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  1. #1

    Expansion Valve Problem?

    Background---I had a Bryant system installed in June 2009 in a 45 year old 1000 sq. ft. rent house that probably is poorly insulated:
    2.5 ton Condenser 165ANA030
    Furnace 350AAV036060
    Coil CNPVT3617ATAA
    We had a pretty cool summer last year and I never heard of any problems, but it's hot this year
    On the 100 deg. days the system struggles to keep below 80 deg. Had it serviced by the installer, who first cleaned condenser coil and claimed it was working properly. Wrong. 2nd visit has diagnosed a bad thermal expansion valve. The system always blows cool air out the registers (although it doesn't feel like much airflow to me), just not enough to keep the house cool in the hot hot weather. The renter has since told me that the system never did work real "good" in hot weather. The installer offered to replace the TXV for 3 hours labor. I'm wondering if that seems reasonable, given the problem. Is a bad TXV easy enough to diagnose if I have another tech come out??



    Thanks!

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,474
    TXVs lately have been very unreliable so could be the culprit. Usually isn't too hard to diagnose. Unless the coil is freezing up, airflow should be good just not very cold air. 3 hours is about right.

  3. #3
    Join Date
    Aug 2010
    Location
    Owensboro, Kentucky
    Posts
    11
    Wrong. 2nd visit has diagnosed a bad thermal expansion valve. The system always blows cool air out the registers (although it doesn't feel like much airflow to me).


    If the above statement is true I would have to ask the following. Was the duct work and system sized right ? Let's used the rule of thump for tonnage 400sqft per ton of cooling, so you have 1000sqft of space, a 2.5 ton unit would cool 1000sqft. (1000/ 400 = 2.5) This is just a rule of thumb to properly determine system and duct size you have to use a manual J and other calculations, now I would say the tonnage is o.k. me personally I always size a half ton more just to account for hotter summers, but that's just me. If my system has been properly sized I would ask, it was installed in 2009, so it has been a year depending on month of installation, that's early to be having problems not that this wont happen but still early, now I would have to check system pressures outside and inside temperatures, sub-cool and superheat and check these readings against the manufactures specs. if they are with in range then the system is running according to design and I would have to look at the possibility that the blower fan is wired to the wrong speed, ( if the air is cool but low air volume I would look here first,). Blower motors are usually three speed HI,MED,LO. but some are two speed HI,LO. I personally use HI speed for summer applications and LO speed for winter applications, but to each his own. I would ask is there any freezing of the line before the expansion valve and/or is the valve freezing? Now I am not saying that the service technician is not doing his job and I am not telling anyone how to do there job, I am just listing possible troubles that can easily be over looked as this happens to all of us. Thank You for allowing me the chance to give my two cents worth.

  4. #4
    Thanks for the feedback. I'm hesitant to believe the TXV is bad because the air from the registers always feels cool. I did check and make sure the fan high speed is operating on the cool cycle. Even while the tech was present and said the system was working properly (18 degree difference between intake and register temps), the temperature in the house went up 2 degrees (It was 85 degrees outside). I think I'll look in the attic to make sure there's not an obvious problem with ductwork--which they didn't do--and then have someone else come check it.

  5. #5
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,841
    You've got a Bryant system so the part is warranted by Bryant for 5-years, unless the system was registed within 90-days of the installation, in which case the parts are warranted for 10-years. All warranties over 1-year are exclusive of labor. I'd suggest you discuss with the company what the guarantee is if the TXV doesn't solve the problem.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  6. #6
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,474
    Where are the ducts? Attic? How many supply outlets?

    I have 1000 sq ft, well built but no shade. 98 a couple weeks ago and I was just over 70 in the house with a 2 ton not running steadily. My return is in the attic but new and with batts of insulation laying on it to avoid it picking up a lot of attic heat. May want to get up there on a hot day. Read air entering grilles in the house and compare to the air entering the furnace. Do the same with air leaving the coil vs leaving the registers in the house. I found one in a new house so bad that over 1/2 of the 3 tons of cooling was lost to attic heat penetrating the ducts, supply & return.

    Sounds like you have duct design/sizing issues if airflow is weak.

  7. #7
    Join Date
    Sep 2008
    Location
    Wisconsin
    Posts
    104
    It really SOUNDS like you have an airflow problem not a TXV problem (18 degrees split-good). Why is your airflow so weak? I would find the answer to this question before I opened up the system to replace a TXV.
    It's not going to fix itself...

  8. #8
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,629
    Could be a lot of things but a TXV is easy enough to diagnose IF it acts up while the tech is there.
    On a side note two and a half tons is a LOT for 1000 square ft . My house is the same size with supply ducts in the attic and it has a two stage two ton heat pump. No problem for the first stage to keep the house at 74 when it's a 100 out and that's not even a ton and a half output.

  9. #9
    Join Date
    Jun 2004
    Location
    Kathleen GA
    Posts
    236
    Gotta ask - have you considered adding a bit of insulation or maybe sealing the windows? Even some radiant barrier insulation would help.

    18 degrees tells me the system is putting out some cold air. So I am agreeing with Baldloonie that you have duct issues or no insulation (or both).

  10. #10
    Join Date
    Jul 2009
    Location
    Lizella, GA
    Posts
    139
    Quote Originally Posted by alex_in_fl View Post
    Gotta ask - have you considered adding a bit of insulation or maybe sealing the windows? Even some radiant barrier insulation would help.

    18 degrees tells me the system is putting out some cold air. So I am agreeing with Baldloonie that you have duct issues or no insulation (or both).
    Its a rent house I don't pay the power bill, thats what my landlord customers would say. LOL

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