it refers to the switch contacts closing when the negative pressure (vacuum) reaches the 1

This Amana furnace replacement part is fabricated from durable

protecting the Thermal Expansion Valve (TEV) and compressor from solid debris that bypasses standard strainers

Designed for rapid deployment

Schneider Electric (Barber Colman) TC-1101-500 Thermostat R-410A it refers to the switchEnsure precise climate control on your next service call with the Schneider Electric Barber Colman TC 1101 500. This bimetal, two position electric room thermostat is a standard tier solution for applications requiring on off control of fan coils, motor starters, contactors, and two position electric actuators. Designed for high reliability switching, this unit features a SPDT snap action switch that supports both low and line voltage (24 to 277 VAC)