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Thread: Condenser motor running in reverse

  1. #1
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    Condenser motor running in reverse

    I ran into a wired one maybe one of you can give me the why of this. Condenser motor running backward.. wire to cap herm used as common common used at herm fan as fan. Everything actually ran just cond fan backwards

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  3. #2
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    Check to see if it is wired for low voltage when it needs to be high voltage or vice versa. Sometimes that will do the trick.

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    Quote Originally Posted by dkalasz View Post
    I ran into a wired one maybe one of you can give me the why of this. Condenser motor running backward.. wire to cap herm used as common common used at herm fan as fan. Everything actually ran just cond fan backwards

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    I can't quite make out what you are saying but yes if you reverse wires on a motor that uses a cap it will run backwards!

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  6. #4
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    Basically whomever installed the cap figured c meant compressor and Herm must just be what's left so Herm and c reversed guess that's a bit simpler.

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  7. #5
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    I've seen how if the capacitor is wired wrong, the fan will run backwards. I have NO IDEA WHY it does this, though. I would ALSO like to know why.

    I heard once that the capacitor gives the fan a "jolt" in the right direction... so I suppose it could give it a jolt in the wrong direction if it's the wrong jolt?

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    Did the compressor pull normal amps running off the capacitor with the c and herm terminals switched? I'm just curious.

  9. #7
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    Quote Originally Posted by LordoftheFreon View Post
    Did the compressor pull normal amps running off the capacitor with the c and herm terminals switched? I'm just curious.
    Don't know I just fixed it and and got back in the truck to hot out for a fat man

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  11. #8
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    I don't know if I can exsplain this right or not, but the cap is alternating with the ac sine wave, but is lagging. Think of a bucket filling and then dumping over. The cap phase shifts the sine wave. There is no polarity on a hp cap. What matters is what leg of the motor is connected to the common. The cap phase shifts relative to the common so the polarity that the motor windings are experiencing relative to eachother would change based on how the motor is connected to the capacitor/L1/L2.

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  13. #9
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    Quote Originally Posted by LordoftheFreon View Post
    Did the compressor pull normal amps running off the capacitor with the c and herm terminals switched? I'm just curious.
    No compressors do not run well in reverse

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  15. #10
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    cool...

    just read about how compressor and fan motors are inductive motors so they shift the phase (or timing) so voltage is out of phase with the current and the capacitor corrects this in order to get the motor full power. The capacitor does this by shifting the phase (or timing) (is phase the same thing as timing?) of the voltage/current in the opposite direction of the inductive motor. So the motor and the capacitor (both out of phase/timing alone) "cancel each other out" and bring everything back in phase so the motor can receive maximum power. So if you hooked up an inductive motor to a capacitor in the wrong direction, since it has no polarity, it would still work but the phase/timing would be off... I guess it would receive less power and the direction of the current that would have been "cancelled out" if wired right, now comes into play and turns the motor the other way?

    Why use inductive motors at all?!! Hello rabbit hole, I wanted to watch TV what am I doing?

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  17. #11
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    The compressor will run normally & draw the correct current if the C & Herm wires are reversed because it still gets the full mfd off the capacitor. The fan part of the cap however would then be in series with the herm side so it doesn't get the full capacitance & also has to deal with the phase shifting of the compressor which is beyond my knowledge. If you test a dual cap from Herm to Fan you'll see the difference in the reading.
    Its not going to be much lower but it will always be lower.
    Gary
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  19. #12
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    I have seen bad caps /underrated uf cause the CFM to spin backwards as well...next to wrong fan blade installed as well..if the motor was recently replaced..

  20. #13
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    Generally this is caused by a shorted condenser fan run capacitor.

    PHM
    --------


    Quote Originally Posted by dkalasz View Post
    I ran into a wired one maybe one of you can give me the why of this. Condenser motor running backward.. wire to cap herm used as common common used at herm fan as fan. Everything actually ran just cond fan backwards

    Sent from my GM1915 using Tapatalk
    PHM
    --------
    The conventional view serves to protect us from the painful job of Thinking

  21. #14
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    This is how I got my condensing unit for $200 in 1988. Someone at the factory put the sticker for start and run wingdings on backwards, the fan would run in either direction depending on where it stopped. Ohm out fan terminals to determine start and run, after that is corrected hook up to capacitor correctly.

  22. #15
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    Quote Originally Posted by LordoftheFreon View Post
    Did the compressor pull normal amps running off the capacitor with the c and herm terminals switched? I'm just curious.
    button test; the answer you seek is yes as like a typical two terminal capacitor

  23. #16
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    Some of these"listen to this story" has me wondering about how I understand my thinking about 240 VAC ,single phase,Res electricity w/ run caps. I'll be contemplating my thought process all the while I'm supposed to be working. "The basic inherent electrical characteristic difference between the start and run windings" enters my brain for some reason.

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  25. #17
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    Picture a 60 cycle sine wave the way it would appear on an oscilloscope. There is a 'zero voltage' line is left-to-right through the center and there are positive waves humping upward and negative waves humping downward - one after the other.

    At this point I always encourage people to physically draw that out on paper.

    At the zero-line the motor using such current produces zero horsepower - and it produces it's maximum horsepower at the peaks of the 'humps' up and down. That is what single phase power looks like.

    Now picture three such sine curves evenly spaced, each overlapping the last by 33%, on the same curve background. That is what three-phase power looks like.

    So again picture the single phase graph. Except that, with a run capacitor in the circuit (which would have no initial charge - it would be 'empty'), on the left side of each upward and downward portions of each 'hump' - the capacitor is being charged with electricity. This is because the circuit's power is Higher than the capacitor's - so it 'equalizes' by accepting the increasing electricity in the connected circuit. At the peak of the curves the power in the circuit and the power in the capacitor are 'even'. Then after the peak of the 'hump' comes the declining side of the wave. The capacitor's internals are di-electric so they do not want to give up their stored power. But at some point on the declining voltage side of the wave - the capactor's charge is so much higher that it's 'reluctance-to-discharge' is overcome and it suddenly releases it's stored charge back into the circuit - in an attempt to balance the differences. The opposite of the process of changing it.

    Now go back to the three phase graph of overlapping power 'pulses'. Take note of the fact that their overlapping eliminates the effect of the zero-line - this is why three phase is so much more efficient at producing horsepower than single phase.

    So now picture that on the 'single-phase-with-run-capacitor' sine curve - the gaps between the humps are filled with the bridged-over line which shows the run capacitor discharging it's accumulated charge back into the circuit from the declining voltage side of each 'hump'. So what the run capacitor actually does is to create a second phase of power - and so cover the zero-voltage-line - which eliminates the 'zero HP production' problem disappear. Which is how / why a PSC motor is so much more efficient than a simple single phase motor.

    That is not 100% technically 'according to Hoyle' accurate in every minute detail - but I find it accurate enough to produce an understanding of what is happening at our level of required understanding. <g>

    PHM
    ---------



    Quote Originally Posted by TechmanTerry View Post
    Some of these"listen to this story" has me wondering about how I understand my thinking about 240 VAC ,single phase,Res electricity w/ run caps. I'll be contemplating my thought process all the while I'm supposed to be working. "The basic inherent electrical characteristic difference between the start and run windings" enters my brain for some reason.
    PHM
    --------
    The conventional view serves to protect us from the painful job of Thinking

  26. #18
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    Wow: I realize that I was trying to stop a roof leak before and after writing that out - but damn! Not even spell-check itself could have injected so many writing-errors! <g>

    I'll fix them here -

    Quote Originally Posted by Poodle Head Mikey View Post
    Picture a 60 cycle sine wave the way it would appear on an oscilloscope. There is a 'zero voltage' line that is left-to-right through the center and there are positive waves humping upward and negative waves humping downward - one after the other.

    At this point I always encourage people to physically draw that image out on paper.

    At the zero-line the motor using such power produces zero horsepower - and it produces it's maximum horsepower at the peaks of the 'humps' up and down. That is what single phase power looks like.

    Now picture three such sine curves evenly spaced, each overlapping the last by 33%, on the same curve background. That is what three-phase power looks like.

    So again picture the single phase graph. Except that, with a run capacitor in the circuit (which would have no initial charge - it would be 'empty'), on the left side of each upward and downward portions of each 'hump' - the capacitor is being charged with electricity. This is because the circuit's power is Higher than the capacitor's - so it 'equalizes' by accepting the increasing electricity into itself from the connected circuit. At the peak of the curves the power in the circuit and the power in the capacitor are 'even'. But after the peak of the 'hump' comes the declining side of the wave. The capacitor's internals are di-electric so they do not want to give up their stored power. But at some point on the declining voltage side of the wave - the capactor's charge is so much higher than the circuit's that the run capacitor's 'reluctance-to-discharge' is overcome and it suddenly releases it's stored charge back into the circuit - in an attempt to balance the differences. This is the opposite of the process of the capacitor charging.

    Now go back to the three phase graph of overlapping power 'pulses'. Take note of the fact that their overlapping eliminates the effect of the zero-voltage / zero horsepower line - this is why three phase is so much more efficient at producing horsepower than single phase: there is no 'dead spot' in it's HP production.

    So now picture that on the 'single-phase-with-run-capacitor' sine curve - the gaps between the humps are filled with the bridged-over line which shows the run capacitor discharging it's accumulated charge back into the circuit from the declining voltage side of each 'hump'. So what the run capacitor actually does is to create a second phase of power - and so cover the zero-voltage-line - which makes the 'zero HP production' problem disappear. Which is how / why a PSC motor is so much more efficient than a simple single phase motor.

    That is not 100% technically 'according to Hoyle' accurate in every minute detail - but I find it accurate enough to produce an understanding of what is happening at our level of required understanding. <g>

    PHM
    ---------
    PHM
    --------
    The conventional view serves to protect us from the painful job of Thinking

  27. #19
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    I ran into that once. I reversed the 220vac legs and it ran in the right direction then. I cycled it a few times and it started in the right direction every time. The capacitor was good and was the right one for that motor. I did not ever figure out how it came to be operating in the wrong direction.

  28. #20
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    Unless it’s a recip 😉

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