Parts Number: 4040 Yellow Solenoid Valve Replacement fit for Aprilaire 550 600 solenoid valve 24V, 2.3 Watts; 60 HZ Fit for Aprilaire Solenoid Valve: 110,112,220,224,350,360,440,550,550A,550-A,558,560,560A, 560-A,568,600,700,760,760A,760-A and 768,fit for Aprilaire 600 solenoid valve 550 solenoid valve Replace Numbers: Humidifier Water Solenoid Valve 4040 replace A2012-S118,B2035-S2,B2035-S5,B2035-S54,B2035-S55,B2015-S51,B2015-S54,B2015-S58,B2015-S65,B2015-S68, B2015-S85,B2015-S87 Increasing Humidity Level: 4040 AP-4040 A2012-S118 humidifier solenoid fit for Aprilaire solenoid valve,ensures proper humidity levels by controlling water flow into humidifiers to increase the humidity keep room with ideal humidity level -30% to 50% About us:If you have any questions please feel free to ask us.Disconnect the power before installing this part. Proper humidification of your home is important for protecting your family’s health and the beauty of your home.The 4040 24 Volt Solenoid Valve controls the amount of water that enters your humidifier,ensuring that the right amount of humidity is delivered into the air every time it turns on.Usually installed by your contractor, the solenoid valve is part of the core of your humidifier,making it possible for you to adjust moisture levels with precision and accuracy.