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  1. #1
    Join Date
    Jul 2011
    Posts
    71

    Evolution Airflow with Single Stage AC

    Hello Gents-

    I have an Evolution 3 stage 80K BTU gas furnace with the Evolution Controller. My AC unit is a single stage 2.5ton Bryant unit.

    On the Evolution controller under Furnace settings there are some airflow control settings for the Air Conditioning. (EFF=efficiency I presume) EFF325, EFF350, Comfort, Max if I remember right.

    I presume Comfort would use a somewhat lower air flow? How to choose the setting to use & why? Pros & Cons of each?

    I'm thinking if I choose a setting with too low airflow I could have icing problems?

    Thanks,
    CxP

  2. #2
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Is the outdoor unit communicating?

    Even if no communicating, there are build in limits on the reduced airflow in Comfort based on indoor temperature and indoor humidity to prevent icing. It also looks at ourdoor tmperature as well if it's a communicating unit and will run lower airflows in hot weather since there's less system capacity... at least that's what I've observed with my system. Carrier doesn't publish the finer details of how it determines what airflwo to use. But the manaul does say that below 70F it will not lower the airflows to dehumidify. When not dehumidifying, the system seems to use 325cfm/ton as the typcial CFM setting, but in cooler outdoor conditions when humidity levels are satisfied, I've seen it ramp up to 350CFM/ton. WIth a 2 stage unit, it gets very, very aggressive in 1st stage on reducing airflows.

    The other downside of comfort mode is that supply air temps will be very low. IF you have a attic or crawlspace installation or even a basement installation, you may need a higher amount of ductwork insulation to prevent sweating on the outside of the ductwork.

    Personally I'd use comfort. Its' one of the primary benefits of the Evolution/Infinity control.

    Also if you like to use the continous fan in summer, I'd set the coil drain time to the full 60 minutes to limit how much moisture gets reintroduced into the home when the fan only comes on.

    The downside of the other settings is that airflow isn't changed to dehumidify, so you won't get much out of the Evolution controller.

  3. #3
    Join Date
    Jul 2011
    Posts
    71
    It has been a while since I logged in here & I just saw the reply here.. Just wanted to say thank you for the feedback, motoguy!

    I don't believe my outdoor unit is communicating but I have the outdoor temperature sensor. It was originally installed inside the AC unit but the sensor was moved to the north side of the house since the AC unit gets lots of sun all day and the temps were reading really high.

    Can you gleam if the unit is communicating based on this info?

    Air Handler: Bryant CAC/BDP CNPVP3617ACA
    Outside Unit: Bryant 116BNA036000


    Maybe this comment in the brochure means it has some communication ability:

    The Model 116B is your trusted source for cool comfort. For enhanced control
    over temperature AND humidity, add a variable speed furnace or fan coil and our
    Thermidistat™ Control. This system will give you full, seven-day-a-week programmability
    and our comfort-enhancing Perfect Humidity® function. Perfect Humidity
    elevates your comfort by providing up to 30 times the humidity control of standard
    air conditioner systems.
    I'll keep the Evolution controller set on the Comfort mode until I hear otherwise from you guys.

  4. #4
    Join Date
    Jun 2006
    Location
    Richmond, VA
    Posts
    2,945
    Not communicating and its a 3 ton

  5. #5
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    If it has the outdoor sensor, I beleive it should use the same logic as if it was communicating. The airflow profiles for dehumidification won't be as aggressive as a 2 stage unit sicne it on low stage, the indoor coil is essentially oversized, so it can run even lower airflows without icing than it could on high stage. I'd expect that it will run at about 300CFM/ton when dehumidifying, about 325/ton when humidity is within 1% of setpoint, and 350CFM/ton when it's more than 3% below humidity setpoint. At least that's what Iv'e observed. With the newer touschscreen controller, it adjusts airflow by 1 CFM increments depending on indoor and outdoor conditions. The basic controller goes in larger steps. Ive seen the touchscreen run it up ot 400CFM/ton when it's cool outside and indoor humidty is more than 4% below setpoint. I've never seen the basic controller do this, but I can;t say I've ever seen my upstairs where it's located have humidity that low when in cooling mode.

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