McDonnell & Miller 51-S-HD Water Feeder Refrigerant Can the RS1100 replace a

Can the RS1100 replace a mechanical 200-503 thermostat

The heavy-duty T-handle adjustment provides tactile control for setting precise secondary pressures

Frequent symptoms include the gas valve failing to open despite receiving 24V from the controller

making it an essential component for industrial burners and atmospheric boilers

Secure Attachment: Dual set-screw design ensures a slip-free connection to 5/8" motor shafts under high-torque starts

McDonnell & Miller 51-S-HD Water Feeder Refrigerant Can the RS1100 replace aThe McDonnell & Miller 51 S HD (Part Number 135800) is a heavy duty head mechanism only replacement designed specifically for Series 51 S mechanical water feeders. Engineered for high capacity systems up to 35,000 sq. ft., this unit is critical for maintaining precise water levels in low pressure steam and hot water boilers. Proportional feed action ensures a steady response to boiler demand, preventing the rapid cycling that stresses high volume