Clothes Dryer Moisture Sensor

We made a BIG mistake in December and purchased a new dryer with "electronic" moisture sensor. It's still under warrentee but with
the trouble we have had these few months, I'm morally certain that I will have to buy the extended service plan or go broke on service calls or overprices repair parts.
The techs have put in THREE timers, THREE "control boards", and one "operating thermostat."
My question for this group is on the details of the operation of the "control board."
Functionally, the board will pass power to the timer motor when the sensor says the clothes are dryer. Problem is that 3 separate "control boards" continually say the clothes never dry.
I am hoping that someone out there has access to a schematic of the "control board." From what I can guess from the dryer schematic, it's kind of scary! The dryer uses 240 for the heater and 120 for the motor/timer/"control board"/etc. It's connected for a 3 wire ourlet (neutral/ground are the same). The "control board" has connections for "chassis", neutral, Line !, timer motor, and sensor. When it's satisfied, it must connect the timer motor to neutral. It must function with separate neutral as well as with neutral/ ground(chassis) being the same. While it's still under warrentee, I don't want to take things apart but it seems to have a 3 wire device which I suspect provides the path for the timer motor, a mess of 2 wire components with axial leads, a small electrolytic cap, and a 14- pin DIP IC.
Does anyone here have a schematic of a "typical" control board?
Again, a new one is under order and the repairs are still in the hards of the technicians. For the time being, I just wanna know for myself WTF is happening.
Thanks in advance
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On Mon, 25 Feb 2008 21:07:20 -0800 (PST), BigJohnG

I worked on a GE a while ago and got the information of how that one works (auto dry) Basically it just looks at the exhaust temp and allows the timer to run when exhaust air reached the set temperature (assuming wet clothes prevent the air from warming up). I looked at this with my heat gun with a clamp on across the power lead and it does seem to be true. Basically the timer only runs when the heat cycles off. It will cycle a number of times before the clothes are really dry. The timer may even be in series with the heater element when the thermostat opens. On my Whirlpool this thing was so inaccurate I just took my label gun and relabeled "economy dry" (or whatever that was) to "a little wet" because that is how the clothes come out. It really only works up close to the highest auto dry setting. I am just going with it.
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Yep! That's how the "non-electronic" ones work. The ones with the "electronics" only advance the timer when the sensor indicates the clothes are dry. The "non-electronic" version became standard by the early 70s. The "electronic" version became available a little later but up to now I didn't buy such a machine. The Consumer Reports type claim that the electronic sensors provide better results but at the cost of a $100 "delicate" part.
For over 30 years I have used dryers without the "electronics" and as far as I am concerned, they work just fine, thiank you.

Yep! That's how I remember it being done. I guess that the timer motor ran on 240 volts in the electric models and on 120 volts in the gas models.
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On Tue, 26 Feb 2008 05:16:59 -0800 (PST), BigJohnG

The motor is still 120v, it connects the other end to the neutral.
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wrote:
| Yep! That's how I remember it being done. I guess that the timer | motor ran on 240 volts in the electric models and on 120 volts in the | gas models.
Timer motor on 240? Oh the horror of it :-)
Now if you ever find a clothes dryer that runs _everything_ on 240 volts line to line, with no need to connect the neutral, I'd like to know about that one.
I'd run my computers on 240 volts L-L if I could find a correct surge protector for that.
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On 27 Feb 2008 02:36:12 GMT, snipped-for-privacy@ipal.net wrote:

I don't know why you would want to except to just be different but you can order a surge strip from UK or some other "across the ponmd" country and get a few line cords for your PC hardware that match the strip. You will have to install a 6-15 plug on it tho. The PC end will be the same (IEC320)
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On Wed, 27 Feb 2008 00:50:37 -0500 snipped-for-privacy@aol.com wrote: | On 27 Feb 2008 02:36:12 GMT, snipped-for-privacy@ipal.net wrote: | |>I'd run my computers on 240 volts L-L if I could find a correct surge |>protector for that. | | I don't know why you would want to except to just be different but you | can order a surge strip from UK or some other "across the ponmd" | country and get a few line cords for your PC hardware that match the | strip. You will have to install a 6-15 plug on it tho. | The PC end will be the same (IEC320)
I have a German one ... Schuko plug, 5 Schuko outlets. But these are designed for 230 volts (close enough to 240) between current carrying conductors as well as 230 volts between either of them and ground. That doesn't match the US system, which needs 120 volt protection between current carrying conductors and ground. So it needs to be of a different design for the different ground relationship.
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If the protection works at 240v it will also work at 120v or anything lower.

Sorry, what different "ground relationship"? It's still less than 240v.
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From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11
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charles wrote:

The thread has, apparently, meandered into the area of "sugre strips". The components and possibly the design of a surge protector for 120v are going to be different than for a 240v one.
--
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| charles wrote:
|>> | |>> |>I'd run my computers on 240 volts L-L if I could find a correct surge |>> |>protector for that. |>> | |>> | I don't know why you would want to except to just be different but you |>> | can order a surge strip from UK or some other "across the ponmd" |>> | country and get a few line cords for your PC hardware that match the |>> | strip. You will have to install a 6-15 plug on it tho. |>> | The PC end will be the same (IEC320) |> |>> I have a German one ... Schuko plug, 5 Schuko outlets. But these are |>> designed for 230 volts (close enough to 240) between current carrying |>> conductors as well as 230 volts between either of them and ground. |>> That doesn't match the US system, which needs 120 volt protection |>> between current carrying conductors and ground. |> |> If the protection works at 240v it will also work at 120v or anything lower. |> |> |>> So it needs to be of a different design for the different ground |>> relationship. |> |> Sorry, what different "ground relationship"? It's still less than 240v. |> | | The thread has, apparently, meandered into the area of "sugre strips". | The components and possibly the design of a surge protector for 120v | are going to be different than for a 240v one.
I think he basically didn't understand that getting the clamping voltage as close to the operating voltage peaks as possible offers the best level of protection ... or that 240 volts USA-style really has 120 volts between both line wires and ground.
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snipped-for-privacy@ipal.net wrote:

. Sounds reasonable. But Francois Martzloff, who was the US-NIST guru on surges, wrote in one of his technical papers http://www.eeel.nist.gov/817/pubs/spd-anthology/files/Enduser.pdf "The fact of the matter is that nowadays, most electronic appliances have an inherent immunity level of at least 600 V to 800 V, so that the clamping voltages of 330 V widely offered by TVSS manufacturers are really not necessary. Objective assessment of the situation leads to the conclusion that the 330 V clamping level, promoted by a few manufacturers, was encouraged by the promulgation of UL Std 1449, showing that voltage as the lowest in a series of possible clamping voltages for 120 V circuits. Thus was created the downward auction of "lower is better" notwithstanding the objections raised by several researchers and well-informed manufacturers. One of the consequences of this downward auction can be premature ageing of TVSS that are called upon to carry surge currents as the result of relatively low transient voltages that would not put equipment in jeopardy."

. Certainly true that the operation of the suppressor is not what the manufacturer intended.
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| Sounds reasonable. But Francois Martzloff, who was the US-NIST guru on | surges, wrote in one of his technical papers | http://www.eeel.nist.gov/817/pubs/spd-anthology/files/Enduser.pdf | "The fact of the matter is that nowadays, most electronic appliances | have an inherent immunity level of at least 600 V to 800 V, so that the | clamping voltages of 330 V widely offered by TVSS manufacturers are | really not necessary. Objective assessment of the situation leads to the | conclusion that the 330 V clamping level, promoted by a few | manufacturers, was encouraged by the promulgation of UL Std 1449, | showing that voltage as the lowest in a series of possible clamping | voltages for 120 V circuits. Thus was created the downward auction of | "lower is better" notwithstanding the objections raised by several | researchers and well-informed manufacturers. One of the consequences of | this downward auction can be premature ageing of TVSS that are called | upon to carry surge currents as the result of relatively low transient | voltages that would not put equipment in jeopardy."
I assume the 330 volt level mentioned it pair to 120 RMS volt circuits, and 660 volts would be the level for a 240 RMS volt circuit. Would his discussion of 600 to 800 volts them be doubled to 1200 to 1600 volts?
Or maybe his 600 to 800 volt experience is actually _because_ a lot of electronics are made to work OK on 240 volts international power per the CE standards he mentions.
If I am running my computer with an autoranging (100-240 volt) PSU on the 120 volt L-N circuit, and some power distribution event (such as a line to ground fault on a different MV phase) raises it to 150 volts or more, I won't be worried about that. But if I am running it at 240 volts L-L, the same event could deliver 300 volts. Tell me just how long a typical PSU (of the autoranging type) can handle that 300 RMS volts (424 volts peak).
Try running one on 277 volts for a year and let me know if it keeps on working.
Sure, a single narrow spike at 800 volts is not going to affect a PSU very much if at all. But some sustained overvoltage might. Big wide spikes might. Repeated spikes might.
If that voltage is what the UL says is right, and tests for (I presume they have surge simulation tests under power to verify that MOV devices don't just open back up under a surge event, etc), then that is what is needed to get UL listing, which is what is needed to get insurance coverage in case some distribution overvoltage event I can't prove is caused by the utility causes my house to burn down. Having my own home made surge protectors, even if they are supplementary to 240 volt ones listed by TUV, is not likely to impress the insurance adjuster. It would be hard enough explaining that the computer is made for 240 volts. All the rest of it would have to be shown to be made for 240 volts as well.
Now I wonder if UL tests computer PSUs for operation at 240 volts, too, or just at 120 volts even though specified to be usable at 100-240 volts.
|> or that 240 volts USA-style really has 120 volts between |> both line wires and ground. | . | Certainly true that the operation of the suppressor is not what the | manufacturer intended.
The only UL-listed 240 volt ones I have seen are the "whole house" type you plug into a breaker panel. I am considering that as an option to run my computers on 240 volts, in a subpanel just for the one computer circuit.
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snipped-for-privacy@ipal.net wrote:

UL verifies products at the conditins specified by the manufacturer. If it is marked 100-240, for example, then they do whatever testing is appropriate at both extremes.
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| snipped-for-privacy@ipal.net wrote: |> |> Now I wonder if UL tests computer PSUs for operation at 240 volts, |> too, or just at 120 volts even though specified to be usable at |> 100-240 volts. |> |> | UL verifies products at the conditins specified by the manufacturer. If it | is marked 100-240, for example, then they do whatever testing is appropriate | at both extremes.
So every PSU specified as a 100-240 volt autoranging device is tested at 240 volts? Can we assume they do that testing with a 120-0-120 power system under the assumption that it only applies to usage in the USA? Or can we assume they do that testing with a 240-0 power system under the assumption it was designed for that in other places in the world?
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snipped-for-privacy@ipal.net wrote:

. I believe you would have to measure immunity levels on actual equipment. .

. I believe Martzloff is talking about equipment like TVs and VCRs which are straight 120V. .

. Surges, which is what Martzloff is talking about, are by definition very short events.
Martzloff has also written "In fact, the major cause of TVSS [surge suppressor] failures is a temporary overvoltage, rather than an unusually large surge." .

. UL1449 has quite a few tests. MOVs fail by conducting. .

. Homemade surge suppressors are not a good idea. MOVs fail by starting conduction at too low a voltage, like normal voltage, and go into thermal runaway. That can be a fire hazard. UL1449 requires, since 1998, thermal disconnects to remove overheating MOVs.
--
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| Martzloff has also written "In fact, the major cause of TVSS [surge | suppressor] failures is a temporary overvoltage, rather than an | unusually large surge."
And these would not damage the TV?
|> If that voltage is what the UL says is right, and tests for (I presume |> they have surge simulation tests under power to verify that MOV devices |> don't just open back up under a surge event, etc) | . | UL1449 has quite a few tests. MOVs fail by conducting.
Conducting when the voltage reaches the specified level is doing the job expected of them. I would not call that a failure. The device may not be usable after that event (the MOV being fused to conduct), but that is part of the design.
I believe UL should be testing surge protectors with respect to things like whether they pose safety risks. Will it electrocute me when I flip the switch on it? Will it break and short out when I try to plug in to one of its outlets? Will the cord on it fail and expose wires when it is handled a little roughly? Will it develop a hot spot and result in my house burning down when I am away or asleep? Will it explode when given the design voltage plus or minus the prescribed margin range?
|> Having my own home |> made surge protectors, even if they are supplementary to 240 volt ones |> listed by TUV, is not likely to impress the insurance adjuster. | . | Homemade surge suppressors are not a good idea. MOVs fail by starting | conduction at too low a voltage, like normal voltage, and go into | thermal runaway. That can be a fire hazard. UL1449 requires, since 1998, | thermal disconnects to remove overheating MOVs.
This is exactly why I need to find who makes a NEMA 6-15 surge protector power strip.
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snipped-for-privacy@ipal.net wrote:

No. Why do you think it would? if the surge suppresser clips at a safe voltage to protect from spikes, it won't go any higher with a overvoltage condition, but the MOV or other protection device quickly overheats as it tries to maintain the proper voltage. If the line voltage is high enough, it will trip the Breaker, or blow the fuse for that AC circuit. The protective device can only dissipate a small amount of heat before it self destructs.
--
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On Fri, 29 Feb 2008 02:23:56 -0500 Michael A. Terrell
| snipped-for-privacy@ipal.net wrote: |>
|> |> | Martzloff has also written "In fact, the major cause of TVSS [surge |> | suppressor] failures is a temporary overvoltage, rather than an |> | unusually large surge." |> |> And these would not damage the TV? | | | No. Why do you think it would? if the surge suppresser clips at a | safe voltage to protect from spikes, it won't go any higher with a | overvoltage condition, but the MOV or other protection device quickly | overheats as it tries to maintain the proper voltage. If the line | voltage is high enough, it will trip the Breaker, or blow the fuse for | that AC circuit. The protective device can only dissipate a small | amount of heat before it self destructs.
This was a discussion about a suggestion tha the MOV condunction voltage should be higher than now used (330V for 120V systems). He wants to raise that voltage to avoid certain situations causing TVSS failure so the protection against spikes (above 800V) is maintained longer. My position is that the swells as high as 565V RMS could in fact cause damage to the TV. Under his proposal, these would be be suppressed. I think that is a bad idea because these voltage swells really can do damage.
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snipped-for-privacy@ipal.net wrote:

. Surge suppressors are intended to protect against surges. Raising the clamp voltage is to lower unnecessary suppressor exposure to surges that do not damage connected equipment.
Surge suppressors are not intended to protect against longer duration swells or even longer duration overvoltage. Martzloff's comment above is that the major cause of failure is overvoltage, which suppressors are not intended to protect against.
If you keep the clamp voltage low, you are likely not increasing protection from swells because a swell may well kill the MOV anyway. To protect against overvoltage get a suppressor that disconnects on overvoltage.
--
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| snipped-for-privacy@ipal.net wrote: |> On Fri, 29 Feb 2008 02:23:56 -0500 Michael A. Terrell
|> |>
|> |> |> |> | Martzloff has also written "In fact, the major cause of TVSS [surge |> |> | suppressor] failures is a temporary overvoltage, rather than an |> |> | unusually large surge." |> |> |> |> And these would not damage the TV? |> | |> | |> | No. Why do you think it would? if the surge suppresser clips at a |> | safe voltage to protect from spikes, it won't go any higher with a |> | overvoltage condition, but the MOV or other protection device quickly |> | overheats as it tries to maintain the proper voltage. If the line |> | voltage is high enough, it will trip the Breaker, or blow the fuse for |> | that AC circuit. The protective device can only dissipate a small |> | amount of heat before it self destructs. |> |> This was a discussion about a suggestion tha the MOV condunction voltage |> should be higher than now used (330V for 120V systems). He wants to |> raise that voltage to avoid certain situations causing TVSS failure so |> the protection against spikes (above 800V) is maintained longer. My |> position is that the swells as high as 565V RMS could in fact cause |> damage to the TV. Under his proposal, these would be be suppressed. |> I think that is a bad idea because these voltage swells really can do |> damage. | . | Surge suppressors are intended to protect against surges. Raising the | clamp voltage is to lower unnecessary suppressor exposure to surges that | do not damage connected equipment.
The last 7 words are the part we do not agree on.
| Surge suppressors are not intended to protect against longer duration | swells or even longer duration overvoltage. Martzloff's comment above is | that the major cause of failure is overvoltage, which suppressors are | not intended to protect against.
I've read discussions and online pages to the contrary. If you have put forth your theory ahead of time, I could have recorded the locations for you.
| If you keep the clamp voltage low, you are likely not increasing | protection from swells because a swell may well kill the MOV anyway. To | protect against overvoltage get a suppressor that disconnects on | overvoltage.
The surge suppressor already does this. Sure, it can _die_ while doing this. The MOV shorts across, causing an increase in current that trips the supplementary breaker in the strip (usually integrated in the switch). There, appliance protected by one low cost device.
Maybe what should have proposed was that we use a more expensive device that integrates higher level MOVs with overvoltage sensors. If he can show that such a MORE EXPENSIVE device is worth the extra cost in the longer term, he wins. But I think he cannot. The reason ons that even a doubling of cost to make such a device (I think it is more than just that) would not produce a win for the consumer because really too few surge protectors have this issue for the total payout to not be increated by the more expensive device.
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