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  1. #1
    Join Date
    Jun 2013
    Posts
    7

    High suction, OK head new system. TXV R22

    Hi Guys
    I installed a 4 ton R22 unit (12seer), 4 ton coil, TXv, furnace. Unit came charged with nitrogen. Evac'd, charger to what I thought was a right amount of 22 then left. (installed in March) Came back today. 90 o/s temp. 80 inside. Put my gauges on 80 lbs suction 200 lbs head. no super heat, warm suction. 5 ton blower so I slowed it down to 4 ton , no change.
    Dumped Freon to get suction to 65 lbs. now warm suction 8 degree split.
    Added r22 to get head up to 225. Now 85 suction, cold suction line and 14 degree split. Mild super heat. ( looks like I'm going the right way, but 85 suction ?)
    what do you think is going on here ? I afraid to get the suction any higher but I need the split up to 20 to cool this house.
    I looked at the coil , looks like all pass's are sweating but still only got a 14 split.
    Any ideas ?

  2. #2
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,060
    Quote Originally Posted by edwyn View Post
    Hi Guys
    I installed a 4 ton R22 unit (12seer), 4 ton coil, TXv, furnace. Unit came charged with nitrogen. Evac'd, charger to what I thought was a right amount of 22 then left. (installed in March) Came back today. 90 o/s temp. 80 inside. Put my gauges on 80 lbs suction 200 lbs head. no super heat, warm suction. 5 ton blower so I slowed it down to 4 ton , no change.
    Dumped Freon to get suction to 65 lbs. now warm suction 8 degree split.
    Added r22 to get head up to 225. Now 85 suction, cold suction line and 14 degree split. Mild super heat. ( looks like I'm going the right way, but 85 suction ?)
    what do you think is going on here ? I afraid to get the suction any higher but I need the split up to 20 to cool this house.
    I looked at the coil , looks like all pass's are sweating but still only got a 14 split.
    Any ideas ?
    High heat load and humidity 85 is not a problem

  3. #3
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    5,004
    You have to check the humidity level in the home; a high humidity will cause a low indoor split.
    It could have a 14F split with a very high latent load.


    Go outside & check the split off the condenser discharge air, it should be around 110F., that's a 20F temp-rise, which seems okay with a high indoor humidity.

    The sensible temp-split will increase up toward 20F as the humidity level is finally pulled down.

    Check to see if there is too much air infiltration into the home, as that will impede the lowering of the indoor humidity.

  4. #4
    Join Date
    May 2009
    Location
    Savannah, Ga/H.H. Island, S.C.
    Posts
    1,524

    High suction, OK head new system. TXV R22

    Specific superheat and subcooling numbers as well as indoor wet bulb will help complete the puzzle.

  5. #5
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,357
    You will never nail a charge until you learn the value of a wet bulb reading, even when working with TXVs. 80 degrees dry bulb return air and a fourteen degree split does not sound out of line. The more readings you get, the better decisions you can make when charging a system. The phrase "get my suction up" should be stricken from your vocabulary. Learn that temperatures rule the roost.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  6. #6
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,629
    Quote Originally Posted by edwyn View Post
    Hi Guys
    I installed a 4 ton R22 unit (12seer), 4 ton coil, TXv, furnace. Unit came charged with nitrogen. Evac'd, charger to what I thought was a right amount of 22 then left. (installed in March) Came back today. 90 o/s temp. 80 inside.Put my gauges on 80 lbs suction 200 lbs head. no super heat, warm suction. 5 ton blower so I slowed it down to 4 ton , no change. That's not "no superheat"
    Dumped Freon to get suction to 65 lbs. now warm suction 8 degree split. ?
    Added r22 to get head up to 225. Now 85 suction, cold suction line and 14 degree split.Mild super heat . What's mild? looks like I'm going the right way, but 85 suction
    what do you think is going on here ? I afraid to get the suction any higher but I need the split up to 20 to cool this house.
    I looked at the coil , looks like all pass's are sweating but still only got a 14 split.
    Any ideas ?
    Are you sure you're checking superheat? That's not how you charge a system with a txv. Did you find the leak?

  7. #7
    Join Date
    Jun 2013
    Posts
    7
    Thank you for your Help Darrell, no the humidity level is in the norm level. I did get heat transfer threw the condenser when I jacked up the head to 225. (hot discharge). I am concerned the head it to high right now but to get any transfer I had to get it up or I would be back at 8 split. This is a 22 unit and only a 12 seer. So 20 is not out of the capacity of this system. I just never had a floodback at such a low head and nice warm air in the return. I cant put my finger on this one. TXV stuck open ???

  8. #8
    Join Date
    Sep 2010
    Location
    Nc
    Posts
    60
    Mr. Ridley and the shop hound provide the level of assistance that is much needed. The word of the day is enthalpy. Yes spelled e n t h a l p y.
    Correct data points and a psychometric chart will enlighten even the most hard headed of us!

  9. #9
    Join Date
    Jun 2013
    Posts
    7
    Thank you

  10. #10
    Join Date
    May 2009
    Location
    Savannah, Ga/H.H. Island, S.C.
    Posts
    1,524

    High suction, OK head new system. TXV R22

    Quote Originally Posted by edwyn View Post
    Thank you for your Help Darrell, no the humidity level is in the norm level. I did get heat transfer threw the condenser when I jacked up the head to 225. (hot discharge). I am concerned the head it to high right now but to get any transfer I had to get it up or I would be back at 8 split. This is a 22 unit and only a 12 seer. So 20 is not out of the capacity of this system. I just never had a floodback at such a low head and nice warm air in the return. I cant put my finger on this one. TXV stuck open ???
    12 Seer? Your condenser (if new) is a minimum of 13 Seer. But if paired with a mismatched air handler, you'll end up with less than 10 seer.

    20 degree split is out of the range of the system if you have a high entering evaporator wet bulb. Search this site for keyword: TEET (Target Evap Exit Temp). That will explain why you shouldn't always expect a 18-20 degree temp split.

    Are you a tech? This is kinda sounding like a DIY.

  11. #11
    Join Date
    Jun 2013
    Posts
    7
    Quote Originally Posted by second opinion View Post
    High heat load and humidity 85 is not a problem
    Not really a tremendous inside load. 80, humidity level norm, not wet That's why I am surprised of the high suction. Combined with only a 200 head . where is the transfer going ?.. The coil is saying I don't need liquid so it's sending it back via the by pass tube, right (high suction)? So why when I increased the head the coil (TXV) says "OK" I'll now flood the coil making the split higher ! But still the suction stays up there.

  12. #12
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,295
    This thread certainly didn't belong in AOP. Moved here but might be something that belongs in the pro section.

  13. #13
    Join Date
    Jun 2013
    Posts
    7
    AC biz 36 yrs. Now retired 15yrs. Out of touch with all the new tricks.

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