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Thread: out of ideas

  1. #105
    Join Date
    Jun 2001
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    Michigan
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    12,077
    The motor isn't hooked up to anything. No pulley. No belt on the pulley. No pulley, no belt. Not even the keyway I bet. Just the motor and it's shaft. Running. And it's high amps. 3rd motor.

    Now if Chris is saying were missing something, what I am not sure, but I'll bite and ask him what he thinks right now. prove the point right now. I'd be tickled to learn something new.
    People who think they know everything are a great annoyance to those of us who do.

  2. #106
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    Nov 2006
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    Quote Originally Posted by TruControl View Post
    I agree with Timebuilder, get the utility to check power factor. This may not be easy - years ago I had building that lost several RTU compressors within a month - while checking out install of new compressor found voltages on all three phases within 5% but current on C phase was 20% high. Then checked other three phase loads in the building and found the same conditions everywhere. Fought with utility to get them to check power factor. They swear they never found anything wrong but a capacitor on their line about 2 blocks away suddenly appeared to be new. The current imbalance went away and we haven't lost another compressor since.
    Bench testing the motor at a different location would be a quick and easy way to help verify if power quality issues are causing your problem.

    The last thing they want to do is admit their feed was bad. Most likely due to liability issues. Biggest problem I have found is bad Burndy connectors. Second is bad transformers.

    I think we are heading toward one of two choices: bad power or bad motors.
    [Avatar photo from a Florida training accident. Everyone walked away.]
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  3. #107
    Join Date
    Mar 2008
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    NY NY
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    181
    I have been tracking this post all weekend, holy s- - t. we still haven’t solved the condition!
    I put my two cents in from the beginning and now offer a third cent.

    The motor manufacture’s provide design hp data under NEC guidelines, using the following equation (hp= voltage x current x motor efficiency divided by 746). I invite all to plug the numbers provided in the original post and you will see a two hp motor running over 3 hp unloaded and loaded.

    There is an element missing here, the data does not make sense. An unloaded motor is subjected to internal losses, reflected in the efficiency calculation, this accounts for the heat loss within and frictional loses on the bearings etc. At 60% efficiency this motor is doing 2hp unloaded. The nameplate RPM would be helpful here to cross check hp calculations using a different formula.

    Are we certain the third motor was tested unloaded out of the box and not after it was overheated. It would not take a long time for an over speed to overheat the windings.
    Last edited by kdocsr05; 12-27-2009 at 07:02 PM. Reason: Typo
    Local 30 New York, New York Operating Engineer

  4. #108
    Join Date
    Nov 2002
    Location
    NJ - WORK IN NYC AREA
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    1,416

    Cool

    Please post each of your power legs to ground?
    "My hands are for sale"

  5. #109
    Join Date
    Jul 2007
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    Quote Originally Posted by kdocsr05 View Post
    I have been tracking this post all weekend, holy s- - t. we still haven’t solved the condition!
    I put my two cents in from the beginning and now offer a third cent.

    The motor manufacture’s provide design hp data under NEC guidelines, using the following equation (hp= voltage x current x motor efficiency divided by 746). I invite all to plug the numbers provided in the original post and you will see a two hp motor running over 3 hp unloaded and loaded.

    There is an element missing here, the data does not make sense. An unloaded motor is subjected to internal losses, reflected in the efficiency calculation, this accounts for the heat loss within and frictional loses on the bearings etc. At 60% efficiency this motor is doing 2hp unloaded. The nameplate RPM would be helpful here to cross check hp calculations using a different formula.

    Are we certain the third motor was tested unloaded out of the box and not after it was overheated. It would not take a long time for an over speed to overheat the windings.
    There is an element missing here, the data does not make sense
    :-)

  6. #110
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    Jul 2008
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    Washington, DC
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    I would have to connect the motor to a different voltage source after everything you have been through, just to rule that out. I worked for a local commercial trane rep. years ago and once found one leg of a compressor where the insulation was not stripped far enough down and one lug of the contactor screwed right against the plastic insulation. Of course it just triupped the overloads and wasn;t hard to figure out, but strange things are found in brand new stuff. I'd hook the motor to a different breaker in the panel with a whip of somekind and just see what it reads.
    Steamfitters Local 602

  7. #111
    Join Date
    Dec 2009
    Location
    Buffalo, N.Y
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    Quote Originally Posted by Chris_Worthingt View Post
    Well, perhaps the 4th or 5th or 6th motor then will workout for you?

    Don't give up, keep changing motors, eventually one of us old guys will takeover and read the specs. Then this burden of yours will be off your shoulders.

    Good luck to you!
    nice, real mature, thanks for the help.

  8. #112
    Join Date
    Dec 2006
    Location
    Middle Tennessee
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    11,347

    *

    well Chris do you still think;

    it's a normal thing to pull a motor out of the box

    wire it up, start it, with no load, then with your meter measure an FLA amp draw

    you can even run it for a minute
    -------------------------------------------------------------------------------------------------

    now; if you took that same motor with no load an ran it for 24 hours, it will probably overheat, draw more than FLA then eventually go out on overload



    .

  9. #113
    Join Date
    Sep 2008
    Location
    Western PA
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    Quote Originally Posted by kdocsr05 View Post
    I have been tracking this post all weekend, holy s- - t. we still haven’t solved the condition!
    I put my two cents in from the beginning and now offer a third cent.

    The motor manufacture’s provide design hp data under NEC guidelines, using the following equation (hp= voltage x current x motor efficiency divided by 746). I invite all to plug the numbers provided in the original post and you will see a two hp motor running over 3 hp unloaded and loaded.

    There is an element missing here, the data does not make sense. An unloaded motor is subjected to internal losses, reflected in the efficiency calculation, this accounts for the heat loss within and frictional loses on the bearings etc. At 60% efficiency this motor is doing 2hp unloaded. The nameplate RPM would be helpful here to cross check hp calculations using a different formula.

    Are we certain the third motor was tested unloaded out of the box and not after it was overheated. It would not take a long time for an over speed to overheat the windings.
    So, you are implying that this motor is doing 3HP with nothing connected to the shaft?

    I don't think that is possible.

    I will be very interested to see the outcome of this.

    Please post when the problem is solved.

  10. #114
    Join Date
    Oct 2007
    Location
    Richmond, VA
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    351
    Quote Originally Posted by Chris_Worthingt View Post
    Someone here mentioned the blower curve, forgive me for being to lazy too see whom, but that is where ya need to start.

    I see a lot of this and that and no actual data, i.e. STATIC?? is this thing in cavitation? do we have an over-sized duct and no static? etc...

    The designed blower curve chart for your application, at designed static, at designed RPM and blah blah blah is doing what real world?? way out of specs?

    wrong this and that, possible? but doubt it, your missing something here...
    I agree with Chris that you need to look at the blower curve and check static on the unit. Check power supply, motor wiring, etc... and then install the motor. Try blocking off part of the blower housing opening, put the doors back on the unit, and check your amperage. I think you'll find it is lower than before blocking the return. By blocking the return, you increase the static. I believe Chris is on the right path here, in suggesting that the blower is cavitating and not doing enough "work". By the way, I'm not suggesting that you block the return as a permanent fix, just as a testing measure. I think that the amp readings taken with no load have done nothing but "muddy the waters" in this case. Just my 2 cents.

    I'm with ya, Chris!!!

  11. #115
    Join Date
    Oct 2007
    Location
    Richmond, VA
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    351
    Quote Originally Posted by fruecrue View Post
    nice, real mature, thanks for the help.
    He's offered you plenty of help, but you are ignoring it. What else can he do? Take his suggestions and take some readings. I've made a couple of suggestions in my other post. Give them a try.

  12. #116
    Join Date
    Dec 2009
    Location
    Buffalo, N.Y
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    101
    Quote Originally Posted by kdocsr05 View Post
    I have been tracking this post all weekend, holy s- - t. we still haven’t solved the condition!
    I put my two cents in from the beginning and now offer a third cent.

    The motor manufacture’s provide design hp data under NEC guidelines, using the following equation (hp= voltage x current x motor efficiency divided by 746). I invite all to plug the numbers provided in the original post and you will see a two hp motor running over 3 hp unloaded and loaded.

    There is an element missing here, the data does not make sense. An unloaded motor is subjected to internal losses, reflected in the efficiency calculation, this accounts for the heat loss within and frictional loses on the bearings etc. At 60% efficiency this motor is doing 2hp unloaded. The nameplate RPM would be helpful here to cross check hp calculations using a different formula.

    Are we certain the third motor was tested unloaded out of the box and not after it was overheated. It would not take a long time for an over speed to overheat the windings.
    The third motor was drawing more than FLA the first time it was started, that was installed with the same sheave set-up that had the previous motor at one point drawing below FLA. I shut it down within 20 seconds, removed the belt and ran it again, same amp draw. I then tried different configurations, limiting run time to slowly build heat in the motor. I have seen in the past, motors draw a slightly higher current in their first couple of minutes, then drop amp draw as they near operating temp. This was not the case here though.

  13. #117
    Join Date
    Dec 2009
    Location
    Buffalo, N.Y
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    101
    Quote Originally Posted by CommtechinVA View Post
    I agree with Chris that you need to look at the blower curve and check static on the unit. Check power supply, motor wiring, etc... and then install the motor. Try blocking off part of the blower housing opening, put the doors back on the unit, and check your amperage. I think you'll find it is lower than before blocking the return. By blocking the return, you increase the static. I believe Chris is on the right path here, in suggesting that the blower is cavitating and not doing enough "work". By the way, I'm not suggesting that you block the return as a permanent fix, just as a testing measure. I think that the amp readings taken with no load have done nothing but "muddy the waters" in this case. Just my 2 cents.

    I'm with ya, Chris!!!
    The unit has been tested with the return blocked, no change in amp draw. Again I agree that design data is crucial and useful, but I need to have a functional drive on the blower before that comes into play. If I had seen any change whatsoever in amp draw during any testing while altering sheave diameter or airflow, I would be right there with you.

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