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Major Appliances/Does this video prove dryer exhaust duct is clogged?


QUESTION: Hi again,

My condo unit is on the first floor of an 8 floor building.  The dryer exhaust duct that leads to the roof is shared by all the condos in my section of the building.  I'm trying to determine whether that shared duct is clogged (or partially clogged).  My dryer (Frigidaire FSE747GES1) overheats and blows the thermal fuse after about 10 minutes of operation.

To check whether the duct is clogged, I filmed a short video (77 seconds) that shows the difference in air flow before and after disconnecting the dryer from the wall vent.  To make the air flow visible, I used smoke from the smoldering tip of a stick of incense, with the tip about 8 inches above the lint trap. (The dryer's top panel was off.  The dryer door was open so the camera could have a good view, which means I needed to manually hold the door switch in order to run the dryer.)

The first half of the video was filmed while the dryer was connected to the wall vent.  The second half was filmed after disconnecting the dryer from the wall vent.  The video shows that the air flow into the lint trap is much stronger when the dryer is not connected to the wall vent.

The video is at Youtube:

I'm hoping you can offer your expert opinion about whether
the video really does prove the exhaust duct to the roof is clogged.

Assuming the duct is clogged, is it significant that the residents of condos above mine, whose dryers share the duct, haven't been complaining that they too have dryer problems?  Might they simply be failing to notice their clothes are taking longer to dry?  Or is it likely that the clog is below the junction where the exhaust vent of the condo immediately above mine joins the vertical duct, so that my condo is the only one affected?

[As I mentioned in an earlier posting, I was very reluctant to detach my dryer from the wall because I can reach behind the dryer with only one hand... I won't know whether I'll be able to reattach the foil duct to the dryer using just my left hand until I give it a try.  But I'd tested as many other possible causes of dryer overheating as I could, so I felt I'd reached the point where I had no choice but to see what happens when I disconnect the dryer from the wall.]

Thanks in advance,

ANSWER: my opinion it does not prove the venting is blocked.  You are not controlling the airflow by removing the drum.  The airflow path is across the heating element, through the clothing and then through the lint screen across the blower wheel and out the duct work inside the dryer to your home duct work.  Leave the house went off and run a few loads.  Monitor temperature exhausting out of the dryer vent and see if it is cycling on and off via the operating thermostat.  Good Luck Eric  

---------- FOLLOW-UP ----------

QUESTION: I don't follow your reasoning about "not controlling the air flow."  The video shows that the exhaust fan can't suck much air through the lint trap when the dryer is connected to the wall.  If it can't suck much air through the lint trap, doesn't this imply it also won't be able to pull much air from the heating coil through the drum through the lint trap when the dryer is connected to the wall?  How could it pull air from the heating coil if it can't pull air into the lint trap?  Are you saying there is another path from the heating coil to the exhaust fan that doesn't pass through the lint trap?

Also, if there is no blockage beyond the wall vent, why would disconnecting the dryer from the wall vent have such an effect on the amount of air sucked into the lint trap?


ANSWER: You have the drum removed for this test....You are not controlling the air flow.  Sorry....I cannot help further.  Good Luck in your quest...   Eric  

---------- FOLLOW-UP ----------

QUESTION: I asked a couple of local companies.  They both agreed the evidence shows there's a clog beyond the wall vent.

What you wrote in your previous message shows you understand the air flow path of the Frigidaire FSE747GES1 dryer.  So I guess you don't seem to understand enough about air flow, since the drum doesn't need to be in place to test whether the exhaust fan will suck air into the lint trap.  If the duct behind the wall vent is clogged, the dryer exhaust fan won't be able to push much air into the wall vent, regardless of whether the drum is installed.  That means the exhaust fan won't be able to suck much air into the lint trap when the dryer is connected to the wall vent, regardless of whether the drum is installed.  And that's what the video shows... the exhaust fan can't suck much air through the lint trap when the dryer is connected to the wall vent.  This means the dryer can't expel much air when it's connected to the wall vent.  And the dryer needs to be able to expel the hot air to avoid overheating.

I do plan to do the test you recommend: run the dryer while disconnected from the wall vent to see if it runs okay that way.  To do this right, I'll need to buy a sufficiently long flexible duct to attach to the back of the dryer to carry away the hot exhaust.  Otherwise the exhaust heat will accumulate behind the dryer, where there isn't much room, which would overheat the dryer and prove nothing.  Home Depot sells an 8 foot flexible duct for about $10.

Thanks for your efforts, and good luck to you too!

You tried your way all the time you were asking for my advice.  You wrote books of information which I did not need.  When you request help from someone with 36 years experience and they ask questions, they need answers to go to the next step.  You did not supply these.  You created your own tests and wanted me to comment or confirm them via on-line...without actually being there.  I still at 62 years old go out and repair 7-10 units a day and have my ways which are proven tests to diagnose a problem and work for me.  Your biggest complaint was if you removed the vent from the rear of the dyer, you would not be able to reattach it.  Bottom line is someone one capable of doing that in the first place or the vent would not have been attached.  I enjoy what I do and am very good at it.  When you question my ability I normally get defensive and loose interest very quickly.  Had you listened to me in the first place and removed the vent and took temperature readings your unit would have been diagnosed several weeks ago and you would have had management take care of the problem with the venting.  Instead, you fabricated unorthodox tests and wanted me to confirm or deny the reliability of these tests when are going back to the beginning and confirming what I said weeks ago.  Not sure what you do for a living but in the future, when requesting help from an old timer.......listen.  Good Luck and no hard feeling, Eric  

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Eric Campion


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