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  1. #1

    Questions about Air flow

    I had a question about the HVAC unit in my home. We've lived here for 2 years now and have always been troubled with very low airflow coming out of the floor vents. Even the vents that are within 8 feet (straight line) from the main unit have low pressure. I don't even think it would be enough air to move a cotton ball placed on the vent. Now the house does get cool but the system has to run for a long time before it cycles off. I want to call a repairman to come out and fix it but I'd like to know if there's another blower that can be used to give higher flow. I think the motor that's in there now is a 1/4HP according to the info sticker.

    The unit is a Rheem RGAC-080C. From what I can gather the unit was made in 1979. I know I need to replace it with a more efficient model but I just can't afford that right now. But if I can spend a couple hundred dollars and get better airflow so the house will cool a little faster it might save us a little money in the long run until I can afford a new system.

    I think the info tag says the blower is a 10-7DU. But I'm not too sure what all the numbers mean. I'd just like to get a little bit of info together before calling someone in that could potentially end up ripping me off.

    I've attached a picture of the info sticker on the inside of the panel. I hope this gives enough info. Thanks in advance!!
    Attached Images Attached Images  

  2. #2
    Your airflow problem is caused by one or more of the following; dirty blower, dirty filter, dirty evaporator coil, motor not running at proper speed due to motor being replace at some point with wrong motor, motor not running at proper speed because capacitor is failing, motor not running at proper speed because motor itself is failing, disconnected duct work, improperly sized duct work, registers closed, dampers closed...Good luck only spending, in your own words "a couple hundred dollars" to fix the problem. You already said the solution yourself; the system is made in 1979 and any money you put into it is a waste. You need to replace it and have the installing company doe a manual J and manual D calculation. Anything less is hackery. Good luck with all that.

  3. #3
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
    Posts
    3,304
    I am a homeowner myself and have received proposals for completely pulling out the duct system and rebuilding it from scratch. Unless I am missing something, that may be the size of the problem you face. If so, sorry to say you need to add a lot to your budget... unless you find some little problem like dirty filter or fan speed set wrong.

    It is indeed *possible* sometimes, to find a little problem that has been overlooked. One AC pro at my home was scratching his head about why airflow was so low on a system (measured 800 cfm on a 3-ton system), and another pro came and noticed the fan was set at medium speed not high. Go figure.

    Best of luck -- Pstu

  4. #4
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Call around ask;

    Can you test the static pressure of my duct system?

    Can you redesign it using Manual D,from ACCA?

    Keep dialing until you find a company that can,saving you a lot of wasted time spent with those who can't!!

    You can post more details and pics of the indoor unit and attached ducts,to get more info here,but you'll need a Pro in yuor area.

  5. #5
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Call around ask;

    Can you test the static pressure of my duct system?

    Can you redesign it using Manual D,from ACCA?

    Keep dialing until you find a company that can,saving you a lot of wasted time spent with those who can't!!

    You can post more details and pics of the indoor unit and attached ducts,to get more info here,but you'll need a Pro in your area.

  6. #6
    Thanks for the tips. I'll check the different parts for being dirty. I'm assuming that could be cleaned myself? Other than that I'll ask around for a Manual J and D calculations to get the ball rolling. If I can get the unit to last another year I"ll be in a better position financially to replace the whole thing. But I'd really like to get someone out to check the static pressure like dash said. Because maybe its just supposed to have that weak of flow because of the age of the unit. Thanks for all the help. I'll try to get more pics of the unit and ducts.

  7. #7
    Join Date
    Dec 2007
    Location
    Cedar Grove, Wi-Sheboygan
    Posts
    1,582
    If you have the manual read it, as it may give you some glues as to the possibility of your troubles, clean the fan, change the filter and put a good filter in, check your duct runs for dampers as some may be closed more then need be and some opened more than needed. If you have hard duct thru out go buy a couple of rolls of metal ducting tape or matic #9 to seal all the duct work and insulate it as well. You state there's barely enough air to move a cotton ball which to me would definately indicate that if you had this serviced someone could have moved a jumper on the motor to the wrong setting causing the low air flow. at any rate do what you can and get a compeitant HVAC guy in there to fix you up until you can replace the whole system. I had a old Tempstar that lasted a for 25 yrs and purred like a ktten until I replaced the furnace so it just may need a few adjustments to get it back to specs and provide proper air flow.

  8. #8
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,793
    On systems that the return leaks more then the supply. Sealing the return will reduce your air flow more yet.

    Sealing the ducts before knowing what the problem is can be like taking aspirin instead of getting a flu shot.
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    How many times must one fix something before it is fixed?

  9. #9
    A friend of mine is getting her unit replaced and the guy that is doing it is the husband of one of her friends. If he does a good job on her system I'll call him and have it checked out. Hopefully it's just a setting on the motor because there are several service stickers on the furnace so maybe there were just too many cooks in the kitchen?

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