Trane DX - Dehumidification Mode; Sensible Cooling Mode

14 Dedicated Outdoor Air Systems: Trane DX Outdoor Air Unit SYS-APG001A-EN
Control of the Dedicated OA Unit
Dehumidification mode
If the outdoor air dew point is higher than the Dehumidification Enable
Setpoint, the unit operates in the Dehumidification Mode (Figure 10). In this
mode, compressor capacity is staged/modulated to dehumidify the outdoor
air (OA) to the desired leaving-air dew point (DH). Depending on the
application, this dehumidified outdoor air may then be reheated—using heat
recovered from the DX refrigeration circuit (i.e., hot gas reheat)—to the
desired leaving-air dry-bulb temperature (CA).
Figure 10. Dehumidification mode
Sensible cooling mode
If the outdoor air dew point is lower than, or equal to, the Dehumidification
Enable Setpoint, and the outdoor air dry-bulb temperature is higher than the
Cooling Enable Setpoint, the unit operates in the Sensible Cooling Mode
(Figure 11). In this mode, compressor capacity is staged/modulated to cool
the outdoor air (OA) to the desired leaving-air dry-bulb temperature (CA).
Figure 11. Sensible cooling mode
CA
sensible cooling
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wet-bulb temperature, °F
dry-bulb temperature, °F
humidity ratio, grains/lb of dry air
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dew-point temperature, °F
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DH
CA
sensible cooling
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wet-bulb temperature, °F
dry-bulb temperature, °F
humidity ratio, grains/lb of dry air
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dew-point temperature, °F
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OA