Thread Number: 68155  /  Tag: Modern Dryers
Dumb dryer question
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Post# 908758   11/27/2016 at 18:24 (512 days old) by LordKenmore (The Laundry Room)        

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I'm using a ca. 2007 WP dryer. The WP design that has been around since forever. Recently, I've been wondering something. There is a switch that has three positions, giving a range from drying for delicate laundry to heavy duty. Just what DOES that switch control? Does it select thermostats (with hotter heat for sturdier clothes, lower heat for delicates)? Does it switch heating elements (more element power for sturdier clothes, less for delicates)?

Or is this switch just there, doing nothing, but looking like a valuable feature? LOL

This not hugely important, but I've wondered...

Post# 908772 , Reply# 1   11/27/2016 at 19:51 (512 days old) by appnut (TX)        

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That's a temperature knob.  Low, medium, and high. 

Post# 908783 , Reply# 2   11/27/2016 at 21:36 (512 days old) by DADoES (TX, U.S. of A.)        

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Depends on the electrical design whether the are multiple thermostats.  Whirlpool changed (at some point in the 1980s?) to a single operating thermostat with a bias heater that tricks it into reading lower air temperatures.  The bias heater fits around the thermodisc thermostat and heats it to offset the normal trigger temperature.  High temp, the bias heater presumably is off and the thermostat operates at its normal rated temp.  Progressively lower temp settings, the bias heater gets hotter to provide more offset.

Electronic control models typically have a thermistor instead of a thermostat.  A thermistor varies its resistance response according to temperature, which the control board reads to operate the heat source according to the setting.

Cite the model number of your dryer so parts diagrams can be searched for details of its design.

Post# 908826 , Reply# 3   11/28/2016 at 08:47 (511 days old) by vacerator (Macomb, Michigan)        
Mine has

a drying temp. selector, but it does not change on automatic dry cycles. Neither does the dry time + or - buttons. It also has a dryness level selector for less, normal, or more, which is only adjustable on automatic dry cycles, and not timed dry cycles. On timed dry cycles, the dry time + or - selector changes the dry time in the display, and the temp. low, medium, or high selector adjusts the drying temp. So, yes, on automatic cycles, the sensors are energized, and the manual selectors over ridden. On timed dry cycles the sensors are not energized. The damp dry light and beep also do not signal.
So even on a top of the line dryer, it's a choice of some features doing nothing.
I have found that loads are often dry before the cycle ends even on the automatic cycles. The sensors are supposed to shut the dryer off when the load is dry according to the users guide, after cool down of course. The timer and sensors must have laylo, and halo limit calibrations which overlap.
The display even says estimated dry time, so I use eco normal which starts out at 38 minutes, and goes to about 54 minutes just before the damp dry signal beeps for moderate loads, and as high as 73 minutes for larger or damper loads. Most loads are dry when this cycle ends, and it never takes as long as the display says.
They are good dryers.

Post# 908861 , Reply# 4   11/28/2016 at 13:22 (511 days old) by alr2903 (TN)        

Glen's reply #2 is exactly what Volvoguy described to me when he looked at my WP made (gas) Admiral.   Low heats at the same rate as high but the burner cycles less frequently, if I understood correctly.

Post# 908867 , Reply# 5   11/28/2016 at 14:04 (511 days old) by vacerator (Macomb, Michigan)        

the burner valve is single stage.
This wasn't a dumb dryer question either.

Post# 908872 , Reply# 6   11/28/2016 at 14:22 (511 days old) by DADoES (TX, U.S. of A.)        

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Mine has a drying temp. selector, but it does not change on automatic dry cycles. Neither does the dry time + or - buttons. It also has a dryness level selector for less, normal, or more, which is only adjustable on automatic dry cycles, and not timed dry cycles. ...
Automatic dry / fabric cycles on electronic control machines nowadays are typically "hard-wired" for a given temperature appropriate for the fabric.  Manual selection of temperature is for timed drying and does not apply to auto-fabric cycles.  Choose a different auto-fabric cycle if you want a different temperature, the composition of the load doesn't necessarily have to match the selected fabric-cycle.

Dryness level selection, of course, does not apply to timed drying.  The point of timed drying is that the machine runs for the selected time whether the load ends up damp or over dried.

Kenmore had a modulating gas burner back in the day that varied the heating rate (higher BTU output at the start, lower BTU as the load progressed toward dryness) for their SoftHeat feature.  IIRC a few other brands had a similar feature.

Whirlpool had a reduced wattage electric element and two-stage (I think?) gas burner for a while on two-speed dryers (NOT meaning two tumble speeds).

My Fisher & Paykel topload dryer has two heating elements.  One is 1/3 of total heat output (1,400 watts), the other is 2/3 (3,600 watts).  Both elements operate at the High temp setting.  Only the 2/3 element operates for Medium and Low to provide a reduced heat input rate for perm press and delicate items.  Only the 1/3 element operates during reverse tumble at all temp settings.

Post# 908901 , Reply# 7   11/28/2016 at 17:25 (511 days old) by LordKenmore (The Laundry Room)        

lordkenmore's profile picture
Thanks for the answers!

I Googled the model number (WED5540SQ0) and came up with a parts list that has a thermostat that has a bias heater. Which I'd sort of expected--this dryer is obviously much newer than the the 1980s design change mentioned above. (IIRC, the apparently matching--or at least very similar looking visually--washer was said to date to about 2007.)

I have to admit...a heater in a thermostat is about the last thought I'd have ever had. It almost seems a little Rube Goldberg like, although one assumes that there were good reasons for making that choice.

Post# 908906 , Reply# 8   11/28/2016 at 18:12 (511 days old) by LordKenmore (The Laundry Room)        
Another thermostat question

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One concern I've had with this dryer is it seems to run cooler than Whirlpools I've used before. I've checked the temperature of the exhaust as best as I can (using a cooking thermometer held in the middle of the air stream) on the "Heavy" (hottest) setting, and it seems like the high is 150/160 degrees or so, and the lowest point low is about 125 degrees or so. Is this in line with "normal"? And is this acceptable from a view of sanitizing laundry via drying in the dryer?

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