24VDC valves?

24VDC valves, i.e. 24V direct voltage valves, are quite rare and cannot be used directly with OpenSprinkler.

While 24VAC and 12VDC valves can work easily with OpenSprinkler AC and OpenSprinkler DC, 24VDC valves cannot be used directly.

The reason is the high voltage. OpenSprinkler DC has an internal voltage converter that can handle a maximum of 12VDC; 24VDC would destroy it.

However, it is possible with the help of an additional 24VDC power supply!  The COM port must not be used. The 24VDC minus connection is connected to GND and the plus connection is then the main connection to the 24VDC valves (on their plus). The minus connection of the valves then goes to the valve controls 1..8.