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  1. #1
    Join Date
    Sep 2009
    Posts
    9

    Chiller Compressor Changed

    Lytron Recirculating Chiller Model# RC 030 J01 M05

    I recently replaced a compressor in a Lytron recirculating chiller. After running
    the unit right after the compressor replacement everything seemed fine. Dishcarge
    line from compressor was hot to the touch while the suction line was cold to the
    touch. The water tank of the recirculating chiller started to drop in temprature.

    However, after four hours of operation the unit became unable to to maintain temp.
    Furthermore, the expansion valve(metering device) got iced up. I tend to think
    that I didn't put enough refrigerant (R134a). It used R134A before the compressor
    replacement. I put the exact same copeland compressor back in and recharged with
    R134A.

    I have actually never replaced a chiller compressor before so I wasn't sure how
    much refrigerant goes in the unit. If I remember correctly I left the low side
    around 20psi which still gave me about 300psi on the high side. I actually wanted
    the low side around 60psi but I figured that'll probably make the high side explode.

    It did bother me that such a low pressure on the low side is yielding such a
    high pressure on the high side but the unit seemed to be working ok so I left it.
    Now I want to add more refrigerant but am afraid to raise the high side pressure
    too much.

    Can anyone guess as to why the high side is so high? which is what scares me from
    adding more refrigerant. I am universally certified but still new to commercial
    refrigeration.

    Thanks

  2. #2
    Join Date
    Jun 2004
    Location
    Howell, Michigan
    Posts
    16,176
    Please review the rules re' posting and in what forum. I have deleted your other thread.


    You are in way over your head, "The suction line was cold to the touch" do you have a boss you can drag out there with you?

  3. #3
    Join Date
    Sep 2009
    Posts
    9
    Sorry about the other thread I realized I put it in the wrong forum. My first post in this forum so I do apologize.

    I do not have a boss but if they send another tech besides me he will fix it which I really don't care so much about as much as learning. Was the suction line not supposed to be cold to the touch? Don't you usually want the temperature differential between suction and dishcharge line?

    thanks

  4. #4
    Join Date
    Dec 2008
    Location
    Dixiana, AL
    Posts
    2,609
    Quote Originally Posted by ncc1701e View Post
    Lytron Recirculating Chiller Model# RC 030 J01 M05

    I recently replaced a compressor in a Lytron recirculating chiller. After running
    the unit right after the compressor replacement everything seemed fine. Dishcarge
    line from compressor was hot to the touch while the suction line was cold to the
    touch. The water tank of the recirculating chiller started to drop in temprature.

    However, after four hours of operation the unit became unable to to maintain temp.
    Furthermore, the expansion valve(metering device) got iced up. I tend to think
    that I didn't put enough refrigerant (R134a). It used R134A before the compressor
    replacement. I put the exact same copeland compressor back in and recharged with
    R134A.

    I have actually never replaced a chiller compressor before so I wasn't sure how
    much refrigerant goes in the unit. If I remember correctly I left the low side
    around 20psi which still gave me about 300psi on the high side. I actually wanted
    the low side around 60psi but I figured that'll probably make the high side explode.

    It did bother me that such a low pressure on the low side is yielding such a
    high pressure on the high side but the unit seemed to be working ok so I left it.
    Now I want to add more refrigerant but am afraid to raise the high side pressure
    too much.

    Can anyone guess as to why the high side is so high? which is what scares me from
    adding more refrigerant. I am universally certified but still new to commercial
    refrigeration.

    Thanks

    I don't know what kind of temps you're looking for here, but my first guess would be that if you're ok with running 300 psig head pressure on R134A, it would definitely be time to get the other guy involved. Ditto for thinking you need 60 on the low side, unless you're doing some really high temps.

    Start at the beginning for troubleshooting and sking others for help. Chances are, no one here is going to have any idea what the charge is for this system. Where's the nameplate? Discharge line is hot and suction line is cold are not normally the method used for measuring temp when troubleshooting. You need info - all of it - about how the unit is operating, if you want to get help. And being new to commercial refrigeration has nothing to do with anything - you don't measure temps on residential that way, either. Best advice that I can give based on the OP -

  5. #5
    Join Date
    May 2001
    Location
    Western Wa
    Posts
    1,831
    My first guess is that the unit is overcharged. But we don't know anything more than you told us. Is this a brine or glycol unit?

    Superheat and subcooling? Chilled loop supply temp? Return temp?
    Is the condenser air or water cooled?
    God Bless our Veterans

    God Bless the USA

  6. #6
    Join Date
    Sep 2009
    Posts
    9
    The chiller is actually a simple one. No brine or anything. Refrigerant (R134A) goes through the condenser so its air cooled. The unit is used to cool a laser machine's hardware so it basically is being used to keep a recirculating water loop at 23C or 73.4F I figured that since the target temp is 73.4F in this application, I'd want my evaporator twenty degrees cooler or so so thats how I arrived at the conclusion of having an ideal suction pressure of about 60-70 basically looking off a P/T chart.

    Im going back there today. I''' check super heat and also check how much refrigerant is mentioned on the nameplate. I was trying to charge it by pressure not by weight. A critical mistake I think I need to buy a scale.

    But I am really glad to see the response on this forum. Thanks to all you guys trying to help. Really appreciate it.

  7. #7
    Join Date
    Jan 2008
    Location
    Dallas ,Texas
    Posts
    3,705
    Nc there are alot of good guys on this forum with alot of knowledge, not just your typical rinky dink ac guys. This place is a learning experience for me daily !
    UA 100

    It takes three people to do anything around here. Two do the work, one explains to the crowd of people who showed up when they seen smoke and flames.

  8. #8
    Join Date
    May 2001
    Location
    Western Wa
    Posts
    1,831
    The old timer's rule of thumb on air cooled condensers is saturation pressure 30 degrees above air entering the condenser.

    I'd also be concerned that the TXV or whatever metering device is not feeding properly.
    That would show up as high subcooling and high suction superheat, usually, and lead to possible overcharging in the effort to bring up suction pressure.

    Don't give up, and don't leave it like it is.
    God Bless our Veterans

    God Bless the USA

  9. #9
    Join Date
    Sep 2009
    Posts
    9
    Ok went back there today and found that the low side pressure was around 10psi while the high side was flying somewhere near three hundred. There was frost
    on the three inch section of tubing between the TXV and the evaporator. The
    whole scene just didn't seem right to me.

    Firstly, I knew there is no refrigerant leak since I tested it with nitrogen at high
    pressure after my compressor replacement for about a half hour and didn't loose
    even a half a psi on my gauges.

    I started messing with the service valves on the unit. They are the type where
    you unscrew a hex-nut cap and that reveals a 1/4" male stud which you use
    to open/close the technician's pressure gauges connecting ports. Well, I found out that the valves don't just close the tech's ports. They also close the refrigeration loop.

    It was hard for me to tell when the valves were fully closed or when they were fully open so I
    Basically cycled both of them from fully opened(or closed) to the other extreme position and counted
    The number of turns in between and then let them back off again half the number of turns. That was my dumb but certain way of making sure both valves are open enough so that the refrigerant
    Flow isn’t blocked.

    Once I did this I was getting pressures: Low 37psi High 275psi. This seemed kinda odd still
    But the unit started chilling just fine without any frost building up on any of the pipes. I put a
    Bucket of warm water at 33C into the chillers water tank and it chilled it down to 18C within
    A few minutes that is the temperature where I had set it at the digital thermistor board. It then
    Shutoff and stayed off for about 5 to 7 minutes until the water rose a degree to 19C and then
    The unit came back on and ran for about 3 to 5 minutes and brought it back down to 18C. I
    Watched the unit go thru several such cycles and it maintained the temp fine for the fortyfive
    Minutes that I watched it without any frosting on the pipes.

    At this point convinced that the unit is doing what it should I called Lytron tech support to
    Ask them how the servicing valves work and in what position I should have them. Tech
    Support guy seemed green and couldn’t tell me his excuse was you’re working on an
    Older unit and im only familiar with the newer stuff. Then I asked him what the pressures
    Are supposed to be and he said he’d have to call a senior tech and ask him then get back to me.
    He called me back in about ten minutes to say Low side 37psi is about right but high side is a bit
    High he said you wanna be at about 200psi. I told him I couldn’t bring the high side down that low
    Cuz then I’ll get frost after the txv. He said to leave it as is. I then asked him whether this unit
    Is supposed to cycle on/off or whether it should run continuously he said it should not cycle off
    The hot gas bypass should make sure of that and I told him this unit didn’t have a hot gas bypass
    (I thought he should have known that since I gave him the model and serial number).

    So he said ok then it *is* supposed to cycle on and off. So
    I thought hmm this looks ok so I left it as is and haven’t had a call back on it yet but I’d like

    To go back and ask a few questions just for my own educational purposes. Im still not sure my pressures are optimal any opinions? Also, back to should this unit cycle or continuously run?
    Are my compressor off and on duration times ok or is this short cycling and not good for the compressor?

    Thanks

  10. #10
    Join Date
    Jan 2008
    Location
    Dallas ,Texas
    Posts
    3,705
    Well I hope that last compressor wasn`t too hard to get from a supplier.
    UA 100

    It takes three people to do anything around here. Two do the work, one explains to the crowd of people who showed up when they seen smoke and flames.

  11. #11
    Join Date
    May 2001
    Location
    Western Wa
    Posts
    1,831
    High side is still too high. Overcharged, non condensables present, condenser dirty, fan not working? I wonder if the valves were in a good position for a real good evacuation.

    Condenser pressure should be in the neighborhood of 30 degrees above entering air.

    If nothing else works, pull the charge, re-evacuate, and then weigh the charge back in.
    Last edited by Randy S.; 09-15-2009 at 11:35 PM. Reason: My glasses must be dirty...
    God Bless our Veterans

    God Bless the USA

  12. #12
    Join Date
    Mar 2008
    Location
    NE Ohio
    Posts
    59
    You need to find out what the factory charge is , pull out the refrigerant,re-evacuate and weigh the correct charge back in.Hopefully its not full of non-condensibles.That will present a whole new set of problems.I would get as much info on the machine as you can.Once the machine is back in operation ,take as many readings as you can , things like superheat, subcooling ,etc."cold to the touch" and "hot to the touch" are no way to check a system.You also need to figure out the reason the other compressor failed.

  13. #13
    Join Date
    Sep 2009
    Posts
    9
    ok I just found out that the factory charge is 3lb 0oz. I guess I"ll evacuate and recharge by weight now.

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