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Thread: Running a ECM at 100% all the time.

  1. #1
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    Running a ECM at 100% all the time.

    So I just installed a Goodman MVBC blower and CHPF coil. The blower is a ECM which Iím not really a fan of. I have the option to run it at 100% when it turns on so it wonít modulate.

    My question is if I do this will it put to much strain on the module? Assuming my static is good havenít taking the pressure yet.
    Also will doing this by pass the module function all together and make it work as like a PSC.

    Thanks

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    If static is good Iíd say it wonít hurt anything. If static was too high it would ramp up more than it should to try and keep the ďloadĒ on the motor within its operating specs. Itís still a modulating motor so no, you wonít be bypassing the modulation. High static i believe is a death sentence to ecm motors because theyíll speed up and run hotter since itís trying to move the right amount of air and working harder to do it. Thatís my understanding of how work but I could be mistaken.

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  4. #3
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    That would only put more strain on the module.
    The motor is a type of three phase motor so no setting bypasses the module as it is required to make the three phases.

    Sent from the Okie state usin Tapatalk

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  6. #4
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    Quote Originally Posted by HVAC Guy7 View Post
    The blower is a ECM which Iím not really a fan of.
    Elaborate please
    Hmmmm....smells like numbatwo to me.

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  8. #5
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    it depends on the style you are using. x-13 constant torque ecm motors are becoming stock minimum for most manufacturers for furnaces and air handlers. with this style motor (very basic) you are sending a constant 230/115 volts to motor with a ground. also you are sending 2 low voltage signals. these low voltage signal wires are for heat and for cool, one of which is shared with G for fan on calls. so when using and X13 ECM (electronicly commutating motor) there is no ramping up and down other than at initial startup when the motor is deciding which direction to turn.

    the other style common to our industry is an ECM constant air flow motor. This motor is designed to maintain a certain static pressure for the application. These motors are commonly referred to as variable speed. You will commonly find between 12 and 15 wires coming to this motor. Some real expensive models are also communicating meaning they are receiving VDC from the board and sending it back to confirm operation.,

    IMO these motors are ok in a high static application as they know only one thing, move airflow. In fact if the airflow is restricted there is less work taking place as there is less air moving. The motor how ever is not magic. It can't move air the duct is not designed to move. The communicating models can report back to the board or interface the internal static of the system. It calculates this value per the amp draw on the motor.
    Say "I just need a little Freon" one more time!

  9. #6
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    Quote Originally Posted by numbawunfela View Post
    Elaborate please
    they don't last , and are expensive as hell .... do you have different luck with them ?

  10. #7
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    Running a ECM at 100% all the time.

    Quote Originally Posted by HVAC Guy7 View Post
    The blower is a ECM which Iím not really a fan of
    I see what you did there...

    Would you say something about them really Ďblowsí?

    My opinion on them varies, it goes through phases. I spent a long time getting one setup just perfectly and by the end i was converted. It has turned a new leaf for me.

    If youíre running the motors on a prop fans then check the rotation. If itís spinning backwards you may find thatís why it seems to suck so much.

    Quickly, I must hurry, for there go my people and I am their leader!

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  12. #8
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    Quote Originally Posted by thatguy View Post
    I see what you did there...

    Would you say something about them really Ďblowsí?

    My opinion on them varies, it goes through phases. I spent a long time getting one setup just perfectly and by the end i was converted. It has turned a new leaf for me.

    If youíre running the motors on a prop fans then check the rotation. If itís spinning backwards you may find thatís why it seems to suck so much.

    The only time I don't like them is when they start rocking out.
    In reality with the number of ecms we have out there we have had a very low failure rate. I don't know if we just have less power spikes than some other places because I'm positive it has nothing to do with static because we have subjected them to some insane static pressures. Quite frequently off the charts.
    Over the winter I worked on a trane that had an ECM that was still working after more than 20 years. I don't remember the exact age but it was from sometime in the '90s.

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  13. #9
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    Quote Originally Posted by Snapperhead View Post
    they don't last , and are expensive as hell .... do you have different luck with them ?
    YES, why yes I do. I have ECM motors/blower assemblies that I have taken out of 15 -20 year old equipment that still has the original motor and I use them for temporary in the rare event when I do have a module fail which is the most common failure.

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  15. #10
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    Quote Originally Posted by HVACmedic911 View Post
    it depends on the style you are using. x-13 constant torque ecm motors are becoming stock minimum for most manufacturers for furnaces and air handlers. with this style motor (very basic) you are sending a constant 230/115 volts to motor with a ground. also you are sending 2 low voltage signals. these low voltage signal wires are for heat and for cool, one of which is shared with G for fan on calls. so when using and X13 ECM (electronicly commutating motor) there is no ramping up and down other than at initial startup when the motor is deciding which direction to turn.

    the other style common to our industry is an ECM constant air flow motor. This motor is designed to maintain a certain static pressure for the application. These motors are commonly referred to as variable speed. You will commonly find between 12 and 15 wires coming to this motor. Some real expensive models are also communicating meaning they are receiving VDC from the board and sending it back to confirm operation.,

    IMO these motors are ok in a high static application as they know only one thing, move airflow. In fact if the airflow is restricted there is less work taking place as there is less air moving. The motor how ever is not magic. It can't move air the duct is not designed to move. The communicating models can report back to the board or interface the internal static of the system. It calculates this value per the amp draw on the motor.
    No, they do not maintain a certain static. They maintain a certain air flow trying to overcome the static change as say a filter plugs or registers get closed. I have seen a ECM push 1.5 static from a dirty filter, once the filter was changed it dropped to .6. These type of motors us an algorithm to calculate power consumption and use that as a basis to speed up or down. The brain in the module knows to move "x" CFM it has to use "y" amount of power. What is interesting is that they will only go so far then they start acting like a PSC and use less. Again a situation with a plugged filter taking amp readings. Amp draw of the motor was higher with the clean filter than the dirty one but highest when the dirty filter was about 3/4 in.

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  17. #11
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    Quote Originally Posted by BNME8EZ View Post
    No, they do not maintain a certain static. They maintain a certain air flow trying to overcome the static change as say a filter plugs or registers get closed. I have seen a ECM push 1.5 static from a dirty filter, once the filter was changed it dropped to .6. These type of motors us an algorithm to calculate power consumption and use that as a basis to speed up or down. The brain in the module knows to move "x" CFM it has to use "y" amount of power. What is interesting is that they will only go so far then they start acting like a PSC and use less. Again a situation with a plugged filter taking amp readings. Amp draw of the motor was higher with the clean filter than the dirty one but highest when the dirty filter was about 3/4 in.
    Your both sorta right.

    The motor nor the module know what the static pressure or the cfm is directly

    What it knows is rpm and power use. Part of the programming is essentially the rpm curve for the application. Which is why your supposed to use the OEM module.

    In a standard blower curve rpm against static pressure will correlate to cfm.

    In this situation rpm and power consumption will suffice. Cause power consumption will essentially equate to load on the blower wheel.

    Which is how it knows that on a less restrictive duct system it can run lower rpm and deliver the cfm desired.


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  19. #12
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    Quote Originally Posted by heatingman View Post
    Your both sorta right.

    The motor nor the module know what the static pressure or the cfm is directly

    What it knows is rpm and power use. Part of the programming is essentially the rpm curve for the application. Which is why your supposed to use the OEM module.

    In a standard blower curve rpm against static pressure will correlate to cfm.

    In this situation rpm and power consumption will suffice. Cause power consumption will essentially equate to load on the blower wheel.

    Which is how it knows that on a less restrictive duct system it can run lower rpm and deliver the cfm desired.


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    And if the static is too high then the motor will increase in speed trying to keep the load on the motor correct? And by doing this wouldnít it create more heat, wear and tear by doing this? If duct system is sized properly then the load and rpm should be in the happy range correct and therefore last longer? Iíve been to places where a module would only last around 6ish years before itís failed, after the second failure I checked static and had over 1.3 inches static, upsized the return and enlarged a couple supply runs and itís been almost 8 years and so far all has been good. Ecm motors have been around for a long time and itís actually very good for our applications since they are more effective so to say over a broader range of conditions, Am I in ballpark with my thinking and logic or bassackwards?

  20. #13
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    Quote Originally Posted by BNME8EZ View Post
    YES, why yes I do. I have ECM motors/blower assemblies that I have taken out of 15 -20 year old equipment that still has the original motor and I use them for temporary in the rare event when I do have a module fail which is the most common failure.
    Then you have these who made it 4.5 years. , I changed them last year , so your luck is better evidently
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    Quote Originally Posted by Snapperhead View Post
    Then you have these who made it 4.5 years. , I changed them last year , so your luck is better evidently
    And then there's the PSC motors that last 8 months. With the quality of things lately it's hit or miss on everything.

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  22. #15
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    Quote Originally Posted by R600a View Post
    And then there's the PSC motors that last 8 months. With the quality of things lately it's hit or miss on everything.
    I have never had a callback on a PSC motor

    Now , I have opened 2 boxes over the years to find they were junk right out the gate , but discovered it within seconds of it running

    One of those I tried to swap the wires for reverse rotation and it made this awful humming noise , so i took it apart and turned the field around instead

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  24. #16
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    Quote Originally Posted by Snapperhead View Post
    I have never had a callback on a PSC motor

    Now , I have opened 2 boxes over the years to find they were junk right out the gate , but discovered it within seconds of it running

    One of those I tried to swap the wires for reverse rotation and it made this awful humming noise , so i took it apart and turned the field around instead
    I have had one fail after 8 months and I couldn't find a cause but I don't use that brand anymore because the condenser fan motors rarely last two years and several were bad out of the box.

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  25. #17
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    Quote Originally Posted by Hurst11 View Post
    And if the static is too high then the motor will increase in speed trying to keep the load on the motor correct? And by doing this wouldnít it create more heat, wear and tear by doing this? If duct system is sized properly then the load and rpm should be in the happy range correct and therefore last longer? Iíve been to places where a module would only last around 6ish years before itís failed, after the second failure I checked static and had over 1.3 inches static, upsized the return and enlarged a couple supply runs and itís been almost 8 years and so far all has been good. Ecm motors have been around for a long time and itís actually very good for our applications since they are more effective so to say over a broader range of conditions, Am I in ballpark with my thinking and logic or bassackwards?
    Yes the motor will increase speed to try and meet the targeted cfm.

    I cant speak to the why individual modules fail, its likely a multitude of reasons: moisture, power quality, overloading.

    It stands to reason that some modules fail because they are running hot. From lack of airflow.

    A module signaling for a lower rpm would logically be not working as hard as one that is signaling a higher rpm. Which could equate to poor ductwork.

    Its certainly good practice to apply an ecm on a duct system that is appropriately designed for the desired air flow.

    Even though they were marketed as a fix for poor ductwork, they should not be.

    Your logic seems sound to me.


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  27. #18
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    A handy article that explains the ECM function...
    https://hvac-talk.com/vbb/threads/25...ing-Technician
    It may clarify a little for this willing to invest a few minutes.

    I do controls now, so it has been a while since I handled an ECM, but as you can see from the article I used to all the time. I typically found they lasted longer and performed better - and they could not make crap ducting good, but it could deal with marginally bad ducts better. Bad power wrecks them. There used to be an accessory from Regal Beloit called an Inductive Choke that improved efficiency and may help with frequent failures from power issues.
    I would run that concern by the local sales rep. You may find it is an installation issue, or someone selecting the wrong model for the application.
    Hmmmm....smells like numbatwo to me.

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