Do you need to protect your refrigeration system from excessively low suction pressure or excessively high discharge pressure with economic prices?Switch-Mate 221 is the answer. They are reliable to start or stop your refrigeration compressors or fans on air-cooled systems. They are easy to set up followed with the instruction manual. InstruMate model 221 offers various application possibilities with non-corrosive media like oil, water and air.