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  1. #1
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    high superheat in 20 years old Liebert mini mate

    Liebert MME018A-X01, found evap. coil iced up, unit low in charge, gas it up, clear sigh glass with 10F degrees of supcooling, superheat came down but remained high at 43F, the TXV is a non-adjustable Alco and there is a solenoid valve installed down stream of it on one of the distributor branches, not sure whats for but the valve coil was not energized when I was taking the readings.
    this is a straight self contained cooling only unit, mounted above the ceiling, I was wondering if the superheat was normal at 43F and it comes down when the solenoid valve is energized and the evap. coil is use full capacity or is the TXV is going bad?.

  2. #2
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    That sol. valve may be for capacity control (2nd stage) and for proper de-humidification control.
    Did you try energizing the sol valve to see if the SH drops?

  3. #3
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    Quote Originally Posted by keviekev70 View Post
    That sol. valve may be for capacity control (2nd stage) and for proper de-humidification control.
    Did you try energizing the sol valve to see if the SH drops?
    Thats what I thought, I did not try to energize it. I'm a little confused cause although the solenoid restricts the refrigerant flow to a section of the coil, the TXV would respond to the high superheat regardless.

    its an ALCO externally equalized TXV,the numbers are 127168P01CT3668 W9643, would like to get some info about the TXV, its a ton and a half unit wonder if they undersized the TXV?

    thanks for your help.

  4. #4
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    Quote Originally Posted by valdelocc View Post
    Thats what I thought, I did not try to energize it. I'm a little confused cause although the solenoid restricts the refrigerant flow to a section of the coil, the TXV would respond to the high superheat regardless.

    its an ALCO externally equalized TXV,the numbers are 127168P01CT3668 W9643, would like to get some info about the TXV, its a ton and a half unit wonder if they undersized the TXV?

    thanks for your help.
    After 20 years of successful cooling your thinking it now may be undersized?

  5. #5
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    Quote Originally Posted by Chris_Worthington View Post
    After 20 years of successful cooling your thinking it now may be undersized?
    I dont think the unit is undersized. I'm trying to understand if 43F degrees superheat was the target intended by whoever designed the equipment or the TXV is going bad.
    you see if they undersized the TXV then when the solenoid closes the TXV wont be able to respond to high superheat till the solenoid opens, its not a flaw if they intended it to be that way, capish?
    I couldnt find the manual anywhere, let me if you have something useful to contribute. thanks.

  6. #6
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    Quote Originally Posted by valdelocc View Post
    whoever designed the equipment

    see if they undersized the TXV then when the solenoid closes the TXV wont be able to respond to high superheat till the solenoid opens, its not a flaw if they intended it to be that way, capish?
    I capish that it has been running without issue for the last 20 years and the thought of it being undersized now is pretty much far fetched. I would put this thought out of your head, JMO though..... Do as you wish

    Is it possible on a smaller coil and a larger TXV that it may run a low SH ? Flooded evap.... and then kick in the other half in when needed?

    You have high SH....

    Straight cool mini mate?
    Condenser reheat?
    pressures?
    Possible bad pump?
    Possible dirty OD coil, assuming its air to air?
    Water cooled and water in and out is?
    etc.....

    How about some information other then "is it an under sized TXV ? "

    My crystal balls say just a bad tvx and that's it

  7. #7
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    I wish I had more to add but this is all I have. If you can read the name plate and the charge I would have weighed in the charge instead of charging to subcooling. You did say self contained so I assuming it is water cooled. I always weigh in the charge on a self contained unit. If I do a start up on a unit I also write it and some of the other info inside the unit so in 20 years hopefully it is still there.

  8. #8
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    Quote Originally Posted by RichR View Post
    I wish I had more to add but this is all I have. If you can read the name plate and the charge I would have weighed in the charge instead of charging to subcooling. You did say self contained so I assuming it is water cooled. I always weigh in the charge on a self contained unit. If I do a start up on a unit I also write it and some of the other info inside the unit so in 20 years hopefully it is still there.
    its an aircooled unit, the heat get dumped over the ceiling. I was hoping to find somebody here that knows the ins and out of that particular unit, never seen the solenoid installed in one of the distributor circuits, cheap way of controlling capacity.
    It was running OK after I charged it but superheat remained high and suction pressure around 60psig,it was an emergency call late on the day, going back next week.

  9. #9
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    I saw a 5 ton Liebert with a solenoid splitting it 3/2 tons.. The 5 ton I worked on may have had a screen upstream of the txv. If it gets dirty you will have high superheat.
    The charge should be weighed in..
    Also, bulb position? and tightness.
    High superheat after the room is cool? When the rooms hot, you will have high superheat.
    You cant really check the charge unless its in 100% demand, open solenoid.

  10. #10
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    I saw an old challenger series unit with a TXV fed by two liquid lines. One of the lines had a solenoid in it. This is for capacity control, if you are going to charge the unit you must have it running at 100% cooling. If you have a 5 ton evap coil and reduce the flow of referigerant into it by 50%, what's the superheat going to do? Is the unit keeping up with load in the room? Check your pressures and temps at full cooling.
    I have done so much with so little for so long, that now I can do almost anything with nothing at all.

  11. #11
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    43 degree SH is really warm, most compressor mfg would tell you thats too high. We have a Drake chiller running at 30 SH and manufacturer said if you get to 40 they would be concerned. The chiller story is for another day

  12. #12
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    You are still undercharged. Did you repair leak? Did you replace liquid line drier?

  13. #13
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    changed the txv today,repaired a couple of leaks and its running like a champ again, superheat down to 22F with 2 stage solenoid closed, 18F fully loaded.

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