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Thread: What can VS do?

  1. #1
    Join Date
    Jun 2004
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    4H: Hot, Humid Houston H.O.
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    3,304

    What things will VS do?

    I would like to ask the board what are the things you can accomplish with a VS (variable speed) furnace or air handler. I have the impression that Carrier Infinity makes the best controller, have been wishing and waiting for Trane to leapfrog them, but so far it doesn't seem likely.

    I have American-Standard AUD-080-R9V4K, attached to single speed AC. Immediately I can see they have different airflow capability form the ancient Consolidated ones they replaced. My understanding is they *will* deliver the airflow stated in the tables so long as the duct system holds ESP down to 0.9" or less. This is good because my duct system causes 0.6" ESP (used to be 0.7") and the prior Consolidateds flatly stated 0.5" was their max. The nearly flat CFM promised at a given jumper setting, almost regardless of ESP, seems like one big advantage. Is that correct as far as it goes?

    The ability to enable Trane/A.S. "Comfort-R" is another benefit I can see, don't know how unique it is. Trane talks it up like it's a great invention, claims 40% better humidity removal if I remember correctly.

    Are there controllers which can select from a spectrum of airflow settings, to manipulate the sensible/latent capacity farther? Is that essentially what a top-line thermostat can do to remove humidity? If so would you please tell me what thermostat models I should be looking at. The Honeywell Vision-Pro has striking good looks, I understand the Robertshaw line is very functional but IMO they really need more artistic styling.

    Any info you can tell me on best practices with VS air handlers, I would appreciate very much.

    Thank you -- P.Student



    [Edited by perpetual_student on 09-03-2005 at 02:00 PM]

  2. #2
    Join Date
    Apr 2004
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    7,680
    The ECM is pretty much the same across the board. The infinity controller only shows you feedback which others are not doing. For example a Rheem air handler can have numerous blower CFM's configured for +10%, -10%, nominal, -15% etc. A humidistat or thermostat control such as the specified WR thermostat with humidity settings can configure the system to operate in "On Demand Dehumidification". This operates at the setpoint, not altering the setpoint to accomplish the task. In a call for heat, any latent settings are ignored.

    Carrier's package (controls) is pretty but other than displaying the CFM, static, and serial numbers, its a high price to pay for basicly the same functions with less sensible control.

  3. #3
    Join Date
    Apr 2004
    Location
    Midwest
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    2,682
    Originally posted by docholiday


    Carrier's package (controls) is pretty but other than displaying the CFM, static, and serial numbers, its a high price to pay for basicly the same functions with less sensible control.
    Oh come on Doc, how do you figure? LOL

    Show me another stat that has,

    a.Keypad lock at a touch
    b.Complete fault history with non-volatile memory
    c.Test modes at the stat for all pieces of equipment including accessories like humidifier and simulated defrost for heat pumps
    d.4 wire communication, never use more than 4 wires
    e.Large display
    f.Day at a glance programming
    g.True filter sensing ability

    The list goes on and on, no manufacture is even close on this one. And, Carrier is using the digital VS communicating motor (2.5) it is a different animal. It does not have pre-programmed fan curves built in but rather is programmed upon start up with a resister card.
    Constant communications (even when it’s not running) provides tighter fan curves over a broader range.

    The problem with Rheem Doc is that God awful green color!
    Live each day like it is your last, for one day you will be right!

  4. #4
    Join Date
    Apr 2004
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    7,680
    Im color blind

  5. #5
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,852
    Variable speed technology, besides being much less expensive to operate, has the ability to;

    * Overcome situations where a wet coil results in a frozen coil by continuing to compensate for the static pressure change due to the condensate. This is why we can utilize lower fan speeds with VS.

    * Have multiple settings for cooling; single and two stage, heating from heat pump and different for heating from auxilliary heaters and different yet for just fan operation.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


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