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Rheem AC Unit with low TD

COLDAIRRANDY
COLDAIRRANDY Member Posts: 19
I just changed out My 5 ton Rheem Condenser and Evap/TXV that was in the house for 15 yrs with the same equipment that was in there. Ran nito through while brazing up the lines, pulled vac and started up. Everything seems normal except the 11º TD across the coil. Checked on all the registers and return in the house.
Charged by sub cooling. I have a 11º sub cool at cond, 14º Superheat at the cond.
The Humidity in the house is 49% it will put out in the middle of the day 55/56 degrees and the the return will stay at 11º about 67. it feels good in the house. But always hearing techs say 16 to 20 across the coil. I install the TXV at 12 o'clock and is wrapped good like supposed too.
There is not space around the evap for the fan to blow it is a tight fit. Discharge at the condenser was about 205 and the suction 62 on 93º day. looking at the pressure chart at 62º psig is about 35. if I add some refrigerant to bring my suction up my sub cooling starts running high above the 9 to 12 rated for.
One thing that I am not sure about on the install is I welded the external cap tube exactly where the old one was. On the main trunk tube that has all the small tubes feeding the suction line about a foot before the TXV. I don't know if mounted there causes the TXV not to give me that Higher TD. But that is where it was before, right or wrong.
Anyone have any idea on what is going on with Low TD. Just wan
Thanks
Randy

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 9,709
    The cap tube from the TXV gets brazed on the suction line coming out of the coil. The txv bulb should be on a horizontal suction line at 3 oclock or 9 oclock. . There can be some variation in this depends on the pipe size

    If you have to put the TXV bulb on a vertical line the cap tube to the bulb must be on top.

    Don't know what's wrong. Measure a bottle of refrigerant for weight and weigh a little in while watching the coil TD and see what happens.

    Is the coil and condenser a matched set? Correct TXV? Air flow correct, clean filter all registers open?
  • COLDAIRRANDY
    COLDAIRRANDY Member Posts: 19
    It is a horizontal unit in the attic. Bulb is on the 7/8 suction line horizontal but at the 12 position. Per Rheem instructions. And inside the air handler clamped good on flat surface and insulated.
    Coil TXV and cond is a match has the correct orfic for R22. I have tried adding gas and all the readings subcooling ect will change but the TD stays around the 10 to 12 depending on house temp I can't get it any higher. Any problem with the way it is running.
  • bburd
    bburd Member Posts: 195
    A return temp of 67 F is much lower than the conditions most comfort A/C units are rated for. 75-80 F return is more usual. This may account for the low TD.

    Do you have a high latent load? Is the return ductwork tight? Voltage ok?  Compressor amperage within specs?

    Bburd
  • mattmia2
    mattmia2 Member Posts: 3,686

    Coil TXV and cond is a match has the correct orfic for R22.

    wait a second here. is it using a txv or an orifice as the refrigerant control?
  • COLDAIRRANDY
    COLDAIRRANDY Member Posts: 19
    The liquid hits the txv then the orifice in the distributor tubes. Here is a picture before it was installed. Also here is a picture of the old one so you can see where the equalizer line is attached and bulb. I have the new one set up the same way.
  • COLDAIRRANDY
    COLDAIRRANDY Member Posts: 19
    The 67 degree return is usually at night when it is cooler and the register is putting out 55/ 56 air. In the day time the return is 70/71 with the register putting out 59/60 air. 
  • JUGHNE
    JUGHNE Member Posts: 8,687
    Are you using both the TXV and the orifice?

    Usually one or the other, but not both.
    IIWM, I would remove the orifice.
  • pecmsg
    pecmsg Member Posts: 2,217
    Correct oriface for R-22?

    that’s a R-410A system. 

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 9,709
    I agree with @jughne & @mattmia2

    You can't use a txv and an orifice. What is the refrigerant R-22 or 404A?

    Something is amiss here
  • JUGHNE
    JUGHNE Member Posts: 8,687
    What gas is in this....R 22 or 410A?

    Don't know where you would get a new R-22 cond unit today.
    pecmsg
  • COLDAIRRANDY
    COLDAIRRANDY Member Posts: 19
    R22 is the gas and from everything I have been reading on Rheem coils they use both the txv and orifice/piston. The distributor on the evap  came with an orific and had a small hole in the orfice. Directions with txv said to change out the piston which had a larg hole. I will call Rheem Monday and get the scoop. The old unit had both and piston hole was the Same size and and I remember few years back the difference between regester and return was about 16/17.
  • JUGHNE
    JUGHNE Member Posts: 8,687
    Can you show us the nameplate on the outside unit?
  • COLDAIRRANDY
    COLDAIRRANDY Member Posts: 19
    Here is a couple of pics.
  • pecmsg
    pecmsg Member Posts: 2,217
    How did you find a 7 year old condensing unit?
  • JUGHNE
    JUGHNE Member Posts: 8,687
    edited June 19
    And a 6 year old R-22 coil to go with it?

    So it is R-22, I am suspicious of using both TXV and orifice together.

    Are you sure the TXV is for R-22?
    mattmia2
  • COLDAIRRANDY
    COLDAIRRANDY Member Posts: 19
    I purchased this equipment 9/11/15 from Gemaire and stored it anticipating on changing this out when the time was right. Here is paperwork on the cond,coil and txv.
  • COLDAIRRANDY
    COLDAIRRANDY Member Posts: 19
    This is what I am reading on line. And my valve is an R22.

    Most all rheems use the piston with TXV in the residential application for the same effect they use in our commercial refrigeration jobs, such as the Bohn, Heatcraft coils and so on.Sep 24, 2014
  • JUGHNE
    JUGHNE Member Posts: 8,687
    Did the old coil use both metering devices?
    Can you show where the equalizer line is tapped on the new coil?
  • COLDAIRRANDY
    COLDAIRRANDY Member Posts: 19
    The old coil used both. Look at the pic of the old coil attached. That is exactly where the new equalizer is installed. Nothing different. I matched it up.
  • wesPA
    wesPA Member Posts: 18
    That was purchased during the period of time when you could buy R22 "dry condensers"
    I'm assuming the nitrogen was released from the condenser, the service valves were opened, and the entire system was evacuated? 
    I've never experienced a situation where 2 metering devices are used, usually either piston, TXV, EXV, etc.. 
    How many CFM of air is being moved across the coil? 

  • COLDAIRRANDY
    COLDAIRRANDY Member Posts: 19
    My background is commercial refrigeration an a anemometer is something I have never needed. So I couldn't tell you without getting one. I can tell you that blower puts out the air even at the longest duct run. Single speed blower.


  • JUGHNE
    JUGHNE Member Posts: 8,687
    Did you look inside the connection where the old orifice would be?

    What size was in there?

    Could you have return air leaks in the attic?

    Maybe check TD right at the furnace in the attic.

    I recall having to put a TXV and also an orifice in a coil for a walk in cooler.
    But I don't think it had distribution tubes.
  • COLDAIRRANDY
    COLDAIRRANDY Member Posts: 19
    The old orfice and the new were the same. Big hole. From what I have read I believe it is in there for equal distribution in the tubes the orfice that came in the evap had a small hole with # and the txv came with the larger one and said it must be changed out. So I did.
    My duct work is sealed tight. I am up there every year doing a check on my coil and my ultraviolet lights I have in there. If you go off what the t-stat is and take a reading at any register I have 16 degrees difference. But put the probe on the return in the ceiling an you get 10/11 degrees difference. My Ac is working good just want to address the 11 degree td because I hear techs say 16/18 td.

  • mattmia2
    mattmia2 Member Posts: 3,686
    You really need to measure wet bulb because most of the energy may be going to condense moisture out of the air, not lower the temp.
  • COLDAIRRANDY
    COLDAIRRANDY Member Posts: 19
    I have some hygrometers in the house and the humidity is at 43%. Right now my home is at 71 and 43% humidity. Feels good. From what I have read 43% is good reading. Here in Fort Worth TX it is hot and humid outside.