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  1. #1
    Join Date
    Jul 2004
    Location
    Florida
    Posts
    4
    Got a very old Chiller sytem. 14.5 Ton.. single Semi-hemetic with dual condenser fan motors...230V 3 ph...Data plate says this piece of junk holds 80 LBs of Freon....can you believe it! Anyway it has a long chiller barrel and also what I believe is a Receiver...maybe an economizer?. We just put a new Compressor in...filter was changed and good vacuum pulled. Unit only took 35 lbs until system balanced.
    Problem: Even though all pressure (HP, LP, and Oil Press and Water flow) switches have been jumped out the unit cycles on/off about every second and continues to cycle on/off every second until you throw the disconnect....
    During initial start up it all ran fine maybe 1-2 minutes with normal pressures but suction was still low so I was continuing to add freon ...I got maybe 45 lbs in the unit and the Flicked unit started cycling on me..pressures were starting to look good at that point 67/220 (still low at that point because I knew I had a heavy load and with most TXVs during initial startup suction is always much higher until the water temp in the barrel and sytem come down. (Water did get cold)
    Any way I currently have about 50lbs in this piece of junk and when it runs pressure come to about 72/225... still being short another 30LBs could that cause a problem??...My thoughts are if I was truely low on freon my suction would reflect that...
    Only things left in the control ciruit for the compressor is the freeze stat which is a manual reset switch that has not been tripping....(I will jumper that sucker Monday)
    The Temp control (barrel water temp) only operates the TXV circuit so when the temp is satisfied and the circuit breaks, power is killed to the txv causing the unit to pump down and go off on low pressure, that circuit works fine, however even though the txv is staying open the compressor pressure when sitting at 72 all off a sudden you see the compressor suction pressure start rising like the system is starting to balance out (like a normal shutdown of a residential unit) the pressure gets to 80 or so and then starts its on/off cycling...The compressor was still running when the pressure starts going up...no changes in compressor noise or pitch... Help

  2. #2
    Join Date
    Jul 2004
    Location
    West TN
    Posts
    983
    Does it have a temperature switch inserted into the head
    of the compressor? (discharge temperature switch)
    I've got a compressor on a church here that goes nuts when
    trying to charge it up. Gets to a point where there's not
    enough freon in the system to 'cool' the compressor. And
    the heat from the high load and compresion are just a bit
    much for it.

    May not be a bad idea to add some kind of cycle protection
    to protect the new compressor.

    Is the compressor equiped with an unloader(s)?
    Your pressures might have been looking about right but the
    unloader may not have been loaded up yet.

    Sounds like an awefull lot of freon for that size unit...
    but I guess the manufacturer knew what they wanted.


    [Edited by wormy on 07-11-2004 at 12:11 AM]

  3. #3
    Join Date
    Feb 2003
    Location
    Wichita Ks
    Posts
    1,486
    i would put what the data plate says and fine tune it from there. i have a 200 ton that holds 900lbs of freon. i also have a 900ton system that holds 42,000 lbs of 134a. i also have a system that has 2) 250 ton compressors and 2) 450 ton compressors that holds app. 74,000lbs r22

  4. #4
    Join Date
    Feb 2004
    Location
    Brooklyn, NY Occupation: HVAC Service Contractor
    Posts
    258

    Chilled Water

    Are you convinced that the secondary waterside of this chilled water system is up to snuff? If not; check out circulating pumps and all valves to make sure you have proper water flow thru the chiller barrel. If the system is as old as you say it is then there might be a chilled water pump strainer that could need cleaning. Just some thoughts I had because trying to get the refrigerant charge into a compressor that's cycling off is a pain to say the least. Also what type of low ambient controls does this system have?

  5. #5
    Join Date
    Jun 2004
    Location
    Tn
    Posts
    21

    Chilled Water

    Dukrster, First of all, you said you have an old chiller.
    What was the original gas, has the TXVs been changed out, why has the controls been jumped out? Is the control on leaving water side or entering.Sorry to ask all these questions.Need more info to help you out.

  6. #6
    does this unit have unloaders. also is this water or air cooled. what is your subcooling and superheat. you will get no correct answere without it. what water temps are you running. if its 45 degree water then you should run about 55 lbs and then unload.
    also the best way to charge any txv system is with subcooling when you get 10 degrees your charged no questions. 85 lbs is a lot for such a small chiller. i would also check and make sure you not using hotgasbypass.
    also water cooled machines should not run over 220 lb head prssure. anything ove 220 lbs and condenser starts scaling up. that reciever is probalby your condenser and that would mean this is a water cooled machine.

    [Edited by airworx on 07-12-2004 at 01:31 AM]

  7. #7
    Join Date
    Jul 2004
    Location
    Florida
    Posts
    4
    WOW !!!!!!just logged back in and will try to answer some questions but don't have enough time to answer all at this time....getting ready for work...

    -Data Plate does say R-22
    -No unloaders
    -Unit has 2 condenser fans and a horizontal condenser coil ( no water tubes going to receiver barrel (air cooled)
    -TXV looks Original
    -Pressure switch were jumped out one at a time and left out of the circuit trying to isolate what was taking out the control circuit.
    -Water temp gauges are inaccurate so at this time no differential temps
    -no superheats or subcooling temps done yet
    -yes I know we need to put a time delay on the system...I am new at this particular place of business, so some of my suggestions are being blown off...My primary background is residential, however, far from stupid on refrigeration theory and electrical knowledge..still got a lot to learn on the industrial side
    -Need to check water flow for the temp purposes, flow switch is jumped (broke flow switch)
    - Wormy - It has two separate tee fittings going into the head (one on each end) with the cap tubes going to different controls supect it is measuring differentials...those controls are bypassed at this time.
    -freonrick- I believe I will dump the last 30lbs in the unit just to to eliminate another step..
    currently the only thing left in the control circuit is the freeze stat that has a button to indicate it is a tripping type manual reset button that has not tripped at all...It is getting bypassed today
    Don't think it has hot gas bypass..refrigeration flow is pretty much standard
    From head to air cooled condenser, out condenser and into receiver, out barrel into filter strainer, then to txv and then into chiller barrel out barrel at back to compressor.
    Will update again tonight....thanks for all the thoughts

  8. #8
    Join Date
    Jul 2004
    Location
    Florida
    Posts
    4
    Actually the correct name of this company I "REFRIGERATION SERVICES CO. INC (RSC).
    Any how...turned power back on with a completely warm barrel all pressure switches hooked up...unit fired up with normal pressures 72/225 and ran 13 minutes straight, we turned the fans on at the air handler to give it a load...within 13 minutes I had 53 degree return water...unit pumped down and cycled off....pump down solenoid is not holding perfect..so as the pressure began to rise the cut in would cycle the compressor back on to pump down again...at this time I put a 10 minute delay in the compressor control circuit to eliminate the cycling ....not really enough load on the water, temp rose maybe 10 degrees within the 10 minute delay.....
    HOWEVER, during the next sequence of operation...the solenoid opened up and compressor started with cut-in pressure...suction ran at about 70 psi and then began rising like it had a heavy heat load however there really wasn't much load on the system...Pressure went from 70psi to 82psi in about 4-5 seconds and then cut out again without dropping the barrel water temp at all. The delay now had it out of the circuit...I dropped the time back to .03 delay and the compressor went back to its on/off on/off mode every 1-2 seconds.
    Never put the extra 30 lbs in ....nor pulled the freeze stat out of the circuit....freeze stat was good with a meter..
    What I could really use is a terrorist attack on this Chiller!!!!
    What makes things worse is I have a couple of guys that think they can redesign this system and remove the Receiver so it doesn't hold as much freon....I feel like I'm back in Vo Tech...
    I seriously feel my problem is with the differential pressures....I am just not real familiar with Semi-Hermetics
    On one side of the head I have a 1/4 tee for the hp switch and on the other side of the head a tee for the Lp cut-out and cut-in switch
    Sorry for the lengthy description

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