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Thread: REDUCE Blower CFM

  1. #1
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    REDUCE Blower CFM

    I am using an HVAC blower for a project that is not exactly HVAC related. I bought a used blower that came out of a 5 ton unit. It has a 220V, 3/4HP, 2-speed, 1075rpm direct drive motor and a 10x10 wheel. My original research lead me to believe that this blower would produce roughly 2000cfm at high speed.

    Now my project specs have changed and I need a blower with a much lower CFM. Can I replace the current motor with a 110V 4-speed motor with hopes of getting lower CFM out of it because of it having 4 speeds? I prefer the 110V but that spec isn't critical.

    Or... is it possible to use a variable speed controller on these types of motors?

    Thanks,
    Brad

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    Quote Originally Posted by bradford0113 View Post
    I am using an HVAC blower for a project that is not exactly HVAC related. I bought a used blower that came out of a 5 ton unit. It has a 220V, 3/4HP, 2-speed, 1075rpm direct drive motor and a 10x10 wheel. My original research lead me to believe that this blower would produce roughly 2000cfm at high speed.

    Now my project specs have changed and I need a blower with a much lower CFM.

    Can I replace the current motor with a 110V 4-speed motor with hopes of
    getting lower CFM out of it because of it having 4 speeds?

    I prefer the 110V but that spec isn't critical.

    Or... is it possible to use a variable speed controller on these types of motors?

    Thanks, Brad
    _ You may wish to add a speed controller and/or
    add DAMPER AND DUMP SetUp
    with the Existing Blower to work at ~ 1/2 flow.

    Is much lower 1,000 CFM or 1,500 CFM?

    Application: ______ ?
    My gmail address: raicngdan11
    Designer Dan __ It's Not Rocket Science, But It is SCIENCE with Some Art. _ _ KEEP IT SIMPLE & SINCERE ___ __ www.mysimplifiedhvac.com ___ __ Define the Building Envelope & Perform a Detailed Load Calc: It's ALL About Windows & Make-up Air Requirements. Know Your Equipment Capabilities

  3. #3
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    Just restricting the airflow would probably be the most cost effective.
    I do a triple evac with nitro to remove non condensables.

  4. #4
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    Application: ______ ?
    My gmail address: raicngdan11
    Designer Dan __ It's Not Rocket Science, But It is SCIENCE with Some Art. _ _ KEEP IT SIMPLE & SINCERE ___ __ www.mysimplifiedhvac.com ___ __ Define the Building Envelope & Perform a Detailed Load Calc: It's ALL About Windows & Make-up Air Requirements. Know Your Equipment Capabilities

  5. #5
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    There are universal ecm replacement motors that would are very adjustable. Of course I don't know what you are using it for so I have no idea if it would work or be safe.

    Sent from the Okie state usin Tapatalk

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    Thread Starter
    The application is for pushing air through a HEPA FILTER to have clean air for working with (gourmet) mushroom cultures. The HEPA will have a 4 or 6 square foot surface area (not sure yet if I will use a 2x2 or 2x3 HEPA) and a static pressure of about .8 WG. Will also use a prefilter before the blower which would add another .1 or .2 WG static pressure. Goal is to have 100 to 200 CFM out of the filter. So if I use the filter with 6 square feet surface area, I need a CFM out of the blower between 600 to 1200 at about 1.0 WG static pressure. For the 4 square foot it would be between 400 and 800 CFM at 1.0 WG.

  7. #7
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    Pretty basic application. Just do not exceed the max inlet static pressure. This can easily be done by throttling the inlet air to the blower.
    I do a triple evac with nitro to remove non condensables.

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    Quote Originally Posted by BBeerme View Post
    Pretty basic application. Just do not exceed the max inlet static pressure. This can easily be done by throttling the inlet air to the blower.
    Can you please explain more what you mean by this? Max inlet static pressure of filter or blower? How would I know what that max is? How does one throttle the inlet air?

  9. #9
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    With all due respect, you need to understand (research) the terms to the questions you asked in the OP.




    Quote Originally Posted by bradford0113 View Post
    Can you please explain more what you mean by this? Max inlet static pressure of filter or blower? How would I know what that max is? How does one throttle the inlet air?
    I do a triple evac with nitro to remove non condensables.

  10. #10
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    Oh, by the way, you got shrooms?

    Been a few decades since I've done shrooms.
    I do a triple evac with nitro to remove non condensables.

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  12. #11
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    Quote Originally Posted by bradford0113 View Post
    The application is for pushing air through a HEPA FILTER to have clean air for working with (gourmet) mushroom cultures. The HEPA will have a 4 or 6 square foot surface area (not sure yet if I will use a 2x2 or 2x3 HEPA) and a static pressure of about .8 WG. Will also use a prefilter before the blower which would add another .1 or .2 WG static pressure.

    Goal is to have 100 to 200 FPM (CFM) out of the filter.

    So if I use the filter with 6 square feet surface area,
    I need a CFM out of the blower between 600 to 1200 at about 1.0 WG static pressure.

    For the 4 square foot it would be between 400 and 800 CFM at 1.0 WG.
    **********
    POST # 1
    I bought a used blower that came out of a 5 ton unit.
    It has a 220V, 3/4HP, 2-speed, 1075 RPM direct drive motor and a 10x10 wheel.
    ************

    I will have to find a representative FAN CURVE for a 10" x10" wheel at ~ 1,080 RPM High speed.
    Low speed: 800 - 900 RPM ?

    1,400 CFM at ~ 1.2" seems like an initial, logical target.
    An adjustable 200 to 700 CFM HEPA Filter By-Pass
    could be an integral part
    TO ACHIEVE Flexibility for your setup.
    Designer Dan __ It's Not Rocket Science, But It is SCIENCE with Some Art. _ _ KEEP IT SIMPLE & SINCERE ___ __ www.mysimplifiedhvac.com ___ __ Define the Building Envelope & Perform a Detailed Load Calc: It's ALL About Windows & Make-up Air Requirements. Know Your Equipment Capabilities

  13. #12
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    Put a choke disc on the open blower inlet side. Adjust to the CFM you need then.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  14. Likes dan sw fl liked this post.
  15. #13
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    Is that a sexual reference?


    Quote Originally Posted by beenthere View Post
    Put a choke disc on the open blower inlet side. Adjust to the CFM you need then.
    I do a triple evac with nitro to remove non condensables.

  16. #14
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    Quote Originally Posted by BBeerme View Post
    Is that a sexual reference?
    LOL, no. Seen them on a few resi units. You screw the disc in or out, to get the CFM you need.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  17. #15
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    Quote Originally Posted by beenthere View Post
    Put a choke disc on the open blower inlet side. Adjust to the CFM you need then.
    Quote Originally Posted by dan sw fl View Post
    **********
    POST # 1

    I will have to find a representative FAN CURVE for a 10" x10" wheel at ~ 1,080 RPM High speed.
    Low speed: 800 - 900 RPM ?

    1,400 CFM at ~ 1.2" seems like an initial, logical target.
    An adjustable 200 to 700 CFM HEPA Filter By-Pass
    could be an integral part
    TO ACHIEVE Flexibility for your setup.
    Any luck on finding a representative fan curve for a 10x10 wheel? I did a lot of searching myself and can't seem to find anything.

    In the mean time, I have ordered my HEPA filter. It will be 24" x 36" x 6". The SP is 0.79" WG and it has a velocity rating of 175 FPM. My calculations tell me that 175 FPM correlates to about 1050 CFM based on the surface area of my filter so I don't want to push much more than this and risk any chance of damaging a $300 HEPA.

    I'm estimating a total static pressure of 1.0 including the HEPA and pre-filter. I want to shoot for about 100cfm out of the filter (a little higher is okay but no less) so... I am looking for the blower to push about 650 - 700 cfm at a SP of about 1.0 WG.

    Like I said in my OP, I already have this blower - 220V, 3/4HP, 2-speed, 1075rpm direct drive motor and a 10x10 wheel.

    I would already prefer to change out the motor and use a 110V. I can wire the 220V but then my work station can't be moved unless I redo the wiring. If I use 110V I can move it around to anywhere I want.

    Some research leads my to believe that I can slow down the air flow by adding more static pressure (blocking intake or output) but I'm not sure exactly how I would do that. Pretty sure that's what beenthere was referring to when talking about choking. I am still curious if I can just use a variable speed controller in the circuit to manually adjust the output. I'm not exactly sure how those work or if they will work properly with these types of motors. They vary the voltage right?

    If I'm going to look for another motor, I am wondering now if I should just look for a whole different blower assembly that has a smaller wheel too. I would still need to try to find a fan curve for any blower I get though so I can guestimate the CFMs.

    I don't plan to measure the exact CFM out of the filter. There is a rule of thumb for my purpose that you want to be able to holder a lighter in the air stream and have the flame bend at 90 degrees without getting blown out. This approximately corelates to 100cfm.

  18. #16
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    Quote Originally Posted by bradford0113 View Post
    Any luck on finding a representative fan curve for a 10x10 wheel? I did a lot of searching myself and can't seem to find anything.

    In the mean time, I have ordered my HEPA filter.
    It will be 24" x 36" x 6". The SP is 0.79" WG and it has a velocity rating of 175 FPM.

    My calculations tell me that 175 FPM correlates to about 1050 CFM based on the surface area of my filter
    so I don't want to push much more than this and risk any chance of damaging a $300 HEPA.

    I'm estimating a total static pressure of 1.0 including the HEPA and pre-filter.

    I want to shoot for about 100cfm out of the filter (a little higher is okay but no less) so...
    I am looking for the blower to push about 650 - 700 cfm at a SP of about 1.0 WG.

    Like I said in my OP, I already have this blower - 220V, 3/4HP, 2-speed, 1075rpm direct drive motor and a 10x10 wheel.

    I would already prefer to change out the motor and use a 110V.
    I can wire the 220V but then my work station can't be moved unless I redo the wiring. If I use 110V I can move it around to anywhere I want.

    Some research leads my to believe that I can slow down the air flow by adding more static pressure (blocking intake or output) but I'm not sure exactly how I would do that. Pretty sure that's what beenthere was referring to when talking about choking.
    I am still curious if I can just use a variable speed controller in the circuit to manually adjust the output.
    I'm not exactly sure how those work or if they will work properly with these types of motors. They vary the voltage right?

    If I'm going to look for another motor, I am wondering now if I should just look for a whole different blower assembly that has a smaller wheel too.
    I would still need to try to find a fan curve for any blower I get though so I can guestimate the CFMs.

    I don't plan to measure the exact CFM out of the filter.
    There is a rule of thumb for my purpose that you want to be able to holder a lighter in the air stream and have the flame bend at 90 degrees without getting blown out.
    This approximately corelates to 100 FPM.
    If the motor speed is decreased in the range of 5% - 10%, the fan curve changes SIGNFICANTLY.
    ... ... ... _____________... ... ... 1075 to 970 RPM

    .... HIGH TO MEDIUM EXAMPLE / MODEL ARUF
    __ IN ADDITON, Change the ESP by adding ~ 0.5" more WITH FILTER & DAMPERS
    and the air flow is reduced from 1,734 to 1,145 CFM +/-

    + An adjustable 200 to 700 CFM HEPA Filter By-Pass could be an integral part
    TO ACHIEVE Flexibility for your setup.

    https://www.goodmanmfg.com/pdfviewer....pdf?view=true
    Page 5

    Example
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  19. #17
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    BALL PARK ...
    _____________
    Attached Images Attached Images  
    Designer Dan __ It's Not Rocket Science, But It is SCIENCE with Some Art. _ _ KEEP IT SIMPLE & SINCERE ___ __ www.mysimplifiedhvac.com ___ __ Define the Building Envelope & Perform a Detailed Load Calc: It's ALL About Windows & Make-up Air Requirements. Know Your Equipment Capabilities

  20. #18
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    I would think that the properties of fans are much different than the properties of blowers.
    I do a triple evac with nitro to remove non condensables.

  21. #19
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    Quote Originally Posted by BBeerme View Post
    I would think that the properties of fans are much different than the properties of blowers.
    Fan is a Blower, the blower blades are just formed slightly different
    so they can move air for unique fan applications.

    https://www.globalindustrial.com/c/hvac/fans/blower

    https://www.globalindustrial.com/c/hvac/fans

    https://www.globalindustrial.com/searchResult?q=blower

    https://www.cincinnatifan.com/index.htm
    Designer Dan __ It's Not Rocket Science, But It is SCIENCE with Some Art. _ _ KEEP IT SIMPLE & SINCERE ___ __ www.mysimplifiedhvac.com ___ __ Define the Building Envelope & Perform a Detailed Load Calc: It's ALL About Windows & Make-up Air Requirements. Know Your Equipment Capabilities

  22. #20
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    To keep it in context, the OP doesn't know the difference between fans and blowers. Or how the terms can be (and are) used properly and improperly. He's got a blower.

    Yo, mister OP . . . Think you're going to be needing to purchase and learn how to use a pitot tube. There are other ways to measure airflow, but they tend to get less and less accurate. Especially those little propeller things you wave around and it is supposed to average the readings.

    My current employer wanted me to do that on this one job shortly after I hired on. I just laughed. Told him I could not have my name and rep attached to any results from that cluster ****.


    Quote Originally Posted by dan sw fl View Post
    I do a triple evac with nitro to remove non condensables.

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