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  1. #1
    Join Date
    Mar 2008
    Location
    Porter,Tx
    Posts
    31

    Carrier 30GTN170 Loading Problem

    Guys,I can't figure out whats wrong.This chiller has a setpoint of 42degrees,but will only provide a 46.7LWT w/55.6EWT.The unit is at 100%,15stages of cooling,it has 17 stages.Circuit A,the EXV is at 100% and the lead compressor is unloaded and has a SH of 30(display) Circuit B is running unloaded,w/EXV at 69% and has a SH of 26(display)I did replace the thermistors(T6,T8) that were off only by 3degrees on B circuit thinking this was why the EXV at 69%.Going by memory,the SGT is at 77 degrees and the SST is at 44 degrees,SH at 26degrees.I also check my actural psi(manifold gage) which was reading 72 suction/225Liq,on the display I was reading 80psi suc/250psi liq. Does T6 provide the suction psi and T4 provide the discharge psi?Is it not the spread of the LWT&EWT that loads the chiller,and why won't it load up to 17 stages and both EXV's at 100%?I won't be back at the chiller till Monday,so if anyone can point me in the right direction,are need alittle more info to help in disnosiging the problem.Thanks for any help CJ Courtney

  2. #2
    Join Date
    Dec 2006
    Location
    Middle Tennessee
    Posts
    11,347

    *

    how many compressors are there!

    the lead compressor should be the last to unload!



    .

  3. #3
    Join Date
    May 2006
    Location
    Western NY
    Posts
    4,356
    T4 is your sat. cond. temp. sensor and T6 is your cooler suct. temp. sensor. I have to ask, why is your 46* LWT not good enough? If you can not cool/dehumidify with 45* water, it seems to me your problems would lie elsewhere, ie air flow for example.
    What's your outdoor temp at the condenser? Condenser coils clean?
    "Excellence is the gradual result of always striving to do better"
    -Pat Riley

  4. #4
    Join Date
    Mar 2008
    Location
    Porter,Tx
    Posts
    31

    Carrier Problem

    Guys, thanks for replying.Here in the south part on Texas(Houston),the normal LWT is 40-42degrees.We also have thermal tanks that is charge a night to 40 degrees.Yes,T4 is for the SCT,is this the thermistor that the display get the discharge pressure?There is 3 compressor for each circuit.What I can't figure is why it won't load up to 17 stages since it is not at setpoint,which is 42 degrees.The ambient temp is at 95 today,coil are clean.The SCT is at 113 degrees.Thanks again

  5. #5
    Join Date
    Jul 2005
    Location
    south
    Posts
    590
    You say the machine is running at 100% but with only 15 of 17 stages working and circuit "b" unloaded? can't be 100% if machine is not fully loaded. circuit "a" exv should not be at 100% --- possibly low on refrigerant. Have you verified refrigerant charge in circuit "a" ? Have you looked under the modes menu to see if you are operating in a mode that will not let machine load up to 100% ?

  6. #6
    Be sure to check the set up in the test menu. If the eprom is upside down on the main board it won't configure the chiller right.

  7. #7
    Join Date
    Mar 2008
    Location
    Porter,Tx
    Posts
    31

    Carrier Problem

    Lic.to chill:No I have not check,the unit is on a EMS and does have temp reset.I look at the control setpoint and its at 42degrees.Since you brought it up,I did have the chiller in test mode to pump down the compressor so I could replace T8.Will the chiller go back into auto when I put the toggle switch back in auto,or will it stay in the test mode?I forgot to check that.Thursday,before I done anything,it would load up to 100% and 17stages of cooling.Circuit B,EXVonly open to 70% while cir.A EXV was at 100%.Your right,how can a chiller say its at 100% when there is 2 more stages to bring on(both unloaders) Thanks for responding

  8. #8
    Join Date
    Jan 2008
    Location
    Dallas ,Texas
    Posts
    3,718
    On gtn`s all the thermistors are supposed to be in a well except for T2. I also think you are low on charge circuit a

  9. #9
    Join Date
    May 2006
    Location
    Western NY
    Posts
    4,356
    What's your deadband multiplier set to? If it is greater than the default, which is 1.0, there will be a delay between adding and removing stages of capacity, regardless of the CW stpt.
    "Excellence is the gradual result of always striving to do better"
    -Pat Riley

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