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Thread Number: 79963
/ Tag: Modern Dryers
What is the difference between Automatic Dry and Sensor Dry? |
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| Post# 1038862 7/20/2019 at 17:31 (1,731 days old) by norgechef (Saint George New Brunswick ) | ||
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Do they both use a sensor? and Is one more accurate than the other? I would assume its sensor dry being more accurate with how common it is among dryers currently on the market. I know dryers with sensor dry have a moisture sensing strip in the drum, but what do dryers with ''Automatic dry'' use? | ||
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Post# 1038863 , Reply# 1 7/20/2019 at 17:44 (1,731 days old) by wayupnorth  (On a lake between Bangor and Bar Harbor, Maine) |
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Post# 1038868 , Reply# 2 7/20/2019 at 18:08 (1,731 days old) by DADoES (TX, U.S. of A.) |
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 Either way refers to "auto"matic drying without specific cycle timing. Thermostatic autodry has the air temperature thermostat control the timer. The timer does not run while the heat source (electric element or gas burner) is operating. Evaporating moisture at the beginning of the cycle keeps the air temperature down so the heat runs longer and for shorter "off" periods to reach and maintain the target temperature, and the timer runs less. Heat runs shorter and less often as the load progresses toward dryness so the timer runs more. Sensor autodry involves a moisture sensor that controls the timer independently of the air temperature. Typically there are two metal bars in the drum connected to a low-voltage electric circuit. Wet/damp clothes brushing across the bars completes the circuit and stalls the (mechanical) timer. Same premise ... that the timer is stalled less, runs more as the load progresses toward dryness. This method also works with fully electronic controls. The control software can count the moisture hits and be programmed with different algorithms for various types of fabrics. Thermostatic autodry can be affected by running the dryer in a cold environment .... very cold incoming air takes longer to heat to the target temperature, although the load IS giving up moisture during the interim. Moisture sensing isn't affected. | ||
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Post# 1038952 , Reply# 4 7/21/2019 at 14:38 (1,730 days old) by ea56 (Cotati, Calif.) |
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| Post# 1038971 , Reply# 5 7/21/2019 at 15:41 (1,730 days old) by vacerator (Macomb, Michigan) | ||
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Oh, I am understanding that higher end models use both a thermostat to sense temp. in the dryer, and a sensor on the drum to sense dryness in the clothing. | ||
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Post# 1038978 , Reply# 6 7/21/2019 at 16:56 (1,730 days old) by DADoES (TX, U.S. of A.) |
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Post# 1038980 , Reply# 7 7/21/2019 at 17:22 (1,730 days old) by chetlaham (United States) |
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@DADoES: if your dryer had a lower wattage heating element you would not need a cycling thermostat ;)
Auto Dry: Typically the cycling thermostat is wired such that the timer does not advance when it is closed. As the clothes loose moisture, the exhaust temperature rises. This causes the cycling stat to open and the timer to advance. As the clothes become dry the length of the open time increases the the length of the closed time (calling for heat) decreases. This helps advance the timer faster into cool down. Auto dry is a solution to the down falls of timed dry. With timed dry its guess work and people often set the dryer above the required time because no one wants to come back and reset the timer for another 10 or 15 minutes. Sensor dry works by having a metal strip which passes a tiny amount of electricity through the fabric. As the clothes loose moisture, the resistance of the fabric increases and less electricity can pass. At some point the resistance is high enough that the electronic control trigger the timer and it starts advancing. In theory sensor dry is more accurate because you are actually "feeling" the clothes for moisture instead of relying on the exhaust temperatures. | ||
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Post# 1038986 , Reply# 9 7/21/2019 at 17:54 (1,730 days old) by DADoES (TX, U.S. of A.) |
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It has two heating elements. 1,400 watts operates during reverse tumble. 3,600 watts during forward tumble for low (127°F) and medium (140°F) temp. Both during forward tumble for high temp (149°F). 5°F differential from the target temp at the thermistor in the airflow outlet housing for heat to cycle back on. (edited to remove erroneous URL entry) This post was last edited 07/21/2019 at 21:16 | ||
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Post# 1039038 , Reply# 10 7/22/2019 at 00:15 (1,730 days old) by LowEfficiency (Iowa) |
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Neither system is infallible, and both have to use some guesswork on top of sensor data to dry a load appropriately.
If you want some insight, reading patents is a great resource. For example, read some of the 1950s auto-dry patents - that's when the basic systems that were common in the 60s-70s were really born, and the descriptions are the most succinct. Everything sounds so rosy and magical - wrap it up folks, the problem is solved. Then skip ahead to the 1980s-1990s, and read the patents on the equivalent modern systems. They will describe the new systems and their merits, going into great detail about what was so wrong with the 1950s-1970s designs, and the complex systems and tables of data it took to improve upon those results. Remember too that "dryness" will always be subjective. Maytag struggled with this a lot in the 1970s - erring on the side of under-drying to avoid going over, but receiving frequent customer complaints for incomplete drying as a result. Both their dryness thresholds as well as machine settings and labeling were adapted over the years, in response to customer feedback, and to ultimately move more of the "automatic" system's control and configurability back into the hands of the operator. | ||
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Post# 1039128 , Reply# 12 7/23/2019 at 02:09 (1,729 days old) by askolover (South of Nash Vegas, TN) |
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