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  1. #14
    Did the manufacturer of your outdoor unit way in the exact charge as what the name plate says?

  2. #15
    Join Date
    Jul 2005
    Posts
    28
    Prod... I am unsure as I did not remove all of the freon and weigh it. ( The Freon Shipped within the condenser..)
    However I am sure that it seems nomatter the brand of equipment we install when we add the freon per the instructions based on the Evap coil size and the Linset length the system is always over charged. Always. Then I get to take some of the freon out that I put in. So what I usually do is use my OEM Chart and usually add none or very little. I just dont understand why this is.

  3. #16
    Stop adding for your lineset. What I was getting at is you cant trust the manufacturers charge. So you may or may not need to add for the lineset and evap. Pull your vacuum crack her loose and charge by superheat or subcooling.

  4. #17
    CT ? EST ?

    This system is definitely overcharged...

    Get the data above with a new (current) ST.

    The unit should be charged for a matching evap and usually 25' of line set length...
    (how much refrigerant are you normally adding to the system?)

  5. #18
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,289
    Originally posted by pliscon

    SP 72LB 42F
    LP 173LB 91F
    ST 44F SH 2
    LT 80F SC 11

    OAT 78F
    IDB 76F
    IWB 63F


    Also my unit has been running for hours..
    Thanks for the help
    What is your delta T (temperature drop) across your evaporator?

    Just going by the data you've given, I'd say you're just a smidgen overcharged. Try recovering a little gas until your suction line temperature rises to 52-55 degrees and do another delta T check across the evap. Take a delta T reading before you start and another one after you make a refrigerant charge adjustment.

    Can you see what I mean by this piston system of yours being one of critical charge (charge must be damn near exact)? There's not much room for guessing!
    • 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. #19
    He already knows its overcharged.

  7. #20
    Join Date
    Jul 2005
    Posts
    28
    Oh.. The CT was 89F sorry.. What is EST?

    As far as the amount added I added .7 oz for every Foot over 15. The Coil/Condenser match said to add 15oz and I had to add 14oz for lineset.

    I am aware that this is over charged. Why does this happen on every system.. As far as factory charge I would think it would be pretty simple to put into the condenser the correct amount. Mabye a small % would be slightly incorrect however It seems every one I install is that way.

  8. #21
    Join Date
    Jul 2005
    Posts
    28
    What is the desired Delta t over the coil? It is hard to check it unless I drill a hole in the plenum. Is there any OEM chart available for luxaire units.. Knowing the properties of freon and the CFM required I would think that one OEM chart would be pretty close to the other. They all want 400 CFM/Ton, and the properties of 22 dont change.. It seems the oriface may be one size too large. I used the manual which matched one of the oriface which came with the condenser.. However it is the same manual that told me to over charge my system... Mabye with a different oriface it would not be overcharged... Shrug

  9. #22
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,289
    If I was still in the change-out/startup side of this trade, I'd right out of the chute toss out factory charge as being reliable. Why shoot the system in the foot from the word "go"?

    I think you're already seeing this for yourself, being you wrote you have to remove refrigerant on many systems when you open the factory charge into the lineset and evap.

    My last reply was to address the performance of your own system. I now understand you know it's overcharged...I was trying to drive home the often overlooked fact that piston orifice systems are CRITICAL CHARGE. Yet one more reason I'd toss the factory charge level out the window as being reliable. Sometimes it will nail it, more often than not it will not.

    If every resi tech out there riding herd on a set of gauges could grasp this concept, think how much better the world would look upon the HVAC trade with so many piston orifice systems with the proper charge!
    • 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.

  10. #23
    Have you ever been to any of the equipment manufacturing plants ?

  11. #24
    Join Date
    Jul 2005
    Posts
    28
    And another thing.. I ordered my system with a Txv valve. Since it was Luxaire the TXV came seperate and I was in a hurry because I had company coming for the 4th. And I silver solder all of my units and did not have brazing equip here at the time of installation. It was very specific that the TXV had to be brazed which I dont really understand. So I installed the pin instead. I could still install the TXV it it would greatly help me. Why do they tell you to braze it? Same pressures as the lineset connections.. I can understand brazing the compresser..

  12. #25
    Call a pro !

  13. #26
    Join Date
    Jul 2005
    Posts
    28
    The little overflow or balancing line on the Txv is what I am talking about being brazed.

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