Dash, are these the numbers u asked about
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  1. #1
    Join Date
    Feb 2005
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    68
    Carrier infinity system...taken from advanced, service of thermostat
    Fan on low
    Airflow 519 cfm
    Blower 442 rpm
    Static pressure .10

    Fan on high
    Airflow 1050 cfm
    Blower 772 rpm
    Static pressure .25

    Fan coil model fe4anf003000
    Heat pump model 38ydb036311

    Those numbers sound about right?

  2. #2
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    Aug 2002
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    Office and warehouse in both Crystal River & New Port Richey ,FL
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    Very low static duct system, for Florida,which is great!!

  3. #3
    Join Date
    May 2004
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    15
    To the more experienced in the audience;

    I've never worked with or even seen one of these carrier infinity systems. Are their readings accurate?? If yes then I'm curious. Why do these numbers NOT work as they should with regard to basic fan laws??

    They appear to suggest that the CFM is more than doubled with only 2.5 times the pressure?? Do not basic fan laws say that to double the airflow would require four times the pressure?(friction varies as the square of the velocity, so SP2=SP1*((CFM2/CFM1)squared))

    Further, with CFM1=519 and RPM1=442 would not attaining a CFM2 of 1050 require roughly an RPM2 of about 894?? [CFM2 = CFM1*(RPM2/RPM1)]

    Really just wondering,

    TJ Baker

  4. #4
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    They are accurate at least the static and cfm part,never checked the rpms .Motor torque is also being changed.

    [Edited by dash on 11-23-2005 at 09:46 AM]

  5. #5
    Join Date
    May 2004
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    15
    Originally posted by dash
    They are accurate at least the static and cfm part,never checked the rpms .Motor torque is also being changed.

    [Edited by dash on 11-23-2005 at 09:46 AM]

    If the basic fans laws as published by virtually all the recognized trade organisations (and all over the web) are correct then these infinity readings cannot be accurate or correct.


  6. #6
    Join Date
    Mar 2004
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    1,042
    You do have to keep in mind when you look at an Infinity that you're looking at total system static, not external static. Everything is included- furnace HX, air handler coils, filters, etc.

    That's not a perfect answer, I know, but it's easy to forget because the industry is so focused on ESP and this isn't exactly ESP. I don't have a better answer than that... though I wouldn't be surprised if the SP number estimated from the ECM is more accurate at more moderate static pressures. 0.10" is very low, so the estimation may not be as accurate there as it would be at a more typical SP.

  7. #7
    Join Date
    May 2004
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    15
    Originally posted by wyounger
    You do have to keep in mind when you look at an Infinity that you're looking at total system static, not external static. Everything is included- furnace HX, air handler coils, filters, etc.
    ......... though I wouldn't be surprised if the SP number estimated from the ECM is more accurate at more moderate static pressures. 0.10" is very low, so the estimation may not be as accurate there as it would be at a more typical SP.
    Well as I stated at the outset... I've never seen or had any experience with these systems. How EXACTLY are these "readings" obtained?? Do they require sensors mounted external to the air moving equipment (furnace) ??

  8. #8
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    The ESp readings of the Infinity are actual ESp,and do not include the enternal static,at least that's true of the air handlers.


    Most know that an ECM motor adjuste the rpm and torque ,to deliver the required cfm of the system.

    I can't explain exactly how but the Infinity nows the cfm being delivered as any ECM does,then uses info. to determine if it's Xcfm,X rpm,and X torque,the ESP equals ?" wc.

  9. #9
    Join Date
    Aug 2004
    Location
    Midwest
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    105
    Just started up my new 38YDB036311 last night (in a blizard) matched with a FE4ANF005000 fan coil. I am also very curious how the CFM and static are determined. I expected to find a couple A/F sensors and a transmitter but there are none. Makes me think it is more of an "expected" CFM and it makes adjustments as per the ECM?
    I replaced a Lennox Pulse G14Q3100 with this fan coil. When this fan coil says it is at 1200 CFM I can hardly feel air flow at the supply registers. Maybe 60% what the Q3 blower was moving on high speed? Just guessing as I have no way to measure it. Current readings:

    High heat
    1200 CFM
    840 RPM
    .32 static

    I also have a couple more questions for the Carrier guys but will post in another thread.

    THANKS

  10. #10
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    Let me try do explain it a little better.

    All the ECM motors are programed to adjust torque and rpm of the motor to deliver the required cfm at statics(duct resistance) within range of the motor.

    So if they can do that it makes sense that they all "know " what the static is,but it's in the module control not on a display.

    With Infiinty,and the newest 2.5 version motor, it displays the static on the Controller.The Infinty control has more control over the motor than the older version,diplay of ESP is just one.Accuracy has been questioned,but I'm sure it accurate,if it wasn't the cfms delivered would be off as well.



  11. #11
    Join Date
    Apr 2004
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    7,680
    I am not sure what fan laws are published all over the web, every blower wheel, housing and motor combination has it's own blower curve.

    As dash mentioned. The ECM has a processor built in, programmed with the specific fan curves for that fan. It then coverts RPM and torque, based on those curves to establish CFM and Static. They are programmed to maintain a given CFM depending on inputs from the main controller.

    The error in actual and calculated is generally very small and probably has more to do with air density than mistakes in the calculation itself.

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