Refrigerator fans

Discussion in 'General Electronics Chat' started by #12, Sep 14, 2011.

  1. #12

    Thread Starter Expert

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    Appliances seem pretty tame for this site, but this is the only forum I am a member at, so...

    I've been meeting 4 wire fans in refrigerators lately. I measured about 13 volts DC that the controller board was using to try to get a fan to run yesterday. I assume the motor is bad and will replace it today but, I wonder if anyone here knows what kind of fan motors the manufacturers are using lately and what kind of drive signal is proper for them. ps, this is a General Electric brand side-by-side ref/freezer, 2002 year.

    If I may rant for a moment, I wish they would just use the old 4 watt 120 VAC motors connected to the compressor leads instead of complicating the job with a microprocessor, but they didn't, so it's up to me to keep learning.
     
  2. SgtWookie

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    You might find this article helpful:
    http://www.formfactors.org/developer\specs\REV1_2_Public.pdf
    ALL appliance manufacturers are "under the gun" to develop more efficient appliances. While that's usually good for the electric bill, the newer fridges don't seem to last worth a darn anymore.

    Anyway, the old AC fans lasted a long time, but there was no means to control the speed. Then they came out with the DC fans with a tach output (3-wire), but it was somewhat difficult to control their speed. The 4-wire fans have integrated electronics that take a logic-level PWM signal to control the speed, and the tach output gives feedback as to what the actual fan speed is.
     
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  3. #12

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    One of the big mysteries in my life...how much energy is saved by replacing a 4 watt fan motor with a 5 watt microprocessor board, 3 sensors, and a 4 watt motor that doesn't run as fast?

    I am very doubtful that slowing down a 4 watt motor is saving a bunch of energy. That much energy could be saved by putting a single cooling fin on the case of the compressor, and it wouldn't require energy to run the computer that controls the cooling fin.

    If I ever get stuck with one of these microprocessor controlled 4 watt fan motors, I will drill a hole in the back of the freezer and install a 4 watt fan motor that is powered by the wires that are hot when the compressor is running instead of replacing $100 processor boards and $65 fan motors. Meanwhile, my customers are stuck because I refuse to redesign retail products for them. (It would violate my insurance policy.) I also wish that the computer that is monitoring the fan speed would notice that the fan isn't running and put up an error message like, "freezer fan is not turning".

    Thanks for the link.

    Edit. That PDF confirms the 13 VDC I saw. I expect the computer is waiting for a tach pulse before converting to PWM. Good. My meter can measure DC just fine. If the signal was already PWM I would have so much fun trying to detect it while trying to wedge both shoulders and a DVM inside a 22 inch wide freezer compartment.
     
    Last edited: Sep 14, 2011
  4. MrChips

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    Oct 2, 2009
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    I'm not a big fan of refrigerators either.
     
  5. R!f@@

    AAC Fanatic!

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    I find much humor in this thread.
     
  6. someonesdad

    Senior Member

    Jul 7, 2009
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    If people really wanted to save energy, they'd go back to refrigerator/freezer designs from 50 years ago (or more). At one point, we had two refrigerators and three freezers in our house, although one of the freezers was shut off. One of the freezers is a relatively new one that my sister-in-law gave to us because it made noise. I took it apart and found some bad motor bearings in a fan and replaced the fan. Anyway, the other freezer was left in this house when we moved into it 24 years ago. And it was an old freezer -- I could tell from the design/shape that it was made in the 1950's -- maybe even earlier.

    Guess what: that 50+ year-old freezer consumed exactly half the energy that the modern refrigerators and freezers do. I measured each unit with a Kill-a-watt integrating the power for at least a week for each unit.

    The only thing "wrong" with that old freezer is that you had to defrost it. I'd imagine that most people younger than 40 or 50 have no clue about what defrosting a freezer means.

    Consumers demand frost-free devices, but they cost twice as much energy-wise. That's because of the heating element to do the defrosting along with running the fan all the time.
     
  7. debe

    Well-Known Member

    Sep 21, 2010
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    Also have customer with an LG fridge with simmilar electronic fan speed & temp control all run by a processor board. Board has been destroyed by Mice in the back of the fridge. Customer says board to expensive, so fridge will probably endup scrap. I gues this is how manufacturers keep you Consuming products.
     
  8. #12

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    Fan motor installed. Freezer happy :)
     
  9. Adjuster

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    Living in a less affluent part of the world, I have a very basic refrigerator, and an equally basic freezer. They both have only compressors, no fans. Of course, the freezer does need periodic defrosting. The fridge has no ice compartment, so it needs no attention apart from cleaning - if I get around to it.

    From what I've just read, maybe it's best to stick with these simple appliances until they wear out.
     
  10. #12

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    I agree, regularly. Putting a microprocessor on a 4 watt fan motor tends to make my head explode.
     
  11. colinb

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    Jun 15, 2011
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    We have a “regular” modern refrigerator+freezer with automatic defrost, and also a large “deep freeze” non-defrosting freezer. Even more than the energy savings in not performing automatic defrost, I find that the deep freeze's consitent low temperature (0 °F or less) make food stay fresh MUCH longer; bread, meat, etc. does not suffer the freezer burn and drying effect caused by automatic defrost temperature cycling.

    Though, as for the debate about putting a microprocessor on a small 4 watt fan to save energy, don't forget that modern microcontrollers and supporting electronics need only milliwatts of power to run and even microwatts average power when efficient power modes are used. Even saving a few percent of that 4 watts would make the microcontroller a win.
     
  12. #12

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    I'm happy to hear that the energy budget can be a win. I hope the energy that gets saved in each refrigerator/freezer does not exceed the energy required to make the silicon, the circuit boards, the extra wiring, and the extra repairs needed to replace this wonderful stuff. Just think...If they are saving the whole 4 watts, 24 hours a day, at 13 cents per killowatt hour, that's $4.56 a year. That's enough to pay for a house call and a new fan motor every 30 years.

    I'm also sure my customers will be happier about the costs of repairs when they hear that they are Saving the Earth by investing in a new microprocessor board or a DC fan motor with tachometer output and PWM speed control.

    My concerns have been quelled.
     
  13. colinb

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    Hey, I agree that modern appliances are poorly designed and unreliable. I'm just saying that if designed right, a microcontroller-based device could certainly be more efficient than a “dumb” device. I don't mean to imply that it necessarily makes sense for your refrigerator fan to be microprocessor-controlled. The technology has to fit the application.
     
  14. colinb

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    P.S. I have a 20-year-old clothes washer and dryer that are still running strong. Simple, robust design and construction. In contrast, my parents' fancy 10-year-old over/under front loading washer/dryer has had several electronics failures due to the manufacturer using under-rated parts. My dad is not an electronics hacker but he went online and found that the failed component (a resistor, I believe) commonly failed and someone had posted detailed instructions on purchasing a higher-rated part and installing it as a replacement. After his fixes, the machine had no more problems... stupid companies saving $0.01 by using an under-rated part. Grrr..
     
  15. SgtWookie

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    My folks had a Sears Kenmore washer and dryer in their Michigan home that worked from about 1965 up until the house was sold earlier this year; I had to replace the timers once about 10 years ago.

    When they bought a home in FL, they got a new pair of Kenmore washer and dryer; Mom broke the washer twice before the repairman told her to have the knob OUT before turning the timer around. She kept blowing a TRIAC that controlled the motor.
     
  16. NM2008

    Senior Member

    Feb 9, 2008
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    Believe it or not, the fridges compressor is one of the most reliable devices in the house.
    I have seen many fridges/freezers practically fall apart around the compressor.

    In the UK and IRL.
    Many fridges/freezers are thrown to the scrap due to doors binding and not sealing properly. Not to mention the unsightly cracks and splits that appear inside door panels and plastic holders.
    There are dozens of these appliances waiting to be scrapped, but yet have perfectly working compressor units that still have years of life left in them.

    I find it interesting that it is, more times than not, the parts responsible for interaction with the human which seems to fail first. Eg...doors, panels.

    Interesting that the part which the average person never comes into contact will last tens of years.

    NM
     
  17. colinb

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    SgtWookie: I suspect something more sinister than simple cheapness of production cost for the appliance manufacturers. This is probably some planned obsolescence along with potential benefits for the manufacturer-certified service technicians and expensive replacement part market.

    Replacement parts are ridiculously priced: e.g., the keypad+display panel on my 10 year old double oven costs over $200 for the replacement part (likely with additional labor costs unless you DIY) and it's already been replaced by the previous homeowner -- not even fixing the problem since the actual problem is in the connector from the display board to the logic board.
     
  18. colinb

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    Yup, the manufacturer wants your fridge to look dated and old after a few years so you'll want to pony up another couple GRAND for a shiny new one.
     
  19. NM2008

    Senior Member

    Feb 9, 2008
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    Seems to be it alright!
    And then they advertise these appliances as being more enviornmentally friendly than the last one they built.

    Yet they seem to forget about the many hundreds of years that the waste plastic panels will be sitting in the landfill.

    The majority being built in Asia having to be transported thousands of miles on crude oil burning cargo ships. Putting out as much emissions in one trip as a hundred cars do in one year.

    Kinda contradicting themselves.

    Thats mad! isnt it?
    NM
     
  20. #12

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    Sorry colin. Nothing personal. You aren't the first person to say microprocessors are great inventions while I was in the middle of a rant. You must know that rants are unreasonable..don't you?

    Meanwhile my car has a microprocessor that is beeping at me.

    You see, it isn't good to bump your face on the windshield, so you drive carefully. Our government decided that wasn't enough so they passed a law requiring a backup system called a "seat belt". Then they decided that wasn't good enough and required a backup for the backup called an "air bag", complete with high speed sensors and electronic firing mechanism. Then some lawyer decided that if you run into some kind of extra-terrestrial vehicle with a blade sticking out 6 feet from it, and the blade cuts your battery cable before the actual impact, you will need a backup for the backup for the backup, and it's called a "backup power supply". Now, if the backup for the backup for the backup fails, you need an idiot light blinking at you from the dashboard, and that is a backup for the backup for the backup for the backup. The idiot light in my car has been blinking for so long that the light bulb burned out, so the backup for the backup for the backup for the backup has a backup, and it's called a "beeper".

    In the morning when I wake up, I'm going out to my car, find the backup for the backup for the backup for the backup for the backup, and rip it out with a pair of pliers.
     
    Last edited: Sep 16, 2011
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