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  1. #1
    Join Date
    Jun 2010
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    Default Refrigerator capacitor/compressor

    Between the central a/c issue below, and my frig, I'm goin nuts.
    The frig is a Maytag side-by-side, about 7 years old. Had been making a "buzzing" noise, then quit when we were away. Lost all the food. Tech came, said capacitor was bad. Installed a "temorary" one and ordered new parts. Frig ran fine. Next week, came back with a 3 part capacitor. Tech had trouble getting it hooked up, but said he had it wired right. It wouldn't run the compressor. Finally said compressor was bad, need new frig. Re-installed the "temporary" part, frig runs fine. He said this is only a temporary part, not designed for permanent use. Said its "stronger" than permanent part, that's why its running.
    Do I need a new frig? Thanks

  2. #2
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    Default Re: Refrigerator capacitor/compressor

    I think you better get a new Company to deal with or at least a new tech.

  3. #3
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    Jul 2010
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    Default Re: Refrigerator capacitor/compressor

    I feel the same way as sten.
    Get another estimate.

    At 7, most refs are still young. However, if you get estimates in the hundreds, it might be possible to find a replacement ref on sale, for less.

  4. #4
    Join Date
    Jun 2011
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    208

    Default Re: Refrigerator capacitor/compressor

    Finally said compressor was bad, need new frig. Re-installed the "temporary" part, frig runs fine. He said this is only a temporary part, not designed for permanent use. Said its "stronger" than permanent part, that's why its running.
    Your appliance repair tech has rocks in his head.

    If the fridge compressor operates properly with the temporary capacitor in place, then there CAN'T be anything wrong with the compressor motor.

    You need a new appliance repair man, not a new appliance.

    PS: You don't need to know the rest...

    The electric motor in your fridge's compressor has two windings in it; a START winding and a RUN winding. Those two windings are physically located 90 degrees to one another inside the stator of the compressor motor. Since the fridge operates on single phase 110 volt AC power, applying this power to the motor would result in both windings being energized at the same time, and the net result would be an OSCILLATING electric field oriented at a 45 degree angle to both windings.

    In order for the rotor inside the compressor motor to rotate, it needs to see a ROTATING magnetic field, not just an oscillating one. That's the job of the capacitor on your compressor motor.

    When you put a capacitor in series with the wire that goes to the start winding, then you cause a change in the PHASE relationship between the current and voltage in the start and run windings. That's because the current OUT of a capacitor is greatest not when the voltage applied to it is greatest, but when the RATE OF CHANGE of voltage in voltage is greatest, and that happens when the voltage sine wave is at 0 (zero) voltage. The result is that the current sine wave going into the start winding occurs 90 degrees behind the current sine wave going into the run winding, and that causes the magnetic field of the start winding to occur 90 degrees later than the run winding as well.

    The result of this time delay in the magnetic fields of the start and run winding is that the rotor in the compressor motor sees what appears to be a ROTATING magnetic field, not just an oscillating one, and that's what causes the rotor to rotate instead of just doing the hippy hippy shake until the stator gets hot and the motor kicks itself out on thermal protection.

    In fact, ALL three phase 440 volt electric motors produce a near perfect rotating magnetic field without any tricks, gimick, smoke or mirrors. So, there is only a single kind of three phase 440 volt electric motor.

    Since ALL single phase 110 volt AC electric motors would produce only an oscillating magnetic field, all the different kinds of single phase 110 volt AC electric motors use some kinda scam to hoodwink the rotor into thinking it's seeing a rotating magnetic field instead of an oscillating one. So, the difference between the various kinds of 110 volt single phase electric motors, like capacitor start motors, split phase motors, shaded pole motors is that they each use a different trick to create what appears to be a ROTATING magnetic field using single phase power. The way capacitor start electric motors do that is explained above.

    You don't need to resort to that kind of trickery using 3 phase electric power. You just position your three electric coils 120 degrees apart around the stator, connect each phase to each coil and your stator produces a perfect rotating magnetic field. It's only when you're limited to single phase power that you need to resort to a trick or two to make what would otherwise be an oscillating magnetic field LOOK like a rotating magnetic field to the rotor.

    In a capacitor start motor like you have in your fridge, if the capacitor is shorted or burned out, then you have no current to your start winding or the current to your start winding is in phase with that to the run winding. In either case, you're left with an oscillating magnetic field, and that means the rotor is just gonna do the hippy hippy shake instead of rotate.

    Now, the previous eight paragraphs have all been a big lie because your fridge probably uses a "RUN" capacitor instead of a "start" capacitor, which means that the capacitor is wired in series with the run winding, not the start winding. That's cuz a start capacitor is only used for the first half second or so while the fridge compressor motor is starting. Once the compressor motor gets up to speed, a centrifugal switch cuts the start winding out of the circuit so that the fridge just runs on the run winding after that. By putting the capacitor on the run winding instead, you can tweak the capacitor mFd rating to make the compressor motor run smoother, quieter and more efficiently during the other 99.999 percent of the time it's running, not just during the half second or so that it's starting. But, the physics of it all remains exactly the same, so you should now understand both start capacitor electric motors and run capacitor electric motors better than most people you know.

    Hope this helps.
    Last edited by Nestor; 08-01-2011 at 02:01 PM.

  5. #5
    Join Date
    Jun 2007
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    5,796

    Default Re: Refrigerator capacitor/compressor

    I agree with sten and dj1. Leave the temporary capacitor in place and the refrigerator will probably run another 7 years. The phase shift caused by the capacitor is to get the motor running in the right direction and unless is is way under sized (the motor would just buzz) or way over sized (the motor would just buzz) it should cause no problem. You can ignore most of Nestor"s post because there is way too much erroneous information to even comment.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  6. #6
    Join Date
    Jun 2011
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    208

    Default Re: Refrigerator capacitor/compressor

    OK, Jack, let's do it this way:

    Anyone interested in learning about various kinds of single phase induction motors should go to Integrated Publishing's web site at:

    http://www.tpub.com/

    Integrated Publishing is a company that makes the manuals used to train your US military personnel available to the general public. Since the information in these manuals was compiled at taxpayer's expense, all of the information in them is publically owned and therefore Integrated Publishing can't charge you for providing this information. What they can do, however, is charge you for the service of copying these manuals onto CD's or printing them out onto paper and sending the CD or printed version to you. But, as part of the deal they made with your government, you can also access exactly the same information free of charge on their web site:

    Go to Integrated Publishing's home page at:
    http://www.tpub.com/

    On that home page, under the "Electronics" heading, click on the link entitled:
    "Electrical Engineering (NEETS) (Most Popular)".
    "NEETS" stands for "Naval Electrical Engineering Training Series".

    On the NEETS Page, click on:
    "NEETS Module 5 - Introduction to Generators and Motors"

    On the NEETS Module 5 home page, scroll down to:
    "Chapter 4 Alternating Current Motors"

    From there, scroll down the subject list in Chapter 4 and click on: "Single Phase Induction Motors"

    Click on the "Next" link near the top right corner of the web page to go to the next page, where the subject of capacitor start motors begins.

    In explaining the effect of putting the capacitor in series with the start winding, the author writes:

    "The currents in each winding are therefore 90 out of phase - so are the magnetic fields that are generated. The effect is that the two windings act like a two-phase stator and produce the rotating field required to start the motor."

    In my previous post, I ALSO explained WHY the addition of a capacitor would result in the currents through each winding being 90 degrees out of phase.

    I purposely didn't mention impedance or reactance in my previous post because most people in here wouldn't know what those words mean. They can understand, however, why the current out of a capacitor would be highest not when the voltage applied to it is highest, but when the rate of voltage change is highest.

    PS: Mr. McDaniel: There is a polite, courteous and respectful way to do things. No one ever lost anything by being polite, courteous and respectful. But, I wish I had a nickel for every impolite and disrespectful person who lost out on opportunities that came their way throughout their lives by being the opposite.
    Last edited by Nestor; 08-01-2011 at 10:06 PM.

  7. #7
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    Default Re: Refrigerator capacitor/compressor

    Nestor, my apologies. I had a senior moment, that was suppose to be "superfluous information" not "erroneous information".

    By the way massive posts of Googled information is also considered impolite.

    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  8. #8
    Join Date
    Mar 2008
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    nova scotia, canada
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    Default Re: Refrigerator capacitor/compressor

    i completely agree with jack about cut and pasting google search info.

    we have dealt with this sort of thing in the past, the person who was doing it had no practical knowledge of the topics just knew how to use google. when it came time to explain what they were posting in lamens terms they didnt have a clue.. they would argue about how to do things with licensed tradesman on a daily basis which only got them banned from the boards..
    fire up the saw and make some dust

  9. #9
    Join Date
    Jun 2011
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    208

    Default Re: Refrigerator capacitor/compressor

    Jack: You said:
    By the way massive posts of Googled information is also considered impolite.
    Haven't you noticed the statement:

    PS: You don't need to know the rest...
    in many of my posts. That's to separate the answer from the additional information the poster might want to know. No one needs to read my posts, and certainly no one needs to read what I write AFTER I tell them they don't need to know it.


    Quote Originally Posted by jkirk View Post
    ...the person who was doing it had no practical knowledge of the topics just knew how to use google.
    You can fake knowledge, but you can't fake understanding.

    Most often the stuff that follows the "PS: You don't need to know the rest..." in my posts explains WHY things are the way they are in layman's terms so that the poster understands why he's gotten the answer he did.

    If someone complains that the plaster is coming apart under their bathroom ceiling fan, how would you use Google to find the cause? You couldn't. You can only use Google to support an answer, but you need that underlying understanding to come up with the answer in the first place.

    Lemme address your statement that I can't explain things in layman's terms: In the case of the fridge compressor motor, the way one would explain the phase difference in the currents through each winding is by talking about the reactance of a coil and that of a capacitor. Inductors have resistance and positive reactance giving them an impedance vector that goes up and to the right. Capacitors have resistance and a negative reactance that gives them an impedance vector that goes down and to the right. If you add the capacitance impedance vector to the impedance vector for the start winding, you end up with a resultant vector that goes in a totally different direction than the impedance vector for the run winding. The angle between that resultant vector (for the capacitor and start winding) and the vector for the run winding is the phase difference between the current sine waves in each winding. Since the magnetic field produced by each winding is created by the current through it, not the voltage across is, the magnetic fields are also out of phase by that same angle.

    Now, did you understand that? I'm willing to bet most people reading this didn't follow that. If I had explained it that way in my post, it would have been of absolutely no benefit to Rfplcp, the original poster. But, he probably understands how a capacitor is made, and it makes horse sense based on that understanding that the current flow out of it is gonna be greatest when the rate of voltage change is highest. Since that occurs when the voltage is zero, Rfplcp realizes there HAS TO BE a phase shift in the current sine wave. That's cuz before, the voltage and current sine waves were in lock step, and now the current is at a maximum when the voltage sine wave is at zero.

    In my view, this is a better way to explain to lay people why that phase shift occurs, CUZ THEY'RE NOT GONNA GRASP A WRITTEN EXPLANATION OF A GRAPH OF IMPEDANCE VECTORS.

    I actually thought my way of explaining that phase shift in layman's terms was very good, and I expect you'd agree.
    Last edited by Nestor; 08-02-2011 at 01:03 PM.

  10. #10
    Join Date
    Mar 2011
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    26

    Default Re: Refrigerator capacitor/compressor

    Maytag has had issues with the side by side refrigerators but they will not tell you that. On the compressor is a overload relay, a white box with a three wire connection. The relay just pushes onto the compressor and inside the relay is a round metal disk that is temperature sensitive. This disk is known to go bad if and when you pull the relay off shake it and if it rattles the disk broke and is bad. I would almost guess the part is #61004918 and can be picked up for about $30. Good luck and i hope it works. Just double check to make sure the capacitor is not over sized that they installed.

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