the FTI series is the appropriate alternative

Direct Drop-In Compatibility: Specifically designed to replace discontinued model S1-024-19878-700 without mounting modifications

Optimized Sealing: Parallel blade design and extruded seals minimize bypass air when the zone is inactive

but the locking mechanism and SPST action remain the same

York S1-THEH21P5S Thermostat 323613-751 the FTI series is theAs a technician, you know that keeping a heat pump system running efficiently requires a robust interface. The York S1 THEH21P5S Thermostat is a high performance 5 2 day programmable thermostat designed specifically for 2 stage heat 1 stage cool heat pump applications. This unit features a backlit digital display that provides clear visibility in dark mechanical rooms or hallways, allowing for easy monitoring of the auxiliary heat indicator and