Results 1 to 11 of 11
  1. #1
    Join Date
    Nov 2006
    Location
    Lincoln, Nebraska
    Posts
    3
    We had a start up on some computer room equipment. We pulled a 250 micron vaccum and held it for 20 minutes. Had a 18 degree superheat. But could not get the subcooling below 35 degrees. I know that it is not overcharged because the circuit can hold 70 pounds, and we only had 35 pounds in it. I was using new refrigerant. Could it be bad refrigerant. Has anyone ever heard of that.

  2. #2
    Join Date
    Dec 2005
    Posts
    1,915
    You are sure about your data??

    35 degrees subcool - I am not saying that is bad. Maybe your unit requires that. It is just strange that's all.

    And if the manufaturer requires 70 lbs of reon than put 70 lbs in by weight is the best method. If 70 lbs are in and you have strange number then you hunt for parts failure and not charging problem.

  3. #3
    Join Date
    Jul 2006
    Location
    Atlanta
    Posts
    20
    So many things to consider....
    Is it 70#'s per circuit, or 70#'s total unit charge?
    That kind of super and sub seem to indicate a full charge- is it fully loaded, hot gas off, airflows check out, etc

    Is this data room equip splits or self contained?
    If self , safe to assume water cooled? What's the head at?
    If split, are the components correctly matched?

  4. #4
    Join Date
    Nov 2006
    Location
    Lincoln, Nebraska
    Posts
    3

    non condensables

    I am getting all of the information from the factory start up guy.
    The unit has a remote condenser.
    He put 73# in the first circuit and that unit had an 8 degree subcooling. Was not told the head pressure. I was just told that it had non condensables, and I am finding that hard to believe, with the vaccum that was pulled.

  5. #5
    Join Date
    Dec 2005
    Location
    Rockhill South Carolina
    Posts
    370
    Your liquid line temp will usually approach the ambient temp by about 5 deg above.If you had non condensibles your l/l temp would be below ambient,wich woud give you a false subcooling reading.If this is a system of any size you need to take your saturated condensing pressure on the liquid line due to pressure drop through the condenser,higher the load the more mass flow rate of refrigerant the higher the pressure drop through the condenser.Even though you pulled a decent vacuum there may have been a part of the system isolated by a valve of some sort and still had air in it.

    Oh yeah and by the way some factory name plate data refering to ref charge are not worth wiping your ass with subcooling@ % of load is the way to go.

  6. #6
    Join Date
    Apr 2003
    Location
    New York
    Posts
    700
    Originally posted by captinsano
    Your liquid line temp will usually approach the ambient temp by about 5 deg above.If you had non condensibles your l/l temp would be below ambient,wich woud give you a false subcooling reading.If this is a system of any size you need to take your saturated condensing pressure on the liquid line due to pressure drop through the condenser,higher the load the more mass flow rate of refrigerant the higher the pressure drop through the condenser.Even though you pulled a decent vacuum there may have been a part of the system isolated by a valve of some sort and still had air in it.

    Oh yeah and by the way some factory name plate data refering to ref charge are not worth wiping your ass with subcooling@ % of load is the way to go.
    Can u please explain your first couple of sentences concernig l/l temp and noncondencables?

  7. #7
    Join Date
    Dec 2005
    Location
    Rockhill South Carolina
    Posts
    370
    Ifit were 80deg f outside about the lowest you could get your l/l temp would be say 85deg f,so if your l/l temp was say 70 deg you got a good bit of air.l/l temp should never be below ambient.

  8. #8
    Join Date
    Apr 2003
    Location
    New York
    Posts
    700
    Can u explain why the l/l temp should never be below ambiant?And why does this mean that there are noncondesables in the system?

  9. #9
    Join Date
    Apr 2004
    Location
    Des Plaines,IL
    Posts
    1,016
    The refrigerant in the condenser chnages from a gas to a liquid in the condenser. The point that this happens is based on the outdoor ambient temperature if it an air cooled condenser, and water temperature if it is water cooled. As the hot gas coming from the compressor flows across the condenser coil, it changes to a liquid that will be fed to a metering device. This will lower the temperature and pressure of the refrigerant. If the condenser was perfect, then the temperature of the refrigerant would be the same as ambient or water temperature, but since the condenser is not perfect, the temperature of the refrigerant will always be warmer than ambient. If you have non-condensables then this pressure would be higher. Thaat 35 degree subcooling seems extremly high, unless you have a low load situation. Give us some pressure readings and maybe we can get a better idea of what's going on in your system.
    Stuart
    Lack of airflow destroys compressors.

  10. #10
    Join Date
    Jul 2006
    Location
    tri state
    Posts
    296
    is this unit txv or fixed? I would add fac. spec.charge and check amp draw on compressor should be 5 amps below RLA.or around ballpark, low amp draw would tell me compressor under charge. too much over RLA tells me over charge compressor is on overtime amd suction will start to heat up cycle txv or look for restriction,hope u replace dryer bud.if not pump it back out and start over again,just cover you ass use acid away.
    life is at its best when u learn something new.

  11. #11
    Join Date
    Nov 2006
    Location
    North Carolina
    Posts
    130
    Pump all refrigerant to the condensor coil and valve it off, run your condensor fan for aprox. 15 minutes. Take a pressure reading and convert it to refrig. temp using a pressure/temp. chart. Your refrig. temp should match the ambient air temp. If not you have noncondensibles in refrigerant. This is the fastest way to prove or illiminate noncondensibles from possible problems.

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