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  1. #1

    Variable Airflow Not Working After Repairs

    Complete newbie to HVAC systems, so please bear with me.

    This is my situation. Want to get your opinion.

    1) I've lived in my home for 8 years now. In that time, the air that was pushed through the vents was always at variable speeds. It made the house (especially upstairs) very comfortable.
    2) A few weeks ago, an a/c repair man changed out the fan that sits on top of the condensor. He also replaced a couple of small parts, but don't know their name or function.

    Now, the air speed from the vents is not variable any more. It is either completely off, or blowing at full speed.

    I called him and he said that the airflow is controlled by the thermostat, not the outside unit.

    What are your thoughts?

    A) Is he correct, and the incident that I've encountered coincidental?
    or B) is he inaccurate in his assessment?

    I am willing to find someone else to fix what he has done, but I would first like to know if I'm on the right track. Your thoughts are greatly appreciated.

  2. #2
    Join Date
    Jul 2000
    Location
    Northern Wisconsin
    Posts
    2,013
    The first thing that's going to be needed is at least model numbers and a better description of the system you have.
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  3. #3
    Join Date
    May 2011
    Location
    Ripley, WV
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    1,169
    Changing a condenser fan motor won't change your airflow, however if you can find your invoice could you look up what other parts he changed and post them? Also model # would help too.

  4. #4
    Thanks for taking an interest!

    The unit is an American Standard, Allegiance 12.
    The tag is dated 03/00.
    The Model Number is: 7A2048A100A2

    To my knowledge, three parts were replaced. I know of two of them in detail. They are:
    1) a Wagner Motors condenser fan was installed. The user manual says, "This is a single-phase permanent split capacitor (PSC) motor designed for use as a condenser fan motor...", etc...
    2) a motor start capacitor was replaced as well. The old one is in my possession and made by BC and has a model number of 3535B8C0135A330B3.

    There was a third item that he completely did away with, however. He said that it was not necessary and "bypassed" it. (In hindsight, this sounds extremely foolish, but he was very convincing at the time.) He assured me that the system would work exactly as always. If memory serves me right, it was located by the start capacitor and may have even been cylindrical in shape as well.

    I can't find the invoice, I'm afraid, but he wasn't very detailed, so will probably not be much help.

  5. #5
    Join Date
    Dec 2007
    Posts
    4,710
    again, the work done on the outdoor unit should NOT change the fan speed inside.
    The Food Stamp Program, administered by the U.S. Department of Agriculture, is proud to be distributing the greatest amount of free meals and stamps EVER.
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  6. #6
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
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    14,914
    Quote Originally Posted by XPAIN View Post
    The unit is an American Standard, Allegiance 12.
    The tag is dated 03/00.
    The Model Number is: 7A2048A100A2

    To my knowledge, three parts were replaced. I know of two of them in detail. They are:
    1) a Wagner Motors condenser fan was installed. The user manual says, "This is a single-phase permanent split capacitor (PSC) motor designed for use as a condenser fan motor...", etc...
    2) a motor start capacitor was replaced as well. The old one is in my possession and made by BC and has a model number of 3535B8C0135A330B3.

    There was a third item that he completely did away with, however. He said that it was not necessary and "bypassed" it. (In hindsight, this sounds extremely foolish, but he was very convincing at the time.) He assured me that the system would work exactly as always. If memory serves me right, it was located by the start capacitor and may have even been cylindrical in shape as well.

    I can't find the invoice, I'm afraid, but he wasn't very detailed, so will probably not be much help.
    Unless someone added something, there are no cylindrical objects in the control box of that unit that are "not necessary."

    If it was a silver cylinder, maybe 5" long, and 1/2" in diameter, it was the crankcase heater mounted in a fitting near the bottom of the compressor, not in the control box where the run and start capacitors are.

    AS/Trane had widespread issues with those failing in units made from the mid/late 90's through 2002 or so, until they changed the design of it.
    While it may not be strictly "necessary" for most residential applications, millions of systems don't have one, it is a nice bit of compressor protection to have.

    As others have said, none of that has any affect on the indoor airflow, something would have to have been changed about the configuration of the indoor unit, or if you have an ECM variable speed blower, and one of 2 particular thermostats, a thermostat setting could be the issue.

    What model of indoor unit and thermostat do you have?
    If more government is the answer, then it's a really stupid question.

  7. #7
    Thanks for the comments, everyone. I truly appreciate you taking the time to comment.

    In case you're curious, I opened up the unit and posted a video of it to you tube. You can see what was done by clicking here:
    http://www.youtube.com/watch?v=PcHFG...ature=youtu.be

    I also uploaded a few pictures.

    i own a Honeywell TrueZone HZ322 system that comes with two wireless TH6320R1004 thermostats. The thermostat configuration is below. Perhaps you'll see something that I don't.

    the thermostat user guide is found here: http://www.alpinehomeair.com/related...structions.pdf

    The configuration of the thermostats is as follows:

    Option 0. Zone Number: <1 for downstairs thermostat, and 2 for upstairs thermostat>
    Option 1. System Type: 0 - 1 heat/1 cool conventional
    Option 3. Fan Control: 0 - O/B terminal controls valve in cooling
    Option 5. Stage 1 heat cycle rate: 5 - Gas or oil furnaces
    Option 9. Stage 1 compressor cycle rate: 3 - Recommended cycle rate [cycle rate options 1 to 6 CPH]
    Option 12. Manual/Auto changeover: 0 - Manual
    Option 13. Adaptive Intelligence Recovery: 1 - On
    Option 14. Temperature Display: 0 - Fahrenheit
    Option 15. Compressor Off Time: 5 - 5 minutes [option 0 to 4 minutes]
    Option 16. Schedule Format: 0 - Weekday/weekend program schedule
    Option 27. Maximum Heat Setpoint: 90 - Max heat setting is 90 degrees F.
    Option 28. Min cool setpoint: 50 - Min cool temp is 50 degrees F.
    Option 32. Temp Display Offset indoor: 0 - dispalys actual temperature
    Option 33. Temp display offset outdoor: 0 - displays actual temp
    Option 35. Humidity display offset (outdoor): 3 - displays actual humidity
    Option 36. Zone Names...
    Option 39. Wireless Setup: 1 - Thermostat is connected to wireless system
    Option 90. Reset: 0 - no reset

    If the option wasn't listed, then it's not available in the thermostat.

    All of the settings appear pretty standard to me. Can't figure out what could have changed. I suspect I'm gong to have to live with the current performance. Seems like a shame. Name:  Telephone Import 150.jpg
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  8. #8
    Join Date
    Jan 2009
    Location
    Keokuk, IA
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    5,520
    Oh my... it's a zone system. Phew, not sure one can troubleshoot this over the internet.

    Again the repairs to the outdoor unit should not have changed anything. I don't think that was a 2 stage unit.


    Lets try something simple. Any chance you have the fan set to "on" and now it's in Auto?

  9. #9
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,002
    Is that a duel cap someone used just for the fan?
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  10. #10
    The gentleman who worked on the A/C system also pointed out through the course of normal conversation that the unit worked at variable fan speeds, opposed to other units that simply turn on the air at full blast and then turn off. Coincidentally, that is what I now have.

    Yes, the fan is set to Auto. Setting to On keeps the fan blowing at full blast. There was a time, however, when the intensity of the air blowing through the vents (with FAN set to Auto) would vary according to the need. It kept the upstairs EXTREMELY comfortable. (I used to stand beneath the vents and admire that feature.) Now I've learned just how drastic 2 degrees can feel -- one moment I'm starting to sweat, and the next I'm shivering.

  11. #11
    Join Date
    Aug 2001
    Location
    Pavilion, NY
    Posts
    2,141
    It appears to me as if the part bypassed is the black square thing on the middle right behind the white wire nut. that appears to be an add on time delay perhaps? If that is the case and you have a zoning system it is possible it was added to the system to prevent the outdoor unit from starting too soon after shutdown if a one satisfies and another calls too soon. If this is the case,, it was probably added years ago because of that issue and bypassing may cause it to be a problem in the future.. If that is the case it is not tragic but would help out.
    ...

  12. #12
    Everyone's comments have helped me out tremendously. I now suspect that the culprit is the upstairs thermostat. I say this because the thermostat has been acting strangely these past few weeks -- may have started around the time that I noticed the airflow was also acting up, come to think about it.

    The temperature reading on the thermostat was not correct at times. This caused very strange behavior -- like the cold air never shutting off even though the temperature was several degrees below what was configured. I had recently installed a wireless router in the house and thought that perhaps the wireless signals were conflicting and causing the problem.

    After I moved the thermostat closer to the central unit, it appeared to somewhat act normal, but has never been 100%. It always worked fine from my bedroom before, but now does not.

    Now, after reading people's comments, I believe that the thermostat may be responsible for the airflow problem. Will order one and configure it. Even if it doesn't resolve the airflow problem, I believe that the thermostat still needs to be changed out.

    Thanks everyone! If anything else comes to mind, please don't hesitate to let me know.

    Take care, and God bless.

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