Operating Thermostat, part number 3387134 Summary This operating thermostat is rated L155*25* differential and includes a 250 Volt 2 Watt heat anticipator. It is identified by the markings 3387134 and KSD301C and is designed as a direct replacement for several legacy thermostat part numbers. Key benefits Accurate temperature control: L155*25* differential provides consistent cycling for heating systems. Builtin heat anticipator: 250 Volt 2 Watt anticipator improves control responsiveness in mechanical thermostat systems. Easy replacement: Matches multiple legacy part numbers for simpler parts sourcing and faster repairs. Clear identification: Markings 3387134 and KSD301C make verification quick during installation or service. Important attributes Function: Operating thermostat for heating control with mechanical switching and heat anticipation. Rating: L155*25* differential; heat anticipator rated 250 Volt, 2 Watt. Terminals: Two outside terminals are 1/4inch male; two inside terminals are 3/16inch male. Markings: Printed numbers 3387134 and KSD301C. Compatibility: Replaces 3387134, 36910, 306910, 3387135, 3387139, 8318268, AP3131939, AP6008270, ET187, PS344510, PS11741405. Use scenarios HVAC service technician replacing a worn thermostat in a residential furnace control panel to restore correct temperature cycling. Maintenance team swapping a failed thermostat in commercial space heating equipment where the original part number is no longer available. Homeowner or contractor updating an older mechanical thermostat assembly to a directfit replacement that matches terminal layout and electrical rating. Installation notes Verify the printed part numbers 3387134 or KSD301C before installation. Ensure the terminal sizes match the wiring harness: outside terminals 1/4inch male, inside terminals 3/16inch male. Confirm system voltage and control requirements match the 250 Volt 2 Watt anticipator rating and L155*25* differential. Compatibility reference Replaces: 3387134, 36910, 306910, 3387135, 3387139, 8318268, AP3131939, AP6008270, ET187, PS344510, PS11741405 This thermostat provides a direct, specificationmatching replacement for systems that require an L155*25* operating thermostat with a 250 Volt 2 Watt heat anticipator and the specified terminal configuration.