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  1. #27
    Join Date
    Aug 2002
    I don't know why they would adjust the blower speed all the way down to 975 on a 3.5ton system that is too low as far as I know...

    The average cfm per ton is 400cfm per ton.. But now they say it is acceptable for 350cfm per ton so I would not set your blower lower than that.. You have a 3.5ton which would be 3.5 x 350= 1225 cfm needed for your unit to operate correctly..

    Did they take any return or supply statics to see what the static pressure was?? This number would indicate if you have a problem with your ductwork..

    Good luck

  2. #28
    Join Date
    Feb 2006
    As far as I know, they did not do any supply statics. I will be asking when I see them on Monday or Tuesday.

    Looking at the Basic Air-Flow Settings chart for a 3.5 there are settings at 880, 975, 1080,1125,1265,1390,1455, and 1590.

    Maybe they were hoping to keep the noise down so we could hear the t.v. lol

    [Edited by melody on 02-11-2006 at 01:09 AM]

  3. #29
    Join Date
    Nov 2000
    Waco, Texas, USA
    Melody if a 3 ton unit won't get any closer than 8 degrees of the set point then you must have a larger than average heat load. If we can identify where the heat is infiltrating your home and stop it, or at least slow it down then a 2.5 ton might be a big enough unit. See the more the heat leaks in the bigger the unit has to be which results in HIGH utility bills.

    I bet your attic gets pretty hot in GA. Does your home have any ceiling penetrations that allow attic air & dirt to leak in the home such as can light, exhaust fans in the bathrooms, air boxes (not registers) in the ceiling etc.?

    What about skylights? How many people? Pets that go in & out? Leaky ducts? Big windows facing west? No blinds? Hot tub?

    How much pressure is in the duct system anyway? Has anyone measured it?

    Why don't you call an outside person to evaluate your system? If you keeping using the installing company you may never get to the bottom of the problem....and I don't think a defective unit is the problem.
    "And remember my sentimental friend......that a heart is not judged by how much you love, but by how much you are loved by others" - Wizard of Oz.

  4. #30
    Join Date
    Mar 2002
    Richmond, Virginia
    Originally posted by melody
    Jacob Perkins -
    Since I live in humid South Ga, what will the high humidity do?

    HVAC Pro - Latent Heat?

    A huge thank you to all who responded.
    Latent heat is moisture in the air, humidity.
    There is nothing more frightful than ignorance in action....Mark Twain

  5. #31
    Join Date
    Feb 2006
    Can you tell if the ductwork is undersized by the size of the ductwork? I went under the house today and measured.

    The supply ductwork was 10" X 21" and the return ductwork was 7" X 26" (metal rectangular type). There are two 20" X 20" returns in the house.

    All the room ducts were either 5" or 6" and are the round metal type that branched off in 90 degree angles .

  6. #32
    Join Date
    Feb 2006

    Problem Mostly Solved

    Just wanted to post back and tell everyone who offered their helpful advice that the problem with the new heat pump is mostly solved.

    The owner of the company (and his distributor) came out and put on a new blower assembly and the unit made the same sound as the first...loud whistling with lots of air. He said, he would try another one as he had brought a couple with him. When he put the third blower on, the noise was cut about 95%. All that was left was a little "ac hum" which he said could be solved by putting in some flex duct at the unit. We'll see on Monday about that.

    The same blower assembly is used on the 3.5, 4.0, and 5 ton unit. At the manufacturer, the blower was mistakenly put in the unit as if it was a 4 or maybe a 5 ton unit. The blower alignment was way off causing most of the air to be forced through a much smaller opening. The ac guy did not notice it at first when he changed out the blower. But when he got to the second blower he noticed that it did not look right and realized what had happened.

    Fortunately, We are down to just a small (but still bothersome) electrical hum.

    Frigidaire had advised them prior to their coming out that they believed they would find the blower making this type of noise due to the fan not having the proper clearance inside the cage.

    Now, I guess the ac guy will be calling them back to let them know some units may be leaving there with the blower assemblies set wrong for the unit.

    Thanks for everyone's help.

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