White Rodgers 1E78-140 Thermostat

The White Rodgers 1E78-140 Thermostat provides a rugged, field-proven solution for single-stage heat-only systems. Operating on 24V low voltage or millivolt systems, this vertical non-programmable unit is the preferred choice for technicians replacing older mechanical mercury thermostats in residential or light commercial applications. Its digital LCD backlit display offers high-contrast visibility, ensuring accurate temperature readings within a 1-degree differential to minimize system cycling and improve fuel efficiency across gas, oil, and electric heat systems.

Built for reliability in the field, the 1E78-140 features RH and W terminal designations, supporting simple two-wire installations without the need for a common wire when battery-powered. The unit operates on two AAA batteries and includes a permanent memory backup, preserving setpoints during power interruptions. Designed with a vertical footprint, it effectively masks wall marks left by legacy footprints, making it an efficient retrofit option for furnace, boiler, and hydronic zone valve applications. The selectable Fahrenheit or Celsius display and a setpoint range of 45°F to 90°F provide the precision control modern contractors demand for hydronic and forced air environments.

• Broad Compatibility: Seamlessly integrates with millivolt fireplaces, single-stage gas or oil furnaces, and electric heating systems.
• Contractor-Friendly Install: The vertical design and universal sub-base allow for rapid mounting on standard junction boxes or direct-to-wall retrofits.
• Precision Performance: Maintains consistent room temperature with a tight 1-degree digital accuracy, reducing mechanical stress on HVAC components.
• Maintenance Alerts: Integrated low battery indicator ensures continuous operation by alerting users before power loss occurs.

• Will this work with a 2-wire heat-only system? Yes, the White Rodgers 1E78-140 is specifically designed for 2-wire (R and W) 24V or millivolt applications, making it ideal for boilers and wall furnaces.
• Does this thermostat require a C-wire? No, this model is battery-powered and does not require a common wire to operate the digital display or system switching.
• Is it compatible with 120V/240V electric baseboard heat? No, this is a low-voltage thermostat. It must not be used with line-voltage systems, as it will cause immediate equipment damage.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.