Liebert TM-10098 service manual Stagecompressors, Unloader State

iCOM Controls Training and Service Manual

and will be supplied with an electrical cylinder unloader valve. The electrical solenoid valve used to unload or reduce the cooling capacity of the compressor. The compressors will operate in an on/ off - loaded/ unloaded configuration method to cool the space. The hot gas bypass solenoid valve option is not available on 4 stage systems.

The temperature controller activates the first cooling stage, lead compressor unloaded, when the return air temperature increases to 25% of the cooling proportional band. The second cooling stage, lag compressor unloaded, is activated when the return air temperature increases to 50% of the cooling proportional band.

The temperature controller activates the third cooling stage, the lead compressor loaded, when the return air temperature increases to 75% of the cooling proportional band. The fourth cooling stage, the lag compressor loaded, is activated when the return air temperature increases to 100% of the cooling proportional band.

The temperature controller deactivates the fourth cooling stage, lag compressor loaded, when the return air temperature decreases to 75% of the cooling proportional control band value. The third cooling stage, lead compressor loaded, is deactivated when the return air temperature decreases to 50% of the cooling proportional control band value.

The temperature controller deactivates the second cooling stage, lag compressor unloaded, when the return air temperature decreases to 25% of the cooling proportional control band value. The first cooling stage, lead compressor unloaded, is deactivated when the return air temperature decreases to the temperature set point value or 0% of the cooling proportional control band value.

The table below shows the devices activated by each of the four cooling stages.

STAGE COMPRESSORS, UNLOADER STATE

1Compressor 1 On, Unloader On (Energized) Compressor 2 Off, Unloader Off (De-Energized)

2Compressor 1 On, Unloader On (Energized) Compressor 2 Off, Unloader On (Energized)

3Compressor 1 On, Unloader Off (De-Energized) Compressor 2 On, Unloader On (Energized)

4Compressor 1 On, Unloader Off (De-Energized) Compressor 2 On, Unloader Off (De-Energized)

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