For multi-speed fan control, you can adjust the point when the medium or high speed turns on. The fan speed is based on the load of the cooling or heating device, and is a percentage between 0 and 100. By default, the Med Speed On Cmd is 33% and the High Speed On Cmd is 66%. When you only use two fan speeds, set the High Speed On Cmd to 100% to disable the third speed.
For VSF control, the output is configurable for any range between 0 VDC and 10 VDC. The parameters are Start Voltage, Full Speed Voltage, and Minimum Command. Start Voltage is the voltage output at which the fan begins running, and Full Speed Voltage is the voltage output at which the fan reaches full speed. Minimum Command is the percentage of the range between the Start Voltage and the Full Speed Voltage. The fan does not go below the minimum command when the fan is turned on. By default, the Start Voltage is 2 VDC, the Full Speed Voltage is 10 VDC, and the Minimum Command is 20%.
When the variable speed fan is off, the FAN binary output is off and the voltage at the VSF output is 0 VDC. When the fan turns on, the FAN binary output turns on and the voltage at the VSF output begins controlling the fan. When the VSF is configured for reverse acting mode, when the Start Voltage is above Full Speed Voltage, the VSF output is set to 10 VDC or the Start Voltage minus 1 VDC, whichever value is the lesser, when the fan is turned off.