Dryer vent length and limit switches

Bob Kontak · Bob Kontak's Garage

Main question - Can a temp limit switch get "tired"? It's a $10 part with a dime sized mechanism with a reset button on it. The drum has to come out to replace.

Temp high limit switch tripping unless vented into laundry/mud room (with door to garage open)

Gas dryer. Grossly over long and "bendy" exhaust system (six 90 degree bends). Dryer and venting system completely cleaned out five months ago after problem started. Did not fix.

Obvious answer is vent straightening. However, why did it work for two years with an under capacity exhaust? This makes me think the limit switch is tired.

wdfifteen · wdfifteen's Garage

How is the air supply into the dryer? Could be restricting the intake duct?
These switches either work or don't work in my experience. I would check really well for a restriction inside the dryer, if you don't find one, then replace the switch.

Bob Kontak · Bob Kontak's Garage

Quote:

Originally Posted by wdfifteen

How is the air supply into the dryer? Could be restricting the intake duct?
These switches either work or don't work in my experience. I would check really well for a restriction inside the dryer, if you don't find one, then replace the switch.

That would explain it. Possibly in or near the blower fan beyond viewing. Intake air will be reduced since it cant escape and heat will build. Pal claims it's clean as a whistle but to go in deep and truly confirm is a PITA with these fancy jobbies. He would not have done that.

Will do that first.

Thanks and regards.

Hads930 · 03-04-2015, 11:00 AM

Is the blower coming on? If not the air is not leaving and could be tripping switch. When I was building houses, if exhaust run was over 20 ft an inline blower was used so the dryer blower did not burn up prematurely from being over worked. Every 90 elbow equaled 5 feet, almost every house I built had a secondary fan.

look 171 · 03-04-2015, 11:03 AM

Yep, another fan pulling the air somewhere along the line will do tha trick. Too many bends

stinkindiesel · 03-04-2015, 11:20 AM

In my experience, limit switches are like circuit breakers. Once "exercised," they seem to trip a little easier than they did when new. Exercised enough, they can trip way prematurely. They're cheap enough to replace, I'd go ahead and replace it.

Course, I agree with the others that you need to simplify your outlet and get rid of as many of the 90 degree bends as you can.

Gary

MikeSid · 03-04-2015, 01:07 PM

Not really on topic, but I can't imagine designing a dryer where the drum has to be removed to replace this particular part. Who manufactured this unit??

rick-l · 03-04-2015, 03:22 PM

On old Maytag dryers if junk got past the lint filter it would shear the key on the shaft for the fan. It would turn but not blow much air.

john70t · 03-04-2015, 03:53 PM

Had the vents and drier cleaned recently by a company.
They used an air compressor w/the drier on. Snaked a pusher and puller tube (with spacer fingers on the heads) through the system.
Quite a bit of lint was extracted from even a short run.

These could be fabricated or bought http://www.amazon.com/Gardus-R3203612-LintEater-12-Foot-Extension/dp/B001652LO6/ref=sr_1_7/178-3837320-2684100?ie=UTF8&qid=1425516742&sr=8-7&keywords=Dryer+Lint+Cleaner

Bob Kontak · Bob Kontak's Garage

Quote:

Originally Posted by Hads930

Every 90 elbow equaled 5 feet, almost every house I built had a secondary fan.

I did see that rule of thumb. 25 feet max straight pipe. Less 5' for 90's and 2 1/2' for 45's. He has about minus 15'.

No secondary blower. Thanks for that info. They are well under $100 and he paid one pro $150 to reset the thermo switch. If the dryer is blowing real well (he did say a tech dismantled it to clean out) I will start there rather than re-crafting the exit pipes.

Dryer is an LG front loader. Spiffy one.

Thanks everybody.