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Thread: out of ideas

  1. #196
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    Quote Originally Posted by Airmechanical View Post
    maybe a private message to CHRIS WORTHINGTON from the controls committee would be in order;

    a private message with your above quote

    then he can come back on here and tell us more specifically what he really meant or thought

    it's sad that after he made his controversial post he just ignored us

    i sort of can't blame him, when i have been wrong on this website, it is a bit embarassing

    but we all make mistakes, admit them and move on

    you will gain a ton of respect that way "CHRIS"

    this particular overheating without a load issue has been fun for me

    simply because "i have" tested these things before

    it was especially fun yesterday testing and coming up with the same conclusion

    you can twist reality, but you can't change it



    .
    Is what I said and still say as backed up by the various manufactures links and others, is that a motor dependent upon its construction can overheat while unloaded and once it is overheated, it can over amp at that point.

    Real world,,,,,, replacing a 1/8th HP condenser fan motor with a 5HP condenser fan motor,,,, will be toast in a short period of time.

    I have been watching this thread and believe that "all" has realized that there is more to a motor then amps and volts alone, there is the design of the motor with its power factors, break horse powers, service factors, etc, etc. That on occasion need to be considered when having issues on a newly installed/problematic system.

    I also stated that on a newly installed/problematic system that sometimes the only thing that can truly help you diagnosis and repair the system is to know and understand the total design of the system. The "system" meaning all of it, the dampers, the coils, the duct work, etc.

    My point, you need know more then amps and volts. A static reading and someone locating the specs on this unit, would have helped us to diagnosis this/ rule out design.

    My problem with this thread and in the real world, is how often the design, the instructions, is ignored. I get several phone calls daily from techs stating that they have done this or that, replaced blah blah blah and now it does not work? when I ask if they have read the instructions and checked the other pieces to the puzzle, the answer is almost always no?

    When I ask them to check "all" the pieces to the puzzle, read the instructions and to call me back "if" they have any more problems, I seldom get the return phone call, crazy eh?

  2. #197
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    That on occasion need to be considered when having issues on a newly installed/problematic system.

    I think this is what caused most of the debate-you saying that this was one of those occasions.

  3. #198
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    what I said and still say as backed up by the various manufactures links and others, is that a motor dependent upon its construction can overheat while unloaded and once it is overheated, it can over amp at that point.

    Well said Chris, design conditions that is the key



    Local 30 New York, New York Operating Engineer

  4. #199
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    Quote Originally Posted by kdocsr05 View Post
    what I said and still say as backed up by the various manufactures links and others, is that a motor dependent upon its construction can overheat while unloaded and once it is overheated, it can over amp at that point.

    Well said Chris, design conditions that is the key



    I agree with this based on general knowledge and from the latest information I've read-never disagreed. The only motor I've ever heard that can burn out pretty quick is a fuel pump in a car, since apparently they are cooled by the fuel.

    But no fan or blower motor in the world is going to overheat and overamp in just a few minutes of running without a load. This is why design conditions and all that other science behind motors does not apply in fruecrues situation. Offering that knowledge to him as if it will resolve his issue at hand is just not helpfull, in fact it reflects pretty poorly on one's understanding of that science in the first place.

  5. #200
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    Quote Originally Posted by zachhvac View Post
    That is correct block off either the supply or return it doesnt matter. Fan motors are designed to do work, if they are not loaded they will not build sufficient speed to cool themselves.
    Ever take a blower out of a replacement furnace and try and run it?
    Sometimes they will overheat etc, block off the supply they build speed and drop amperage and run fine.
    Hello?
    You sure are cocky for a starving pilgrim.

  6. #201
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    Capacitors

    The more I re-read thru this thread the more my mind has a chance to look back in my past and see where I have seen this before. I have been working on motors for over 25 years and have never seen a free wheeling motor burn out.They have been warm but not hot enough to trip the thermal overload. The only time that I have seen motors consistently overheat and trip the thermal or burn up is when the capacitors fail and / or when there is a phase imbalance and or failure.There is more to the comment on tight bearings than you realize, wholesalers here in Tucson remove all motors from the boxes and spin the shafts to make sure that the bearings are free.It is easy to tweak a motors bearings by dropping them and or bumping them. All motors that have overheated that I have seen usually have the signs of grease melting and running out of the felts or caps and running down the edges of the mounts.
    Lately I have seen a large amount of capacitor failures. I have heard from a very good souce that high voltages can cause cap failures. Your situation has all the signs of a cap causing your problem. High amps/overheating. Could possibly be from being miswired and or high voltage.
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  7. #202
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    *

    here is what was said;


    THE OP stated this;


    Quote Originally Posted by fruecrue View Post
    new motor runs the same, 12.6 amps without belt

    then, chris stated about how he should check blower curve

    then i told chris, the unloaded NEW motor will draw no where near FLA

    therefore (chris's) blower curve theory can wait till the motor problem is solved

    then we seen the next post;


    Quote Originally Posted by Chris_Worthingt View Post
    So your saying an oversized/undersized/caveatting blower motor will not run hot/over amped? I find this hard to believe
    so we ALL assumed you new the motor was not hot, therefore no reason to be drawing anywhere near FLA

    so were both on the same page right

    do you still think there is not a blower motor problem?



    .

  8. #203
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    Quote Originally Posted by ACFIXR View Post
    There is more to the comment on tight bearings than you realize, wholesalers here in Tucson remove all motors from the boxes and spin the shafts to make sure that the bearings are free.It is easy to tweak a motors bearings by dropping them and or bumping them.
    We have started spinning the shafts whenever we pick up a motor. I had one at Grainger just last week. I asked the guy if I could open the box and see if the shaft spins. He gave me a funny look and said "sure."

    I opened the box and sure enough, it would not budge. I said "here, you try it." He went and got another, and that one worked just fine.

    It is amazing to me how often this happens today.
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  9. #204
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    Ditto on the motor shafts not turning or very hard to turn fresh out the box.

  10. #205
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    Attached is a spreadsheet to calculate amps vs load. You input the power factor at full load and the amps at full load. It has some assumptions listed (neglect leakage reactance and losses). Under the assumptions the real component of current varies directly proportional to the load and the reactive component of current is constant. The total current is of course square root of sum squares of real and reactive components. If that sounds complicated, remember all you have to do is fill in those green cells labeled FLA and PF (PF corresponding to full load conditions). If there is an efficiency listed on the nameplate, then nameplate data can be used to estimate power factor. If know the horsepower and speed, we can estimate power factor.

    In addition, if your voltage deviates from nameplate voltage you would need to correct for that.

    Try working the number for the OP’S motor and see what you find. By lowering, the pf to .3 this motor draws close to full load amperage unloaded, and the same amperage loaded.

    The answer to this condition now becomes apparent the building has conditions affecting power factor.

    In a purely resistive AC circuit, voltage and current waveforms are in step (or in phase), changing polarity at the same instant in each cycle. Where reactive loads are present, such as with capacitors and inductors energy storage in the loads result in a time difference between the current and voltage waveforms. During each cycle of the AC voltage, extra energy, in addition to any energy consumed in the load, is temporarily stored in the load in electric or magnetic, and then returned to the power grid a fraction of a second later in the cycle. The "ebb and flow" of this nonproductive power increases the current in the line. Thus, a circuit with a low power factor will use higher currents to transfer a given quantity of real power than a circuit with a high power factor. A linear load does not change the shape of the waveform of the current, but may change the relative timing (phase) between voltage and current.

    You may need the local power company to resolve this one.

    Trying to get the file formated to attach please stadnby. I'm not able to upload this spreadsheet i will e-mail to all that request,
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    Last edited by kdocsr05; 01-01-2010 at 08:36 PM.
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  11. #206
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    Quote Originally Posted by fruecrue View Post
    In response to plainjs, thanks for your input. You are not the first nor only one with these suspicions. Unfortunately, I can't get back to test these theories just yet. I added in the original post that I had shed lighting, which was very vague. In fact, what I had done was shut down approx. half of the total lighting at a control point in the master suite. I did not disconnect power to the lighting panels as you suggest, and I did not measure for DC voltage as above quote recommends.

    I have yet to bench test the motors(lots of opinions on this), which I believe will be informative as to whether I am dealing with motor or power supply issues.

    whatever the outcome, I'll gladly join you at the bar. how long is the ride from Buffalo?
    http://www.saunderselectric.com/PDFs...-harmonics.pdf

    I'm officially casting my ballot for non-sinusoidal load of the new lighting system causing the op's motor problem. The following link is just one of the articles I have read that leads me to this conclussion. Comming from 4 years of experience this may be just a guess and I may very well be mis-understanding what I've been reading.
    Last edited by tipsrfine; 01-01-2010 at 10:57 PM. Reason: forgot link

  12. #207
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    Quote Originally Posted by tipsrfine View Post
    http://www.saunderselectric.com/PDFs...-harmonics.pdf

    I'm officially casting my ballot for non-sinusoidal load of the new lighting system causing the op's motor problem. The following link is just one of the articles I have read that leads me to this conclussion. Comming from 4 years of experience this may be just a guess and I may very well be mis-understanding what I've been reading.
    From what I read there, you need loads that interrupt the normal sine wave loading to generate the harmonics. A gate-controlled device like an SCR (silicon controlled rectifier) or its AC cousin, the TRIAC are given as examples of the devices that only flow current during a portion of the sine wave cycle.

    Unless these types of devices are in use, they are not the cause of the problem.

    I'm leaning more toward the idea that a large number of fluorescent ballasts are putting a lot of inductive reactance on the system, which could be corrected with power capacitors to change power factor to a more acceptable value.
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  13. #208
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    Quote Originally Posted by timebuilder View Post
    From what I read there, you need loads that interrupt the normal sine wave loading to generate the harmonics. A gate-controlled device like an SCR (silicon controlled rectifier) or its AC cousin, the TRIAC are given as examples of the devices that only flow current during a portion of the sine wave cycle.

    Unless these types of devices are in use, they are not the cause of the problem.

    I'm leaning more toward the idea that a large number of fluorescent ballasts are putting a lot of inductive reactance on the system, which could be corrected with power capacitors to change power factor to a more acceptable value.
    I read that light balast produce non-sinusiodal draws on the supply. No that's wrong, I was thinking about dimmer switches. Maybe that fancy new lighting is converting ac to dc? Maybe this home shares a transformer with someone else that is drawing a large non-sinusoidal load?
    Last edited by tipsrfine; 01-02-2010 at 12:06 AM. Reason: mis-info

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