The York S1-TBSU305-Y is a commercial 7-day programmable digital thermostat designed for precise control of multi-stage HVAC systems with up to three heating and two cooling stages. It operates by monitoring indoor temperature and activating the appropriate heating or cooling stages according to programmed setpoints and schedules. Suitable for commercial gas/electric package units, he... https://www.partshnc.com/s1-tbsu305-y-york-7-day-programmable-thermostat-comm-l-3h-2c