Honeywell solenoid water valve 50027997-001 assembly for all TrueSteam models.
This valve contains two solenoid valves. Both valves operate on 120 vac and can be tested by unplugging it from the humidifier and connecting power from an external 120v source.
One solenoid controls filling the water tank. This valve is normally closed when no power is present. The inlet for this valve has a SpeedFit push-in fitting. The plastic water line just needs to be pushed in to this line.
The second solenoid controls draining tank. This valve is normally closed when no power is applied. This valve also connects to the tank overflow hose that always provides an open path to the drain.
See the installation manual, page 21 for trouble shooting.