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
Reply to
BigJohnG
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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.
Reply to
gfretwell
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.
Reply to
BigJohnG
The motor is still 120v, it connects the other end to the neutral.
Reply to
gfretwell
| 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.
Reply to
phil-news-nospam
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)
Reply to
gfretwell
| |>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.
Reply to
phil-news-nospam
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.
Reply to
charles
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.
Reply to
Palindrome
| |> |> | |> |>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.
But it won't work correctly. It won't provide the full protection.
|> 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 clamping voltage is at a certain percentage above the waveform peak voltage. Less than that risks false clamping. More than that and you don't get the protection of smaller surges.
I don't recall exactly what that best ratio actually is. Clearly it has to be above the waveform peak. So for 120 volts it needs to be above 170 volts. For 240 volts it needs to be above 340 volts. For the sake of discussion for now, I'll assume the ideal value would be 200 volts for a 120-volt L-N system (US) and 400 volts for a 240-volt L-N system (UK).
A surge protector for a L-N system would have the MOV devices wired not only L-N, but also L-G and even N-G (offering protection against surges relative to ground on the neutral wire, but not going mad if the wiring is reversed). All these would be 200 volt devices for a surge protector in the US, and 400 volt devices for a surge protector in the UK.
Using the UK surge protector in the US would be "safe" in the sense of no false clamps. The reverse is not true.
A surge protector for a L-L system, as 240 volts is in the US, needs to be wired differently. The 200 volt MOV devices would be used between each line wire and ground. But 400 volt MOV devices would be used between the two line wires.
Using a UK surge protector on the US 240 volt system would provide less protection of any L-G surge. A surge of 360 volts L-G would not be clamped to ground.
I suppose what I could do is take my Schuko surge protector and replace all the L-G wired devices with lower voltage ones taken from a common NEMA 5-15 surge protector. But I would rather just have an engineer with specific experience in this be sure it is designed correctly, and manufactured correctly, and even tested at the UL or other labs. Would they know what to do with a surge protector that comes in for testing with a NEMA 6-15P plug and a few NEMA 6-15 outlets? I bet they would.
Reply to
phil-news-nospam
|> |>> |>> | |>> |>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.
Reply to
phil-news-nospam
. Sounds reasonable. But Francois Martzloff, who was the US-NIST guru on surges, wrote in one of his technical papers
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"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.
Reply to
bud--
| Sounds reasonable. But Francois Martzloff, who was the US-NIST guru on | surges, wrote in one of his technical papers |
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| "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.
Reply to
phil-news-nospam
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.
Reply to
Ben Miller
| 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?
Reply to
phil-news-nospam
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.
Reply to
bud--
Electronic power supply must withstand 300 volts for 3 milliseconds without damage and repeatedly - an industry standard. Appliances typically do better. If suffering usually long surges of the type suspected, then dimmer switches and GFCIs throughout the building are being replaced routinely. Changing incandescent lamp intensities elsewhere would be an obvious symptom. However, if a suspected surge is a different type (the typically destructive type); then damage, what those voltages are between, and a solution are different.
As usual, best evidence is the dead body. What on that electronics failed would say so much about why.
A 'whole house' protector for 240 volts (North American) means everything (including 120 volt appliances) has protection; if that protector also has an essential and short earthing connection. If electronics damage still occurs, then surges do not explain the failure.
Reply to
w_tom
. An IEEE guide on surges and surge protection at:
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an illustration of a surge coming in on a cable service (pdf page 40). The problem is the ?ground? wire from cable entry block to power service is too long allowing a damaging voltage between cable and power wires. A power service suppressor would do nothing to solve the problem.
Cable, phone, ... other entry protectors need to protect to ground and have short ?ground? wires to the earth conductor at the power service. Otherwise the guide says "the only effective way of protecting the equipment is to use a multiport [plug-in] protector". A N-G bond in the power service also helps limit the voltage difference, particularly if a power service surge suppressor is not used.
A guide on surges from the US-NIST cites US insurance information that indicates equipment most likely to be damaged by lightning is computers with modem connection and TV related equipment - presumably with cable connection. All can be damaged by voltage between signal and power wires.
Reply to
bud--
| 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.
Reply to
phil-news-nospam
|
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| has an illustration of a surge coming in on a cable service (pdf page | 40). The problem is the ?ground? wire from cable entry block to power | service is too long allowing a damaging voltage between cable and power | wires. A power service suppressor would do nothing to solve the problem. | | Cable, phone, ... other entry protectors need to protect to ground and | have short ?ground? wires to the earth conductor at the power service. | Otherwise the guide says "the only effective way of protecting the | equipment is to use a multiport [plug-in] protector". A N-G bond in the | power service also helps limit the voltage difference, particularly if a | power service surge suppressor is not used.
If you do not have the proper common entrance for all services in one place, then the effectiveness of the surge protector power strip will be reduced. It's still better to have one than not. But it is no replacement for having the correct entry protection, which includes cable, phone, and power coming in at the same location and grounded together so voltage differences between these types of wiring are eliminated (at least with respect to surges coming in from outside on the wire).
| A guide on surges from the US-NIST cites US insurance information that | indicates equipment most likely to be damaged by lightning is computers | with modem connection and TV related equipment - presumably with cable | connection. All can be damaged by voltage between signal and power wires.
The differential voltage is the most common event, so this is certainly the issue most needed to be addressed.
Reply to
phil-news-nospam

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