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  1. #1
    Join Date
    Jul 2014
    Location
    West Columbia, SC
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    HVAC Problem After Service

    Good Evening...

    Had a strange situation, and I would like input.

    Basically, last night, a friend and I serviced his system a Goodman 2.5 Ton 14-Seer Heatpump system, and the instructions for charging were that it should have 7 to 9 degrees of sub-cooling with an indoor TXV which this system has.

    That the running super-heat should be 7 to 9 degrees as well, and to adjust the TXV first... Anyway, last night (and I cannot remember the exact pressures but I think 120/300).

    Superheat was 13 and Subcooling was 12. TXV is NOT adjustable!

    We slowly recovered a small amount of refrigerant (less than a pound) such that over 20 minutes we got it to run at a Subcool of 8.8 to 9.0 watching it for around 10 minutes... The superheat maintained around 13.


    It cooled fine last night...

    Today, finished the service, blew out the drain lines, cleaned the indoor coil and had a bit of an issue with a float switch, but ultimately the system was up and running when I left. Per my buddy's request, he wanted to re-check everything, so we put on the gauges.

    Suffice it to say the numbers were different. Now it was up to 10 degrees of Subcool and the Superheat had climbed up to around 19!

    Anyway, I ultimately told him that we do not want to recover any more refrigerant in that the cause is most likely the TXV. What do you folks think?

    He called me and reported it is not cooling quite as well as it had been. I asked and he reported it is 76 indoors. I had him check the vent temperature and he reported it is 53, which is where it had been (always on the cold side).

    Anyway, Then a few moments later he is rechecking and he reports the vent temp is like 57... Then a few minutes later he reports it is 55...

    I had him verify the outdoor system is running, and it is running.

    I had him take a thermometer and measure the suction line, which is coming back at 57, which quite frankly seems a handful of degrees warmer than I would expect.


    He does NOT have a set of gauges, and I live a couple hours away. Any ideas?

  2. #2
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    18,708
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    Wash the condenser then recheck and put the refrigerant back in you took out

  3. Likes udarrell, lions_lair, throrope liked this post
  4. #3
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
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    cleaned the indoor coil
    Cleaning the indoor coil may have increased its absorption of heat & therefore tended raise the superheat temp; even though the TXV is supposed to control he H target perhaps its bulb & other TXV factors were not installed correctly...?

    Many times SH won't be where mfg'er says they should be when SC is on target.
    If he could take a wet bulb reading or convert indoor temp %RH to wet bulb temp m& use outdoor temp for the SH target; that might provide some insight.

    SC targets will vary some with outdoor temp & indoor loads.
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  5. #4
    Join Date
    Feb 2014
    Location
    Montreal, QC
    Posts
    50
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    So it was 76 indoor and it was 53 coming out of the vents? Something seems funny, either that or I misunderstood the post

    Also why would you remove a pound, did you charge it from empty?

  6. #5
    Join Date
    Jul 2012
    Location
    WA
    Posts
    2,457
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    Never adjust the charge before cleaning the coil. I agree on cleaning the condenser and putting back in what you took out.

  7. Likes Nuclrchiller, BALloyd, Fridgieguy liked this post
  8. #6
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    8,513
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    Leave it be. Working good.
    At 75^F, 50%RH, 53^F supply great.
    Keep us posted.
    Regards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  9. Likes Fridgieguy liked this post
  10. #7
    Join Date
    Oct 2002
    Location
    Plano, TX
    Posts
    2,126
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    Could be your tools. slight reposition the pipe thermometer. Thermocouple plug may be a little loose. And my analog gauges have some play in it.

  11. #8
    Join Date
    Dec 2005
    Location
    Cleveland, OH
    Posts
    3,735
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    Congrats on learning the first rule of A/C pm's: if it's working fine DON'T FIDGET WITH THE CHARGE. Rule #2, of course, is if you are going to fidget with the charge do it after you clean everything.

    It's fine to check pressures and all, but if you're just there to clean and the customer reports that it works fine then leave it alone.

    (Rule #3 is that if you do fidget with the charge never tell the homeowner. Once they hear that you did something - even if what you did is correct - you're asking for a callback. They will swear it works different now that you took some freon out and they will insist you put it back. Seen it plenty of times.)
    Good? Bad? I'm the guy with the gun.

    Statements made by me are strictly my opinions and do not reflect the opinions of my employer. I am not authorized to make any official statements on behalf of my employer.
    Any technical advice offered by me is for educational purposes only, all HVAC related repairs should only be attempted by qualified personnel.

  12. #9
    Join Date
    Aug 2009
    Location
    Where ever i hang my hat! Preferably in B.C.
    Posts
    94
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    What kind of refrigerant was it? Did you take it out in Liquid or Vapour? Some of the refrigerants are blends.

  13. Likes Fridgieguy liked this post
  14. #10
    Join Date
    Jun 2014
    Posts
    14
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    If your that into system dynamics watch your SH / SC as you add the refrigerant back to the system. I would never alter a charge based on a few degrees of SH /SC which could easily be in thermometer calibration or sensor placement.

  15. #11
    Join Date
    Aug 2012
    Posts
    3,886
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    im curious why it took two days to service a ac that was not broken

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