply energize to open the gas safety valve so the gas can flow.

Could a bad spring in a valve cause it to happen?

Is it possible, yes....most broken springs or pins prevent the gas safety valve from working.

There is a sensor of some kind on the top of the metal tube around the gas burner

Flame sensor is one, this must sense the heat from the ignitor or the gas safety valve will not open up and allow gas flow. Safety thermostat is another one, this will shut off the heat if we get poor air flow and the flame lifts up and doesn't pull down the tube.

jeff.

[Reidan]

So, if the flame normally fills the tube, then you think my dryer is fine?

[jeff1]

Originally Posted by Reidan

So, if the flame normally fills the tube, then you think my dryer is fine?

We can't see it for ourselves.

is exiting the end of the metal tube and going up into the back of the dryer.

That's the part that bothers me. Just -slightly- pulled up is normal for most that I see.

jeff.

[Reidan]

I can not tell how far up the duct that the flame is traveling, if at all. But it is hitting the back of the 90-degree elbow and has a lot of turbulance in that area. It may be going past the elbow. How would I be able to tell?

[jeff1]

Visually is the only way I can think of...the heat travels up an air duct between the bulk head and outside cabinet wall...#5...

jeff.

[Reidan]

Originally Posted by jeff1

Visually is the only way I can think of...the heat travels up an air duct between the bulk head and outside cabinet wall...#5...

jeff.

Yes, where part 46 meets part 5, the flame appears to be making a upwards turn into part 5. And there is a lot of turbulance in that area. Now, if the main vent is blocked as badly as I suspect, the turbulance may be caused by back pressure from the air not being able to excaps the drum as freely as it should. Once I get the vent cleaned I will re-inspect the flame to see if it has changed.

[jeff1]

Once I get the vent cleaned I will re-inspect the flame to see if it has changed

Great.

jeff.