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  1. #1
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    Trane 90 ton DX will not bring in 3rd and 4th stages for cooling

    Calling on you PROs for this one. When looking into this situation the supply and return air is not cold enough to satisfy the demand. For some reason the 3rd and 4th stages are not kicking in. Looking at all temperatures and WC everything looks good. Running in test mode everything is perfect. Go back to auto run and the values of all sensors are great, but the darn thing will not bring in the last 4 compressors. These are scroll compressors not semi hermetic, and there are 6 total. I have walked threw the configuration and it matches the other RTUs on this BAS. I can't figure this one out. SMH

    TRANE MODEL SXHGC9040775CEBD8001A0W00G000NRT0000 SERIAL C09D13917

  2. #2
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    Moved to Tech to Tech Commercial.
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    How many times must one fix something before it is fixed?

  3. #3
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    We need to know how the unit is being staged in order to answer the question

  4. #4
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    I agree. Also, what is the discharge air setpoint and actual. What is the discharge static pressure vs setpoint. Any alarms? Anything locked out?

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  5. #5
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    If it runs in test mode, the configuration is identical, and the BAS is correct, then I would first look at the zone sensor to see if the BAS should be asking for the additional stages.

    In order to understand why this is happening, you need to understand when and why the BAS would call for all stages to run.
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    2 Tim 3:16-17

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  6. #6
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    If I'm not mistaken, Trane Intellipaks control themselves. They get a discharge air, static, etc. setpoints and go. The BAS system does not control staging of the unit. Most other control companies dumb them down. These things can control VAVs too, just need to give it setpoints and monitor.
    Go line by line and check ALL parameters against a known working one with the same model #.
    I would also like to see some numbers so we know what we are dealing with.

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  7. #7
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    While they can control themselves to an extent, there would be no reason to have systems like Tracer and Tracker if they weren't needed.

    The fact that the system will work properly in test firmly suggests to me that we have a data issue with this unit.
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    2 Tim 3:16-17

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  9. #8
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    Hopefully Jayguy will stop by with some additional insights, because he works with Intellipaks a lot more than I do.
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    2 Tim 3:16-17

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  10. #9
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    You can stage them using the BAS, or run as standalone, or combination of both.

    I believe The vertical terminal blocks at the lower left center of the control panel are for external staging control. If there are field installed relays in the cabinet, or field installed wires connected to those TB’s, then the BAS is likely controlling staging.

  11. #10
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    Per the model number, that unit is a VAV with VFD, is cooling only, and operates to discharge air.

    So all the BAS is gonna do is start stop, maybe remote discharge air setpoint, but you would need to program the unit for that.

    So if your not staging up, either the discharge sensor is out of calibration, the setting is too low, or its working fine, and you simply dont need all the compressors to run to maintain the desired discharge air.

    That unit does have settings for discharge air reset, so on milder days and cold weather you allow for a warmer discharge air then you need when its hot out - saves alot on reheat.


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  12. #11
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    Heres the rest



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  13. #12
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    Mar 2017
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    Thread Starter
    Thanks my brothers. The unit is set for 65 in the BAS and I have checked the thermisters in the unit. I did tell the building engineers to have the BAS company come in and check the controls. Most of which is on the BAS side. I skimmed threw the set up and diagnostics. The RTM sensor is throwing code for the roof too on both units. The set point is at 55f for the supply air in the unit. With 65f supply and oda at 80.1 with 93 on the condenser. However that is only one compressor running. It is configured for lead lag in the unit. I will possibly get more data today.

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