High-Pressure Cut-Off Switch
The high pressure cut-off switch (dual-pressure switch) is mounted on a Schrader valve-type fitting on high-pressure side of condenser to evaporator line, and is used to interrupt compressor clutch operation in case of high system discharge pressures. High pressure cut-off switch has 2 sets of contacts. One contact is normally closed. When system discharge pressure increases to about 450 psi (31.6 kg/cm2 ), normally closed switch contacts open and compressor clutch will be disengaged. When discharge pressure decreases to 250 psi (17.6 kg/cm2 ), switch contact close allowing compressor operation.
A second set of contacts in high-pressure cut-off switch is used for high speed fan control. When compressor discharge pressure reaches 325 psi (22.8 kg/cm2 ), normally open switch contacts close engaging high speed fan control. When pressure drops to 275 psi (19.3 kg/cm2 ), switch contacts will open disengaging high speed fan control.