American Power Conversion DX Benutzerhandbuch

The System controls the room environment by engaging one of four modes: Cool, Dehumidify, Reheat, 
or Humidify. These modes may work differently depending on the options and equipment installed in the 
Modules. 

Note: The environmental controls are set when your System is installed. Making changes to 
the settings described in this section after the System has been commissioned may result in 
improper operation.

Cool mode output is determined by the difference between the setpoint and the average return 

air temperature of each of the Modules in the System (if more than one Module is present). The 
deadband is used to engage the compressors incrementally with increasing demand. Each compressor in 
the System is assigned an equal division of the deadband. As the average return temperature rises above 
the setpoint, a compressor is engaged. If the average return temperature reaches the setpoint plus the 
entire deadband, all of the compressors will be engaged. As the temperature drops through each 
increment of the deadband a compressor will be disengaged. When the temperature drops below the 
setpoint the remaining compressor will disengage.

See “Deadbands” on page 34 for instructions on setting the DX cool deadband.

When the cool mode uses a MultiCool or Economizer coil, the output is determined 

by the difference between the setpoint and the average return air temperature of each of the Modules in 
the System (if more than one Module is present). The Proportional plus Integral plus Derivative (PID) 
control loop calculates the output as demand increases and opens the valve controlling the flow of 
coolant into the coil. As the average return temperature increases, the output will increase until it reaches 
100 percent of capacity. For Modules with an Economizer coil, one stage (compressor) of DX cooling 
can be engaged per Module to help meet the demand. The rule for engaging the compressor is the same 
as for DX cool.

See “PID controls” on page 38 for a description of the PID controls and see “How to tune the 
PIDs” on page 38 for instructions on tuning the fluid coil PID loop.

The silicon controlled rectifier (SCR) electric reheat function is controlled by 

the reheat PID controller. When the return temperature of the Module drops below the reheat setpoint, 
the reheat output will increase as the return temperature drops until output reaches 100%.

See “PID controls” on page 38 for a description of the PID controls and see “How to tune the 
PIDs” on page 38 for instructions on tuning the reheat PID loop.