White-Rodgers 1F51N-619 Thermostat

The White-Rodgers 1F51N-619 is a heavy-duty, low voltage evaporative cooler thermostat engineered for precise performance in 1C (cooling only) applications. Designed as a direct, mercury-free replacement for legacy models like the 1F51-619, 1F51W-619, and 1D51W-632, this mechanical thermostat features a rugged snap-action switch rated for 24VAC systems. It provides a specialized interface for swamp cooler operation, including a system switch with OFF, COOL, and VENT positions, alongside a dedicated high/low fan speed selector. The internal bi-metal sensor operates across a 55°F to 95°F range (represented by a 1-5 scale), ensuring reliable single-stage cooling control. This analog thermostat is specifically optimized for use with the 8A18Z-2 evaporative cooler control transformer relay, utilizing R, W, Y, and G terminals to manage motor and pump sequencing. Its horizontal profile and classic white finish make it a standard kit-bag essential for field technicians servicing older residential or light commercial cooling systems.

• Precise Snap-Action Control: Utilizing a high-reliability SPST snap-action switch to prevent arcing and ensure clean signaling to the 24V control board.
• Versatile System Switching: Integrated VENT mode allows for fresh air circulation without engaging the water pump, reducing energy consumption.
• Dual Fan Speed Selector: Direct manual control over HI and LO fan settings provides immediate airflow adjustment based on ambient load.
• Direct Cross-Compatibility: Seamlessly replaces discontinued mercury-bulb models, fitting the same mounting footprint to minimize installation time.
• Environmental Compliance: Fully mercury-free construction meets modern disposal regulations while maintaining the tactile feedback pros expect.

Is the 1F51N-619 compatible with line voltage swamp coolers?
No, this is a 24VAC low voltage thermostat. Scaling it to 120V or 240V circuits will cause immediate component failure and poses a safety risk. It must be paired with a transformer or a relay control box like the 21D28-6.

Can I use this thermostat for a heating and cooling system?
This model is specifically designed for cooling only (0H/1C) and evaporative applications. It lacks a heat anticipator and the necessary switching logic for furnace or heat pump integration.

What is the temperature differential for this unit?
The 1F51N-619 maintains a tight mechanical differential of approximately 1°F, ensuring stable setpoints and preventing excessive motor cycling.

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.