I have a Whirlpool Duet Drier. The lint trap is in the bottom of the door opening.

It stopped working (heating elements). I bought a new dryer and I get an AF fault - air flow.

I inspected my permanent venting - it's almost plugged full of lint - 18 feet of 4" pipe.

What caused this? The vent is uninsultated and is in the crawl space of my house - is this the problem?

Could it be the dryer itself? On two occaisons I took it apart and found the bottom of the assembly full of lint - 2" deep. It actually ruined the motor - I had to replace it.

Was my dryer letting out too much lint? My new dryer has the lint trap on the top. I hear this is better.

First you are extremely lucky your home didn't catch on fire due to the lint build up!

And yes, 18' is way too long for any sort of vent pipe. What made the builder give you such a long, long vent in the first place?

You need to totally remove all the lint build up from the first dryer you had before even thinking of running your new dryer. All you are doing is making a fire hazard worse if this vent is not properly cleared out prior to use.

And yes, your old dryer was letting out way too much lint for it to be built up that bad or you did not clean out the lint after EACH use of the dryer. It's amazing that lint can build up that much just after one use.

Before you use your new dryer (after having your 18' of venting completely cleared of any lint build up) each time you need to check the lint trap and remove any lint build up whatsoever - even if it doesn't seem like "much", it will still build up and cause problems.

One word: gravity. You run is likely mostly horizontal and there may not be enough air velocity ot get the missed lint out.

You need to inspect the duct periodically. Find a good frequency good for you. Make sure the door opens on the dryer exhaust too.

Install a dryer duct booster fan. Tjernlund Retail Store—Dryer Duct Booster (Model LB1), 5 Year No-Clog Guarantee (http://tjernlund.com/retail/dryerductbooster.htm?gclid=CIjR7qjSv5wCFR9N5Qod_w6 1og)

Equlivelent feet is not feet. A 90 deg elbow is equal to 5 feet and you probably have at least two. So, that's 28' of equivalent pipe.

PS; This is why the heating element burned out.

Guys - thank you both for your answers. A little more information:

1. I just replaced all of the venting and eliminated 5 right angle pieces. I am guessing I was at 45 feet of vent (considering a right angle to be 5 feet).

2. We always check the lint trap.

2. A year ago my motor quit working. I took the drier apart and found a ton of lint - it was actually 3-4 inches at that time. It was so thick and dense, I thought it was insulation at first. I cleaned out all of the lint and replaced the motor and sealed all of the internal venting with silicon - I did nothing with the heating element.

3. I just took it apart on Saturday and found two inches of lint - after a year.

4. With the right angles, I'm estimating 28 feet of pipe. Without right angles about 18 feet of pipe. It's still in the basement crawl space. I insulated it with 3" of insulation. Do I still need a booster pump?

Wow! I don't see any reason for insulation. The pipe is hot, so condensation won't form.

On a cold day, you MIGHT get some dripping, but I doubt it.

To evaluate the need for a booster pump, your going to have to inspect periodically.

Give it 2 months, 6 months and then a year depending on what you find.