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  1. #27
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,198

    I understand why you may think what you said was true

    Originally Posted by genduct

    I think the underlined sentence agrees with " result in higher operating costs the system is working more." that you said you disagree with

    But I like your point about amp draw. Counter intuitive isn't it!

    Quote Originally Posted by hvacrmedic View Post
    With a constant cfm ECM blower the amps will go up as the filter becomes restrictive.

    I assume that Gib's Son was responding to Desuperheater's statement. But here's what he actually said "Less ESP at equal CFM means the blower is working less, might last longer and will use less energy." Which is correct. HTH.
    BUT I believe the counter intuitive situation we mentioned should still be true even though the more efficient, and smarter moptor is going to try to hunt for the "sweet spot' delivering the CFMs it want to "shovel" into the duct system
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  2. #28
    Join Date
    Sep 2007
    Location
    Boise, ID
    Posts
    4,395
    Quote Originally Posted by hvacrmedic View Post
    With a constant cfm ECM blower the amps will go up as the filter becomes restrictive.

    I assume that Gib's Son was responding to Desuperheater's statement. But here's what he actually said "Less ESP at equal CFM means the blower is working less, might last longer and will use less energy." Which is correct. HTH.
    The original discussion did not mention an ECM motor. That being said, I would have to run my own real world test to confirm ( in my mind) that amps would go up as ESP increases with an ECM motor in order to believe it. I have never tested this. On the surface it sounds logical, but before I ran real world test's on non-ecm motors, I never believed that more static = less amp draw either.
    If a nation expects to be ignorant and free, in a state of civilization, it expects what will never be. (Thomas Jefferson 1816)

  3. #29
    Join Date
    Jul 2005
    Posts
    5,576

    Post

    [QUOTE=Gib's Son;11478882]The original discussion did not mention an ECM motor. That being said, I would have to run my own real world test to confirm ( in my mind) that amps would go up as ESP increases with an ECM motor in order to believe it. I have never tested this. On the surface it sounds logical, but before I ran real world test's on non-ecm motors, I never believed that more static = less amp draw eitherOTE]

    His statement was valid for PSC motors too, given that he specified "at the same cfm."

    What he meant, best I can tell, is that given the choice of a lower speed tap and and a lower ESP vs. a higher speed tap and a higher ESP, the former would consume less energy "at equal cfm."

    The fan laws will tell you the same thing.

    I brought up the constant cfm ECM blower because it's a more direct example of this effect.

  4. #30
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,198

    I see your point

    What he meant, best I can tell, is that given the choice of a lower speed tap and and a lower ESP vs. a higher speed tap and a higher ESP, the former would consume less energy "at equal cfm."
    And you are right I misread your quote "With a constant cfm ECM blower the amps will go up as the filter becomes restrictive" and now agree that as the Smart ECM ramps up RPM trying to maintain CFMs it will use more watts to do it.

    Good call, I should read more slowly I heard you without listening
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  5. #31
    Thank you all who responded to answer my original post. Now I have another question:
    The static pressure rating that is located on the manufacturers plate is that SP as it pertains to the unit operating in the fan or cooling mode?
    Since that heat operation is on a lower speed than cooling what pressure should I be looking for in regards to the manufacturers specs and installation design?

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