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  1. #1
    Join Date
    Apr 2005
    Location
    SWFLA
    Posts
    4

    Infinity Static Pressure/AC Setup

    I have two identical 2-ton Infinity systems which have different readings when running the AC Checkout.

    .................Unit One(low/high)....Unit Two(low/high)
    Airflow CFM..........734/441................743/441
    Blower RPM.........760/524...............1162/742
    Static Pressure...0.39/0.20..............0.78/0.32

    Q1. Does the system automatically adjust Blower RPM to compensate for the higher static pressure on unit 2 to maintain a preset air flow? The techs are coming out to add another return to fix the increased static pressure on unit 2.
    Q2. In the AC Setup, setting the AC DEHUM AIRFLOW to HIGH, does it counteract the AC AIRFLOW setting that is set to COMFORT? I am experiencing some sweating on the air handlers. This is happening on both units.

    Thanks in advance to all the professional comments of the pro and alike in this forum. Your input to this forum has been very helpful.
    Redlining

  2. #2
    Join Date
    Jun 2001
    Location
    Louisville, KY
    Posts
    12,178
    A1: Yes.

    A2: Not really. It raises the DEHUM minimum airflow from 275 CFM per ton to 325 or 375 (one of those two) CFM per ton.

    Looks like unit 1 is quiet in operation compared to unit 2.

  3. #3
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,967
    I would would think there are rather major ductwork issues on the high static pressure unit, and "possibly even duct air leaks on the low static pressure unit."

    Unit one's static is unusually low which is good, unless there are duct air-leaks or leaks around the plenuum, etc.

    Unless you have an unusual humidity problem, I would want around 900-cfm on the high blower stage, instead of 734 and 743-cfm, so you get a full Btu/hr load on the evaporator coil.

    Make certain there are NO leaks in the duct system and that it is properly insulated.

    To insure the necessary air handling capacity of a duct system, each of the system's components (trunk lines, takeoffs, runs, register, and grill free areas) must be properly sized and matched together.

    For example, a 12x8 duct with a 400-CFM capacity, for example, WILL NOT flow 400-CFM if the register/diffuser(s) can only flow a total of 200-CFM.

    http://www.udarrell.com/proper_cfm_b...g_systems.html


  4. #4
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Since you're in SW FL,I'd keep the airflow as low as possible,for dehumidification.Sweating air handlers ,are a problem in that area,higher airflow can reduce it.


    Where are the air handlers located?Horizontial or vertical?

    If horizontial,higher then .3 Static on the return can pull water off the coil,and make the air handler sweat,in your humid climate.So they may want to check the return duct static.

  5. #5
    Join Date
    Mar 2004
    Posts
    1,042
    Carrier equipment is designed for a nominal 350 cfm/ton, not 400. You wouldn't want to run 400 cfm/ton on Carrier unless you were in a dry climate like udarrell is

    Infinity systems will only go to 400 cfm/ton (or higher?) if you set them in Maximum airflow mode or if current indoor conditions demand a great deal of sensible cooling and little latent removal. In Georgia, much less in Florida, that basically never happens. Even in Comfort mode, my Infinity system did 400-450 cfm/ton on the day it was installed (it was over 85 in the house by the time we fired it up, but fairly dry for once). Since then has run at 350 cfm/ton unless there is was need for extra latent removal.

    Assuming the air handlers are in conditioned space, give the systems a couple days to dry the house out before switching the Dehum Airflow to High. They may only be sweating because the house is still too humid. If they are in a garage, attic, etc., though, sweating is probably inevitable in that climate. At that point worry about keeping the indoor air dry and just make sure the sweating doesn't hurt anything near the air handlers. Using the Dehum Airflow on High reduces the systems ability to dehumidify, which isn't what you want in south Florida.

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