Daikin MICROTECH 4 Operation Manual page 65

DEHUMIDIFICATION
Staged Compressors
When Dehumidification is active, compressor stages are controlled to maintain the leaving coil temperature between the minimum
leaving coil temperature set point (MinLCTSpt) and the maximum leaving coil temperature setpoint(MaxLCT Spt) . During
dehumidification operation, the number of compressor stages increases or decreases to maintain the leaving coil temperature between
the minimum and maximum leaving coil temperature set point .
Figure 23: Compressor Staging Psychrometric Charts
Variable Speed Compressor
When dehumidification is active, Variable Speed Compressor capacity is modulated to maintain the leaving coil temperature within the
deadband near the leaving coil temperature set point .
Reheat Control
The reheat process is a critical component of the dehumidification process. All MicroTech controlled rooftops use a fully modulating
reheat control to provide precise discharge temperature control during dehumidification. There are several forms of reheat that can be
used . Reheat types can be Liquid Subcool Reheat, Hot Gas Reheat, or the standard heating equipment (Gas or Steam/Hot Water) .
• Cooling: In the cooling state, the modulating hot gas, liquid subcool, and standard heat reheat will be controlled to the DAT
Cooling . This is demonstrated in
reset . For Zone Control units, this set point is the result of a calculation based on the control temperature .
• Fan Only: In the fan only, state, the modulating hot gas, liquid subcool and standard heat reheat will be controlled to the reheat
set point . The reheat set point equals an editable MaxReheatSpt (Default = 65°F) when the control temperature drops to the
Occupied or Unoccupied Heating Set point, and equals an editable MinReheatSpt (Default = 55°F) when the control temperature
rises to the Occupied or Unoccupied Cooling set point. The Dehumidification Reheat Set point varies linearly between these two
points . Users can choose to set these to be the same value (Example = 65°F) if they desire neutral air when there is no sensible
cooling load .
OM 1373-1
Figure 23 . For DAT controlled units this is the normal DAT Cooling set point resulting from any
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