Xylem-McDonnell & Miller 851-S 851 W/Higher Capacity #136800

The Xylem-McDonnell & Miller 851-S 851 W/Higher Capacity 136800 is a high-capacity pressure switch intended for use in commercial and industrial HVAC systems, notably those that include boilers. It works by keeping an eye on the system's water pressure and taking appropriate action when preset limitations are reached. This version has a larger capacity than the ordinary 851-S type, which enables it to withstand higher pressure demands. It detects changes in pressure using internal contacts and a diaphragm. The switch opens or closes an electrical circuit to activate or deactivate equipment such as pumps and fans when pressure exceeds a setpoint. Restricting operation over safe pressure limits protects the equipment. By regulating pump operation by system demand, it may also maximize efficiency and performance.