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Thread: A smokin' hot motor

  1. #21
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    Quote Originally Posted by Jraef View Post
    This is what a breaker does after it has tripped, as opposed to being turned off. There are three positions of a breaker handle, not just two; On, Off and Tripped. The "Tripped" position of a Q0 breaker is a mid-point and in order to reset it, you must push is all the way to the full Off position first and make it latch, only then you can snap it back on.
    The breaker was in the on position. It had not tripped. From the on position, I think it should "snap" off even under load.

    Quote Originally Posted by Electric-Light View Post
    This thing will cost him like dollar an hour to run it even if you get the motor running within the rated load.
    I don't think this is an issue. The main house is the size of a hotel. I can fit my entire house in the lobby area. On the grounds behind the main house are two "guest houses" both over 2000 sq ft each with a pool. Between the main house and the guest houses is an artificial river running between two artificial lakes. The waterfall sits on an artificial mountain at one of the lakes. There is a cave inside the mountain so you can stand behind the waterfall. It looks similar to the "grotto" area at the Playboy mansion (from what I've seen on TV).

    Quote Originally Posted by Sahib View Post
    The OP did not confirm it is a centrifugal pump. A positive displacement pump such as a piston pump will overload severely with obstruction on the output side.
    It's a centrifugal pump. From the pump to the output is about 15 ft in height. I can't remember the pipe size.

  2. #22
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    Were they ever able to run the pump for more then a few minutes?

    Any kind of valve on the piping that will allow flow adjustment has probably been opened for more flow - but is now more then the motor can deliver without overloading.

  3. #23
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    Quote Originally Posted by Ingenieur View Post
    Pump hp = head (ft) x gpm / (eff x 3957)

    look at a pump curve
    as head decreases flow increases (as does hp)
    so too low head will ol the motor for some pumps

    http://cdn.qleapahead.com/zoeller-63/132945.pdf?P185
    Your pump curve doesn't say that. Look at the performance curve on the second page of your link. Notice that the HP curve is really pretty flat over the entire operating range. The HP peaks at about 34 feet of head and then decreases (slightly) as you lower the head and increase the flow. Check all the curves in fact; none of them show runaway motor loads as the head drops and flow increases. QED.

  4. #24
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    Quote Originally Posted by gadfly56 View Post
    Your pump curve doesn't say that. Look at the performance curve on the second page of your link. Notice that the HP curve is really pretty flat over the entire operating range. The HP peaks at about 34 feet of head and then decreases (slightly) as you lower the head and increase the flow. Check all the curves in fact; none of them show runaway motor loads as the head drops and flow increases. QED.
    inaccurate

    some show 1.2 HP draw on a 3/4 HP pump

    in fact first curve 1/3 HP motor shows 0.5-0.6 HP at low head
    the second a 1/2 HP drawing 0.8 HP



  5. #25
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    Quote Originally Posted by GoldDigger View Post
    It does not matter whether you restrict the input or the output, the physics of the moving (or not moving) water is the same.
    From a power consumption standpoint, I 100% agree. While I'm in the positive displacement pump side of things, even with impeller pumps, restricting the inlet isn't good as it contributes to cavitation.

  6. #26
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    Quote Originally Posted by Ingenieur View Post


    inaccurate

    some show 1.2 HP draw on a 3/4 HP pump

    in fact first curve 1/3 HP motor shows 0.5-0.6 HP at low head
    the second a 1/2 HP drawing 0.8 HP
    Something is screwy with those curves. Many of them show the motor pulling above it's listed HP over nearly the entire operating range, the second curve being a prime example.

  7. #27
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    OK, I checked with the manufacturer, and the motors used on those pumps have service factors from 1.5 to 1.95.

  8. #28
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    Quote Originally Posted by kwired View Post
    Were they ever able to run the pump for more then a few minutes?

    Any kind of valve on the piping that will allow flow adjustment has probably been opened for more flow - but is now more then the motor can deliver without overloading.
    I don't remember ever seeing it run. I've been there twice before.

    I did see a valve with a straight arm. It was on the input side I believe. It was fully open.

  9. #29
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    Quote Originally Posted by Coppersmith View Post
    ...
    I did see a valve with a straight arm. It was on the input side I believe. It was fully open.
    Bingo. Most likely when it was originally designed, that valve was not supposed to be fully open, It was there to make fine adjustments based on conditions. But someone came along afterward and opened it, now the pump is overloading the motor.

    Get an ammeter and watch the motor current as you throttle back that valve. When the motor current equals the motor FLA, you're done. If the end user doesn't like how the waterfall looks, then tell them they need a bigger motor.

    Then remove the handle off of that valve and put a sign on it saying that adjusting this valve is punishable by termination of employment.
    __________________________________________________ ____________________________
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  10. #30
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    Quote Originally Posted by Jraef View Post
    Bingo. Most likely when it was originally designed, that valve was not supposed to be fully open, It was there to make fine adjustments based on conditions. But someone came along afterward and opened it, now the pump is overloading the motor.

    Get an ammeter and watch the motor current as you throttle back that valve. When the motor current equals the motor FLA, you're done. If the end user doesn't like how the waterfall looks, then tell them they need a bigger motor.

    Then remove the handle off of that valve and put a sign on it saying that adjusting this valve is punishable by termination of employment.
    And based on what I read here, we could start with the valve fully closed and there would be no danger of damaging the motor, correct?

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