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Low suction pressure condition

Try charging your system according to Sub cooling, not S/H. Your figures suggest that you are overcharged. Try 10 to 15 Sub/Cooling. Your TXV is trying to close down, BUT,... You are slamming too much r-22 through it. Bulb location and how it's attached can be critical, but check you S/C first. Your head pressure is probably hi to.

Mike T.


  • mike faust
    mike faust Member Posts: 58
    condemning a txv???

    We are repaired the suction line accumulator on a 3.5 ton heat pump( it rotted and leaked). After reintroducing the proper charge we could not get the suction pressure to come above 55 lbs. (r22). Superheat testes suggested there was liquid present. subcooling was very high. 78 outdoor temp 76 indoor. 20 degree split. Is this a mental block or is my txv not opening properly. Would improper bulb placement cause this??
  • Ken D.
    Ken D. Member Posts: 836

    What were your exact readings? Head, back,liq.temp.,suc. temp., ret. temp. supply temp. outdoor ambient, indoor ambient, SH, SC, split.
  • lee_7
    lee_7 Member Posts: 458

    55lbs of refrigerant. What is amount on nameplate from manufacturer? It sounds like you could be completely full of liquid. Charge to manufacturer spec with correct amount added for lineset and go from there.
  • lenny_6
    lenny_6 Member Posts: 2
    priceing and charging sys s/c & s/h

    I am a fairly new company I have been in the trade for at least 20 years, I have yet for somebody to show me the propper way to charge a AC system, I have done lots of research and have spent lots of money on tools could you just tell me step by step how to charge a sys with r-22
    s/c & s/h, i would apreciate it so much I just want to do it right and not on someones opinion, thank you so much.
    dont get me wrong I feel I have a pretty good idea on how to charge I just want to make sure i am doing it as acurate as i can, to better my customer and myself.
    allso what is the going rate to do a start up for ac considdering ther are no problems.
  • Empire_2
    Empire_2 Member Posts: 2,343
    Hi Lenny:

    While charging is a matter of performance and is always adjustable, The manufacturer has their own specs on how to charge and that's what they recommend and prefer you to do. Example,....TXV systems use sub-cooling method to charge the system and can range from 10* to 25* and that's where you have to do what the manufacturer wants you to do. If there is a problem with the TXV, well then that's a whole different ball of wax but again you have to have a base line to go by. Fixed restrictors using S/H also have these requirements by , You know who, but can vary widely due to outside adverse affects.

    Just as an example, I can start up a system with TXV and I can get my sub-cooling where they want it, BUT I can also vary my S/H to suit what I want. Is it 5, 10 15*? well It all depends on variables. I am sorry if this is not what you want as an answer, but there are so many things that can affect a charge.

    My .02

    Mike T.

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