The McDonnell & Miller Model 551Sis a mechanical float-type make up water feeder. The water feeder float chamber is piped into an external water column via 1” NPT equalizing pipes. This is strictly a mechanical assembly, it does not include any electrical switches/contacts. The float is mechanically linked the makeup control valve.When the water level drops, the valve modulates open to allow water into the tank. As the level rises, the proportional valve starts closing off. Once, the level reaches the center of the float chamber, the valve will completely close off. The 551S is typically used to control makeup water to steam separators, receivers, feed tanks, and other vessels. The 551S can handle a maximum water supply pressure of 75 PSI at 120°F and a maximum vessel pressure of 25 PSI. Within boiler feed systems, the McDonnell & Miller 551S is commonly used on small, economical, atmospheric feed tanks. The 551S is used to control the makeup water into the tank.

• Mechanical level controller with valve
• Maximum water supply pressure: 75 PSI
• Maximum water supply temperature: 120°F
• Maximum vessel pressure: 25 PSI
• Connects to tank via 1” NPT equalizing pipes
• 3/4” NPT makeup valve connections